Caps amplitude dependent

The value of the resistance/impedance at that point can be important. R's combined with C's produce RC time constants which determine how frequencies are rolled off. You just changed some rolloff frequency by a factor of 25, I bet.

Tim.

Why did you change the capacitor in the first place? Was it broken?

It sounds as if there is something clipping. One cause could be that the new capacitor or something else is bad (such as shorted) so that the amplifier is running near one of the extremes of its swing.

Another thing that sounds a lot like clipping is if something is breaking down when the swing is large.

In the first foto, the yellow caps, the red cap and the small blue cap are ceramic; these have capacitance that change with voltage (and temperature). The top right large blue cap is the best. The small green cap in the second foto is acceptable.

I replaced the cap because all the action of the pot was at less than

10%. I thought by changing the cap I would move the cutoff point lower and allow the pot to function over a wider range. I suppose looking back on it I wired up the log pot backwards which was causing it to function wrong. The strange thing is, I measured the pot and it seemed linear so that shouldn't have happened. Or maybe it is linear but was just too large and I really needed a log pot properly wired. I'm not sure all of the things I've tried so I might have just got confused at some point. But when I used the 10k log pot I did try various possibilities and it seemed to work the best.

It might be clipping but it's not hard clipping and then some type of ringing going on. Maybe at that point there is inductance from the pickups that is forming some type of resonance? Obviously as you pick harder you do get higher frequency content but i do not ever remember it sounding like it does now.

What kinda cap is the large long blue one in the center middle?

It's called 'clipping' and means part of your signal chain can't cope with the output voltage of the pickups when plucked hard. It has NOTHING to do with capacitors.

Simple answer, turn the guitar volume knob down and the amp volume up. If that doesn't work, your gear is junk.

Graham

-- due to the hugely increased level of spam please make the obvious adjustment to my email address

output

doesn't

This works on junk, too.

to my email

-- Les Cargill

output

--- Tsk, tsk, tsk...

Being the audio guru you claim to be, one would think that the term "is the capacitance parametric?" would have floated by you at least once or twice.

No?

Here:

Since the capacitance of a capacitor goes inversely with the thickness of the dielectric, if the pressure exerted by the electric field between the plates causes the thickness of the dielectric to change, then the capacitance will vary as a function of voltage, and will be parametric.

Probably the best examples of that characteristic are ceramic capacitors with piezoelectric dielectrics like lead zirconate or lead zirconate titanate, where the huge dielectric constants of those compounds allow tiny decoupling capacitors to be made where the change in capacitance doesn't matter much.

For audio though...

---

doesn't

--- Hard to keep from saying that your "in depth" advice is junk, so I won't.

JF

th the output

citors.

Never use the high K ceramics in a filter if the swing is going to be largish. That is about the only case of a passive making enough distortion that you can hear it.

I think that if the OP really has a problem with a capacitor, it is shorted. Depending on the circuit, this could pull the bias point way off center but not all the way to the rail.

the output

capacitors.

You are correct that certain caps do have certain types of non-linearities but I don't see the point in bamboozling the OP with science that will clearly be over his head and irrrelevant to his problem. That's what audiophools are for.

Graham

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At Neve we had a simple rule rule. Never use even medium, never mind high K ceramic caps in circuits passing audio.

Graham

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