yet another use for the iFi micro DSD

[Monte]

I like to bias the input tube of a tube amplifier with a quasi-differential circuit and not have to use a by-pass cap on the cathode resistor. It's has always looked so tempting to zero bias the input grid and not have any cathode circuit and have better linearity. The iFi micro DSD apparently has a dc coupled output (amplifies 1 Hz signals) and probably won't mind sinking a milliamp or so sometimes. Amir has already measured the output resistance as less than an ohm (thanks Amir), so there should not be a runaway condition. Yes it does work. For the last 10 minutes of playing music at least. And I got rid of the volume control circuit (one of those things that you just want to be S.E.P., in this case, iFi). Next simplification is replacing the cathode circuit on the output tube with a small 3 terminal regulator and either 2 resistors for fixed bias or 1 resistor and a pot for super simple bias adjustment. And no cap needed. No parts on hand for that though.