Using a crossover to blend two pickups?

[dNA]

This is a random thought that crossed my mind once a long time ago and just occurred to me again now.
I've never much cared for the middle position setting on a two-humbucker electric guitar. I mean, it's not totally useless. but it was always one of those things where I felt like it grabbed the negative qualities of each pickup - the lows are kinda loose and inarticulate, and the highs sound thin and "unmusical."

I was wondering if it's possible, and if anyone has tried, to put a crossover in the middle position setting, so that you blend the tight lows of the bridge pickup with the highs of the neck pickup, and not have any phase interaction in either range. Anybody know anything about this has been done, or is technically possible? I don't actually know how the mechanics of a standard 3-position switch works, but i think it shouldn't be too hard to do.

 

[tangent]

you can achieve this by setting up one of your pots as a blend pot, with a high pass filter on neck input and a low pass filter on the bridge input

the filters mentioned above are nothing more than a resistor and a capacitor, their values determine what frequency range is allowed to pass
see here: http://en.wikipedia.org/wiki/Electronic_filter

 

[m4rk0]

I wired this one:
http://www.unofficialwarmoth.com/index.php?topic=9329.0
with just a volume and a blend knob... is that what you meant? works great for me!!

 

[drewfx]

If you don't have any active electronics to buffer the signals, a classic treble bleed cap to ground will always affect both PU's to some degree. If really you wanted to do this passively, I suppose you could use an inductor in series on the neck PU to cut highs, and a cap in series on the bridge PU to cut lows. Or you could forget about the treble cut part of it, and just use the Ric-style bass cut cap on the bridge PU by itself.

 

[dNA]

Sorry, I don't just mean a blend pot. a crossover is actually where you take a single signal and you use high pass and low pass filters to split the signal into low and high. common use is for sending signal to the woofer and tweeter separately in a speaker system. but i don't know if that's actually the right terminology for what i was talking about.

basically i'd like to have a high pass filter on the neck pickup and a low-pass filter on the bridge pickup, but only when both pickups are on.

drewfx - you seem to generally get what i'm after. would it be possible to put an inductor and a cap, on each pickup respectively, in series but only in the middle position? Like, I don't actually know physically how the signal travels to the switch on a standard LP style toggle. I know with the dimarzio 4PDT switch I could probably do it because i know where the signal is jumped across from the separate positions.

 

[drewfx]

You can't do it with a "standard" LP-style toggle, but I suspect there are toggles out there that would allow it. You need a small cap in series for bass-cut. Ric traditionally used an .0047 (not .047) on their bridge PU's; a bigger cap like a .0068 will allow lower frequencies to pass.

I'm actually planning to try this on a bass I'm building (that is, I'll be building it whenever W gets around to getting the body done and shipping it to me  :sad1, but that will be buffered through an active blend control, so I won't need to use an inductor.

The problem with inductors will be finding one of the appropriate value, the potential for adding noise, and they can be big (much bigger than a cap). Despite these questions, I'd at least jumper things up and try it out if you can find one. I've heard some people have used little RatShack transformers as inductors (in Gibson-style passive mid-cut circuits).

 

[Dan025]

yes it is possible but you will change so many things that it may not get what you desire. the problem with passive crossovers in a guitar is the losses which might be too much on a system that has such a low voltage. you could do it but you need inductors, well you can get away with just one if you need to. the best way however would be to buffer each pickup and simulate an amps input stage and the guitar cable capacitance on the buffer. or you could not do that and get a hifi sound. all up to you.

to do it passive you would shunt one pickup with a capacitor(can use the tone circuit for this, you may need a specialized switch with more poles otherwise), and after the shut it would be in series with the inductor. this will pass only bass and the inductor will prevent the capacitor from shunting treble of both pickups. the other pickup will be in series with a capacitor. you can shunt it with an inductor before the capacitor but unless you like that type of tone control it may be difficult to wire it to cut the inductor out of the circuit. the switch will need to be a dpdt on/on/on switch, a tele switch may also work but i haven't though about how to do that yet. the pickups will need to wired to the lugs that are off in the middle position and the series cap/inductor will go from the lugs that are off in the middle position to the lug that is on in the middle position. this will shun the cap or inductor on themselves and efectively take them out of the circuit when you select a single pickup.

there are many ways to do it active and the results would be more predictable. but more engineering will need to go into it to get the filters to only work in the middle position. maybe a tele switch would be beneficial for that. 

 

[dNA]

yes it is possible but you will change so many things that it may not get what you desire. the problem with passive crossovers in a guitar is the losses which might be too much on a system that has such a low voltage. you could do it but you need inductors, well you can get away with just one if you need to. the best way however would be to buffer each pickup and simulate an amps input stage and the guitar cable capacitance on the buffer. or you could not do that and get a hifi sound. all up to you.

to do it passive you would shunt one pickup with a capacitor(can use the tone circuit for this, you may need a specialized switch with more poles otherwise), and after the shut it would be in series with the inductor. this will pass only bass and the inductor will prevent the capacitor from shunting treble of both pickups. the other pickup will be in series with a capacitor. you can shunt it with an inductor before the capacitor but unless you like that type of tone control it may be difficult to wire it to cut the inductor out of the circuit. the switch will need to be a dpdt on/on/on switch, a tele switch may also work but i haven't though about how to do that yet. the pickups will need to wired to the lugs that are off in the middle position and the series cap/inductor will go from the lugs that are off in the middle position to the lug that is on in the middle position. this will shun the cap or inductor on themselves and efectively take them out of the circuit when you select a single pickup.

there are many ways to do it active and the results would be more predictable. but more engineering will need to go into it to get the filters to only work in the middle position. maybe a tele switch would be beneficial for that. 

thanks for the input man. this sounds a little complicated. But it also sounds like it might actually be/look less complicated than it sounds on paper. I don't think I'm ready right now to dive into any extensive experiments now, but it's good to have this in my back pocket when I do get in the mood again.

 

[Jusatele]

Stereo output and 2 preamp/equalizers  then into 1 amp ?

 

[Dan025]

^yeah sure do it the easy way, but yeah i was thinking about possibly shrinking that down into a guitar or doing it passively

 

[dNA]

Stereo output and 2 preamp/equalizers  then into 1 amp ?

it's a thought. but that would be affecting each pickup's output all the time, making each pickup essentially useless by itself.