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Tube Technology Unisis Amplifier

This Tube Technology Unisis amplifier came in with the complaint that the sound was simply not good enough. Measuring the distortion levels gave the reason since they were; 0.1% at 1 Watt rising to 0.3% at 10 Watts.

The amplifier originally had a built in phono stage and as it wasn't being used, is now replaced by the input stage of a new driver design replacing the original inferior single ECC81 input/driver located on the main circuit board. The amplifier is also converted to cathode (automatic) bias and triode operation plus fuses are added to the HT supplies of each channel and a fused IEC mains socket fitted in place of the unnecessarily thick fixed mains cable. The distortion figures are now; 0.03% at 1 Watt and 0.06% at 10 Watts.

The top picture is of the amplifier in its original form.

Customer's comment -

Hello Geoff,
Here is my belated verdict on your rebuild of my Unisis as promised. You may add them to your "Comments" if you wish.

I have a large collection of wartime live concerts and have always felt the sound of many of them was beyond saving. However, the congested, overloaded full-orchestra passages now stand revealed as having had loads of headroom all the time! The sound emerges freely into the (cough-ridden!) concert hall with virtually no strain. Highs are no longer as harsh, bass has heft and timbre with satisfying differentiation of instruments. I've just noticed a first violinist lift his fingers off the instrument in the middle of a phrase, would you believe!
As for modern piano, curiously, the quiet passages seem even quieter, while the impact of a concert grand in full flood has to be heard to be believed.

The amp is expressive at moderate settings and so doesn't demand high volumes. The range of expressivity of your rebuild is astonishing. The bass goes down for ever (I have a pair of transmission lines) and I can hear individual notes terminating right down to a blacker background. In fact, the quality of the SILENCE is as impressive as the sound, and the soundstage, instrumental and vocal colour are exceptional.

We all probably have a few records that are hard on the ear, but I have to say that your rebuild has to a considerable degree eliminated that problem too. It is sweet, delicate, powerful and analytical all at once. You have achieved the perfect balance of virtues. and the soundstage, instrumental and vocal colour are exceptional.

So thanks for all you did. Worth every penny.

All the best,
Graham

Tube Technology Unisis Amplifier
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