Roger's Williamson Amplifier Mk IV
Designed by Roger Knopp, M.Sc.EE
phone/fax: +46 31 252345

The amplifier KEW88-91D seen in this page is my fourth and final attempt in building a modern, good and cheap stereo Williamson Power Amplifier. The chassis is handmade of solid Pine.

Main Data:
Power Consumption: 150W@230/115V 50-60Hz
Supply Voltage: 2X440Vdc@150mA
Heater Voltage: 2X6.2V@4.2A (1.5A@6550)
Closed Loop Gain: 20dB
Std Feedback (BF+1): 15dB
BW (+/-3dB): 7Hz-280kHz@67mW
Output Power (4-8R): 2X20W/6Ohm/1kHz/10%THD

KEW88-91D, The Williamson Amplifier Mk IV using triode connected 6550's from Sovtek.

More info:
KEW88-91D, Mk IV Circuit Diagram
KEW88-91D, Mk IV Component List
KEW88-91D, Mk IV Bottom View
Sovtek KT88 Stereo System I
Sovtek KT88 Stereo System II
Power Amp Options