two pickups + master vol + master tone + blend knob setup

[fredj]

Hi folks,

I'm looking to wire two single coil pickups with the following setup:

• master volume
• master tone
• blend knob w/ center indent

In addition, I'd like the two pickups to blend in parallel by default, but to blend in series when a push pull or push push pot is activated.

I found this very informative post here on this site discussing the different merits of various blend knob setups Link here and it seems like if I want a blend knob that (i) has 100% output at the center, and (ii) a good sweep that isn't just around the center indent, that I'd need to use a setup similar to the one woodstockwizzard used in the link above (wiring diagram snipped below).

Could someone please help provide me with a wiring diagram for this setup and tell me which parts I need to use? Seems like there's a bunch of various types of blend pots, etc. so want to make sure I use the right parts.



For pot values, I'd want 500k or 300k pots. Not sure if I'd need capacitors or of what kind.

Thank you!

[fredj]

Bump any chance anyone can help on this one?

Yogi B perhaps?

[stevewf]

Howdy. I'll bet this forum can help you, eventually.

But first, quick: do you have center-tap potentiometers? Those aren't easy to get!

[newey]

Nov 17, 2024 23:55:42 GMT -5 stevewf said:

But first, quick: do you have center-tap potentiometers? Those aren't easy to get!

If you're looking for these, the nomenclature is "center detent".

As to the "right type" of blend pot, this is required reading: Blend and Pan Pots

[Yogi B]

Nov 18, 2024 8:39:22 GMT -5 newey said:

Nov 17, 2024 23:55:42 GMT -5 stevewf said:

But first, quick: do you have center-tap potentiometers? Those aren't easy to get!

If you're looking for these, the nomenclature is "center detent".

No, woodstockwizzard's scheme uses pots with a fourth terminal: an actual centre-tap in the middle of the potentiometer's resistive trace (this is a workaround for there not being 'half-logarithmic' pots in the style of the 'half-linear' M/N-taper 'true blend' pots).

These, in general, are pretty rare — and I don't think I've ever seen a one of these preconfigured as a log/anti-log pair as you'd want for W.W.'s scheme. Most commonly you'll find either: linear taper centre-tapped pots; or logarithmic taper pots with an offset tap at 60% rather the centre, for a so-called loudness control — and generally all of them in values too low for use in a passive guitar.

Sporadically you might find someone randomly selling a NOS part from their stash which fits the bill, but these by Peavey are the only relatively suitable one ones I've found that are routinely available. But they'd still need a lot of work: buying two, plus a suitable dual gang pot; trimming the terminals on the Peavey wafers into something usable; adding cutaways to the body of the donor dual-gang so as not to short the connection to the centre-tap terminal.

Honestly it seems like not much more work to mod an existing A/C-taper blend pot with conductive paint and/or 'stitching' a wire across half the wafer similar to this video adding a centre-tap to a regular pot, but recalling that in our case a an actual centre-tap isn't the end goal, we just want as close to zero ohms across the entire 'first' half of each wafer.

All that being said though...

Nov 14, 2024 12:12:10 GMT -5 fredj said:

In addition, I'd like the two pickups to blend in parallel by default, but to blend in series when a push pull or push push pot is activated.

Unfortunately, there really is no good way to achieve 'bidirectional' blending in both series & parallel using only one pot. Trying to that solve problem is part of the reason why my blending post is still unfinished.

The reason being that parallel blending ideally wants a reverse-log taper whereas series blending wants either a linear or log taper depending on the variation used. Obviously you don't have to use the ideal taper, but then you have to live with the blend pot acting more like a switch than a smooth blend in one (or, in the worst case, both) of the modes.

At that point it might be better to have the blend work in parallel only and have the push/pull bypass it to give both pickups in series regardless of the blend pot position (or vice-versa: blend in series, bypass for both in parallel). Another option might be to have separate blend controls, one for series mode & one for parallel mode.

---

It is possible to do a reasonable job of series/parallel 'unidirectional' blending (where one end of a blend pot selects a single pickup & the other end of rotation blends in both) using an A/C taper dual-gang pot, a 3PDT to swap between series & parallel, and a 4PDT to switch which is the 'main' pickup. However, doing the same the same with 'bidirectional' blending (i.e. what you want, with alternate pickups at the extremes and both at the centre) is more complex. I can't think of a way that would give a good sweep in both series & parallel without at least a three- (or four-) gang pot, each gang using a different (and for ideal behaviour, sometimes non-standard) taper.

The final potential alternative I'll mention is a blend pot that goes both in series / a single pickup / both in parallel, with a 4PDT to switch which pickup is selected in the centre. Again, this would require pulling a few pots apart namely you'd want to replace one of the wafers of a M/N blend pot with a modded W-taper wafer that's got a trace cut near the centre of its resistive track.

[fredj]

Nov 18, 2024 8:39:22 GMT -5 newey said:

Nov 17, 2024 23:55:42 GMT -5 stevewf said:

But first, quick: do you have center-tap potentiometers? Those aren't easy to get!

If you're looking for these, the nomenclature is "center detent".

As to the "right type" of blend pot, this is required reading: Blend and Pan Pots

This is helpful reading, thank you. Would the following pot work? I don't believe it has a center indent, but I believe is the appropriate type of pot. If I'm not mistaken, center indents can be added after the fact based on yogi's post?

darrenriley.com/homepage/fender-500k-pan-alpha-potentiometer-0056097000/

Yogi B, this was a very informative post, thank you. I think to make things easier, perhaps I just have one blend pot that blends in parallel, and then a push / pull switch that puts the pickups in series with no blend. I could alternatively just add a fourth knob to also blend the pickups when the series mode is engaged, but I'm wondering if the juice will be worth the squeeze. I've never had the opportunity to observe or test a blend between two pickups in series. Any thoughts on the usability / variability of the tones in that mode?