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What do different capacitors do?

rainbowreality

rainbowreality

Guest
May 28, 2013
48
0
#1
This is probably a dumb question but I'm a newbie to modifying bass guitars (and playing them!)

I've hooked up a dpdt switch with 2 capacitors - one 0.1 and one 0.068. The switch outputs go to tone pot.

My question is why I am I not hearing any difference in tone when I switch over the caps? Sounds exactly the same, or does it have more subtle effect?

Any words of wisdom would be appreciated!
 
#3
I think therefore the difference in value is too small. The bigger the capacitor's value, the darker the tone gets. Replace the 0.068 by a 0.022, and you'll hear a difference, but I guess both are a bit too heavy.

This is the "tone-switch" as found on gretsch guitars, it gives you an idea of the values they use, and the big difference between the two.

gretschtonesw.png
 
#6
The cap does two things. A pickup's frequency response starts with a gentle bass rolloff, and then is fairly flat, until the resonant peak of the pickup. Here there is a steep peak, followed by a pretty rapid high end rolloff.

The resonant peak of a pickup is largely responsible for the characteristic tone of a pickup. The peak for bass pickups is somewhere between 1.5k and 6k...usually around 4-6k.

A cap will move the resonant peak lower which will also lower where the treble rolloff starts. The typical caps used in a bass are between .022uf and .1uf with .047uF being very common. These have too much of a sledgehammer effect for me, moving the peak too low, and making the tone too muddy.

With smaller caps, things can really get interesting. Smaller caps will move the peak more into the midrange, and leave enough range to maintain some clarity.

The Tonestyler does this, using a sequence of small to larger caps where you can clearly hear the movement of the resonant peak.

If you have a switch picking two caps, try one at .047uf, which is pretty standard, and for the other try .01uF. The .01uF will make you think you have a different pickup. The tone will get punchier, not muddier.

Or replace the tone control with a 6 position switch, leave the top terminal open (bypassed) and then wire 5 different caps on the other positions. I'd start with 333pF or 470pf, and then increase up to .022uF or .047uF. (actually, I'd probably to 333pf to .01uF.)

There are lots of things that affect a pickup's resonant peak. The size of the volume control for instance. A larger pot will smooth the peak, while a smaller pot will make it more prominent. Caps also have resistance and the resistance of a cap will change tone. A high resistance cap will sound different than a low resistance cap, taking two different caps of the same capacitance but different construction.
 
#7
Sounds to me like the 0.1uF has a low value and the 0.068uF has a high value. Remember that those are only ratings, and actual capacitance falls within the tolerance specified for the caps. For instance, 20% 0.068uF capacitors can be anywhere from 0.0544uF to 0.0816uF. And 20% 0.1uF capacitors can be anywhere from 0.08uF to 0.12uF. A lot of film capacitors are 5%, ceramics can be as bad as 80%. Depending on what you have, your capacitors could be close in value.
 
#8
To answer the original question, different cap values filter out different frequencies. So the other answers about them being too close in value would mean that the frequencies being filtered are too similar to hear any difference.
 
#9
Cheers for all this info, it's really helping me!

The 0.1 is an orange drop but the other is just the factory standard. I was thinking of swapping them for some cheap military grade ones off ebay or ones with 0.1% tolerance rate. Would that keep the values sufficiently apart?

I like the idea of the multiple caps rotary switch but I'll have to see if I can fit it in (just the switch and 2 caps was a bit of a struggle).

I'm also playing round with volume/tone pots configuration. Originally they were all 500k linear expect the tone pot which is a linear d500k (I've read they have a sharper curve). All of them mini. I swapped them all for full size CTS linear 500k but the tone became a really narrow working range but good volume range. I've now swapped the tone back to the original d pot and the others to alpha mini audio 500k. Now the volume range isn't as great but the tone range is nice.

Next I'm going to try the CTS linear volume back and keep the d500k linear. Trouble is I don't know where you can get more d pots when that one goes!

I'm hoping that configuration will give me a smooth volume and tone!
 
#14
rainbowreality said:
Cheers for all this info, it's really helping me!

The 0.1 is an orange drop but the other is just the factory standard. I was thinking of swapping them for some cheap military grade ones off ebay or ones with 0.1% tolerance rate. Would that keep the values sufficiently apart?

I like the idea of the multiple caps rotary switch but I'll have to see if I can fit it in (just the switch and 2 caps was a bit of a struggle).

