Change a pickup's resonant frequency and tone with a loading capacitor

[fermata]

Is all this very much different than what a tonestyler does, or just attaching a bunch of different capacitors to a rotary switch and selecting the one you want that way?

I think it is different but I could and can be wrong.

It is different. Sort of. The small-value caps used as loading capacitors aren't about treble roll-off, in the way what we would typically think of a 'tone cap.' Small loading caps are about shifting the resonant frequency of the pickup. (Think of them as 'pickup swap' caps.)

For example, I had a single-pickup bass with a volume control and a tone control (pot + .047 uF capacitor), the standard thing, like a P-bass. I added a loading cap on a switch (.002 uF); in the 'off' position, the bass was electrically stock; in the 'on' position, that little cap shifted the pickup's resonant frequency down, resulting in a different tone. In either switch position, I could still use the volume and tone controls as usual. In other words, the loading cap fundamentally changed the tonal character of the instrument (much like swapping pickups); the normal tone and volume controls were downstream from that 'fundamental' effect.

On another bass, with a MM-position pickup, I added a .001 uF cap where the pickup connected to the volume control, and I got the extra bit of low mid oomph I was looking for. This time, the loading cap wasn't on a switch, so the character change was built-in. Again, there were also downstream volume and tone controls.

This kind of thing is doable with a ToneStyler arrangement. On a six-position switch, one could have something like: no cap, .001, .002, .005, .022, .047. The .001 - .005 uF caps would behave like loading caps; the .022 and .047 would offer the sounds of a typical tone control turned to 0.

Of course, there's not really a value range that equals 'loading cap' and a value range that equals 'tone (control) cap.' It's a spectrum. But values above about .005 uF add so much capacitance to the circuit that they create a tonal response that's quite different from the small value caps, so that's why I would draw a semantic distinction between 'loading caps' and 'tone caps.'

 

[DJ Bebop]

It is different. Sort of. The small-value caps used as loading capacitors aren't about treble roll-off, in the way what we would typically think of a 'tone cap.' Small loading caps are about shifting the resonant frequency of the pickup. (Think of them as 'pickup swap' caps.)

For example, I had a single-pickup bass with a volume control and a tone control (pot + .047 uF capacitor), the standard thing, like a P-bass. I added a loading cap on a switch (.002 uF); in the 'off' position, the bass was electrically stock; in the 'on' position, that little cap shifted the pickup's resonant frequency down, resulting in a different tone. In either switch position, I could still use the volume and tone controls as usual. In other words, the loading cap fundamentally changed the tonal character of the instrument (much like swapping pickups); the normal tone and volume controls were downstream from that 'fundamental' effect.

This kind of thing is doable with a ToneStyler arrangement. On a six-position switch, one could have something like: no cap, .001, .002, .005, .022, .047. The .001 - .005 uF caps would behave like loading caps; the .022 and .047 would offer the sounds of a typical tone control turned to 0.

Of course, there's not really a value range that equals 'loading cap' and a value range that equals 'tone (control) cap.' It's a spectrum. But values above about .005 uF add so much capacitance to the circuit that they create a tonal response that's quite different from the small value caps, so that's why I would draw a semantic distinction between 'loading caps' and 'tone caps.'

 

[Jazz Ad]

It's an excellent way to alter your tone but it's hardly a novelty or the elusive "secret pickup makers wouldn't want you to know".
Back from the Gibson EB-3, through Aria SB or Bill Lawrence Q system to Villex, it's hardly a secret at all.

It has its downsides though. Energy as to come from somewhere and with passive electronics, a boost can only happen at the expense of a cut somewhere else. On bass typically you get rid of a bit of highs to get a mid hump to alter the resonant frequency.
Some pedals, fuzz mostly absolutely hate dramatic changes in impedance or resonant frequency and behave badly when you alter them, delivering artifacts and a difficulty to get the same output twice.

I think it never became very common because it's way easier to use a preamp with an EQ to achieve this kind of result.

 

[fermata]

It's an excellent way to alter your tone but it's hardly a novelty or the elusive "secret pickup makers wouldn't want you to know".
Back from the Gibson EB-3, through Aria SB or Bill Lawrence Q system to Villex, it's hardly a secret at all.

It has its downsides though. Energy as to come from somewhere and with passive electronics, a boost can only happen at the expense of a cut somewhere else. On bass typically you get rid of a bit of highs to get a mid hump to alter the resonant frequency.

