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RE: The Monster Amp

So here's the story:

The power supply uses 9 rectifers (6AU4 or 6AX4, 8 for the HV+ and one for the bias. The bias supply is regulated by an OA3. There are 4 OD3 tubes in there, they provide two 300v regulated sources for the screen grids, when the amp is in pentode mode.

The amp has knob selectable operating modes; Ultralinear, Pentode, and Triode connected, either in SE or PP.

The HV+ supplies 550VDC at 600ma. The outputs are nominally KT-90s, but can take just about any standard based octal tube. It can run either 2 or 4 tubes per channel, and can output over 100WPC in pentode or UL modes.

The metering is quite extensive, you cannot only measure bias, you can also measure output at the various driver stages, as well as the power output to the speakers. The meter circuits use two tubes for voltage regulation and reference voltage, and can be self-calibrated.

All pots are either 10-turn precision wirewounds, or in the case of the adjustable feedback and volume controls, stepped attenuators (ladder and series type)

The interstage transformers are Lundahl 1660, and the outputs HK Cit II. (thanks to Jim McShane!). The driver tubes are 6SN7, but with socket adapters, can make use of 6CG7 and lots of other twin triodes.

The power supply includes a standby switch, as well as an hour meter, which is very useful for knowing real numbers about tube life.

Most of the heavy design, SPICE modeling, etc. was done by a very well known and respected analog engineer, I am mostly responsible for the topology choices and the build.

All wiring is mil-spec silver plated copper w/ Teflon jacket. Octal sockets are NOS Amphenol ceramics

Please let me know what you think.

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