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Sony Tuners

Tuners are listed in alphabetical and numerical sequence by model number. In parentheses after the model number are the year of introduction and most recent list price, and/or the original list price if indicated by "orig." Special thanks to David Rich of The Audio Critic for copies of historical material from his reference library.

There are a couple of Sony tuners in our On-Deck Circle that we'd like to consider listing here if we can get some basic information on them (types of controls and features, and any personal anecdotes or comparisons to other tuners). Please post in our FMtuners group if you have any information about any of them. We have posted updated eBay sale price data on this page through April 2016; data for "as is" or damaged tuners, or otherwise unrepresentative auctions, may be excluded.

Sony ST-636 open, inside, dial driver board, detector and MPX) search eBay
The ST-636 is a very odd, cool-looking, so-called "FM-AM Program Tuner" that was supposedly sold as part of a two-piece set. This probably accounts for the hardwired RCA cables and remote control jack on the back panel, and the two little protruding metal pegs on the top panel must mate with the amp when they're stacked. The ST-636's front panel is jam-packed with marketing buzzwords, including "Computerized Xtal-Lock Synthesizer," "Fluorescan Memory Display," "Programmed Tuning," and "Accelerated Scanning" printed on the tuning knob. The tuning knob can be twisted slightly to click up or down in .1 MHz increments, but if twisted and held while in the Auto tuning mode it flies up or down the dial (the Accelerated Scanning, apparently). The ST-636 has 5 FM and 5 AM presets, the varactor equivalent of 4 gangs, and two green 4-pin ceramic filters. Muting is automatically engaged when in Stereo mode, meaning that one cannot choose to listen to a weak station in slightly noisy stereo. The tuning increments for AM can be changed from 10 kHz to 9 kHz, for use outside North America, with a switch on the back panel.

Our panelist Eric couldn't rate the ST-636's performance because his sample appeared to be out of alignment, so he sent it to our panelist Ray for tweaks: "A generous tweak of the 76 kHz VCO brought stereo sound and beacon to life." Ray adds, "There were many analog tuned with both dial and digital frequency readout units made in the 1978 to 1981 time frame. I always thought that at the time marketing saw the dreaded fork in the road and in cowardly fashion decided to take both paths. To my knowledge the ST-636 is the only tuner of that era to have what is commonly referred to as digital tuning but with an additional analog-looking dial. They used the varactor tuning voltage to chase a lit LED along a linear scale emulating an analog dial. If you look closely at the dial you'll see what are truly linear FM and AM scales... neat! Sony also added tuning sound effects: as the 'pointer' moves along it makes a clicking sound reminiscent of the cardboard flap against the spokes 'engines' we used to put on our bicycles. At first touch I thought all of this rather silly, but then I began to appreciate all the technology Sony expended on this. The driver board is huge.

"The tuner hidden amongst all this trickery, though not super, is also unique and quite OK to listen to. I measured a de-emphasis time constant of 82.5 µS with response +0.25 dB, -1.10 dB 40 Hz to 12 kHz. It was -2.90 dB at 20 Hz and -4.0 dB at 15 kHz. The pilot filter started digging in at 14 kHz. 19 kHz and 38 kHz pilots were waay down. Methinks it sounds pretty good as it is. A couple of nice surprises were found in the schematic. After the detector there's a discrete transistor amp pushing an LC low pass filter and after the MPX chip and pilot filters we find passive de-emphasis and discrete voltage gain transistor amps. Nice.....that's the way ol'RFM likes it." Some specs from the manual: IHF sensitivity 10.3 dBf; 50 dB quieting sensitivity 16.1 dBf mono, 38.3 dBf stereo; S/N ratio 75 dB mono, 70 dB stereo; THD @ 1 kHz 0.1% mono, 0.2% stereo; separation 45 dB @ 1 kHz; selectivity 80 dB @ 400 kHz (to which Ray says "Really? With 2 ceramic filters?"); image response ratio 80 dB; frequency response +0.5 dB, -2.0 dB, 30 Hz to 15 kHz. The ST-636 is seen only once or twice a year on eBay and usually sells for less than $50 (with a low of $20 in 6/09), but up to $125 is possible, and one inexplicably went for $290 in 6/03.

Sony ST-2950SD (1977, $220, front, inside, back) search eBay or search eBay
and
Sony ST-3950SD (1977, $300) search eBay or search eBay
The ST-2950SD and ST-3950SD are big, heavy, well-built tuners from the line that includes the underrated ST-4950 and ST-5950SD. The "SD" denotes Dolby capability, which is irrelevant today, and Sony also made an ST-2950 and an ST-3950 that did not have it. The ST-2950SD had 3 FM gangs and 2 AM gangs. While we hesitate to make judgments solely on specs, it must be noted that the ST-2950SD had far worse specs, particularly for selectivity and sensitivity, than its bigger brothers. The ST-2950SD usually sells for $10-25 on eBay (with a recent high of $90 in 4/13), while the ST-3950SD usually goes for $35-75 (with a recent low of $10 in 7/14 and a recent high of $119 in 6/12). Two examples of the ST-2950S, apparently a European model that included a shortwave band, sold on eBay for $52 in 5/04 and a shocking $224 in 5/06, while the presumably similar ST-2950F (with a longwave band as well as shortwave) usually sells for $85-110. Some or all of these tuners were sold with optional wood sides.

Sony ST-4950 (1977, $350, front, inside, back) search eBay
The ST-4950 was second from the top of the overlooked ST-5950SD line. The ST-4950 is an analog tuner with 4 gangs for FM and 2 for AM, a multipath indicator and a hi-blend switch. For some reason, it appears to have been the only tuner in the line that was not available with Dolby capability, as indicated by the "SD" in the model numbers of the others; this is irrelevant today, and the ST-4950 may even have a simpler signal path (generally considered to be an advantage for audio quality) due to the absence of the Dolby circuitry. Our contributor Herb reports: "I have owned several super tuners, a Sansui TU-X1 among them. I currently own a Sansui TU-9900 (which I consider to be the equal of the TU-X1), a Kenwood KT-8300, a Mac MR 77 and a Mac MR 78. In blind A-B testing, to my ears, though the Sony comes up a little short of the two Sansuis (especially in terms of soundstage and imaging), it is superior to the Macs and the equal of the KT-8300. The ST-4950's build quality is also excellent. It is on my list of super tuners." The ST-4950 usually sells for $60-110 on eBay, with occasional lows around $25 and a highs of $177 in 4/11.

Sony ST-5000 (ST-5000W) (1967, $399, photo) search eBay or search eBay
and
Sony ST-5000F (ST-5000FW) (1968, $450) search eBay or search eBay
Intended to compete with the Marantz 10B, the FM-only ST-5000 was the first audio component widely distributed by Sony in the U.S. Built like a tank, more like military gear (or McIntosh tuners) than later Japanese electronics, it has a strong following even though the styling was not great (very typical of '60s hifi gear). The version that says "5000F" on the front panel is the "5000FW", as it says on the back panel. The two variations had different front panels -- the ST-5000 had three switches in the center of the faceplate, while the ST-5000F had a single switch in the center of the faceplate -- and differences in the front end, IF filter, and MPX section as well. Both had 5-gang tuning capacitors, with the ST-5000's being silver-plated. Both had an 8-stage IF filter section, and an all discrete multiplex section. The 5000's filters are adjustable LC type, and the 5000F uses the 4-pin ceramic type, so don't buy an ST-5000 or 5000F expecting to swap 3-pin filters. The ST-5000 is the earlier version and is very rare. Our contributor Charles says that his ST-5000FW has a beautiful sound, and that "in the next room, it really seems like you have musicians in your house." He also finds it "almost as good as my KT-7500 [for DXing]... in situations that try the adjacent channel selectivity of any tuner. That's amazing performance for a 30-year-old unit with all LC filters and only one IF bandwidth."

Mike Zuccaro comments: "The ST-5000 had LC IF filters, a CdS Rf attenuator in the front end, fully bipolar front end (no FET's yet), CdS muting and switchable AFC. The ST-5000F ("F" for FET), introduced about one year later, had 4 FET's in the front end- 2 RF amps, mixer and oscillator. It did not need AFC. The 3 ceramic filter blocks used in the 5000F actually each contain 4 filters (!). It's not shown this way in the schematic (just a filter block), but is buried in the circuit description ('uses 3 4-section multi-unit ceramic filters'). The 5000F had standard transistor-driven muting (no CdS cell) and marginally better sensitivity specs. Both are very highly rated tuners - I'd consider them sleepers. Replaced by the AM/FM ST-5130, which I have worked on and is a nice unit, but the build quality was not the same as the 5000. The ST-5000 was Sony's first tuner, aimed at a heavyweight (the Marantz 10B), and like McIntosh's MR-55, Sony spared no expense. Later tuners may have had equal or better specs, but were certainly 'made to a price' whereas the 5000/5000F seem to have been built with more care."

