Sony TA-F7
A 44-pound integrated amplifier that Sony built to two different mains voltages and one very high standard.
Overview
The TA-F7 is a stereo integrated amplifier from Sony's European distribution. The service literature documents it as the TA-F7 (AEP model) and TA-F7B (UK model). No year is printed anywhere in the surviving documentation, and no production run is confirmed. The manual gives voltages, weights and distortion figures, but not a date. What it does show is a thoroughly overbuilt integrated amp: 20.3 kg net, 430 mm wide, and rated at 70 watts per channel into 8 ohms with both channels driven from 20 to 20,000 Hz.
The 70 W rating is the headline, but the number that tells you what kind of amplifier this is sits next to it. Harmonic distortion is less than 0.015% at rated output, and the same less than 0.015% at 1 watt. Plenty of amplifiers quote a flattering figure at full power and let it drift at low levels, where most listening happens. Sony specified the same number at both ends. Intermodulation distortion gets the identical treatment - under 0.015% at rated output and under 0.015% at 1 W, measured with a 60 Hz to 7 kHz signal at a 4:1 ratio.
The power bandwidth runs 5 to 40,000 Hz at 8 ohms at that same 0.015% THD. The small-signal frequency response is wider still: 5 to 100,000 Hz, ±10/1 dB across the tuner, aux, and tape inputs. Damping factor is 60 into 8 ohms at 1 kHz, which is a firm grip on the woofer without being a current-dumping showpiece. Signal-to-noise on the power amp section is quoted as greater than 110 dB into a short-circuited input, with residual noise under 0.12 mV.
The preamp side is where the phono stage lives, and it is not an afterthought. Both phono inputs present 50 kΩ and take 2.5 mV for full output. Maximum input is 250 mV before the 0.015% THD threshold is reached, which is enough headroom that a high-output moving coil or a hot moving magnet won't paint itself into a corner. Signal-to-noise on phono is 75 dB, A-weighted, referenced to 2.5 mV. The line inputs (tuner, aux 1 and 2, tape 1 and 2) want 150 mV into the same 50 kΩ, and return 95 dB A-weighted. RIAA equalization is held to ±0.2 dB, which is tight enough that nobody is going to hear the curve.
Tone controls are unusually flexible for the period. Bass offers ±10 dB at 30 Hz with a 150 Hz turnover, or ±10 dB at 60 Hz with a 300 Hz turnover. Treble gives ±10 dB at 20 kHz with a 4 kHz turnover, or ±10 dB at 40 kHz with an 8 kHz turnover. The service manual's alignment table confirms the switch positions: turnover treble at 4 kHz, turnover bass at 300 Hz, high filter off, low filter off, tone off, muting off, mode reverse, monitor source, tape copy source. The filters are 12 dB per octave, low filter below 30 Hz and high filter above 9 kHz, steep enough to actually do something rather than just soften the edges.
Around the back, REC OUT 1 and 2 deliver 150 mV into 10 kΩ. There's a pre output at 1 V into 1.5 kΩ, so the TA-F7 can drive a separate power amplifier if the owner wants to split the system later. Speaker outputs A and B accept 8 ohms or more. The headphone jack takes both low- and high-impedance stereo headphones, a small courtesy that a lot of amplifiers of this size skipped. The power amp input wants 1 V for rated output into 100 kΩ.
Two things are worth flagging for anyone shopping one today. First, the mains configuration. The AEP model is 220 V at 50/60 Hz and draws 400 W. The UK model is 240 V at 50/60 Hz and draws 410 W. Neither is a 120 V machine, so North American buyers are looking at a step-up transformer as a permanent part of the setup. The model identification labels in the service manual make the distinction explicit: the TA-F7 and TA-F7B are both marked AC 240V in the UK sheet, and the AEP sheet shows AC 220V. Second, the weight: 20.3 kg net, 24.3 kg in the shipping carton. That's a two-person lift, and the mass comes from a substantial transformer and heatsinking rather than from ballast.
Inside, the regulated power supply is an interesting piece of design. The service manual describes a class-B amplifier fed by a regulator built around control transistors Q704 and Q705, with a constant-current circuit Q706 in the base-bias network. The manual's own explanation is that this arrangement yields high input impedance, low output impedance, and good regulation against input voltage fluctuation. A Darlington configuration stands in for the single pass transistor to get a low output impedance from a high-gain device, and a bootstrap circuit using R709 and D711 improves ripple rejection. The regulation factor is expressed as the ratio of the diode's active resistance to that resistance plus R1. The larger R1, the better the regulation, which is why the design leans on an FET constant-current source to make R1 effectively large.
One period listing places a Sony TA-F700ES, a different, later integrated, at $649 with 105 W per channel, nonmagnetic G-chassis construction, a twin-drive power supply, and super legato linear circuitry (HiFI-Stereo, February 1989, p.94).
The TA-F7 has no price, no production year and no confirmed period review in the surviving paperwork. Collectors chasing one should verify the voltage variant first. A 220 V AEP unit and a 240 V UK unit look identical from the front and behave very differently on the wrong mains. Beyond that, the usual integrated-amp caveats apply: switches and pots on a machine of this age are the first things to need attention. The service manual's alignment procedure for the power meters is worth having on hand if the meters ever drift. It calls for attenuator at maximum, function set to tuner, tone controls mechanically centered, filters and muting off, then adjusting RT801 and RT851 for a 10 W indication on an 8.9 V reading.
It is a heavy, conservatively rated, thoroughly documented amplifier with a phono stage that was clearly taken seriously and a power supply that Sony's own engineers bothered to explain in the manual.
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