When I first got the amp, I added a Wima MKP10 .1uf as a bypass to the last filter cap in the power supply. That is the only other change to the amp.
Just to clarify, 70 is the bias for both plates combined (keeping apples to apples across amplifier designs from previous posts). Each triode is individually biased at 35mA.
The PS bypass sits right on the 6AS7 tube socket between pins 5 and 8. One side of the heater (pin 8) is grounded and plate pins 2 and 5 are jumpered on the socket to B+ in the stock WA3.
Other than the bypass cap, the only other change is adding a CCS to each cathode in place of the 1.5K cathode bias resistor. To make the mod as simple as possible (and easily reversible) I just clipped the grounds off the cathode resistors and left them hanging in the circuit. The CCS board then has three easy connections to the amp: B+ (right off the tube socket), ground from a nearby existing post, and a wire to the circuit side of the abandoned cathode resistor.
Edited by GrindingThud - 3/1/13 at 11:17am
Originally Posted by rosgr63
Did you make any other changes apart from setting the bias to 70mA?