Our contributor Glenn says that his recapped and aligned ST-5000FW "has the best sensitivity of any tuner I've owned and is a wonderful, smooth and sweet-sounding tuner." And our contributor Al adds, "The ST-5000F is the best shielded tuner I have and one of the most attractive inside that I've seen. The tuning gang cover has a soft copper pad that presses against the section dividers, sealing them along the top edge. I've never seen anything like this before. The later Sony tuners have plastic covers over the tuning gang (ST-5130) or no cover at all (STR-V6?)." There's an excellent page on the ST-5000/5000F at The Vintage Knob. The ST-5000/5000F shows up a few times a year on eBay and usually sells for $170-350, with occasional lows around $100 and highs over $400 for mint ST-5000Fs. [BF]

Sony ST-5130 (1973, $370, front1, front2, inside, back) search eBay
The ST-5130 is a 5-gang, 8-filter tuner that was a favorite of DXers in the '70s and '80s. It has multipath output jacks for an oscilloscope, a headphone amp with built-in volume control (which allowed Mike Bugaj to bring his modified 5130 for DXing on trips), and some other nice features. Our contributor Thrassyvoulos says, "My 5130 is a truly amazing reception machine. Even with a T-shaped wire it is one of my very best, comparable to my Yamaha T-85 and Sansui TU-9900! Now having said that, it is not the best-sounding tuner, as it has an overly warm, rounded sound in my system." Sale prices for the ST-5130 on eBay are erratic: most often $60-100, with a low of $10 in 11/12 and a high of $232 in 10/11.

Sony ST-5150 (1974, $280, front, back) search eBay
The little brother of the ST-5130 is a surprisingly solid performer. The ST-5150 has 4 gangs and two green Taiyo ceramic filters that apparently have a very wide bandwidth, as one might expect in a tuner manufactured when the FM band was much less crowded. In stock form, adjacent channel selectivity is lousy, but the ST-5150 springs to life with 2 narrower filters installed. It has excellent sensitivity and a full, rich sound with particularly natural-sounding bass. The ST-5150 has multipath output jacks for connecting an oscilloscope, separate right and left channel level knobs for the variable output jacks, and a 75-ohm antenna input - unusual for an early-'70s tuner. There's a nice page on the ST-5150 at The Vintage Knob. The ST-5150 is much more common than the ST-5130 and usually sells for $35-90 on eBay, with a low of $10 in 9/10 and a recent high of $202 in 1/14 for one with a wooden cabinet. [EF]

Sony ST-5555 (January 1974, $1,700, head shot, top view 1, top view 2) search eBay
There are a couple of videos on YouTube showing the unique ST-5555 in action. Here's Mike Zuccaro's review:
A random-access tuner using Sony first generation RAM chips, the ST-5555 searches and memorizes all 100 FM channels. The ST-5555 is fully shielded, with all plug-in circuit boards. Most of the circuitry is necessary for the search/scan feature. You'd need an extender board to work on any of the boards. Fewer than 100 ST-5555s were manufactured, and almost all of them were bought back. I never could get a straight answer on why that was so, except that they were so complicated they could not be fixed by the authorized or even factory servicers. I have an ad slick and I'm sure there was an owner's manual, but no service manual was ever published. I've got the Japanese engineering schemos, that's it, and an early internal spec sheet. I asked every Japanese engineer that come from Consumer Audio in Japan when they visited, and could not learn more about this tuner. The field guys did not report any unusual failures. The ST-5555 was way, way too pricey, though, and my guess is that it just didn't sell. Like the Sherwood Micro/CPU 100 tuner, much engineering went into the random access feature. Lotsa 100db specs, though, and it would hold its own against any modern tuner. I would be glad to answer any specific questions by email at mjzuccaro@aol.com. [The only ST-5555 seen for sale anywhere since the beginning of 2001 was bid up to $415 on eBay in 2/04, but failed to meet the reserve. - Editor]

Sony ST-5950SD (1977, $470, photo) search eBay or search eBay
The ST-5950SD was at the top of Sony's overlooked (and overbuilt) line that also included the ST-2950SD, ST-3950SD and ST-4950. The "SD" denotes Dolby capability, which is irrelevant today. The top three tuners in the line all seem to have been sleepers, but the ST-5950SD had particularly excellent specs, particularly for sensitivity, quieting and stereo separation. It also has fixed and variable outputs and a front-panel headphone output jack. Our contributor Graham in the UK prefers the sound of the ST-5950SD to that of the Quad FM4, which he says has rolled-off highs. The ST-5950SD has 5 gangs for FM and 2 for AM. Our panelist Bob analyzes the schematic: "It's 5 gangs for sure. Looks like two filter blocks, likely Murata ceramic with the equivalent of two 3-pin filters per block. This filter setup was quite common in tuners of this vintage. One single IF path. Ratio type detector. Looks to have a very complete output section, but details of MPX chip or output device type are unknown." There's an excellent page on the ST-5950SD at The Vintage Knob, but note one error: it uses a 5-gang tuning capacitor, not varactor tuning as TVK states. The ST-5950SD usually sells for $100-175 on eBay, with occasional lows around $60-70 and occasional highs well over $200.

Sony ST-A6B (1978, $310, front, inside, gangs, with ST-A7B, schematic left middle right, more schematics, alignment guide, circuit description, specs, "new circuit operation" brochure) search eBay
The ST-A6B is a scarce FM-only tuner that was mostly unknown until we outed it. Our panelist Bob was "shocked to pop the lid and count 7 gangs." Bob reports: "This is a special tuner. I think the RF front end may be on par with some of the better designs *ever done* out there. It slices the RF pretty good. The dial is long and very articulate, like a 600T or KT-917. The ST-A6B is a really good tuning unit, sensitive, selective, looks good, sounds good. What else can you want? It is not a really 'full box' inside, but part of that is because it is FM only (no AM stuff in the way), and it's a BIG box. Bottom line: It's not a KT-917 or TU-X1, but it does have those 7 gangs and wide/narrow IF filters, so it's worth at least $200-300 for rarity plus performance alone. And it *does* perform in the reception category, incredibly so. I love the big dial and oversized meters. One of Sony's best. Too bad this tuner is so rare." Here is what appears to be an excerpt from some Sony marketing material: "The ST-A6B has no AM circuitry. It is designed strictly for excellent FM performance. It has a 7-gang tuning capicitor with circuitry for high selectivity, low distortion, a high S/N ratio and good capture ratio. To ensure its performance is maintained under all types of broadcast signal conditions, it has an IF bandwidth selector for a 'normal' or 'narrow' mode for weak incoming signals. The A6B has no subcarrier leakage that would cause audible beat-frequency on tape, making it an excellent tuner for off-air recording. There is a 400 Hz test-tone calibrator to set record level for overload-free taping."

Our contributor Przemek adds: "In my collection I have, among others, three Sony ST-A6B tuners with 7 gangs and one Sony ST-A7B with 5 gangs. The front end of the ST-A6B is a really precise and solid instrument. The only weak point, especially in locations where the local stations are very strong, is the lack of an AGC line to the RF stage MOSFET. I have redesigned the front end of one of my ST-6ABs to add an AGC signal to one gate of the RF and a PIN diode to the input coil. I also replaced the old RF MOSFET with a new low-noise one. After these changes, the front end seems to be more flexible to different levels of signals." Our contributor Eli says, "The ST-A6B is an exceptionally elegant design, visually and ergonomically, even compared to the other Sonys of the same vintage. And it's really a great performer in terms of picking up a difficult signal." Our contributor Michael adds, "I just have to say, this is the best FM tuner I've ever owned. The sound quality is just phenomenal. It's ridiculously quiet. I now realize what a hollow sounding piece of equipment my Yamaha T-80 is." The U.S. version of the ST-A6B has switchable de-emphasis of 25/75 µS, while the UK/AEP model is switchable between 50 and 74 µS. There's a nice page with photos and information on the ST-A6B at The Vintage Knob. ST-A6Bs in decent condition usually sell for $220-320 on eBay with a recent low of $190 in 5/15, recent highs around $375-400, and a stunning all-time high of $510 in 10/07.

