Plate load resistors on LTP PI

[iknowjohnny]

Tom....when you nail the tone just right with that trimmer, have you then checked to see where the balance was? Was it balanced or off, and if so by how much if you know?

[Structo]

I just double checked my notes and I currently have a 5K trimmer in mine.

I think I may prefer the 10K I had in it before.

Johnny, when I have hit the sweet spot on that trimmer, I have found there is usually a 6-7 DCV difference, with the higher on the input side.

[PCollen]

I just double checked my notes and I currently have a 5K trimmer in mine.

I think I may prefer the 10K I had in it before.

Johnny, when I have hit the sweet spot on that trimmer, I have found there is usually a 6-7 DCV difference, with the higher on the input side.

Can you give the final plate load resistance measurements , vs. the voltage difference.

[Structo]

Sure.

Pin 1 294v (110K) , Pin 6 289v (120K)

On my amp, Pin 1 is the input side.

Now even though that is only a 5v difference, that is where that particular tube sounded best.

There can be a lot of trial and error in this amps and finding what tubes float your boat.

As most of us know, just trying different tubes of the same type in a socket like V1 can swing the plate voltages 8-12v, so you can see where we can get into trouble by tuning components to one particular tube.

Best to roll a few tubes through each spot to get an idea what is going on before adjusting any resistor values.