We introduce our first integrated valve amplifier based on a modernized Williamson circuit. It is a 30 Watt per channel Push-Pull, operating in ultra-linear mode, optionally switchable to triode mode.
Soviet triodes 6N8S are used as driver at the pre-amplifier stage. The power stage operates on excellent GU-50 radio frequency valves, Soviet-made for the military in the 1960s (NOS).
In order to minimize distortion, the power supply is separated from the amplifying section by placing it in a completely separate, screened case.
While designing the circuit we managed to achieve identical topography of the left and right channels, which resulted in a fully symmetrical signal path.
It should be noted that loudness control does not employ a common potentiometer, but a 64-step attenuator (based on relay switches) by Khozmo Acoustic, which minimizes signal inequalities in both channels of the amplifier. The circuit employs a small number of capacitors in the signal path, which also improves sound quality.
The amplifier uses only top quality components:
Ogonowski speaker transformers on EI core
Khozmo 64-step attenuator with IR remote control
Nichicon, WIMA, Jantzen Superior capacitors
Top quality PCBs made in Poland
gold-plated ceramic valve sockets
WBT speaker terminals and Neutrik input sockets
metering socket for setting BIAS for power valves
Omron high quality source selector switches
The power supply uses:
two toroidal TELTO transformers
Nichicon electrolytic capacitors
Schurter filtered mains socket
Amphenol military 10-pin output socket
Connection of the power supply to the amplifier is realized with a cable line in military technology of Raychem.
AC voltage was separated from DC voltage by screening and cable twisting.
All the technical solutions and components used in this construction met or exceeded our expectations. We achieved superb sound with wide and deep soundstage with high separation, sweet vocals, deep bass and detailed higher frequencies.
max output power: 30 Watts/8Ω per channels
max output power: 32 Watts/4Ω per channels
output impedance: 4,8 Ohm
frequency range: 7 Hz – 28 kHz ( -3 dB)
input impedance: 50kΩ
input sensitivity: 800mV
Valves: 4 x 6N8S, 4 x GU50,