Sony ST-A7B (1978, $900, photo1, photo2, with ST-A6B) search eBay
The ST-A7B is a very rare FM-only tuner with 5 gangs and 3 filters that, surprisingly, does not seem to be as fine a performer as the (originally) much less costly 7-gang ST-A6B. Apparently, the ST-A7B's very high list price was primarily due to unusual circuitry or features. Our contributor Eli reports, "Although it had only 5 gangs versus the lower model's 7, it sold for $900 versus ~$300 for the ST-A6B, so it must have had something going on. Some of that money went into crystal lock and digital display, but some of it went into shielding and what looks like overall more robust construction. I guess this was SONY's last top-of-the-line analog. There's a switch for Dolby FM, but there is no built-in circuitry, it's just a switch for an external signal loop." ST-A7Bs seen on eBay in the past few years have sold for $521 in 2/11 and $880 in 1/16, and one deep-pocketed lunatic paid $1,650 for a sealed "new" ST-A7B on Audiogon in 11/08. There is also an even rarer ST-A7 (front, back), which we assume (without foundation) is mostly identical to the ST-A7B. There's a superb page with lots of photos and information on the ST-A7B at The Vintage Knob, where a gentleman named Mirko states: "In my opinion the ST-A6B can't equal the ST-A7 in sound quality. Take a look on the audio section of the ST-A7, it has the size of the ST-A6B's complete main board, and that for a good reason! The ST-A6B's audio section is implemented as a low cost solution with a cheap MPX chip and cheap LC-Filters. That FET-in-the-feedback-path trick, which was also used in the ST-5950SD, has an incredible influence on MPX performance/sound of the ST-A7. My ST-A7 has a measured stereo separation of 56dB at 1kHz - this is not far away from being world record and it sounds like that!"

Sony STC-7000 (1974, $590, front, back) search eBay The scarce STC-7000 appears to have been the tuner/preamp equivalent of the fine ST-5130 tuner, with both having 5 gangs, but the STC-7000 has only 2 ceramic filters versus 8(!) for the ST-5130. It usually sells for $135-200 on eBay, with an all-time high of $430 in 10/07.

Sony ST-J55 (1978, $310) search eBay
The digitally tuned ST-J55 is the baby of the line that also includes the ST-J60 and ST-J75. Our contributor Dan says: "The ST-J55 has 4 gangs [actually the varactor equivalent - Editor] and 4 filters, with 3 IF amp sections. It has surprisingly decent sensitivity, but the selectivity isn't as good as it should be - probably needs some narrower filters. It tunes in .05 MHz increments, has manual tune, autoscan and 8 presets. The AM section seems only fair. The sound quality is pretty decent as well. I ran it for about two days, then decided to put in the OPA2604 op-amp in place of the 4558. Sound quality improved, especially the midrange (it already had pretty decent bass), and the treble opened up. Separation was good but seemed more 'focused' with the 2604. This is a very easy tuner to mod since the entire circuit is on one board and the bottom removes for easy access. Lots of caps in this tuner and the 3 IF amps probably make it a very good candidate for Black Gates and Bill Ammons' filter add-on. Definitely a 'sleeper' model."

Our contributor Don, who found his ST-J55 exceptionally quiet, speculates that this is "because it has 4 ceramic filters and a post-detection filter. In comparison with a tuner with 2 filters in Wide IF mode, you might expect some subtle effects on sonics." Don notes that the J55 "has the dreaded 4558 op-amp driving the outputs. Sonic upgrades should include a better op-amp. The J55 also has stereo/muting on the same button, which was my major gripe with it. I finally figured out a mod that disables muting in stereo mode completely (adjusting the muting level pot didn't quite do it), without any adverse affects with auto tuning. This should also be adaptable to the ST-J75." Like the ST-J60's, the ST-J55's ceramic filters have a wide 280 kHz bandwidth. The ST-J55 usually sells for $20-40 on eBay.

Sony ST-J60 (1978, $400, ad, owner's manual) search eBay
If the ST-J55 is a sleeper, so is the digitally tuned FM-only ST-J60, which has the varactor equivalent of 4 gangs and decent manufacturer's specs. It tunes in .2 MHz increments with either manual or automatic tuning and has 8 presets that can be denoted with slide-in frequency cards. Our panelist Eric notes that, like the ST-J55, the ST-J60 urgently needs an Ammons intervention or at least a simple filter mod, since its 4 stock ceramic filters all have a wide 280 kHz bandwidth and adjacent channel selectivity is poor. The ST-J60's features include a record calibration tone, and an LED meter that switches with the push of a button from displaying signal strength to multipath. It tunes as low as 87.5 mHz, enabling one to listen to audio from Channel 6 (or, in New York City, a commercial radio station that uses the Channel 6 frequency). On the negative side, the ST-J60 uses a common pushbutton for stereo/mono and muting on/off, meaning that one cannot choose to listen to a weak station in slightly noisy stereo. Our contributor David Rich notes that the ST-J60 has a single-tuned filter at the antenna and is double-tuned after the RF amp.

Our panelist JohnC has been modding: "I've finished up an ST-J60 after the pleasant results I got from the J55. It's FM only, still 4 gang equivalents and 4 filters, but a different IF layout. Same FM system and MPX IC, even the same audio op-amp, yet it specs out and sounds better. I did a quick look at the schematic of the J75 and there are significant changes there: 5 gang equivalents, still 4 filters, but 250 kHz filters instead of 280s. Different FM, MPX and audio op-amps. Interesting thing is that in the J55 and 75 the +/- 30V rails and display/control circuits are on the tuner board, in the J60 the entire 30V supply along with all display and control circuits are isolated on their own dedicated separate board." The ST-J60 usually sells for just $20-50 on eBay, with a high of $101 in 12/11.

Sony ST-J75 (1981, $450, photo, service manual, Audio review) search eBay
The FM-only ST-J75 was the top of the overlooked line that includes the ST-J55 and ST-J60. Our contributor Brian Beezley reports, "I've had my ST-J75 since the early 1980s. I got it because it was the first tuner I had seen whose S/N approached 90 dB in stereo. It's always sounded great to me. Now that I have more tuners, I can report that it sounds exactly the same to me as all the others. The ST-J75 uses four 250-kHz GDT ceramic filters, which give it great alternate-channel selectivity, and it uses discrete bipolar differential isolation amps between the individual filters. I believe it uses a ratio detector. Distortion is well under 0.1%, but I forget how low it actually goes. There is one critical adjustment that keeps the tuner from muting on deep bass notes, which mine began to do this after I had owned it for a number of years. See the Sony ST-S555ES writeup below for what to tweak to fix this very annoying problem." Our contributor David Rich notes that the ST-J75 has a double-tuned filter at the antenna and is double-tuned after the RF amp.

Our contributors Tim and Ann add, "The ST-J75 is very quiet with good sensitivity and very good sound. What we like most about its sound is that it has great dynamic range and the background is extremely quiet during pauses in the music. IOHO, the ST-J75 is the ultimate 'sparrow feed' tuner: It's as good as anything out there and will more than hold its own with the the top vintage tuners from the big boys (Accuphase/Kenwood/Marantz/McIntosh/Sansui/etc.) and it was, we think, a truly undiscovered gem because it looked so overwhelmingly unimpressive and was at the far negative end of the 'eye candy' spectrum. We bought our first one for either $12 or $18, and when we hooked it up, we were stunned at just how good it was. Then we quickly acquired four additional ones (they were cheap and we wanted spares if we needed parts for one)."

Our contributor Glenn says his recapped and aligned ST-J75, with a new power cord and the 75-300 Ohm balun removed, "is, without a doubt, the best-sounding tuner I've owned to date. And Warren Bendler, the tech who did the recap and alignment in exchange for one of my spare ST-J75s, agrees with my assessment. He also finds the overall performance and sound of his aligned ST-J75 to be about as good as it gets. I just couldn't be happier with mine (unless, of course, it somehow developed the ability to be used with a remote ;-) ). Of all the tuners that have gone through this place, I believe the ST-J75 simply has the quietest background of them all. Like the Yamaha TX-950, a real 'sleeper' for the money." Glenn adds, "As I listen to my stock Yamaha TX-1000 and McIntosh MR 75 and then the ST-J75 I am struck, as always, at how 'black' the background is. Also, it ties with the TX-1000 in its ability to pull in a weak signal and sort it. Not sure how Sony accomplished all this, but they certainly got it right."

