Shared tone filter cap??

[BigSteve]

Just a quick question. I use different value tone caps to change the roll off response. I'll switch .047 for .022, or vice versa, or just play around with different values and different configurations until I like what I hear.

Looking at the diagrams on the SD web site, I noticed they use a shared filter cap for both tone pots. Caps are cheap, so why not use independent filter caps? Is there an advantage to sharing a cap when using single coils or stacks? Other than having them connected to the exact same capacitance rather than two caps which, although they are the same value, vary within tolerance, electrically they look the same.

[PFDarkside]

Re: Shared tone filter cap??

It's a carryover from the Fender design which was all about cost. You can absolutely use two different caps for different roll off values. Be aware that if you do add two independent tone circuits to the same path (so either tone pot affects a single pickup) you'll get more impedance loading due to the additional pot. It might be worth experimenting with different (higher) value pots at the same time if this is the case. In the example of a Gibson type vol/tone arrangement, there's no reason not to use the value you want for each pickup.

[DreX]

Re: Shared tone filter cap??

Yes, independent caps are fine.

[BigSteve]

Re: Shared tone filter cap??

[QUOTE=PFDarkside; ..........you'll get more impedance loading due to the additional pot. [/QUOTE]

Thanks for the reply.

I'm not talking about adding any additional resistance to the circuit. The tone circuit already has two pots in parallel, making their effective resistance equal to 1/(1/R1+1/R2), which would vary depending on the degree of rotation. My understanding is that impedance is roughly equal to the voltage drop across the load divided by the current passing through it, and this would vary depending upon the frequency at which it was measured. All this makes for a very dynamic system.

Would the addition of a .022µf cap change the current flow enough to significantly effect the total impedance of the system? Would this negatively effect tone?

[DreX]

Re: Shared tone filter cap??

Would the addition of a .022µf cap change the current flow enough to significantly effect the total impedance of the system? Would this negatively effect tone?

Without knowing 100% what you're saying, I'm nevertheless confident the answer is no.

[BigSteve]

Re: Shared tone filter cap??

Without knowing 100% what you're saying, I'm nevertheless confident the answer is no.

Yeah, me too. This thread got a little deeper than I intended. I was just wondering if there was a reason SD diagrams used the shared filter cap AND uses two different wiring configurations for the pots. Seems a little strange.

Anyway, thanks for replying.

[DreX]

Re: Shared tone filter cap??

What are the two different wiring configurations you're referring to?

[uOpt]

Re: Shared tone filter cap??

With both pickups on with the pots full open you would have double capacitance.

[frankfalbo]

Re: Shared tone filter cap??

If you're referring to the vintage Strat diagrams, the cap is wired that way simply because that's what Leo Fender did. He used one cap, and sent the signal through one or both pots depending on the switch position.

What I can't tell is whether you're asking what if you made 2 tone pots, with different cap values, and left them both hot for all switch positions, or whether you just mean to have one cap value for the neck pickup and one for the middle pickup. That would work fine, and only the n/m position would have both capacitors. But that's a parallel single coil signal, so the impedance drops and the peak frequencies go up. So having the 2 caps is pretty insignificant. If you'd like to use two different values, it'll be fine.

[BigSteve]

Re: Shared tone filter cap??

What are the two different wiring configurations you're referring to?

One has the circuit input at the wiper (middle terminal) and the filter tied to the end of the resistance, as I have always done. The other has the input at at the resistor and the filter tied to the wiper. Electrically equivalent, just sloppy. Having worked 16 years for a military electronics contractor, that sort of rubs me the wrong way.

[BigSteve]

Re: Shared tone filter cap??

....... or whether you just mean to have one cap value for the neck pickup and one for the middle pickup. That would work fine, and only the n/m position would have both capacitors. But that's a parallel single coil signal, so the impedance drops and the peak frequencies go up. So having the 2 caps is pretty insignificant. If you'd like to use two different values, it'll be fine.

That's exactly what I'm talking about. I wasn't really looking for guidance about whether or not to use multiple caps or their values. After looking at the diagrams, I was just wondering if there was some supposed "Singe Coil Mystique" regarding sharing a filter cap.

Thanks to all for you time and replies.