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Friday, September 22, 2017

300B Mono Amplifiers Landscape Style - Part 1


So far all 300B amps I built were mainly in portrait chassis as seen here and here or in tower style. Now I have a set of 300B monos in the work in the classic landscape shape.

Here a few photos which give a preview how they are going to look like. Each mono block has it's separate power supply, so 4 chassis total. This is an amplifier section with all parts mounted on the top plate:

Tribute finemet core output transformer on the left behind the 300B output tube. The 10Y driver tube sits at the back for a short signal path from the input jack. It drives a Tribute finemet core interstage transformer which is placed at the front to the right. In between the oil capacitors painted in metallic blue.

The power supply chassis houses a big B+ transformer on the left and all the oil caps for high voltage smoothing on the right. A full wave rectifier bridge with 4 6AX4 or similar TV damper tubes at the front.

Next we see the bare metal plates of amp and PSU:

The top plates on the left and each chassis has an internal support plate which carries the chokes and other components which did not find room on the top plate.

Wiring of the amp section. The 10Y is fed through an input transformer which is placed right beside it (lower right). The chokes are on a second level:

Wiring of the PSU:

The two small transformers are the separate filament transformers for DC filament supplies of 300B and 10Y. All other components are mounted on the internal plate:

Stay tuned for more photos when the amps are finished.

Best regards



  1. Hi Thomas, can you comment on the cathode resistors and "u.p." caps on the output tube? I don't think Ive seen that before. I see the primary RK for the 300b bias, I'm guessing it has to do with the dc filament supply.

    1. Hi!
      Please understand that some of the details are propriety. The photos show more already than I should ;-I

  2. I understand! Your work continues to inspire me.

  3. Where do you get that mounting hardware? (The railing)

    1. They are available from me, also most of the transformers and chokes I use