Here's our panelist Ray's very tasty recipe for mods to the ST-J75:

Audio section:
C224 and 225 - 10 μF, 16v to 33 μF, 50v Panasonic FC w/0.1 μF polypropylene bypass.
C230 and 231 - 4.7 μF, 16v to 47 μF, 6.3v Black Gate NX non-polar.
C226 and 229 - 100 μF, 16v to 330 μF, 16v Panasonic FM.
I.C. 201 and 204 - NJM4560 to OPA2134.

Detector circuit:
C217 - 3.3 μF, 25v to 33 μF, 50v Panasonic FC w/0.1 μF polypropylene bypass.
C206 - 22 μF, 16v to 50v Panasonic FC w/0.1 μF polypropylene bypass.
C201 and 202 - 100 μF, 16v to 680 μF, 16v Panasonic FM.

Power supply:
C601 - 2200 μF, 35v to 3300 μF, 35v Nichicon UHE.
C605 - 470 μF, 16v to 820 μF, 25v Panasonic FM.
C615 - 100 μF, 25v to 820 μF, 25v Panasonic FM.

Ray adds: "Also of note the signal out of the detector is non-inverted from that received and the audio out is inverted. The HA11223W MPX IC does the inverting. The stock passive de-emphasis response is very good at +0.13 dB, -0.33 dB from 20 Hz to 15 kHz and is only down 2.74 dB at 10 Hz. Time constant was 73.5 μS. After audio mods it was the same except down 0 dB at 20 Hz and 0.23 dB at 10 Hz. I think that's the flattest I have ever measured."

See our writeup of the Denon TU-660 to read how Ray and our panelist JohnC compared the ST-J75 to their respective Denons and modded Hitachi FT-5500MKIIs. JohnC's quick comparison of the ST-J75's quieting to that of the awesome Sansui TU-X1 appears in the writeup for the latter, and he has some more J75 tidbits in his comments on the ST-J60 above. The ST-J75 can sell for $40-115 on eBay, with an all-time high of $173 in 3/14.

Sony ST-J88B (1978, $900, photo, service manual) search eBay
The ST-J88B is a solidly built (15 pounds) and very attractive rack-mount style FM-only digital tuner with 7 presets, wide/narrow IF bandwidth settings and defeatable muting. It has the digital equivalent of 6 gangs (varicap diodes) and 7 ceramic filters, is fairly sensitive and sounds pretty good, especially compared to other digital tuners. Sony claims a phenomenal 120 dB alternate channel selectivity in the narrow IF bandwidth mode, and an unmodified ST-J88B is indeed more selective than most stock digital tuners because 3 of the stock filters have a fairly narrow 180 kHz bandwidth. The ST-J88B might be a DX tuner to be reckoned with, on the level of an Onkyo or Yamaha, if those 180s were replaced with 150s (or even one 110 kHz filter) to eliminate adjacent channel splatter. One would have to partially disassemble the tuner to replace the existing filters, however, because the underside of the circuit board is not easily accessible. Like the Technics ST-9030 from the same era, the ST-J88B is one of the few tuners to provide a separate detector for both the wide and narrow bandwidths. Our contributor David Rich notes that the ST-J88B is single-tuned at the antenna and quad-tuned at the RF output. Our contributor Ryan tells us that the ST-J88B "uses the good (for a vintage piece, anyway) HA11223W multiplex chip. It has 6 gangs, one for the antenna, two for the RF amp, two for the mixer, and one for the LO." See how one ST-J88B sounded compared to other top tuners on our Shootouts page. The ST-J88B is rarely seen on eBay and usually sells for $150-250, with a low of $110 in 9/11 and an all-time high of $461 in 12/06. Here's a photo of what may be a Japan-only variation, the ST-J88, courtesy of k-nisi's site. [EF]

Sony ST-S7 search eBay
Our contributor Tim believes that this extremely rare tuner, which has wide and narrow IF bandwidth settings, was manufactured in the early 1990s. According to our contributor Joseph, the ST-S7 was part of a set of components called "Scenario 7" that Sony introduced circa 1991. Joseph reports, "Given the ST-S7's heavyweight styling, I was aghast at how light and flimsy-feeling it is. Opening it up shows a lot of empty volume but a neat and clean arrangement. The front end has a shiny shielding box but the power transformer is mounted on the sole circuit board. It has three ceramic filters. Since it has wide and narrow bandwidth modes, I assume two are for wide and the third is for narrow. It is an attractive piece with reasonable construction quality, good selectivity, good sensitivity, and very good ergonomics." Two ST-S7s sold for $51 and $232 on eBay in 5/07, and one went for $11 in 2/11.

Sony ST-S333ESXII search eBay
Rarely seen in the U.S., the ST-S333ESXII was the European version of the ST-S730ES. Our contributors Tim and Ann report: "We have an ST-S333ESXII and an ST-S730ES and they are virtually identical on the outside, and the user manual that came with the ST-S333ESXII is an international one labeled as the manual for the 'ST-S333ESXII/ST-S730ES.' What's even more interesting is that the performance specs in this manual for this dual-labeled tuner are slightly better than the specs for our American market ST-S730ES. In our system, the ST-S333ESXII is actually a better tuner than our ST-S730ES - the ST-S333ESXII is a really close second to the Macs in sound quality, and just as good as the McIntosh MX 117 and Hitachi FT-5500MKII for DXing. This leaves us wondering if Sony somehow cheapened the ST-S730ES for the U.S. market. We've not done an A/B of the ST-S333ESXII vs. one of our ST-J75s. Sony also made an ST-S333ESG [mostly $75-150 on eBay - Editor] and an ST-S333ESGII in their ES series line of tuners (we have seen several of each on eBay), but they have a different external design than the ST-S333ESXII and the ST-S730ES and poorer performance specs." The ST-S333ESXII usually sells for $125-210 on eBay.

Sony ST-S444ES (1984, $340) search eBay
A cautionary note to eBay buyers: the ST-S444ES's back panel has a proprietary "Audio Current Transfer" output jack rather than RCA output jacks. If the required cable is not included in the auction, you'll need to either have the tuner modded or use it as a doorstop. The ST-S444ES usually sells for $20-60 on eBay.

Sony ST-S444ESII (1987, $250) search eBay
The low-end ST-S444ESII usually sells for $25-40 on eBay, with a low of $10 in 8/09.

Sony ST-S444ESX search eBay
The ST-S444ESX shares a service manual with its mostly-identical European sibling, the ST-S700ES. Our contributor Brian Beezley offers this review: "The ST-S444ESX is part of Sony's high-end ES audio component line. It is a good-looking, black AM/FM digital tuner in an all-metal enclosure. It has wide/narrow IF selectivity and a number of bells and whistles. Unlike some earlier ES tuners, it uses ordinary RCA output jacks. The front panel proclaims 'Extremely High Standard' and the user's manual offers these remarkable specs: 1 kHz THD of 0.005% in mono and 0.0095% in stereo for the wide IF mode, and 0.04% and 0.07% for narrow. The same figures are specified for IM distortion. The signal-to-noise spec is 96 dB in mono and 91 dB in stereo. The other specs are less remarkable but excellent. The circuit features a single RF stage with three tracking resonant circuits before the mixer, which uses a single 3SK74 dual-gate MOSFET in a Micro-X package. I was surprised to find no evidence of RF intermod in my high-RF location with the unbalanced mixer circuit. The IF has two 250 kHz MX GDT filters in wide, plus two 180 kHz filters in narrow. The IF uses 'Wave Optimizer' technology, which compensates for IF group-delay distortion. It consists of two adjustable transformers and a trimpot, with separate circuits for mono and stereo. The detector is a phase-locked loop, which offers the highest S/N ratio of any detector, although not the inherent linearity of a pulse counter. The PLL has a distortion adjustment.

"The stereo decoder uses a 28-pin Sony CXA1064 chip that has a pilot canceller and individual left- and right-channel separation adjustments, and requires no 19 kHz adjustment. Memory is maintained by a 0.039 Farad capacitor. The tuner has another trick circuit called 'Super Sound Tracing' that modulates the front-end varactor tuning voltage to minimize distortion. This circuit automatically engages and lights a panel indicator whenever the input signal is greater than 35 dBf in the wide IF mode. It has one adjustment. The frequency synthesizer uses a Sony CX-7925B chip, which requires no prescaler. Sony calls this a 'Direct Comparator' and used it in many of its digital tuners. Unstuffed on the PCB, which is marked ST-S333ESX [a tuner sold in Japan - Editor], are components for long-wave reception. I'm not into fancy capacitors, but for those who are, there are 10 Nichicon Muse capacitors scattered throughout the detector, audio, and power supply circuits. I'm also not particular about op-amps, but the one used in the audio-output stage is a JRC 4560. The tuner has an unusually large power transformer. The power supply regulators use PCB-mounted heatsinks, one rather large. Line voltage can be 120V, 220V, or 240V.

