Blend pot that supports 3 pick ups. Possible or not?

[David Angus]

I'm thinking that there are technical issues with this suggestion, as I'm assuming that if it were possible, they would be available?
Can anyone shed any light to this technically ignorant bass player?

Ideally, I'd like 1 that operates on a push/pull function which means that, (as a secondary function) if you pull the switch out, it bypasses the middle p/up and the blend will operate between the neck and bridge pick up.
Otherwise, between full c/wise & centre, is blend between neck and centre p/up, between centre and full anti c/wise is blend between centre and bridge p/up.

Sorry if this has been asked before, but it's got to be more practical than 3 volume controls?

 

[line6man]

That's definitely not possible.

 

[Will_White]

Just use two blends one for neck and middle and one for that blends output and bridge

 

[Doner Designs]

Most of my basses have three pickups. Normally I have an on/off toggle for each and feed both the middle and the neck to the neck side of a standard blender pot. Why? The tone of a bridge pickup is dramatically different than that of a middle or far-neck but the difference between a middle and a far-neck pickup is much more subtle so it makes sense to me to have those together on the blender with two mini-toggles or a 3 way switch.

 

[line6man]

Just use two blends one for neck and middle and one for that blends output and bridge

That's a lot of loading on the circuit. It would be best to opt for ungrounded blend pots.

 

[Will_White]

That's a lot of loading on the circuit. It would be best to opt for ungrounded blend pots.

Yeah I'm of the opinion to go with a well planned switching theme, either rotary, 5 way, or three toggles, with three J pickups maybe a variation on the brain may scheme, three toggles and a series/parallel.

 

[ctmullins]

Somewhere I saw a thread in which one of our brethren posted a diagram for using a six-position rotary switch with three pickups. It worked just like a five-position Strat switch, with the sixth position being bridge+neck. It's saved somewhere, but I can't find it just now...

 

[RobbieK]

if you want a blend control, you could go with a 3-way switch that selects three pairs before feeding the blend.

 

[khutch]

I would say that it can be done if you have tens of thousands of dollars available to pay for the tooling on a custom pot. Maybe under ten thousand if you shop around. I think you would need a five section pot with a push pull switch with more poles than I have seen on one. Not that I have ever seen any push pull blend pots....

 

[RobbieK]

tens of thousands of dollars available to pay for the tooling on a custom pot

or learn how to programme digi-pots I guess!

 

[RobbieK]

Actually I've never tried this (3-pickup basses are pretty rare!), but I'd think if you buffered each pickup (opamps would be ideal), you'd only need a single gang linear pot with a centre tap. These aren't that common, but I'm sure you'd find one on e bay. You'd connect the signal from the three buffers to the tap and the outer lugs, then the wiper is your blended signal. I guess you could also load up say an 11-throw rotary switch with resistors to act the same way... If you disconnect the middle pickup, it would work just as a regular blend; bridge to neck. This is just what @David Angus was asking for.

I know guys can be scared of active circuits, but an opamp buffer is as simple as it gets. And it's easy to set the input Z so the bass still sounds passive. As for a centre tap pot with push-pull. Well maybe a poultry dentist would have one... I guess you could try disassembling a regular push-pull and swapping in the tapped wafer. Or realistically, put the switch on another control.

You could use one of these, in a circuit like this:

Thinking out loud here. No worries if you shoot me down...

PS: a cool circuit to try in a strat.
PPS: actually with a little tweak, this could also work in a bass with a piezo bridge and 2 mag pickups...

 

[David Angus]

Thanks to everyone contributing to this.
I really am technically (electrically) ignorant in these matters, so, you never know, some bright spark might just get it and be able to put an affordable one together.
Maybe, maybe not, but hey, never say never

Thanks again.

 

[RobbieK]

last night I simulated this little set up, and it should work fine. Unfortunately I won't get to try this out myself for several months, but I did go ahead and buy some of these. If you have a mate with an electronics background, puting a circuit like this together on some strip board will take maybe half an hour, and the parts will be 10-20 bucks. And the circuit will be the size of a postage stamp. If your bass is passive to start with, you will need to find a place for a battery, plus you'll need to change the jack.

This thread encapsulates the main reason I contribute so much to this board. Creative guys with a cool idea, everyone (including me!) originally thinks it's a crazy one, then after a bit of a think, it seems possible, and actually kinda useful. Albeit in a fairly niche way. Several of my designs have stemmed from a non-technical TB'er asking "is this possible?"...

 

[mileyj]

Not to hijack this thread, but I have a similar question, but I was wondering if it could be done with a single blend pot where 10 was neck, 5 was middle and 0 was bridge pick up and would blend in the middles?

 

[RobbieK]

Yep, that circuit I posted should work for that. Just leave out the switch. I'm still waiting on those centre-tapped pots I ordered from Thailand so I haven't actually tried it yet. (Not sure why it's taking so long - I emailed the guy and he says he posted them on the 5th!)

Anyway, I don't like to post anything I haven't actually tried myself, but as I said it's a very simple circuit and I even simulated it just in case I missed something obvious...

As I mentioned, if you don't want to wait for a centre tapped pot from Asia, then I guess you could use a rotary switch or even a stepped attenuator. If you can fit it in your guitar, you can get ones where you solder all the resistors up. Or you can get ones that are prewired with SMT resistors. I'd think it would be pretty easy to hack a centre tap with one of these. Any value from 10K to 100K should work. (Although with larger values, you may want to increase Vref resistor of the output buffer.)