Do I need to fix these voltages?

[Joost]

As you may remember, I am very happy with my amp's clean channel, the addition of the dumbleator, the PAB etc. However, I was never satisfied with my OD sound. The basis of this amp is the 124 low plate skyliner

So this weekend, I changed the OD side very close to 183 specs (high plate with a 100k trimpot for initial gain). I changed the 272k drive to 100k and modded it so that I got rid of the fizziness.

It sounds much better! However, I should hit around 200V on the 220k plate and 195V on the 150k plate on V2. I get 186V and 193V respectively.

Do I need to fix these voltages?

[ToneMerc]

The only thing that matters is that YOU like it and if so, why fix something that's not broken. One of the big advantages of rolling your own is the ability to season the amp to your own tastes.

enjoy

TM

[passfan]

A lot of older Fender schematics say + or - 20% when it comes to voltages. You too close to bother IMO.

[Joost]

Ok, great thanks!!!

I know I can just judge if I like it, but what I wanted to know was whether changing the dropping string would be worthwhile tone-wise if it could get me closer to that 200V. I do like the dynamic response as is. But maybe the tone becomes more transparent or even more dynamic when I up the voltage 16V

[CHIP]

You can try swapping tubes on V2. Depending on the tube you might be able to raise your voltages 10v on each plate.

[CHIP]

Joost,
After changing the 272k OD drive pot ,what mods did you do to the 100k pot in order to get rid of the fizziness?

[Structo]

Joost, as Chip said a simple tube swap can bring about the voltage you are seeing at the plates.
All tubes draw different amounts of current which changes the plate voltage.
So before getting the soldering iron out is to try several tubes in V2 and listen carefully to each one.
Ignore the voltage because you are close enough, now you can just audition tubes for tone.

And don't forget that V1 also influences the OD tone as well.

[Joost]

Thanks Tom that is great news!!! BTW, I got a great tip from a friend of mine. He said with that type of overdrive, you should audition a 5751 tube for lower gain. I will try that tomorrow

@CHIP: I took out the 150k resistor to the ratio and just put in a 250k pot for the ratio control. Then I added a network of a 120k resistor in series with a 0,001 uF 6PS cap in parallel to the input and ground lugs of that 250k ratio pot. Works like a charm.

So you have a 100k trimpot (just like 183), a 100k drive pot and a 250k ratio pot (minus the 150k resistor to ratio). I did keep the 270p ceramic bypass caps across both plates and cathodes like the original #124. I also kept in the .01 uF coupling cap from #124 instead of changing it to .015uF

The rest is all just basic 183. Highly recommended!