"I like high-end Sony tuners and I liked this one, even though I could not get it to meet its extraordinary specs. The problem was that distortion varied with signal level. Tweaking the IF compensation circuits, I could reduce distortion to very low levels, only to see it rise if I changed the input level. THD varied between 0.3% and 1% at low signal levels in wide IF mode, but at more usual levels it was typically < 0.1%. THD was 0.45% in narrow with a pair of 110 kHz filters replacing the original 180s. The tuner had audible background noise when receiving HD Radio signals with the wide IF filter. Installing a postdetection filter quieted it. With the modifications, I measured mono sensitivity as 20.5 dBf in wide and 21.4 dBf in narrow, and stereo sensitivity as 39 dBf in wide and 39.9 dBf in narrow. These numbers are typical of what I measure for high-quality tuners, although worse than spec and a few dB behind the most sensitive tuners I've come across. The 110s yielded adjacent channel selectivity of 43.5 dB, which is an excellent figure and really useful for digging out weak stations next to strong. The ST-S444ESX normally tunes in 50 kHz steps. This is too large to avoid adjacent-channel interference by tuning off-channel, and it requires four button pushes to reach the next channel, making manual station scanning a real chore. You can convert to 100 kHz tuning steps as follows. In the lower left-hand corner of the PCB, look for a cluster of diodes. Clip one lead of the diode marked "50/100." The microprocessor reads this diode on power-up, but only when the 9/10 kHz AM-spacing switch on the bottom of the chassis has changed. Change the switch, turn on the power, turn it back off, restore the switch, and you're done." The ST-S444ESX usually sells for $35-80 on eBay.

Sony ST-S500ES (1987, $300) search eBay
The ST-S500ES usually sells for $35-70 on eBay.

Sony ST-S550ES (1991, $400) search eBay
Our panelist Ray offers this review: "The ST-S550ES is actually a pretty basic tuner but with a few extra features. It accepts only a 75-Ohm FM antenna lead which goes to a relay actuated straight through or "T" resistor attenuator to the front end "can." Within the can is an antenna coil/varactor tank feeding a dual-gate FET. This is followed by two more tanks and a mixer transistor. So, counting the oscillator, it has 4 varactor gangs in a very low parts count front end. The rated sensitivity is high at 10.3 dBf so that little front end is probably easily overloaded, and thus the need for the front panel switch operated attenuator. The IF strip is a bit unusual with 3 250 kHz ceramic filters separated by two gain stages in Wide mode, with Narrow mode adding another 230 kHz ceramic filter and a gain stage after that. The ST-S550ES claims very good alternate channel separation of 80 dB in Wide and 90 dB in Narrow. Sony chose an LA3401 MPX chip and uses it just as the data sheet advises, with feedback de-emphasis at its outputs feeding low-pass filters and a 4558 output buffer. I measured the time constant to be 73.2 µS and resultant audio response to be within - 0.20 dB to + 0.45 dB from 40 Hz to 15 kHz. It was down only -0.70 dB at 20 Hz. The service manual lists variations for U.S. and Canadian, U.K. and A.E.P. models. Mine is the U.S. version.

"Other specs: Sensitivity for 46 dB S/N, 16.8 dBf mono and 38.5 dBf stereo; THD: wide = .04% mono and .05% stereo, narrow = .06% mono and .08% stereo; 1 kHz separation = 65 dB. That's 10 dB better than the LA3401 data sheet claims as max. The front panel claims a 'radial power supply' feature. It would appear this means placement of the power supply physically in the center of the active circuit blocks, with power feed thus splayed radially to each. Upside is short leads, downside is P.S. 'dirties' right next to the sensitive front end. Overall, the ST-S550ES makes me think of Jim's Texas: Big, big box and within?... wide open spaces. Overall I find it about par with most of my vintage sparrow feed digital tuners and that ain't bad. It sounds good, stock, and that 'flywheel-feel' tuning knob makes for retro fun. IMHO, though, at $400.00 in 1991 it was a bit overpriced. I snagged mine for $60.00 B.I.N. and that's OK." We assume that our contributor Al's comment on IBOC self-noise in the ST-S555ES writeup apply as well to the ST-S550ES. Note that the ST-S550ES has standard RCA output jacks rather than the proprietary output jack used by some other Sony ES tuners. The ST-S550ES usually sells for $50-90 on eBay, with a low of just $7 in 1/12 and a recent high of $200 in 11/12 as two crazed bidders ran it up from $44.

Sony ST-S555ES (1985, $450, audio stage schematic) search eBay
The FM-only ST-S555ES is a PLL quartz-locked digital synthesizer tuner with dual-gate MOSFETs in the RF amplifier, 5 varactors in the front end (equivalent to 5 gangs), and 4 ceramic filters. It tunes in .05 MHz steps, has Wide and Narrow IF bandwidth settings, and has two 75-Ohm antenna inputs with a selectable attenuator of 20 dB on antenna B. Our contributor Paul Baptista reports that the main chips are LA1235, uPC1223C, TL071CP and TL072CP. The ST-S555ES uses a proprietary output jack called "ACT" (Audio Current Transfer) which is intended to avoid having the signal source current and the power supply current flow through the same ground. This is not compatible with normal RCA jacks that use voltage transfer. The 555ES uses high-grade audio caps (Elna and Nichicon) and 1% metal film resistors in the output section. Paul found it very easy to modify, including replacing the output op-amps and changing to normal voltage transfer via a series resistor. The case is easy to open and both sides of the PCB are accessible. Paul's modded ST-S555ES is now his main tuner: "It has an added EMI/FRI module AC input, oversized power cord, about 45 caps replaced (Panasonic FC, Elna ROA Cerafine, Black Gates), matched filters, op-amps changed to OPA134 and OPA2604, IF Filter Adder Board in Narrow IF mode with two extra filters, and finally an alignment by Bill Ammons. Definitely bass-shy... so much so that I suspect that I have a series capacitor somewhere of too small a value creating a 'high-pass filter' effect. Everything else is sweet, widest soundstage, lowest noise floor, and the highs extend the most" out of all his tuners.

Our contributor Brian Beezley adds: "I like mine, especially after I replaced the filters with narrower ones. The stock tuner has excellent alternate channel rejection but not much for the adjacent channel. The dual antenna input is particularly handy. My 555ES isn't especially sensitive (about 20 dBf for 50 dB quieting), but sounds clean, works well in the face of a 15 kW station 2.3 miles away that makes some other tuners stumble, and is easy to modify. The audio output is nonstandard - the tuner emits audio current instead of voltage on a special connector. You'll need the Sony adapter cable to RCA plugs. Alternatively, you can solder a 620-Ohm resistor across each output and then install RCA cables or jacks. Beware of one critical adjustment: Variable inductor IFT101 tunes the off-channel detector that is used with the automatic scan. If misadjusted, even by a small amount, strong low-frequency signals will momentarily mute the audio. Both my 555ES and its cousin, the ST-J75, exhibited this problem during deep bass notes, record or hall rumble, and microphone air blasts. It's very annoying. The adjustment is extremely touchy, perhaps why these tuners don't seem to leave the factory with it set quite right."

Our contributor Don offers these detailed instructions on modding the audio output: "The ST-S555ES does not have normal RCA jacks for audio output. It has a 4-pin circular connector that outputs what Sony calls 'Audio Current Transfer' (ACT), which is a current source output. The Sony adapter cable converts this into normal line-level RCA jacks for input to a preamp or receiver. In many cases, a unit purchased on eBay will be missing the adapter cable, in which case there are a couple of options for wiring audio out:

1) The only option that would not involve modifications to the tuner itself is to build your own adapter cable. Find the mating connector to the ACT output (it may be a mini DIN, but I'm not sure) and wire up a cable as shown in the schematic. A 620 Ohm 1/2 watt resistor is wired from pin 1 (left) and pin 2 (right) to ground (pins 3,4). Then a 10 F or larger electrolytic cap (I would recommend a bipolar cap) is in series with the left and right output to the RCA jack. The cap is optional if the input to your preamp/amp/receiver is AC coupled (most are).

2) Assuming you can't find a mate to the ACT connector, another variation of the above is to put the 620 Ohm resistors inside the tuner, one in parallel with R219 and one in parallel with R269. Then for the left channel, connect one end of a 10 F (even better, 33 to 100 F) bipolar cap to the junction of R218 and R219. The other end of the cap should be wired to an RCA jack for the left audio out. For the right channel, one end of the cap connects to the junction of R268 and R269 and the other end is right audio out. You can drill holes to install RCA jacks, or remove the ACT output jack and run wires out and just let the jacks dangle.

