This is the tube PA Amp from which I took the transformers used in the GFR AR-15 project. For the AR-15 I had the power transformer rewound, so as to be able to use it with a tube rectifier (with a center tap on the HV secondary and a rectifier heater winding added).

The amp itself is very simple. Note at the output transformer the feedback winding and the separate winding called "MONITOR" which allowed the user to power a small stage monitor cabinet besides the PA cabinets. Click on the picture to see it at full size.

The most interesting thing in this design is the power supply. The B+ is regulated using a ECL82 tube (pentode + triode in a single package). The pentode is used as a series regulator and the triode as a rudimentary differential amp. The voltage reference is a solid state zener. Click on the picture to see it at full size.

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