These amps started in life as some Audio Innovations The First Monos. They were produced by the factory built in AI 800 stereo chassis. Someone got hold of them and added a choke input GZ37 rectified power supply and converted the phase splitter from ECC82 to 5687 operation. The trouble was they got in a frightful pickle in implementing an earth lift system, as well as the heater supply. Worst of all, the chassis was not earthed at all, potentially exposing the user to dangerous voltages. The amp hummed like hell, but did show good promise for sound quality.
The amps have now been totally rebuilt with Hashimoto tranformers and chokes. Heating is all DC regulated. The amps now sound amazing, and run completely silently even on my 96DB speakers. Just as well really as the owner will be using them to drive his £4k headphones!
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They also measure incredibly well with those Hashimoto transformers as these photos of 1 and 10khz square waves show
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