Sony ST-A7B

Sony ST-A7

October   1 9 7 6 october 1976
1 9 8 0 1980

Almost as pricey as a TA-N7B, three times as expensive as an ST-A6B and built very much like its 1965 ES equivalent, the ST-5000 !

Das Meisterwerk as germans would say and quite a rare piece nowadays. New of course was the digital display and... slightly useless was the Dolby FM compatibility :-)

Digital was done in grand style however : the display isn't some early FLuoresent tube but four 7-segement incandescent lamps housed in separate air-free glass/ceramic housings !
These were named Minitron, Numitron or, more commonly, "Nixie".
They cost a lost back then, they still do and they are still made today - for aerospace and military applications. Yes. In other words they will last forever.

The ST-A7B is an FM-only tuner with "ultra" build-quality, X-Tal Locking, Dual-Gate Mos-Fet RF amp, PLL MPX loop, 5-gang varicap, FETs and dual-FETs all over the place and UNIPHASE filters.
Also a continuously variable muting level, a dual-purpose meter (multipath or signal) and two outputs (fixed or variable).

Also a design and finish which makes everybody else's 1976 offerings pale in comparison : all thick steel, double aluminium plates, real glass windows and the magnificently anodized color which renders the Sony "7s" unmistakable and beautiful to look at wherever they are placed in the room, day or night.
Instead of abruptly reflecting or absorbing the ambient light, that color + anodization team plays with it.


Also, otherwise it wouldn't be worth making such a fuss, the ST-A7B is one of the best FM tuners ever made.
Yes, yes, yes, even if it is written "SONY" on it !
The amount of bass, the stereo width, depth, separation and overall "musicality" truly are... unbelievable. Mirko Essling measured 56dB in stereo separation and it sounds as such.

It should be remembered that the ST-A7B did not replace the previous year's topper, ST-5950SD : it replaced the 1968 ST-5000F which, in 1976, still was in production and still was more expensive than said ST-5950SD !


However, in true Sony style, there are a few meanderings to consider - here goes :

The japanese version :
The japanese version had an AM section discretely added on the right side of the scale.
In those versions, the continuously variable muting function is replaced by AM tuning while a fixed 1-step muting is added to the function switch.
In such a statement unit, this addition wasn't very à propos, especially since it wasn't deemed important for the export versions.


The display & locking problems :
The more congenital problems are probably what kept this sleeper out of sight for so long : rabid soldering on crucial PCBs either make the display go crazy and/or freeze or randomly provoke a sudden loss of station locking.

These annoying symptoms are due to the way several double-sided boards were finished : tiny metal pins soldered together to "link" both sides of the PCB suffer from a bad soldering material and develop contact problems depending on heat, hygrometry and general age.

This isn't addressed in any service manual and necessitates the entire unsoldering and removal of all old solder on the three boards related to the display, the locking function and the control section.
Three dual-sided boards here makes in excess of 300 solder points ! Argh.


This seems due to the very limited production run and "on the side" status of the product : mainly an export item, for the show, not for the long run.
There probably were quite a few hesitations before production began as well, due to several factors :

> Despite FM being (then) of excellent quality, high-end FM tuners in Japan never were big sellers : tape decks or records it was. And, tuner-wise, Kenwood ruled.
Technics' and Pioneer's biggest efforts (ST-9700, TX-9900, F-26) suffered the same fate : unseen, invisible, unknown.

> Sony hesitated a lot between fianl market target, designs and colors (is it still ES-II or not, do we make it silver, B for bronze or B for gunmetal ?) while it was at the same time preparing its big foray into high-end compact components such as the (terribly successful) pre-Esprit series.

> The service manual itself shows this hesitation waltz : attempting to align an ST-A7B with it will result in error for there are printed mistakes in it and no corrective papers were ever issued anywhere !

> Even more to the point : Sony didn't advertise for the A7B, at all.

The production as well was quite waltzy.
Although all catalogs advertised them as "ST-A7B", pre-production japanese A7B were dark grey, neutral, gunmetal in color but did not always bear the name "ST-A7B" (B for bronze) on their frontplates : the scripting says "ST-A7", although they are "B" in color !
The production models were however all bronze (ie. greenish/bronze undertone).

The ST-A7 silver version was only for Europe and lasted only for the very beginning of the export : a sort of pre-production color.
Those silver ST-A7s are very very rare ; the scripting on them isn't engraved/stamped like on all the other ST-A7B but simply silkscreened.
It really was a pre-production item rushed to the local Sonys until the definitive color (and name) was set.
If you wish to complicate your manufacturing processes, follow Sony's example !


Despite all this typically Sony meandering, just as the ST-5000F from 1968, the ST-A7B is one of the best FM tuners ever made : the amount of bass, the stereo width, depth, separation and overall "musicality" truly are... unbelievable.

It slashes my ST-J88B to pieces by a huge margin, kills my (ex-) ST-S707ES and does also sound vastly more inviting, accurate, linear, extended, smoother and more transparent than my beloved (ex-) Denon TU-850.

One just has to listen to it, a properly restored one being better to do that, to fully grasp the musical qualities of this FM tuner : FM received as such is beyond most of the digitalia which plague our senses.
The paradox being that frequency modulation is a very old technology and that its response stops at a mere 15Khz ! Since LPs and tubes offer the same "feeling", maybe there was "something" to those old technologies ;-)

The worldwide production run seems to have been set at around 2500 units (tops), among which were around 200 silver versions.

To a lesser extent, the ST-A7B is like the 1974 TC-880-2 : it's for those in the know.

And there can only be few of them.

Sony ST-A7B, image 1 Sony ST-A7B, image 2 Sony ST-A7B, image 3
Sony ST-A7B specifications
Title Value
Tuning range : 87,5...108MHz
Usable sensitivity : 8,8dBf (1,5µV)
50dB quieting (mono) : 14,2dBf (2,8µV)
50dB quieting (stereo) : 34,6dBf (30µV)
S/N ratio : 80dB (mono)
75dB (stereo)
Selectivity : 50dB (400Khz)
AM suppression : ??
Image rejection : ??
Alt. channel selectivity : ??
??
RF intermodulation : ??
Subcarrier suppression : ??
THD (mono) : 0,04% (100Hz, normal)
0,2% (100Hz, narrow)
0,04% (1Khz, normal)
0,2% (1Khz, narrow)
0,05% (10Khz, normal)
0,2% (10Khz, narrow)
THD (stereo) : 0,08% (100Hz, normal)
0,3% (100Hz, narrow)
0,08% (1Khz, normal)
0,3% (1Khz, narrow)
0,3% (10Khz, normal)
0,6% (10Khz, narrow)
IM Distortion (mono) : 0,04% (100Hz, normal)
0,2% (100Hz, narrow)
IM Distortion (stereo) : 0,08% (100Hz, normal)
0,3% (100Hz, narrow)
Stereo separation (norm/narrow) : ??
??
??
Frequency response : 20Hz...15Khz (+0,2 / -1dB)
40Hz...12,5Khz (+0,2 / -0,5dB)
Capture ratio : 0,8dB (normal)
1,8dB (narrow)
Fixed outputs : 750mV / ?? Ohm
Variable output : 1,5V max.
PC : ??
Dimensions : 43 x 17 x 42cm
Weight : 14,1kg.
NOTE
These specifications are incomplete to say the least but I have misplaced my ST-A7/B manual...
I do have complete specs but from JP sources - but it isn't the same tuner, at all.
Until I find that EU manual again...
Sony ST-A7B : 0 topic
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page online since : march 2006
page updated : july 2010
page type : LGT / KNB
page weight : 1.77 Mb / 1.58 Mb

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