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Tuesday, December 4, 2012

Making of a 45 amplifier


In earlier posts I already showed various single ended 45 amplifiers and also the assembly process of a version with directly heated driver and it's power supply. This article details the assembly of a 45 amp with indirectly heated dirver triode, namely the 6A6, a predecessor of the 6N7.

The circuit of the amp is similar to my 46 amp but with external and more elaborate power supply and Tango interstage and output transformers instead of Lundahl.

The metal plates with sockets, connectors and switches mounted:

The two switches near the output tube sockets configure the amp for use of either 45 or 2A3 tubes. The one in the middle is the ground lift switch.

The power supply plates:

Then the plates get mounted into assembly jigs for the next steps. amp section with capacitors, interstage and output transformers added:

All signal wiring is done with teflon insulated solid core silver, additional sleeving added for mechanical protection. Cathode resistors also added:

The power supply section with power transformer and capacitors:

Some initial wiring already done:

4 Chokes (separate choke for B+ decoupling of each tube), two more caps and the filament transformer for the output tubes are added on the second level:

This photo shows the completed amp already in the wooden frame (maple). The filament transformer is located in the amp section rather than the PSU in order to have short wiring of the cathode circuits.

PSU completed with chokes and bleeder resistors:

The finished amp:

Amp with PSU:

Some more photos:

The amp has terminals for 4, 8 and 16 Ohm speakers:

More 45 amps are in the planning. Next will be mono SE 45 amps with another 45 as driver. These will be in a different chassis style. Stay tuned for photos!

Best regards



  1. Hello Thomas, That is {as usual} meticulous superb craftsmanship. Might you send me the schematic of the 6A6 45 SET?

    Kind Regards,

  2. Hi Ken,

    Thanks! I will provide the schematic with the purchase of a kit or partial kit for such an amp. Drop me an email if you are interested.

    Best regards