Heavyweight SET amp


DIY tube amplifier by Stavros Danos

This gorgeous heavyweight SET amp uses the Direct Heated 813 tubes triode connected, runing at 120mA. OPTs are the excellent Sowter SE18 SE.

The filaments power supply uses batteries for eliminating hum.

The main power supply uses a toroidal Amplimo Power transformer (850V secondary), followed by an CLCLC filter separately for each channel using polypropylene and oil capacitors only.


It is a full bridge rectified Power Supply with 4 damper diodes 6D22s ( running at 1,1 KVolts DC!) In the first stage there are 14 capacitors total (seven in series and seven in parallel all Russian Κ75-24 ) 1uF,1000V and a choke 15Η @500mA. The second stage consists of 3 capacitors 47μF,500V in series and three Russian Κ75-24 in parallel, and the choke is 20Η @ 100mA.

Third filter stage are two packs of 2X12 parallel 47uF 500V polypropylene capacitors.

Driver stage is a triode connected 814 direct heated tube,running @380V ,55mA,loaded with a double c-core 1:1 interstage,made by AE Europe.Secondary loading with BI thick metal resistors,6.8Kohm.

There is also a separate power supply for the 814's,using a 5Y4 tube,with dual CLC filters,using pp+Teflon capacitors and 10H chokes.

Separate bias supplies for the 4 tubes,with separate windings and rectification - filtering for optimal isolation.

There are three digital displays in front of the amp, displaying bias voltage , filament voltage, and transformer's temperature.

Power output : 25W in A1,40W+ in A2 bias setting.Used usually in A1 class driving the 99db DIY speakers:)