Sony TA-F7B (1976/1977–1981)

Twenty kilograms of V-FET iron that Sony almost certainly sold at a loss.

Overview

The first thing you notice is the weight: 20 kg in a chassis measuring 43 x 17 x 42 cm. The TA-F7B is a DC pre-main amplifier built around vertical field-effect transistors - V-FETs - the output devices that made Sony's late-seventies flagship integrateds famous and that are now genuinely scarce. It was the junior member of Sony's "sevens" family, alongside the ST-A7B tuner, TA-N7B power amp, and TA-E7B preamp, and it sold for 178,000 yen at launch.

The headline number is modest by modern standards: 2x 70W into 8 ohms across 20 Hz to 20 kHz. The distortion spec is the interesting part - 0.015% THD at rated power across the full audio band, and the same 0.015% at 1W output. The damping factor is 60 at 1 kHz into 8 ohms, the signal-to-noise ratio is 110 dB, and residual noise measures just 0.12 mV. Power bandwidth spans 5 Hz to 40 kHz, and the frequency response runs from DC to 100 kHz within +0/-1 dB. It is DC-coupled from input to output. One source also lists an 80W+80W (1 kHz) rating, a short-burst figure that appears alongside the stricter full-band measurement rather than replacing it.

The circuit topology is what makes the TA-F7B interesting, not the wattage. The power amplifier stage uses V-FETs in a cascode-connected parallel push-pull SEPP-OCL configuration. The first stage is a cascode-connected differential amplifier using dual FETs, with a current mirror circuit on the output. The manual's power amplifier section confirms the rated output is specified at less than 0.015% harmonic distortion, with both channels driven simultaneously. The preamp section is DC-coupled as well, with the phono input feeding a dual-FET differential amplifier with current mirror, and FET inputs on the line stages. There are no coupling capacitors in the signal path.

Key Features

V-FET Output Stage with Cascode Differential Input

The TA-F7B uses the same BJT and V-FET differential cascode mix as the TA-N7B, Sony's larger reference amplifier, but with three transformers instead of four and slightly reduced capacitance - 4x 15,000µF rather than 4x 22,000µF. The output stage runs four heatsinks, each carrying a row of three 2SJ18 or three 2SK60 V-FETs. Those devices are now a genuine rarity. Collectors of Sony's V-FET series - the TA-F5, TA-F6B, and TA-F7B - know that output transistor availability is the single biggest long-term concern with any of these amplifiers. The first stage uses dual FETs in a cascode-connected differential amplifier, with the output taken through a current mirror circuit. That topology was chosen for stable operation and low distortion rather than raw gain.

Three-Transformer Power Supply with 60,000µF of Smoothing

Sony split the power supply into three separate transformers, each feeding an independent block. The power amplifier stage gets dedicated toroidal transformers for left and right channels, custom-ordered from Nippon Kinzoku, a supplier that provided toroid transformers to much of the Japanese high-end industry through the seventies and early eighties. The twin toroids are stacked one atop the other to save space. A separate transformer handles the Class A preamplifier section. Four 15,000µF smoothing capacitors per channel give a total of 60,000µF, and an FET buffer power supply further reduces crosstalk between channels. That overbuilt supply explains the 192W power consumption and the 20 kg weight.

DC-Coupled Signal Path with Dual-FET Phono Stage

The phono stage is a dual-FET differential amplifier with current mirror, directly coupled, with two phono inputs at 2.5 mV sensitivity into 50 kΩ with 100pF loading. Maximum phono input is 250 mV at 0.015% THD at 1 kHz, and the phono S/N ratio is 75 dB (IHF-A). Line inputs take 150 mV into 50 kΩ with 95 dB S/N (IHF-A). The RIAA equalization holds within ±0.2 dB. The flat amplifier is a two-stage direct-coupled DC design with FET differential input, and the tone amplifier uses the same direct-coupled two-stage FET topology. A DC feedback circuit using an FET stabilizes the operating point of the phono stage alongside the RIAA feedback network.

Switchable Turnover Tone Controls and 32-Step Attenuator

The tone controls aren't the usual fixed-corner afterthought. Bass turnover switches between 150 Hz and 300 Hz, with ±10 dB of boost or cut at 30 Hz or 60 Hz respectively. Treble turnover switches between 4 kHz and 8 kHz, with ±10 dB at 20 kHz or 40 kHz. The filters are 12 dB/octave, the low filter cutting below 30 Hz and the high filter above 9 kHz. Volume control is a 32-step detent type. The rear panel offers REC out at 150 mV into 10 kΩ and PRE out at 1 V into 1.5 kΩ, with speaker outputs rated for 4 to 16 ohms. A relay handles phono input switching and speaker selection.

Mechanical Construction — Aluminium and Steel Front Panel

The front panel is assembled from several plates of aluminum and steel. The secondary-function sub-panel is a separate aluminum plate welded to the main panel via a steel surround finished in matte black. The metal case houses a chassis whose mechanical build quality, according to collectors who have handled the full "sevens" lineup, puts most contemporary components to shame. The panel doesn't flex when you pick it up.

Historical Context

The TA-F7B entered production in November 1976 and ran through 1981, though one source dates the start to 1977.

It cost 178,000 yen — around 1977, according to the Audio Database listing. Sony positioned it at the lower end of the genuinely expensive Japanese high-end bracket, and given the build quality and measured performance, the consensus among collectors is that Sony made very little profit on each unit. Production is estimated at roughly 3,000 pieces worldwide, with the export version — the silver TA-F7 — accounting for only about 300 units. That export version was quickly replaced by the standard green/bronze TA-F7B, and the silver TA-F7s all bear low serial numbers. The same pattern held across the entire "sevens" line: ST-A7, TA-N7, TA-E7, TA-F7 — the silver versions are exceedingly rare.

The TA-F7B belongs to a five-model TA-F series review that runs from the bipolar TA-F3A and TA-F4A up through the V-FET models TA-F5, TA-F6B, and TA-F7B. Within that lineup, the TA-F7B and TA-F6B are the flagships. The series as a whole is still regarded as one of the peaks of Japanese amplifier engineering from the period, and the V-FET models in particular are described as objects of collectors' desire.

Collectibility & Value

Recent asking prices vary a lot. A listing in Ulan-Ude asked 205,000 rubles; one in Omsk asked 167,000 rubles. A Yahoo Auctions listing recorded a bid of ¥86,000 in September 2026. The spread is wide, which is typical for V-FET Sony gear - condition, originality of the output devices, and whether the unit has seen a proper service all move the number significantly. Sellers describe units as having received full maintenance and note the 100V power requirement, which matters for buyers outside Japan.

The critical issue with any TA-F7B is the V-FET output devices. The 2SJ18 and 2SK60 transistors used in the output stage are a genuine rarity today, and there is no modern equivalent. A unit with failed outputs is a parts unit unless you have a stash of originals. Beyond that, no specific common failure points have been documented in the available sources - only a general caution from a repair thread warning against dishwasher cleaning, which would damage the sealed electrolytic capacitors and the aluminum front panel. A 24-page service manual exists for the TA-F7 and TA-F7B, covering both models, and it's the essential document for anyone attempting a restoration. Spare parts availability is undocumented, so assume you're on your own for anything beyond standard components.

The silver export TA-F7 is the one to watch for if you're a serious collector - 300 units worldwide, low serial numbers, and a finish that was replaced almost immediately. The standard green/bronze TA-F7B is the more practical buy, and at roughly 3,000 units produced, it's not exactly common either.