3) The current output stage can be bypassed completely. In this case, wire a 600 Ohm resistor (value not critical) to IC203 pin 1. Wire a 33 to 100 F bipolar cap to the other end of this resistor. The other end of the cap goes to an RCA jack as left audio out. For clarity, the 600 Ohm resistor and cap are in series. Similarly, wire the right audio out from IC203 pin 7 using a resistor and cap in series to the RCA jack. Again, the caps in most cases will not be necessary if driving an AC coupled input. In that case there is only the resistor connecting from the op-amp output to the RCA jack.

The downside of taking the audio out from this location is that you lose the muting relay. The tuner will emit a noisy burst when powered up, but otherwise I have not noticed any objectionable noises when tuning because the tuner is obviously muting in another place also. Also be aware that if the current output stage (IC204) is not loaded, it will bang the rails and possibly cause noise. To avoid this, the ends of R216 and R266 that connect to IC203 can be lifted and connected to ground."

We don't vouch for this person, but other possible mods for the ST-S555ES are described here. Our contributor Al adds, "Sony premium tuners since the ST-555ES seem to be immune from IBOC self-noise, that is the noise generated in the analog portion of a station's signal by the same station's digital HD signal. In LA I listen to classical music on KUSC and my fine vintage tuners often have a relatively high level of background noise that I assume comes from the HD signal being broadcast on separate carriers within the station's passband. When this happens, my Sony ST-555ES, 730ES, 707ES and SA50ES are about 20 dB quieter than my other, older high-end tuners." The Vintage Knob has a nice page on the ST-S555ES with photos and specs. The ST-S555ES usually sells for $40-80 on eBay when an output adapter cable is included or when the seller has failed to disclose that the outputs are not standard RCA jacks. When the seller does disclose this and does not have the adapter, $10-30 is the more common range.

Sony ST-S700ES(1987, $400, search eBay
The ST-S700ES is the mostly identical European sibling of the ST-S444ESX, with which it shares a service manual. See the ST-S444ESX listing for a detailed writeup. Although the ST-S700ES has a wide-narrow bandwidth button, it has mono/stereo and muting on one button, making it impossible for one to choose to listen to a weak station in noisy stereo. The ST-S700ES usually sells for $40-100 on eBay. The record low and high were $15 in 1/08 and $202 in 5/07.

Sony ST-S707ES (1995, $600) search eBay
The ST-S707ES has wide and narrow IF bandwidth settings for both FM and AM, 40 presets and dual antenna inputs. See our contributor Al's comment on IBOC self-noise in the ST-S555ES writeup, and his comparison of the ST-S707ES, ST-S730ES and ST-SA5ES in the ST-SA5ES writeup. We hope to add more information on the ST-S707ES eventually. It usually sells for $120-230 on eBay, but as little as $70-80 and up to $350 or so are both possible. The all-time high was $420 in 8/06.

Sony ST-S730ES (1988, $550, photo) search eBay
The ST-S730ES's front panel consists of a Program Switch (off, set, lock, check), CAL TONE, MPX FILTER, TUNE MODE, IF BAND MUTING, FM MODE (stereo, high blend, mono), FM/AM, MEMORY (20 presets), PRESET/TUNING and an analog-style tuning knob. Our contributor Ryan tells us, "The ST-S730ES features a unique front end system that is very immune to any sort of overload. The front end specifications are among the best for any tuner that I have seen. Sensitivity, however, is sacrificed for this ability, and potential DXers should bear that in mind. For urban audiophiles, however, this should prove beneficial. The detector is a very good PLL, and the multiplex is Sony's in-house version of the LA3450 also used in many top modern tuners. The ergonomics on this tuner are among the best of any modern digital, and feature very smooth rotary flywheel tuning and full user control over all major features, including separate buttons for muting and mono. Like most top modern tuners, it uses GDT ceramic filters in the IF tuned with 10.7 MHz transformers and amplitude adjustment pots. Proper matching of the wide filters is critical for best performance, and any audiophile should have his 730ES checked for 6 kHz THD. The filters in my unit are way off and need to be replaced, but this is possible with any tuner, so I don't blame the 730ES for it. As is, I measured 1 kHz THD that did meet the Sony spec. Only at the high end were the filter problems more evident. Overall, this tuner is very user-friendly, and seems to be solidly built and well-designed. My only quibble is the lack of a double balanced mixer, which could have jacked up (IMHO) the RF intermod rejection even higher while retaining acceptable sensitivity."

Our contributor Gary responds, "Given the raves for Sony tuners and Ryan's trumpeting of the wonders of the ST-S730ES, I picked up one of these on eBay. It just arrived today, so consider this a very preliminary view. In terms of ergonomics, this is a great tuner. It's digital, but it has an analog tuning knob and all sort of controls to optimize listening such as wide/narrow filters, multipath filter, stereo blend, etc., and all these settings can be programmed separately for each preset. The sound quality also appears to be quite good right out of the box. The one area where the 730ES falls short compared to the Pioneer F-9 and TX-9500II is its ability to pick out a weak signal adjacent to a strong local. Where the Pioneers allow me to listen to these signals in stereo, the Sony forces me to switch to mono, and even in mono there is some noise coming through from the adjacent channel. It's not terrible, but not up to the standard set by the Pioneers." Our contributor Andrew adds, "I went through four 730ESes before finding a good one. There can be audible differences between 730ES tuners in terms of noise, distortion, selectivity, etc. The good 730ES is a great tuner that sounds as good as a TU-919, CT-7000 or L-07T, and has a smooth sound, close to a Marantz 10B for much less money. Really quiet. Poor ones, however, are common. For me, the best way to select one is by direct comparison in my system, switching between tuners while listening to stations I like. In my experience, price generally does not reflect the tuner's functional quality as much as the cosmetics."

Our contributors Tim and Ann report that the ST-S730ES held its own in a shootout with the Mac MR 74 and MR 78 and Sansui TU-919, among others. Our panelist Jim may have had a bad one, because he tried to enter it in a Shootout and found that it "did not impress me at all." But our contributor PZ says, "I had two good ones. I checked them against each other before I sold one. The only difference I found was in the calibration of the S-meter. One reads a step higher than the other, but the reception was the same, and so was the audio quality. According the the owner's manual, the tuner's 'SST' circuit stands for 'super sound tracing.' It operates when the tuner is in wide mode and receives a strong enough station, and its effect is much lower distortion. The word 'tracing' reminds me of the 'ARTS' (Active Real-time Tracing System) in the Pioneer F-91. These tuners are from the same period and tend to use the same buzz words." See the ST-SA5Es writeup for our contributor Al's comparison of the ST-S730ES, ST-S707Es and ST-SA5ES.

The late Sumo Charlie designer James Bongiorno chimed in: "The main problem with the 730ES tuner is absolutely terrible drift. I did a private review of this tuner for Sony before they released it and told them about it. I suspect that they didn't heed my advice. The problem was that they totally ignored one of the foundational necessities of FM design and that is temperature compensation for all the tuned circuits. This is an absolute no-no and you would think that they would have learned. If they would have fixed this main problem, I think that this could have been an outstanding tuner because the distortion and noise were the lowest that I have ever seen, that is in the short time frame for measurement before it drifted off kilter." And a technical note from our panelist Bob: "One other thing on the 730ES: the front panel MPX switch. So what is this doing? There is already a 'hi-blend' function selected from the FM Mode key. After I received the schematic, it made sense finally. There are two relays AFTER the MPX decoder that switches in a L and R channel 15 kHz filter implemented with an op-amp buffer circuit. With the 'MPX Filter' out, you are running wide open without the sharp cutoff 15 kHz filter, or op-amp buffer in the circuit. On some weak stations I could hear a small reduction in noise with the MPX filter in, but on strong stations it sounded better 'out' to me." Bob compared the ST-S730ES to a Yamaha TX-1000 and says, "They are both pretty good stock. I tend to like the TX-1000 better as it has more capability for difficult station reception, which I need."

