roll off point

[iknowjohnny]

I replaced the .022 coupler coming out of V1A with a .01 the other day. The gig i did last nite was good, but i think i should have left the .022. Where would the .01 start rolling off compared to the .022?

[Structo]

That cap is part of the treble and mid boost (if you have one) circuit.

What are you trying to achieve?

[iknowjohnny]

I'm talking about the coupling cap coming off V1A's plate. I swapped the .01 in there because everyone is always telling me to do that, but it seems like it always ends up sounding really thin at a gig. Last time i did the power tube grid ones too, and that was pretty bad. This time i figured i'd just do that one, but even that thins the one out too much. I have been told to do that so many times, but truth be told i have never used the amp in a live setting where it sounded boomy with all .022's. So i guess i should have left them alone. But i just wanted to know at what frequency that first coupling cap in the amp starts rolling off because it seems like i lost low mids.

[Andy Le Blanc]

You're right parallel the .01 with a .005 for the next gig.

[Jana]

The roll off point depends on the impedance of the other components associated with the cap. That is why when I suggested that you change the cap before your CF to .01 I also suggested to change the 68k too.

A capacitor has an impedance that changes depending on the frequency.

How that cap reacts in a circuit depends on the impedance of the rest of the circuit.

[iknowjohnny]

What is that top one? I can't tell....it looks like it says .06 but thats not a normal cap value.

[iknowjohnny]

I did change the 68k's, tho only to 100k because i didn't want any more gain. What i'd like to know tho is all things being equal, whats the difference between a .01 and a .022 as far as roll off.

[Jana]

The difference between .022 and .01 = .012

[martin manning]

I replaced the .022 coupler coming out of V1A with a .01 the other day. The gig i did last nite was good, but i think i should have left the .022. Where would the .01 start rolling off compared to the .022?

It's about half the size, so about 2x the frequency or one octave higher if you leave everything else alone.

[Andy Le Blanc]

If you know it gonna be a critical variable, put in something like this with a trim pot.

Give yourself a little control with a screw driver in stead of the iron.

The roll off is gonna change as the tube ages too, then you'll be going nutz
looking for the right tube.

[iknowjohnny]

The thing is, i can't really A/B it like that because it's really not at all apparent till i'm at a gig.(and i have with a switch) It sounded fine with the .01 at home. I can make all the changes i want based on what sounds best, but many things don't reveal what they will sound like till i'm at a gig. Coupling caps especially seem to always sound totally different in the band mix. In any case, i'm just going to put the .022 back in, as i have yet to have any issues with that value throughout the amp. I just wanted to know where the .01 rolls off compared to the .022 to see if it matches what i seemed to hear last nite, which seemed like it rolled off somewhere in the 400-500 Hz neighborhood where the .022 normally doesn't.

[Merlinb]

I just wanted to know where the .01 rolls off compared to the .022 to see if it matches what i seemed to hear last nite, which seemed like it rolled off somewhere in the 400-500 Hz neighborhood where the .022 normally doesn't.

If you changed nothing else then the .01s will roll off approximately one octave above the .022s (because they're about half as big. If you used .047 the roll off would be about one octave below the .022)
400Hz seems unlikely though.

[Structo]

I must have missed something.
Did you mention what amp this is you are using?