[Reynaldo]

I set my millet,DIY cable board, to 14 volts using 12FM6 tubes, just to check a couple of days letter that now my Bias point reads 14.4 or 14.2, is this normal? How about if I don[t want to deal with this bias setting anymore, what resistor value would I need to get 14 volt flat, I have experimented with several tubes and bias poits and found that 14 volts with the 12FM6 is the best match for my sein HD590, thanks guys

 

[n_maher]

1. I wouldn't be at all concerned about the bias floating like that. I've never been able to hear the difference between 10% bias shift. Just in case you might be adjust the bias correctly here's how I do it: to set the bias properly you need to let the amp warm up for a half hour or so and then each time you adjust the bias you need to wait a while to see where it settles again. Also, I've found that these ajustable resistors don't hold a value very consistently. Around 5 to 10% either way is usually about all I worry about.

2. The bias will change every time you change tubes.

HTH,

Nate