Here's our contributor Brian Beezley's review: "The ST-S730ES surprised me with a circuit nearly identical to that in the ST-S444ESX. I found a few minor differences (3SK122 mixer instead of 3SK74, no output op-amps) but the architecture is the same. Unlike my 444, distortion didn't increase at lower signal levels. In wide-IF mode all distortion products were well below -70 dB (0.03% THD). I saw no hint of drift in anything I measured during hours of testing. There are five thermistors in the IF strip and detector. Maybe Sony took Bongiorno's drift complaint seriously, although the thermistors won't affect the tuned circuits he mentioned. Unlike the 444, the 730 does not have audiophile capacitors scattered throughout. The only one I found was a large Nichicon cap in the power supply amusingly marked 'Great Supply.' The AC cord is thick and polarized; I found both inconvenient.

50 dB quieting sensitivity was around 20 dBf in mono and 42 dBf in wide. The two wide IF filters were low-group-delay 220 kHz MX2s and the narrows were 230s. I replaced the narrows with 150s. Separation was 58 dB in wide and 35 dB in narrow. The detector changes the PLL loop-filter time constant in narrow, a nice touch. HD Radio self-noise was about 10 dB weaker than usual in wide, probably due to the 220s and the PLL loop filter. [See our contributor Al's comment on IBOC self-noise in the ST-S555ES writeup. - Editor] The IF circuit has a test point you can short to bypass the IF strip and measure the PLL detector and stereo-decoder circuits by themselves. I found this useful for all kinds of circuit exploration. The SST circuit, which modulates the front-end varactor tuning voltage with audio, can be set to one of four activity levels. I found no benefit until I realigned the front end one more time. Then one SST level reduced distortion slightly. 100 dBf signals at 98.9 and 99.3 yielded an IMD spur down 40 dB at 98.5 MHz. I thought this was pretty good for a tuner without a balanced mixer. I had no IMD problems on the air in my high-RF location.

"The multiplex filter drops the output level 1.5 dB at 1 kHz. This filter should be needed only when tape recording since the pilot is cancelled and the stuff around 38 kHz is already 25 dB down. The high-blend function provided 2.5 dB of noise reduction with 18 dB of stereo separation. This type of high-frequency blending smears instrument locations when their harmonics collapse to the center while the fundamentals pretty much stay put. In addition, low-frequency noise remains quite audible. I changed the blend to a flat one that provides 6 dB of noise reduction with 9.5 dB of separation. This amount of separation still yields a surprisingly good stereo image, with the instruments positioned closer to center but not in any way smeared. The noise reduction is quite noticeable and useful.

When listening on the air, it sounded as if pressing the mono button didn't quite make the output entirely monophonic. I thought I could still hear some out-of-phase stereo noise on weak signals. Sure enough, there was a 2.2 dB difference in channel levels in forced mono when fed a pure L or R stereo signal, and the distortion was higher. In mono a JFET shorts the L and R outputs, but its channel resistance is too high to do the job properly. Adding a diode and resistor to force the CXA1064 stereo decoder into mono fixed the problem. The tuner has a selectable narrow AM IF filter, and its effect is quite audible. The owner's manual mentions that the tuner turns off the microprocessor clock one second after a command is executed. I thought this was a cute trick but I couldn't hear anything leaking into the audio with the clock on or off. I did find annoying the one-second muting period after certain button pushes. Any switching click will be much more brief." The ST-S730ES usually sells for $75-205 on eBay, with a low of $30 in 6/11 and recent highs of $335-375 for no discernible reason. [JR]

Sony ST-SA5ES (1996, $800, inside, service manual) search eBay
Our panelist JohnC compares the ST-SA5ES with the ST-SA50ES: "Both have 4-gang equivalent front ends and both have 4 ceramic filters, but the layout is different: The 50 has 3 filters in Wide and one in Narrow, while the 5 has 2 in Wide and adds 2 in Narrow. Both have an LA1235 IF IC. The MPX in the 5 is the Sony equivalent of the Sanyo LA3450 but the 50 uses an LA3401. Both have PLL detectors and the 5 adds an M5220P op-amp in the output." And our panelist Ray takes a look at the SA5's de-emphasis circuit: "De-emph is via feedback around the output of IC301 MPX. For one channel its composed of R308, R309 and C313 in parallel (220K, 100K and 1200 pF). These equate to a time constant of 82.5 S or an F3 of 1929 Hz. This should measure a few tenths of a dB soft above ~2,000 Hz. and would sound pretty good to most. I have usually found T.C. errors to be around 68 S, or a little bright (75 S is standard)."

Our contributor Al compared the ST-S730ES, ST-S707ES and ST-SA5ES: "I have examples of each. The 707 and SA5 have almost identical circuit boards. The 730 is different. The RF sections look identical among the three (4 gangs plus attenuator). The IFs are also very similar. Any differences in sound are subtle because I can't hear them. Theoretically, the SA5ES is the most advanced of these designs." The ST-SA5ES usually sells for $160-300 on eBay, with a low of $131 in 8/12 and a high of $461 in 3/12.

Sony ST-SA50ES (2000, $600) search eBay
Our panelist Ray provides this review of the remote-controlled ST-SA50ES: "This tuner showed up on eBay for $79.99 shipped so I, once again, weakened and snagged it. It has some very nice features like a dBuV signal level meter, A/B FM antenna inputs, wide/narrow IF bandwidths and lots of operational feature selections. An operations manual is needed for old users like RFM. It has the typical Sony ES looks, black and sleek. A look at the schematic does not solve the first question, i.e., gang count. The RF section is a black box! Popping the hood is of minimal help as you face a rather large sealed box that claims 6 gangs, balanced mixer. A usual hint toward gang count is the rejection ratio (I find rejection ratio dBs divided by 20 to be pretty close), but Sony left that out of the specs! My present guess is 4 RF gangs and 2 local oscillator gangs. Wide IF contains 3 250 kHz ceramic filters with Narrow adding one 150 kHz CF. Discrete transistors provide the IF gain.

"The detector is an LA1235 and an LA3401 is used for deMPX. After that is a switchable stereo noise filter, pilot notch filters and muting. That's it, no audio output buffers. The use of ICs (even the power supply regulators are in a 7-pin IC) allows for a compact circuit board and thus another 'empty box' tuner. But, stock, the ST-SA50ES is a good getter and a fine sounder. I did like this tuner but my iron is still heated and thus attacked. A few P.S. caps, change to passive de-emphasis, and an OPA2132 output buffer made this a tuner I can love. These seem very reasonably priced on the used market and ol' RFM can heartily recommend it." A contributor in our FMtuners group opined that the ST-SA50ES sounds good, perhaps due to the many ELNA caps inside. Our contributor Glenn found its sound to be "'better than average,' though not up to several older Sonys, like the ST-J75, ST-S730ES and ST-5000FW."

See the ST-SA5ES writeup for our panelist JohnC's comparison of its guts to the ST-SA50ES's. In addition to the features outlined by Ray, the ST-SA50ES has 40 presets and an antenna attenuation switch. Operation of the tuner's Active Selection Mode (ASM) is described as follows in the owner's manual: "Press ASM. The ASM indicator appears in the display. This tuner's Active Selection Mode (ASM) is factory preset to find the best antenna attenuator (ANT ATT), intermediate frequency band (IF BAND), and FM MODE settings for each frequency automatically. You can, however, choose each setting manually according to your preference. If you don't want to use the ASM function, turn it off by pressing ASM again." The ST-SA50ES can sell for anywhere from $55-200 on eBay, way down from its usual range a few years ago. [RFM]

Sony XDR-F1HD (2008, $100, photo, service manual) search eBay
Well, it's not "vintage," but this tiny (car stereo size) HD Radio tuner is a terrific performer except for audiophile use. Our panelist Bob says, "In my situation, it's about the same sensitivity and selectivity as my modded tuners, which is OK. I'm not a DXer. I can't listen to it for too long, though, on my reference system. A stock Yamaha TX-1000 just kills it for sound quality. The difference with a modern outboard decoder with quality parts is even more pronounced." The definitive review of the XDR-F1HD can be found on Brian Beezley's website, and The Audio Critic did another. DXer Tim McVey's review includes bench test results, and Australian DXer Todd Emslie compares the tuner to other modified tuners for DXing.

Our contributor Ken K. adds, "No doubt, this is one of the more sensitive and selective tuners available. AM selectivity is better than anything I remember from 40 years (off and on) of listening, including a Hammurland SuperPro, Heathkit AJ-30, Alpine car cassette, a National NC-109, and all the hi-fi tuners I've used: Yamaha T-85, TX-1000, T-1, Onkyo T-4711, and others. Having said that, it's not orders of magnitude better -- it's just better. For the first time, I've managed to pull out some obscure daytime stations that are adjacent to weaker local ones with the Sony. However, it's just as susceptible to adjacent-channel HD hash as any other radio. It may be no more sensitive on AM, or slightly more so, but the noise floor is a little lower, allowing this kind of reception. It has also made me more aware of the RFI in my system. HD for casual listening does sound better. I haven't attempted any long-term listening for various reasons. So far, besides locals, I've gotten WOR and WFAN to decode, at about 300 miles, and WBZ, at about 470 miles, when conditions are good. It's almost completely immune to overload and harmonics, and definitely more selective. I'm using a 150' outdoor antenna, and without attenuation it overloads everything but the Sony. I've seen comments elsewhere that the Sony isn't that good with the supplied loop.

