Sony TA-F55

A nicely understated little bolid - with a few twists : capacitance selectors for the phono inputs, a Pulse Power Supply, a double Heat-Pipe and High-fT transistors
In other words : a TA-F80 made slim and sonically an excellent performer : fast, deep, clean yet hot.

The F55 is a low-THD, low-TIM, low-NFB design thanks to the high bandwidth of its output bipolar transistors (80MHz) and Pulse Power Supply (PPS).

High-fT transistors are made of a string of normal transistors connected in parallel offering lower switching distortion and better stability.
The PPS rectifies the line voltage, chops it at 20Khz, DC-AC inverts it and then rectifies and filters it again to output pure, clean, stable, DC current.

The freon-filled Heat-Pipe allows to dissipate heat more evenly over the multiple thin fins and also to place the output devices closer to both pre/power stages to avoid long cabling ; due to the immediate cooling of the system, the output devices are mounted directly on the pre-driver board !

Like most mid-end Sony amplifiers, the F55 can receive MC cartridges and even has two-step capacitance and impedance switches !
Internal cabling is done entirely with 99,99% pure copper and the preamplifier stages are separated from the main amp by a FET buffer stage. Source selection is done by electronic switches relaying switching MOS-Fets placed in the signal circuits.

But the real twist is the strange design retained for the volume control : if the "soft-touch" buttons were already old salad by 1979, the volume indicator itself is... not what you think it is : it uses an ALPS-built motor assembly moving a green ribbon which is pulled behind a backlit window ! Two speeds can be triggered by pushing the buttons softly (slow) or frankly (fast). Nakamichi devised the same system for its 730 receiver.

The thirteen lamps are, silly, connected in series : one pops out and all turn off. Replace with 8V / 40mA / Ø 3mm equivalents.


The F55 also existed as a very good-looking grey-faced Wega V700 in Germany between june 1980 and 1981 ; the green volume control was redesigned and the color changed to red (see one in action here) while the color scheme reversed : black buttons, warm grey front, hellgrau scripting.

The production run of the V700 version must be of 2000 units, few of which still exist ; for the original F55... we're closer to 35,000.


The F55 was first presented in Japan at the 1979 Japan Audio Fair with a very good-looking TAC-70 wood enclosure which was alas made available only during and briefly after the october 1979 launch.
Out of three spotted in Japan in ten years, I managed to get two TAC-70, both in excellent shape, with serial numbers... #3 and #5. Yes, only a handful were made. But they are beautiful, very finely finished and my Wega V700 and T700 now reside in them :)