bias pots?

[Tdale]

What do you guys use for bias pot(s)? A normal alpha panel mount pot or a trim pot?

Also, is it recommended to use two pots, one for each output tube, or is using one fine?

Tommy

[mlp-mx6]

I have used 2 panel-mounted 50K pots. I wire them such that if the wiper disconnects then the FULL bias voltage will be applied (for safety's sake).

There is a variety of opinions on what bias scheme to use. Individual pots (or a range control and balance control) allow you to balance the currents at idle. However, if the two tubes are not at least closely matched then the dynamic currents (esp. at the point of overdrive) will not be matched, regardless of the idle currents. This would point to using just one control for the range (voltage) and depending on the tubes to be (and stay) relatively well balanced.

The choices are yours...

[Bob-I]

I use panel mount pots with screwdriver adjustment. Here's the pics of my amp's bias pots. I also have test points on the back so I can reach in and make adjustments without taking the chassis out.

[Tdale]

Looks nice. Is that the 3-channel amp? I have a nice layout of a 3-channel amp, named "layout4_386.jpg is that yours? The wiring looks the same.. One pot for each tube, Bias enters on one side-lug, and leaves for the bias resistors through the center lug..

Tommy

[mlp-mx6]

+1 on the screwdriver pots and bias test points as well.

[Bob-I]

Looks nice. Is that the 3-channel amp? I have a nice layout of a 3-channel amp, named "layout4_386.jpg is that yours? The wiring looks the same.. One pot for each tube, Bias enters on one side-lug, and leaves for the bias resistors through the center lug..

Tommy

I bet it is. My file is named Layout4.jpg... I'd bet the _386 was added when I attached it to a post.

That amps sounds amazing now.