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Thursday, January 14, 2016

Custom 300B Amplifiers


Pretty much all my amplifiers are built to order and can be tailored to specific requirements. These latest amps are an example how far customisation can go.

In this case the customer provided the interstage and output transformers and also participated in the chassis layout. The transformers are made by Monolith Magnetics in Belgium. The layout and chassis is based on my portrait style but adapted to fit the different output transformers.

The circuit is based on my earlier 300B/300B amps but with some circuit modifications requested by the customer. Shown above one channel of the amp equipped with EML tubes.

The power supply uses a classic rectifier instead of my favourite full wave bridge with TV damper tubes. Switches are placed on top which allow adaption of the filament voltage to different brands of 300B tubes which draw different filament current. The power transformer was also provided by the customer.

One channel, amplifier and power supply.

The amplifier chassis with Electro Harmonix tubes:

With Elrog ER300B:

The full amplifier set:

Best regards



  1. I know you don't generally comment on the sound, but... emmm.. how's the sound?

    1. Yes, I am hesitant to write about sound. What's the point if I praise the sound of amplifiers which I build and sell anyways? Sound descriptions are too subjective. If you are interested in the sound of my amps, come and visit for a listen, or come to the High End fair. Or check the video in this link for at least *some* impression of 300B/300B amps: http://vinylsavor.blogspot.de/2014/12/300b-drives-300b-part-2.html

  2. Dear Thomas
    From reading many of your posts it is clear that you are very particular about your transformer choice. Did these monoliths meet your expectations?
    Kind regards

  3. Hi! The transformers are only one part of an amplifier. It is always the entire concept which makers the sound, not the tube or transformers used. Since I am working with different transformer winders I will not post any preference of one over others.

  4. Dear Thomas
    Thank you for sharing. Your views are always refreshing as is the look of your finished products.
    kind regards