What cap value....

[daz]

.....would i want to put in series with my LP's neck pickup to start rolling off low just after 100Hz?

[mozz]

I have to ask why. If it's muddy lower the low side.

https://www.digikey.com/en/resources...gh-pass-filter

1600pf into 1 meg will start at 99hz.

EDIT: don't know why i figured 1meg, so 3200pf into 500k is right as said below.

[daz]

mud, and no, p/u height, pole height, amp settings, nothing works.I've done it all. This works but i just wanna cut it past 100hz where lows are of zero value and only add mud.

[pdf64]

3n2F with a 500k volume pot

[daz]

3n2F with a 500k volume pot

Thanks. Thats .032 MF? Will .033 (common value) make any notible difference?

[Chuck H]

Nope. 3n2 equates to 3200p. 3300p is the closest "standard value". Try 2200p and see how it goes. if it cuts too much lows try the 3300p. If that doesn't cut enough you'll need to combine caps in series or parallel to get a value in between.

[daz]

Nope. 3n2 equates to 3200p. 3300p is the closest "standard value". Try 2200p and see how it goes. if it cuts too much lows try the 3300p. If that doesn't cut enough you'll need to combine caps in series or parallel to get a value in between.

Ahh. ok. I have a 2200pf so i'll try it. Seems awfull tho.

[Chuck H]

Ahh. ok. I have a 2200pf so i'll try it. Seems awfull tho.

I know indicating values in pF "seems" awful, but it's all about impedances. The value is also dependent on series resistance so things change if you use the guitars volume control. So be prepared for that to happen. lowering gain with the guitars volume will actually lower the frequency knee of the cap. This might actually be beneficial since lower gain tones allow for more low end without mud. Hope springs eternal

[Helmholtz]

It's a high pass filter essentially consisting of the series cap and the following AC resistance load.
This load results from paralleling the resistances of Vol. pot, Tone pot and amp input impedance.
For a typical LP this results in about 200k total.
A 6.8nF cap would give a corner frequency of 117Hz.

The load as seen from the cap won't change much (20% max.) with vol. settings - except if 50s wiring is used.

[Chuck H]

It's a high pass filter essentially consisting of the series cap and the following AC resistance load.
This load results from paralleling the resistances of Vol. pot, Tone pot and amp input impedance.
For a typical LP this results in about 200k total.
A 6.8nF cap would give a corner frequency of 117Hz.

The load as seen from the cap won't change much (20% max.) with vol. settings - except if 50s wiring is used.

6.8n sounds more like what I would expect actually. I do trust your calculation above but I'm off to run some CAD simulations

[Chuck H]

Ok... In the simulation there's a slope all the way to 950Hz. So the visible "knee" does seem to be as Helmholtz says but is actually down about 4.5dB at 100Hz. For -3dB at 100Hz my simulation shows a 8200p (8.2n) cap would be ideal. At any rate I think a 6.8 should be fine for what daz wants.

[Helmholtz]

Simple RC filters never have a sharp corner. At half the "corner" frequency, so around 50Hz there will still be a signal level of 50% (-6dB).
8.2nF would give 97Hz with my simple model.

[mozz]

Does the cable capacitance come in to play, or only when volume is full?

[Helmholtz]

Does the cable capacitance come in to play, or only when volume is full?

Cable capacitance affects high frequencies only.

[mozz]

Right, wasn't thinking, it's in parallel.
Moveable, adjustable bandpass filter would be the ticket. Not so easily made though.