The AIG FM Tuner Project: Sony ST-5950SD, A Rare Successor to the ST-5130

      Date posted: May 2, 2008

Read the AIG FM Tuner Project Introduction
ST-5950SD, left
This tuner quickly became one of my favourites. The Sony ST-5950SD was the successor to the ST-5130, which is one of my keepers, but that’s another story. A sibling model, the FM-only ST-A6B, is even rarer, and we have one of those coming soon in The FM Tuner Project. But let’s stay with the subject at hand, and here’s what www.fmtunerinfo has to say about the ST-5950SD:

“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 had 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. We hope to have a chance to try an ST-5950SD eventually to obtain first-hand information. In the meantime, 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.”

Though it has only one IF path, like the remarkable 5130, it also has auto variable IF, so can actually be more selective than many tuners with dual path switches. And there’s no AFC or Quartz Lock to pull it away from weaker signals to adjacent strong ones, so it’s an excellent DXer, holding distant signals well. Though the Hi-Blend is not up to that of the ST-5130 in reducing noise, the Dolby feature can be used for this in extreme situations while maintaining stereo reception. In our reception tests on a quite average late March day’s reception, it received 53 stations on both 75-ohm yagi and 300-ohm omni antennas, but the latter showed less multipath and better stereo with lower noise. With respect to multipath, the ST-5950SD has a momentary pushbutton, which when pressed shows multipath intensity on the signal strength meter. Speaking of which, this is one SS meter that doesn’t pin right all the time, and gives useful information about relative signal power, as well as quality in the multipath setting.
ST-5950SD, left
The sound quality of this tuner is excellent, with good deep bass, lucid midrange, and good top end extension. It’s not quite in the league of the Accuphase tuners, but very much in the running with such models as the Kenwood KT-8300 and similarly priced Sansui models. In sum, it’s very much in the great Sony ES tradition, and a fine tuner in all respects.

This example has a few nicks and scratches to befit its age, and the headphone knob shaft was broken off, and the knob missing when I purchased it. I bought a set of matching Sony knobs for the same series components, and used one with a plastic extender to repair this problem. Thus the knob has a slightly soft feel, but works fine for the times when you want to listen on phones. And, as with the 5130, it’s a really nice, clean headphone amp, with more volume than you’ll ever need, working well with my reference Grado SR-125 Prestige Series cans.

Interestingly enough, the week after I sold this tuner, I discovered a listing for another example of the ST-5950SD, whose author plagiarized not only much of my headline, but a lot of my written text as well, including my own test results, along with the quote from When I emailed my annoyance to the offender, he was unrepentant, stating he had only borrowed the quote from tunerinfo. His handle for eBay is pwrmtr, and maybe his text theft was evident to Sony tuner aficionados, since he received no bids at all after listing with the same starting price as I did. To paraphrase (not plagiarize without attribution) the late great Carl Perkins, “you can steal my money, you can steal my car, you can drink my liquor from an old fruit jar…but Baby, lay off of my blue suede prose!”

Andrew Marshall

Response from  ST-5950 Buyer:

Hi, Andrew.

After receiving the tuner, I replaced your plastic piece with a sawn off,
(spent), .22 long rifle case. JB Welded it on the shaft and slotted it with
a Dremel tool. Works great, no wiggle. Replaced the stereo and almost
useless Dolby lamps with red and yellow LEDS, added a second 270 ohm
resistor in series to reduce the current from 40 to 20 mA. Works great. Made
some end panels from oak, planed the oak from 3/4 inch to about 7/16 to
match the stock look, (we refuse to think metric down here). Added some nice
soft rubber feet and replaced the dial lamps, (auto parts store, 3 watt
instead of 5). The thing looks real good sitting next to my TAE-5450 amp at
work. Thank you again for the nice tuner, I’ll continue to give it a good
home. Don’t lose too much sleep over the guy from Oshkosh stealing your

AM Responds:

Hi Vic,

You are indeed a man of my own heart! But you are one with greater mechanical and carpentry talents, to be sure. I did some work on the ST-5130  that I kept (of 4 I bought), some of which can be seen in the photos. A light went on (head-wise), and I used a pair of rack handles purported to be for Kenwood  tuners (I had 8 various KTs at the time and the pair fitted none); all I had to do was hacksaw the inner plate corners to miss 2 screws, and they fitted perfectly in an almost Frank Lloyd Wright way, if you look at the contours and trim. I also used uncoloured lights for the meters, so I can see them from more than a foot away (not a problem on your tuner).

And, of course, there was the mod I did on all 4 5130 s, shielding the tuning capacitor with metal duct tape, which improves the S/N ratio (especially stereo quieting) by at least 6 dB. I’ve attached a photo or two: I also decided to keep the ST-A6B, because it’s sooo pretty, like your tuner, and I’ll put it in my home theatre room as backup.

cheers, Andrew

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