Blend pot...series wiring

[natbers78]

Hi, I have a passive Dingwall Super P5 and I've got plans that include adding a Dingwall FDV at the bridge, as well as a Nordstrand 3B. On Dingwalls with multiple pickup configurations, there is a rotary selector where one can choose bridge solo/bridge & neck series/bridge & neck parallel/neck solo.

In past Dingwalls I've had, I never really used the parallel setting on the rotary knob, so I'm thinking of having the neck and bridge wired in series, nixing the rotary knob, and just using an additional volume pot or a blend pot.

Are there any P/J users (or others) out there who have done away with a rotary selector in favor of a blend or additional volume pot? Would like to hear about it.
Also, when I searched this topic, I read that there might be some issues with my plan in terms of using a blend pot with the pickups in series. I'm not sure if that's only with the preamp engaged or what.

I'm not very knowledgeable in this area, so If anyone has experience with this and can speak to it, I'd certainly appreciate any feedback.

Thanks.

 

[bholder]

Blend knobs don't work (can't work) with pickups in series. Or separate volume knobs, for that matter. My question is how to wire it so that the blend knob is useful in parallel mode and harmless / bypassed in series.

 

[Killed_by_Death]

A blend must operate in parallel, there's just no other way (that I'm aware of).

Here's how to wire it in series with two independent volumes:

Jazz Bass Series Wiring - No Switch

 

[RobbieK]

A blend for coils in series... Hmmm... Surely this must be possible... I've never wired it, but I'll have a think.

I wonder if a single gang would work with the series connection wired to the wiper and the outer lugs at earth and hot. You'd probably need a w-taper pot though... That would be hard to find in 250K... Perhaps an dual gang A/C pot would work with the wipers connected.

Or have the resistances in series with the coils....

Just thinking out loud here... I might try some ideas out tomorrow and get back to you...

FWIW, if it works, I'd think the volume would swell slightly in the middle...

 

[bholder]

A blend for coils in series... Hmmm... Surely this must be possible... I've never wired it, but I'll have a think.

I wonder if a single gang would work with the series connection wired to the wiper and the outer lugs at earth and hot. You'd probably need a w-taper pot though... That would be hard to find in 250K... Perhaps an dual gang A/C pot would work with the wipers connected.

Or have the resistances in series with the coils....

Just thinking out loud here... I might try some ideas out tomorrow and get back to you...

FWIW, if it works, I'd think the volume would swell slightly in the middle...

The problem with this approach is that one volume (or half of the blend) will control the signal from one coil, but the other volume (or blend half) will control both coils together, no way around that with series wiring (as far as I know, would love to be proven wrong, but don't see how).

 

[RobbieK]

The problem with this approach is that one volume (or half of the blend) will control the signal from one coil, but the other volume (or blend half) will control both coils together, no way around that with series wiring (as far as I know, would love to be proven wrong, but don't see how).

OK I've had a chance to play around with this and it works just fine. I was over-thinking it (as usual!). There's no need for a W taper pot or two halves of an A/C pot in series or anything, a single gang 500K linear pot works quite well in my jazz (with traditional alnico single coils, 7.5k and 8.2k).

So if you wire a single-series-single switch, it looks like this:

So a pot in place of the switch looks like this:

I tried a few linear pots, then a few other ideas, but this is the simplest and seemed to work the best. Most of the change does happen towards each end of the pot's rotation, but not so abruptly that you can't adjust it. Plus of course, you get the slight volume boost with the pot in its middle range associated with the pickups being in series. But I've had an idea about that...

 

[RobbieK]

OK, I've tried out my idea. And it works OK.

When you connect the outer lugs of a linear pot together, the resistance between this and the wiper is 1/4 of the pot's value when the wiper is in the middle, and tapers to zero ohms at each end.

So this resistance can be used to attenuate the signal when the pot is in the middle (series), tapering to a short (no attenuation) at each end (for single coil).

Or, if you prefer...

This gives a nice smooth blend.



I really like this idea. This bass sounds much better with the pickups in series. I think I'll wire it in permanently but with a pull switch to have both pickups parallel and bypass the blend. Sort of a "bright" or "slap" switch...

 

[natbers78]

Cool! Great info. Thanks.

 

[fig]

I've been interested in the series passive volume solutions lately. walterw did a diagram that's quite promoted around here (the diagram in this thread, post #3). Killed_by_Death says it works great. I did an electrical schematic of that one for my use because I'm not good at seeing how things work with a wiring diagram...being simple minded and such. Thought I'd share:

Next, for a single control (vice dual volume controls) is a re-purposing of walterw's schematic. Essentially it's the same, but with both volume wiper arms mechanically linked together. Exactly what a dual decked blend pot does. The blend pot reference is the Bourns Dual MN Taper 500k pot. In operation, this turns down the pickup of your choice while leaving the other one at full volume. Equivalently, this should work like walterw's dual volume diagram with both starting at full volume (10) and turning down only one of the pickups:

RobbieK, I like, and will be trying, your idea.

I haven't had a chance to try any of these yet. Will be when life gets out of the way for a bit.

Anyway, was toying around, made some schematics, thought I'd post 'em.

 

[RobbieK]

I just used an old B500k dual gang from my junk box, but FWIW, I've seen these, complete with long thread and centre click, on ebay advertised as pickup "balance" pots. In fact they are pretty much useless for balancing pickups in the traditional, cris-cross wired way. (You need MN or A/C for this.) But for my posted diagram they would be perfect.

 

[Matteo Marziali]

Hello there!

View attachment 2993429

This idea remind me the Peavey mode/tone pot. You can find more info here: Chapter 5 - The Ancient Order of the Mystic Magnetic Pickup and here: US4164163A - Electric guitar circuitry - Google Patents
But the 2° coil will start working when the resistance of the pot is equal to coil resistance?

 

[fig]

A blend for coils in series... Hmmm... Surely this must be possible... I've never wired it, but I'll have a think.

I've been sick this holiday, mostly housebound and fevered, but I actually looked at this again the last few days.

So here's what my hazed brain came up with. It hasn't been eyeballed for accuracy, so please check for obvious boo-boos LOL. It's based off the shunt type volume control diagram that Killed_by_Death provided up thread. M/N style blend pot.

Series blend:

Parallel. I think this is the commonly used circuit:

I think the following might be good switchology to select between the two using a rather common 3P2T on-on switch.
Series switch positions:

Parallel switch positions:

Not sure if it works, don't have the parts around to test it, not sure switching between series and parallel is even practical. Thought I'd throw it out anyway 'cause it looks good on paper LOL.

I have some schematics with a regular volume control, too. Same thing as the blend, really. If there's no obvious boo-boos in the blend postings, I'll post the volume control schematics. Been busy while I've been sick LOL.

 

[Max3000]

I think the following might be good switchology to select between the two using a rather common 3P2T on-on switch.
Series switch positions:
View attachment 3644994
Parallel switch positions:
View attachment 3645015

I think you might run into a problem in the parallel. You have it wired sort of like the volume controls on a Les Paul, which is fine except that, on a Les Paul, if one volume is at zero, the whole guitar goes silent. That translates to silence here whenever the blend pot is at either extreme. I think if you trace it you get that at either extreme there’s a short (double check it). Obviously if you’ve implemented this already and it works then you can disregard. I was on a thread a couple years ago about this same blend-with-S/P-switch problem, I wonder if I can find it. I think we arrived at two possible solutions.