"FM selectivity is on par with the Onkyo, which is very good. It will, however, still lose adjacent channels to a strong local station or to HD buzz. Early on, it seemed the Sony would lose stations entirely at the edge of reception, or they'd pop in and out. On the Onkyo, these stations will fade, but usually not drop out entirely. There was some difference in the handling of that in the two tuners. I haven't encountered drop-outs lately. I really miss a dB strength meter on the Sony. As a result, I've settled into a pattern of chasing stations with the Onkyo and then switching to the Sony. It will get just about everything the Onkyo will, which I think is pretty good. During strong (not exceptional) conditions, I've been able to decode two or three HD FM stations from Washington DC at about 110 miles away, and Virginia Beach/Norfolk area stations at about 90 miles. It won't do this regularly, though. Locals are no problem, of course. The switch to an HD signal on FM isn't nearly as dramatic as the difference in sound on AM. I couldn't hear any difference on stations I tested with headphones. That might be an individual thing. Wish list: digital out, fine tuning, adjustable bandwidth, tuning knob, dB strength meter, designer display. I like it. It's my new AM king, and a companion to the Onkyo. It's a keeper."

Our panelist Ray did a shootout: "Since many have touted the XDR-F1HD's DXing capability, that's what I checked it for last night running against a Pioneer TX-9800. Equipment was a 10-element Yagi on a rotor about 28' above ground level. Both tuners were fed from a low-gain buffer/distribution amp. The contest results? They both won. The Sony is super easy to DX with; just tune the station freq. and point the antenna. That's as good as it gets and it IS good. In each case the Pioneer could equal or better the Sony's reception but only after very careful tuning and tweaking. Without the Sony leading the way I wouldn't have found so many signals to hone in on. It's too early for me to comment on the Sony's sound but, as others have reported, it's one helluva DXer. In my 24+ tuners none has come this close to the Pioneer at signal grabbing and if you're a tad lazy like ol'RFM tends to be, the Sony XDR-F1HD is the champ... and a lot of tuner for $100 new." Ray supplemented his report with this assessment of the XDR-F1HD's sound: Even with a clear HD signal, "the cellos had no wood." At the same time, the same station's analog signal as received by his Technics ST-S505 had a full and rich sound, i.e., "the cellos had plenty of wood."

Our contributor doug s. chimes in: "I have a lot of sub-$500 tunas that sound better than the XDR-F1HD, unless you are talking about marginal signal-strength stations. Then, the Sony's superior reception moves it to the front, because of its amazing quieting with marginal signals. Its sound is a bit hard and fatiguing for serious listening, even with strong signals, and even on non-HD broadcasts. But it's fine for background listening, and its quieting ability with marginal signals makes it a great DXer. My XDR-F1HD gets one particular station I listen to, in stereo without any noise whatsoever, something that I cannot say about my better analog tunas, including Rotel RHT10, modded Sansui TU-X1, modded HK Citation 18, modded Sony ST-A6B, and since-sold modded Sansui TU-9900, to name a few." And our contributor Greg adds, "I don't find the XDR-F1HD's FM sound quality to be world-class. For example, to my ears its definition and breadth-of-life are significantly inferior to same via good, conventional solid-state tuners such as the Mitsubishi DA-F20. Your mileage may vary. Also, IMHO, the XDR-F1HD's soft-mute errs significantly too far on the side of HF rolloff for the sake of noise reduction as a function of low signal strength. Even for strong signals, the XDR-F1HD's de-emphasis errors are too great for my ears. And for weaker signals, the de-emphasis errors are a show-stopper to me. Too bad the XDR-F1HD doesn't include the option to disable soft-mute. As-is, the tuner's low-noise on weak signals is partly 'fake' SNR by my criteria because it's accomplished by severely rolling-off the upper mids and highs."

Our contributor Pete says, "My unit was a brick as far as performance. There had to be something grossly out of alignment, or perhaps the FM front end suffered some electrostatic damage, either through handling or during manufacture. To make matters worse, the Sony tuner seemed to have a very soft limiting curve. It sounds like it was poor implementation of the Philips chipset in this Sony tuner. The AM performance, however, was very good. It is actually suitable for MW DXing when used with a tuneable passive loop antenna such as the Terk AM loop. I've got 18 other communications receivers that already do a better job at that, so I couldn't justify keeping this unit around." And our contributor Ken W. adds, "The muting curve on the XDR-F1HD is from their implementation of the post-demodulation signal processing. Some people seem to like it, but for my weak signals I find it annoying. Recently I measured the noise figures of the front ends on the XDR-F1HD, Sangean HDT-1, Denon TU-1500RD, and Kenwood KT-7500. The XDR-F1HD's was 8 dB, HDT-1 was 7 dB, TU-1500RD was 4 dB, and KT-7500 was slightly less than 3 dB. You can guess which tuner is used for weak signal reception here. However, I do routinely use the Sony for listening to tough signals adjacent to any of the local stations." But our contributor Dave O. points out that Ken is "getting dramatically different measurements from what Brian [Beezley], other engineers (even in Europe), others here [in the FMtuners group], and myself are getting from our Sony tuners. I don't have many strong signals around me, and I get similar measurements to Brian's, and fabulous DX results from the Sony. I have four of them in my home BTW, and the DX performance is similar on all of them."

Our contributor Nick tells us how the XDR-F1HD fares in the UK, where stations can be heard 100 kHz away from strong locals: "It is a HOT DX machine! Is it better than the Onkyo T-4970? Yes it is - the DSP filters are razor-sharp and totally symmetrical, unlike the DYNAS asymmetrical response from the Onkyo. I've still not had the time to do a really thorough tune around, but I'm already hearing things on the Sony that were either impossible or very unlikely on the Onkyo. As for the audio quality, the sound is very clear and 'bright' and the tuner produces noise-free stereo on stations that before had some hiss. However, compared to the Onkyo the audio seems to lack 'authority' and the Onkyo just sounds more 'natural.'"

Our contributor Chuck speculates on the marketing strategy behind the XDR-F1HD's design: "The RF section of the tuner is extremely sensitive, allowing it to pull in many more stations with only a poor antenna, so you have the illusion that you have the same selection of channels on FM that you have now on satellite. Some folks called the Sony tuner's great DXing ability a fluke, but it seems to me that high sensitivity was the plan all along. It also has an overabundance of digital processing in its front end, so FM noise is lowered, but everything sounds like an MP3, just like satellite and internet radio. What common listener will be able to tell the difference? It's interesting that the analog reception is processed digitally in this tuner, possibly to match the noise level of the HD signal. This is probably important for fringe reception where the HD sidebands are not always receivable, and blending of the two is required. But, an important side effect is that even astute listeners now can't tell how 'digital' HD radio sounds, since there's no way to compare directly when listening to a strong local station. No wonder there is no way to defeat the IBOC detector or the adaptive noise reduction. I think this is the likely strategy of terrestrial broadcasters, and why industry conglomerates are so hot on HD radio. They don't care about the audio quality issues, since clearly the majority of the consumer market does not care. They simply want to provide more ways to broadcast ads, and they recognize that satellite radio and the internet are taking their listeners."

And our contributor Scott needed a more sensitive tuner than his Naim NAT 05, so he bought an XDR-F1HD from our panelist Eric. Scott reports: "The Sony is simply an outstanding tuner (all comments on analog FM only). The Naim was great until KDFC 90.3 classical moved their transmitter. The Sony pulls in the signal and plays it in full stereo amazingly. The NAT 05 is the best tuner I have ever heard, still, but one must have a good signal. With a good signal it sounds better than the Sony, no doubt. However the little Sony is so great I purchased another one as a backup!"

After Sony discontinued it, eBay sale prices for the XDR-F1HD shot up and since early 2013 seem to have stabilized in a typical range of $180-325 for unmodded units, or $450-600 or higher for upgraded ones. We've seen frequent lows around $150 and a high of $544 for an unmodded piece, but don't overpay -- this is an extremely common tuner! [BF][EDF][RFM]

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