‘Simulating’ series wiring with capacitor- fishing for memories

[Eddododo]

Hey all- this will be a very hand-flapping struggle to convey, so bear with me if you will. I've been trying to find an old comment that I just can't seem to dig up.

I don't think it was here, but rather on talkbass, but I DO think it may have been @davidravenmoon .. but it's all very fuzzy.

The short version is that someone had referred to a simple capacitor arrangement, something like a single cap in parallel, that would more or less create the inductance characteristics that give such as would yield the sound of series-wired pickups out of parallel-wired pickups.
I hope I'm remembering enough that someone can point me in the right direction..

I believe the context of the conversation was the discussion of strategies for ameliorating the volume difference when switching series / parallel, and whomever, perhaps @davidravenmoon, suggested the capacitor arrangement in lieu of something like a trimpot tied to the series arrangement when switched


Hope this made enough sense to get some traction.. I was a very obsessed little diystomoboxes member for years and years but I've let a lot of cobwebs accumulate in the interim

Edit- I guess @ tagging usernames doesn't work how I expected either, lol

[Eddododo]

Okay, of course I found it 2 seconds later after looking for hours... I'll quote the talkbass post here, from a user micguy

I'd love to discuss the accuracy / merits of his ideas here.. it's of particular use to a bassist like myself

Micguy:
""""""The resonance (a large part of the sound of a passive electric bass) is the result of a poorly controlled system. The inductance of your pickups is part of it. The capacitance of the cable you use is part of it. The input impedance of your amp, DI box, preamp - whatever you plug into, is part of it. Vary one thing, and the sound changes. Maybe a lot, maybe a little. This results in all sorts of things - guys changing pickups to change their sound, hoping the next pickup will have that "magic". I'm an engineer/scientist by background, and like being able to predict and control things. The sound of my basses is no different to me.

If you wire humbucking pickups (say, a P bass pickup) in parallel, rather than in series, the impedance goes down - by a factor of 4. Many of us are familiar with the change in sound - it sounds "thin". But, it doesn't have to. What happens when you wire a pickup in parallel, and don't change anything else, is you move the resonance frequency of your bass/cable combo up in frequency. You don't have enough inductance to have the resonance where your ears like it. This can be fixed, however. All it takes is a capacitor.

When you wire the pickup in parallel, its impedance goes down by a factor of 4. If we lower the capacitive loading impedance by a factor of 4 (quadruple the capacitance), the system will behave like before - same resonance frequency. So, we add a capacitor in the bass - before the volume control.

What have we gained?

1) By lowering the impedance of our bass, we have made it less sensitive (by a lot) to cable variations - as we have 4 times as much capacitance, a little more or less doesn't change things as fast as before.

2) We have made it less sensitive to resistive loading variations - adding a DI box won't change the sound that much. In fact, the change from resistive loading variations can be compensated with the tone control.

3) The volume control won't affect the tone as much. When
you turn down the volume on a normal bass, you put resistance between your pickup and the cable capacitance, and the resonance goes away. The capacitor we add to the bass is before the tone control, so that resonance (while it shifts some) stays when you turn the volume down.

4) We have control over the sound of the bass - by changing the capacitor in the bass, we can change the sound of the bass. It's like changing pickups, but at a small fraction of the price, and we can move the resonance up or down at will.

5) The tone control will work over a wider range - it will go "up" and "down". A lot of bassists use their bass with the tone control full up a lot of the time. By lowering the impedance of the pickup, the tone circuit loading is less, and at the top of the control, it'll be brighter sounding. The sound they used to have at the top will be more in the middle of the range.

Drawbacks:

1) You have to turn the volume up on your amp a little, as you have less voltage at the output of your bass. If the circuit you're using is a decent one, you'll actually get less noise, as the impedance of the source (your bass) is much lower.

2) Doing this is more work than just changing pickups, and involves a little more understanding of what's going on. I measure the impedance of my pickups, and do circuit modelling so I can nail the sound I want in fewer tries.

OK, so I've talked/typed your ear off. What practical use is this to other folks?

As a first step, if you have humbucking pickups your don't like the sound of, don't throw them out. Try this instead:

1) Wire them in parallel. Yes, they'll sound thin. We can fix that.

2) Get a couple of capacitors - start with 1000pF and 2000pF. Solder the 1000pF across the volume control on your bass. that should change the sound towards "less thin". If you want to go further, try the 2000 pF cap. If that's still not enough, use both capacitors in parallel (3000pF).

OK, rant off, except for one question: Is anybody else doing this?

Micguy  """"

[Eddododo]

And later he commented in response
"Actually, you don't have to switch between series and parallel to get the difference in tone, if that's what you're after. Wire the bass in parallel, and switch in a capacitor as a load if you want to get the "series" tone. No change in volume, just in tone. That's part of the point of my original post - you can get whatever tone you want by loading down a parallel wired pickup capacitively, and you get the other benefits I talked about therE"

[Fancy Lime]

So far so true. Is there a question? I have implemented various variations of this idea in basses. One useful option is to install several caps and make them switchable. There is an online calculator that can be used to simulate this in simplified form:
http://sim.okawa-denshi.jp/en/RLClowkeisan.htm
Here, the resistor is the DC resistance of the pickup, the inductor is the inductance of the pickup, the cap is the cap (duh) plus the cable capacitance. The volume and tone pots as well as other parasitic resistances, inductances  and capacitances are ignored, which is usually good enough unless you use a very bad cable.

HTH,
Andy

[Eddododo]

So far so true. Is there a question? I have implemented various variations of this idea in basses. One useful option is to install several caps and make them switchable. There is an online calculator that can be used to simulate this in simplified form:
http://sim.okawa-denshi.jp/en/RLClowkeisan.htm
Here, the resistor is the DC resistance of the pickup, the inductor is the inductance of the pickup, the cap is the cap (duh) plus the cable capacitance. The volume and tone pots as well as other parasitic resistances, inductances  and capacitances are ignored, which is usually good enough unless you use a very bad cable.

HTH,
Andy

Haha there 'was' a question before I immediately found the post again, but I figured I'd share and discuss after that.

That's generally my plan.. I'm a sucker for switched options on my bass anyway, and having a quasi-series switch without the volume bump is pretty great.

[Dormammu]

There is a lot of mythology around pickups, which only distracts from the main thing (playing music). In most cases with different pickups, I hear only a difference in the output. With a million options today, you can produce any sound from any pickup.