Amp cap for treble control

[samdjr74]

Hi All,

I want to replace the 130pf cap on my treble circuit with a 470 to see if it brightens things up. My question is what value on the voltage of the cap should I use?

Thanks,
Sam

[darkbluemurder]

Hi,

The voltage rating should be at least for 400V, more does not hurt.

However I doubt that 470pf will brighten things up compared to 130pf. You will get more high mids with the bigger treble cap.

Cheers Stephan

[phsyconoodler]

The treble circuit on most amps is either 250pf or 500pf.You must mean the bright switch circuit?

I would tread carefully here.It gets brighter as you increase the value but it gets to a point where it boosts the signal and as samdjr74 said,it boosts the mids.
If you want brighter tone you may need to look elsewhere.Like maybe lowering the value of your preamp tube cathode bypass caps.
Fendery amps use typically 25uf cathode bypass caps which can be woofy.Try a lower value like 1uf or even .68uf to get highs to pass.

[samdjr74]

So maybe I'm looking at this wrong.

The amp was originally designed to have a 470 on the treble control but was changed out to a 130. The problem is the amp is very dark or woofy when using humbuckers. I need to max out the treble and mid and keep the bass at 0 and it's still a little dark for my taste.

So if any one has any suggestions I'm open to them.

Thanks,
Sam

[phsyconoodler]

You still aren't making any sense.What amp is it and what treble control are you talking about?
It sounds like maybe a Tweed Deluxe? If so,put the 470pf back in there and do what I said with cathode bypass caps.

[samdjr74]

The amp is AX84 Hi-octane. And the treble control I'm talking about is the treble control of the tone stack, the actual treble knob I guess you might say.

Coming off of the pot is a lead that goes to the main board, on the main board is a 130pf in the C7 postion instead of the factory cap which was a 470pf in the C7 position.

[phsyconoodler]

those amps aren't known for being too bassy,that's for sure.
I'd put that back to stock.What speakers are you using and have you tried other cables and guitars?

Did you build the amp?If so,you may have made an error somewhere else like THE CATHODE BYPASS CAP values.
Home-built amps are hardest to diagnose because we don't know how it was built and if any mistakes were made right off the bat.

What I'm trying to say is that the treble cap you are talking about is not where you should be looking.500pf is just fine.

[pdf64]

Yes, replace the treble cap with the stock value of 470pF. That circuit isn't really a 'tone stack', as it loses effectiveness at full volume, the tone control being in parallel with the volume. Pete.

[samdjr74]

Gotcha, and I'm still looking for a 400V value correct?

Originally Posted by pdf64

Yes, replace the treble cap with the stock value of 470pF. That circuit isn't really a 'tone stack', as it loses effectiveness at full volume, the tone control being in parallel with the volume. Pete.

[phsyconoodler]

Yes,use a 400v silver mica or ceramic cap.It still won't solve your issue however,toy need to dig deeper.

[samdjr74]

I didn't build it, I bought it from the builder. I explained what I was hearing and he said he swapped out the cap from 470 to 140 on the treble control. But I hear what you're saying, it doesn't look like a 130 cap in there now, it looks like a .15 or .22 size cap you would see in a guitar. I need to check the values tonight.

I'm using a 1x12 open back mesa cabinet with a swamp thang in it. Tried other cables and guitars. P90's sound great, single coils sound a little thin and humbuckers are bassy

Originally Posted by phsyconoodler

those amps aren't known for being too bassy,that's for sure.
I'd put that back to stock.What speakers are you using and have you tried other cables and guitars?

Did you build the amp?If so,you may have made an error somewhere else like THE CATHODE BYPASS CAP values.
Home-built amps are hardest to diagnose because we don't know how it was built and if any mistakes were made right off the bat.

What I'm trying to say is that the treble cap you are talking about is not where you should be looking.500pf is just fine.