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Wednesday, August 5, 2020

The Black 300B Mono Amplifiers - Part 1


Here some photos of a newly finished pair of mono blocks.

These will be paired with the all black 10Y line preamp shown in the previous post.

Each mono block will get it's own power supply (still to be finished).

The driver tube is an ELROG ER801A transformer coupled to an ELROG ER300B.

Interstage and output transformers are silver wound on finemet cores, made by Tribute.

The output transformers offer 4, 8 and 16 Ohm output impedance.

The impedance is selected by inserting a plug which configures the output windings for the chosen impedance.

Some photos of the assembly.

First the signal path is wired on the top plate all done with solid core silver wire.

The chokes and 2 additional capacitors are mounted on a separate support plate and wired to the top.

Then the whole assembly gets inserted into the chassis and wired to the back plate.

The power supplies will be shown in part 2.

Best regards



  1. Very nice piece! Question, where do you get the transformers' cans? Have some hum problem with the inductors, but can't find a suitable shield anywhere... Thank you!