You'll have to forgive a bit of creative license! I learned about loading caps from G&L circuits (the L-1000 uses one, I think), so no, it's not a secret -- at least not to electrical engineers/instrument designers. But I would wager it's less well-known among non-professionals.

Good point about energy coming from somewhere. Yes, a loading cap does result in less open or full-range response, but in the cases where I've used them, that was part of the desired effect. Despite -- or maybe because of -- their quirks and limitations, passive systems have their own charms.

 

[SteveCS]

It is different. Sort of. The small-value caps used as loading capacitors aren't about treble roll-off, in the way what we would typically think of a 'tone cap.' Small loading caps are about shifting the resonant frequency of the pickup. (Think of them as 'pickup swap' caps.)

Electrically the function is the same, and the formula for the filter circuit is the same. You cannot change the resonant frequency, or any other characteristic of the pickup in isolation - it is the resonance of the filter circuit as a whole which gets changed. Just like a regular tone control with the knob rolled right back.

 

[spatters]

Back from the Gibson EB-3, through Aria SB or Bill Lawrence Q system to Villex, it's hardly a secret at all.

I'm not sure about the others, but the Bill Lawrence Q-filter is quite different. It involves a very large inductor, comparable to the inductance of the pickup itself, connected where the tone cap would normally go. AAnd it results in a different frequency response: dialing it into the circuit not only moves the resonant peak, it dramatically raises the peak as well. (Strictly speaking, it lowers the frequencies below the resonant peak.)

I frequently find myself using a Q-filter instead of the volume knob. Traditional volume controls become darker and muddier as volume drops...but the Q-filter gets more of a sparkly single-coil Strat sound as volume drops, which is much more musically useful.

Thread derail over. Thanks to @micguy for the post, and @fermata for bringing it to greater attention! This, in particular, is gold:

One more note, it's easy to test out different capacitor values without popping the hood (keep the volume and tone controls at 10): unscrew the barrel of the instrument cable where it plugs into the bass; attach one alligator clip lead to the cable's hot tab; attach another clip lead to the ground tab; clip a capacitor between the free ends of the clip leads to hear how it affects the tone; try different values and then hardwire in the one you like.

 

[mrperkolator]

subbed. I've read where the comments OP mentioned came from. Good reads.

 

[Tim Skaggs]

This was a legitimate question, for those of you that might know the answer. I have a tonestyler kicking around and thinking about giving it a try

From @micguy ‘s description copied into the original post by @fermata , he’s calculating the induction change when switching a pickup from parallel to series, and adding a cap to approximate the same reduction in high end. That eliminates the jump in output that happens when switching to series, but yields the same tonal change.

To answer your question, a Tonestyler can / will do very much the same thing, but there might not be cap in any position of the Tonestyler that has a value as specific as micguy describes. I have a “home made” Tonestyler for which I selected the caps. It’s in a P-bass as my tone control, but I don’t have the pickup in that bass set up to switch between parallel & series, so the caps I selected are just for different amounts of high end roll off.

When I built my rotary cap selector, I read some info about the Tonestyler, and I *think* I recall seeing that the Tonestyler also has some resistors in play, but those might just be for preventing cap discharge pops when switching between caps.

The difference in a cap selector vs. a pot with a single cap is that individual caps of selected values will take a very narrow bandwidth of high frequency “off the top” of the pickup’s output without affecting the high mids & mids. As you begin turning down a common tone control on a bass, (if it has the stock value cap, usually around 0.047uF) you are attenuating a very broad range of frequencies starting at the very highest and extending down into the midrange. You do have control on how much that broad range is attenuated with the pot, but I like the ability to cut the very high end without affecting the midrange much, if any.

 

[sunbeast]

This was a legitimate question, for those of you that might know the answer. I have a tonestyler kicking around and thinking about giving it a try

To clarify what others have said a bit- it is the same function (a Tonestyler is also just a bunch of capacitors to ground), but only the first few options on some of the more extended Tonestylers (like the 10 position? if they still make that) really fit into the general range talked about here. In fact a guitar-spec Tonestyler would probably be a better one to try for these kinds of tones as the values are all a bit smaller. Still fundamentally the Tonestyler is doing the exact same thing just with some much deeper resonances than would be typical from a pickup soloed.

 

[600 Ohms]

I own one of [Invalid or Expired Link Removed]. Is this essentially doing the same thing?

