Star SA-30 valve integrated amp of Japan

Star SA-30 valve integrated amp:

Model produced in the mid '60s as a budget priced amp capable of outperforming virtually all the competition for the price at the time, especially the abysmal solid state offerings of the same period which purported superior specifications of frequency response but were mostly aurally horrible. I think it sold for AU$112.50.

Was sold in Adelaide S.A. by the store known as Mac's Hi Fi in Rundle Street City.

Having this stereo amplifier in my bedroom set the course for my future listening preferences. Other people had early solid state offerings which to me sounded awful - and they did. Sporting superior specifications, the protagonists insisted that valves were Inferior. The cart before the horse thing. Of course that's all changed now. It's not the way it's done, it's how well that matters.

Unusual features were individual bass/ treble controls with concentric knob and lever for the right and left channels. Also channel reverse function and phase reverse function switch on the speakers (which I have wired out to improve sound quality ...) On this example, the lever had been removed from the bass and treble controls unfortunately. Click on pics for full view...

Star SA-30 valve integrated amp chassis underside showing the high reliability point to point wiring. All the high voltage coupling capacitors were of an oil filled type predating modern plastics and polymers (not electrolytics, used for the usual filtering and cathode coupling), which in the main seem quite reliable considering the age of the unit. Two had to be replaced on the mains on/off switch filtering as can be seen on the left. The resistors are all wire wound paint coated of standard values predating the modern stepped values. e.g. 250K; 100K; 50K etc rather than 270K; 100K; 47K; 380K etc. I don't think they were precision types. I have changed the feedback resistors (middle top of pic) to decrease negative feedback to free up the sound. I figure the original values were partially designed to impress with low distortion and wide response measurements.

RIAA equalisation combined with the tone cctry is not bad considering, but sounds a bit lower mid thin, requiring some use of the bass boost controls to produce a balanced sound. As a consequence I dispensed with the ceramic p.i. input and facilitated a direct to power stage which brings out the true potential of this little amp - it simply sounds wonderful.

The unit was physically quite small, measuring only 14" x 4¾" x 8¾", but quite heavy, and tended to run stinking hot in summer due to the small size.
Another shot of the Star SA-30 valve integrated amp chassis underside:
The top chassis: the outputs were 6GW8s which had the little driver triode and pentode output in the same tube package. Although econonical at the time, these valves are pretty hard to get now - and expensive. Power output was rated at 10 watts RMS both channels, over 50 - 20,000 Hz, and response at 1 watt 10 - 100,000 Hz.