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DUD 120 ampmods

Posted by Stewen (A) on March 6, 2007 at 14:03:30

Hallo ! Have built this amp with four 807 in triodemode instead of the four KT88. Driver is a 6SN7 as a cathodefollower. Splitter is a doublecascode with CCS with a NPN- transistor. This part of the amp is called CAE PCB 1A from evatco. Think its used in some upgraded Dynacoamp. My first question is: why is the powersection only giving the 6SN7 tube a higher voltage connected to the heater? Shouldn´t the upper ECC88 have a similar higher voltageconection to the heater ? Or can the two ECC 88 tubes manage without this ..... as in the schematic. Have someone of You guys seen a nother, upgraded schematic ? My amp has only 45V over the upper ECC88 and 130V over the lower. Isn´t that because the 100 ohm resistor is too low in value ? Will 100 ohm really bias that tube correct ? Hope You will understand my strange english. Thanks for Your comments.

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