KT66 Class A CFB amplifier
KT66 Class A CFB amplifier:
KT66 (or 6550) cathode feedback design.
2x12W class A (KT66) or 2x18W class AB (6550).
4dB CFB, 7-8dB gNFB.
Choke loaded LTP driver stage.
Some measurements with 2x KT66 + 6FQ7 + 6SR7 pr channel:
- Max Po: 2 x 13W
- Frequency response: 10Hz - 100kHz (Low power +0/-3dB)
- Output impedance: 0.8 ohm
- THD (1dB below max Po): 0.4%
- THD (1W Po): ~0.05%
- S/N greater than 80dB below rated output.
10 kHz square wave response:
Transformers by Sowter UK
Plate chokes by Lundahl SE
Tubes and other stuff from
Overall design by: Jan Erling Veiset.
(c) Jan Erling Veiset, 07-NOV-2008 - E-mail: valhalla[at]mikke-mus.com