I'm also playing round with volume/tone pots configuration. Originally they were all 500k linear expect the tone pot which is a linear d500k (I've read they have a sharper curve). All of them mini. I swapped them all for full size CTS linear 500k but the tone became a really narrow working range but good volume range. I've now swapped the tone back to the original d pot and the others to alpha mini audio 500k. Now the volume range isn't as great but the tone range is nice.

Next I'm going to try the CTS linear volume back and keep the d500k linear. Trouble is I don't know where you can get more d pots when that one goes!

I'm hoping that configuration will give me a smooth volume and tone!
Click to expand...

You are really homing in on the answer here. What you want is CTS linear 500k for volume and CTS 500k "audio taper" for tone. This will give the widest control range for both. The size of the pot has nothing to do with it. It's about the pot "taper" which usually has to be figured out from the numbers on the pot (usually like an A or B on the end) or by what you ordered in the first place.

By the way, my favorite Jazz bass tone caps is a switch that does .047 (factory original) and 0.015 which isn't as heavy a roll off but still not a huge difference. Then my switch also has an "off" position to set the bass as bright as it goes. (no cap). I love it. Just try values yourself. Radio shack caps are cheap and easy to try different values.

A hint from my experience is that you should try a tone value(s) and then play the bass in situations for a while. It often takes a while for one to get your head around if the value is doing something you like or not. Which is how I came to figure my "standard" values.
 
#16
markjo said:
The guitar capacitor is a high pass filter. It obstructs low frequency signal, and permits high frequencies to pass, thus high pass. The frequency cutoff is determined by the value of the capacitor.
Click to expand...

Actually, it does the opposite. Since the capacitor is parallel to the signal path, the passed high frequencies see a decrease in output impedance, and are thus "blocked" from reaching the output. And since low frequencies are blocked by the capacitor, the capacitor has little affect on the circuit at low frequencies, so they are "passed" to the output. A tone control is a low pass filter, not a high pass filter.
 
#18
Steve Dallman said:
The cap does two things. A pickup's frequency response starts with a gentle bass rolloff, and then is fairly flat, until the resonant peak of the pickup. Here there is a steep peak, followed by a pretty rapid high end rolloff.

The resonant peak of a pickup is largely responsible for the characteristic tone of a pickup. The peak for bass pickups is somewhere between 1.5k and 6k...usually around 4-6k.

A cap will move the resonant peak lower which will also lower where the treble rolloff starts. The typical caps used in a bass are between .022uf and .1uf with .047uF being very common. These have too much of a sledgehammer effect for me, moving the peak too low, and making the tone too muddy.

With smaller caps, things can really get interesting. Smaller caps will move the peak more into the midrange, and leave enough range to maintain some clarity.

The Tonestyler does this, using a sequence of small to larger caps where you can clearly hear the movement of the resonant peak.

If you have a switch picking two caps, try one at .047uf, which is pretty standard, and for the other try .01uF. The .01uF will make you think you have a different pickup. The tone will get punchier, not muddier.

Or replace the tone control with a 6 position switch, leave the top terminal open (bypassed) and then wire 5 different caps on the other positions. I'd start with 333pF or 470pf, and then increase up to .022uF or .047uF. (actually, I'd probably to 333pf to .01uF.)

There are lots of things that affect a pickup's resonant peak. The size of the volume control for instance. A larger pot will smooth the peak, while a smaller pot will make it more prominent. Caps also have resistance and the resistance of a cap will change tone. A high resistance cap will sound different than a low resistance cap, taking two different caps of the same capacitance but different construction.
Click to expand...

You have my vote for the best, and more through answer to this question. I've also struggled to understand exactly how different caps effect tone.

A+
 
#19
Something's wrong if a .1 and a .068 cap sound the same (unless both caps are way out of spec in opposite directions).

Maybe you have it wired so both caps are on all the time in both positions? Does it sound very bassy, as in .168uF bassy?
 
#20
line6man said:
Actually, it does the opposite. Since the capacitor is parallel to the signal path, the passed high frequencies see a decrease in output impedance, and are thus "blocked" from reaching the output. And since low frequencies are blocked by the capacitor, the capacitor has little affect on the circuit at low frequencies, so they are "passed" to the output. A tone control is a low pass filter, not a high pass filter.
Click to expand...
Components are either in series or shunt position. Don't know which of those "parallel" is supposed to be.
A series capacitor acts as a high pass filter (blocks low frequencies).
A shunt capacitor acts as a low pass filter (bleeds off high frequencies).
 

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