SONY TA-F70
¥ 89,800 (around 1978)
Commentary
A pre-main amplifier developed under the theme of reducing total dynamic distortion.
In order to realize the concept of simplicity and straightness, straight transmission and pre-power separation structure are adopted, and the shortest wiring of input / output terminals, natural arrangement of parts along the signal flow, avoidance of signal intersection, etc. are strictly enforced.
In the TA-F80, the preamp section is arranged in the front panel section and the volume switches are directly attached to eliminate unnecessary wires and transmit them to the power amplifier which is shielded by a shield plate. In the power amplifier section, the installation location of the power transistor can be arbitrarily determined by the heat pipe, which has been a difficult problem, so that the power transistor is arranged in an ideal position in the signal flow.
A heat pipe structure is used for the cooling system.
The heat pipe instantaneously transfers heat from one end of the pipe to another by enclosing a special liquid in a copper pipe under reduced pressure and continuously performing vaporization and liquefaction. As a result, the thermal conductivity is several hundred times higher than that of copper or silver metal rods of the same diameter.
This heat pipe structure increases the freedom of placement of the power transistor and avoids wiring by wires.
The power transistor has Hi-f with reduced transient intermodulation distortion (TIM distortion).TTransistor is used.
This transistor was developed by taking advantage of Sony's semiconductor engineering. It is like an integration of an infinite number of low-power transistors with good high-frequency characteristics. It realizes safe operation even at high power.
In terms of characteristics, the cut-off frequency is significantly improved from 4 MHz to 20 MHz to 60 MHz or more, and the high-frequency response is extremely fast.
Pulse power supply is used for the power supply part.
The pulse power source rectification system consists of direct rectification of 100 VAC, conversion to 20 kHz pulse with a power oscillator, high voltage with a high-frequency transformer, and re-rectification. High voltage with a high-frequency transformer makes it highly efficient and easy to obtain excellent regulation characteristics. Unlike sine wave rectification, almost DC state can be obtained only by rectification, so smoothing is easy and the pulse current component is almost 0.
In addition, the direct rectification of 100 VAC virtually eliminates the AC hum source, which is also a significant effect.
By adopting a high-gain DC amplifier for the power amplifier, the flat amplifier can be omitted.
This allows DC transmission between the Tuner, Aux, and Tape inputs and the speaker out in the "Direct" state. In addition, when the MC cartridge is being played back, only the minimum necessary circuits (head amp → equalizer, power amp) pass through, minimizing the loss of sound quality.
In the MC head amplifier section, noise reduction is achieved by a circuit combining differential amplification by super LEC transistor and IC.
Equipped with 3 Ω ⇔ 40 Ω impedance selector.
Equipped with a 20-step peak power indicator that can read directly from 0.008W to 130W.
Equipped with a Low filter.
Model Rating
| Type | Stereo pre-main amplifier |
| Circuit system | Preamplifier section : Head amplifier for low-noise MC, NF-type equalizer amplifier Power Amplifier Section : Pure complimentary service SEPPPDC Power Amplifier Power Supply Part : Pulse Power Supply (PPS) |
| Power Amplifier Unit | |
| Effective output (both channel drive) | 90W + 90W (8 ω, 0.007% distortion, 20 Hz to 20 kHz) |
| Output bandwidth | 5 Hz to 30 kHz (IHF, 0.007% distortion, 8 Ω, 45W) |
| Harmonic distortion factor (20 Hz to 20 kHz) | 0.007% (at effective output) |
| Cross modulation distortion factor | 0.007% (at effective output, 60 hz : 7 khz = 4 : 1) |
| Residual noise (A-network) | 100 μ V (8 Ω) |
| Damping factor | 100 (8 Ω, 1 kHz) |
| Suitable speaker impedance | 8 Ω ~ 16 Ω |
| Preamplifier Section | |
| Input Sensitivity / Impedance | Phono1, 2 mm : 2.5mV/50k Ω Phono1, 2 mc : 0.125mV/33 Ω, 100 Ω Tuner, Aux, Tape1, 2 : 150mV/50k Ω |
| Signal-to-noise ratio (A network) | Phono1, 2 mm : 88 dB Phono1, 2 mc : 78 dB Tuner, Aux, Tape1, 2 : 105 dB |
| Output Level / Impedance | Rec out1, 2 : 150 mV (maximum output 20.0 V) / 4.7k Ω |
| Phono maximum allowable input | Phono1, 2 mm : 300 mV Phono1, 2 mc : 15 mV |
| Frequency characteristic | Phono1 and 2 : RIAA deviation ± 0.2 dB Tuner, Aux, Tape1, 2 : DC ~ 100 kHz + 0 -1dB |
| Tone control | Bass : 25 Hz ± 10 dB (turnover frequency : 250 Hz) Treble : 50 kHz ± 10 dB (Turnover Frequency : 5 kHz) |
| Low Filter | 15 Hz, 12dB/oct. (Phono input only) |
| <General> | |
| Power supply voltage | 100 VAC, 50Hz/60Hz |
| Power consumption | 145W |
| Power outlet | Power switch interlock : 1 system, 100W Power switch not linked : 2 systems, 100W |
| External dimensions | Width 430x Height 160x Depth 410 mm |
| Weight | 8.7kg |
| Attachment | Code clamper |