 

[micguy]

26234120[/URL], member: 210613"]I own one of [Invalid or Expired Link Removed]. Is this essentially doing the same thing?

it kinda is, but not quite. The proper place for a load capacitor is before the volume control. That device places it after the volume control- at full volume, the two act the same, but at less than full volume, that device will not work the same as a loading cap in the right place.

 

[DarkStar90]

it kinda is, but not quite. The proper place for a load capacitor is before the volume control. That device places it after the volume control- at full volume, the two act the same, but at less than full volume, that device will not work the same as a loading cap in the right place.

Makes for an easy install on a jazz bass, as I usually keep at least one of the volumes full up. Could put a cap on a three way switch, with a clipping diode on one of the positions for some fun. Wired to the jack.

With a 0.0039uf cap, the jazz bass neck pickup sounds a lot like a precision pickup.

Will pot values affect the capacitor value? ie 250k vs 500k

 

[micguy]

Makes for an easy install on a jazz bass, as I usually keep at least one of the volumes full up. Could put a cap on a three way switch, with a clipping diode on one of the positions for some fun. Wired to the jack.

With a 0.0039uf cap, the jazz bass neck pickup sounds a lot like a precision pickup.

Will pot values affect the capacitor value? ie 250k vs 500k

Pot values, so long as both volumes are at fulll, only affect damping of the resonant peak- the rolloff in the treble above that doesn’t change with the pot value.

When you turn the volume to less than full, things change. In a VVT circuit especially. I have basses with 2 pickups, but NONE with a VVT setup - not even close to something I find usable. Some folks disagree, and that’s OK.

 

[DarkStar90]

Pot values, so long as both volumes are at fulll, only affect damping of the resonant peak- the rolloff in the treble above that doesn’t change with the pot value.

When you turn the volume to less than full, things change. In a VVT circuit especially. I have basses with 2 pickups, but NONE with a VVT setup - not even close to something I find usable. Some folks disagree, and that’s OK.

Ok thats cool. For me with a vvt setup, one of the volumes is on full of not both. I've tried it and it works fine for me.

 

[micguy]

I've tried it and it works fine for me.

That’s success. I will refrain from trying to make you think the way I do, as that’d be a setback for you….;-)

 

[lark_z]

Great thread and very timely for me. Ripping into the dumpster special in a few days to reshield it. I've never been that happy with the pickup, finding it a bit too shrill (trebly). It's a Wilkinson MWPB (P-bass ceramic) with "standard" wiring (250K pots and 0.047 uF cap). I don't want to start throwing money at it by going down the pickup swapping vortex.

Anyway, just got out the electronics box and used the hint to short across an instrument cable with several caps. The 0.01 uF sounds interesting. Takes just a bit of the upper edge off. I'll solder it in while I have the beast opened up.

[EDIT] Glad I re-checked it with the amp without headphones. 0.01 uF is too much. I found one 'old-maid' ceramic capacitor loose in the bottom of the capacitor bag that sounds pretty good. Some time with a magnifier and Google and it seems to be a 0.0047uF. Upper end of what it seems is recommended and my ears would agree. [/EDIT]

Thanks!

 

[lark_z]

Wow - I just had a strong desire for Radio Shack to be back in business. Having to order $20 of "stuff" to get one $0.16 capacitor (0.0022 uF). I guess I'll just install the 0.0047 one that I have first.

 

[micguy]

Wow - I just had a strong desire for Radio Shack to be back in business. Having to order $20 of "stuff" to get one $0.16 capacitor (0.0022 uF). I guess I'll just install the 0.0047 one that I have first.

Mouser is a good source - no minimum order, but you do pay for shipping.

 

[Dave TB Killer]

Wow - I just had a strong desire for Radio Shack to be back in business. Having to order $20 of "stuff" to get one $0.16 capacitor (0.0022 uF). I guess I'll just install the 0.0047 one that I have first.

Check Amazon and eBay. Sometimes you can find smaller packe of these.

 

[DarkStar90]

Wow - I just had a strong desire for Radio Shack to be back in business. Having to order $20 of "stuff" to get one $0.16 capacitor (0.0022 uF). I guess I'll just install the 0.0047 one that I have first.

If you have a second .0047uf cap, connect the two in series with eachother for .0023uf, close enough to a .0022uf. FWIW, .0022 made little difference for me on my pbass. Took off some of the edge, but a .0039 had bit more mid bump which I liked, so I've gone with that.