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Sunday, September 6, 2020

The Black 300B Mono Amplifiers - Part 2


The all black single ended 300B mono amplifiers are finished.

This set consists of 4 portrait style chassis.

Two mono blocks, each with outboard power supply.

The driver tube is an ELROG ER801A, old production 801A tubes can of course be used as well.

The output tube is ELROG ER300B which can be substituted by any other 300B tube.

The output tube is placed between interstage and output transformer for short signal wiring.

All signal transformers are silver wound on finemet cores, made for me by Tribute.

Of course both the driver and output tubes are DC heated for hum free operation and best sound. This is done by separate elaborate choke filtered filament supplies for each tube.

The power supplies use a bridge rectifier scheme with two 866A mercury vapour tubes, augmented by a pair of 6AX4 TV dampers for slow ramp up of the high voltage. 836 vacuum rectifiers can be used instead of the 866As as well.

The 866As have an eerie blue glow when in operation.

Together with the bright light from the thoriated tungsten filaments of the ELROG tubes this is quite a show.

Email me if you are interested in such an amplifier.

Best regards



  1. Do the Finemet transformers sound better or simply different than ones previously used in your top of the line amps? I heard this Finemet transformers are the best ones to use for bass reproduction, possibly exceeding their ss counterparts in terms of grip, impact, and extension.

    1. the previous silver single ended 300B amps used finemet as well.