Roger's First Tube Amplifier
Designed by Roger Knopp, M.Sc.E.E
phone/fax: +46 31 252345

The Power Amplifier KEW807-91B seen in this page was and is, with some small exceptions, my first attempt in building a cheap but good stereo Williamson tube amplifier. The MkI-differences are the mains transformer (KE77003-B vs huge ABB EI-core 1:1), the output transformers (ABB C-cores vs std 30VA mains toroids), true Williamson biasing (rectified 350V vs 230V) and the black paintjob. The amplifier comes with a Party-Plug visible in the upper right corner. The 5U4GB may be changed to this Party-Plug whenever tube distorsion becomes too irritating. The OPT's are made of outstanding ABB C-cores and my Siemens QE 06/50's (i.e European 807) was actually, until recently, still working! That is almost 10 years of warm tube sound!!

Main Data:
Power Consumption: 150W@230/115V 50-60Hz
Maximum Output Power: 2X15W@8R/1kHz/10%THD
Input Sensitivity: 1.5V/1M
Closed Loop Gain: 7.3dB
Standard Feedback (BF+1): 15dB (6.8k@8R)
Power Bandwidth: 7Hz-70kHz@1W/8R/0.1%THD
External Speaker: 6-8R

KEW807-91B, My first tube power amplifier using triode connected QE 06/50's from Siemens (May be sold to highest bidder).

More info: