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Series/Parallel pull/push jazz bass controls


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[quote name='ikay' post='1096428' date='Jan 20 2011, 03:04 PM']Look at it this way - imagine you have one single coil pickup with a volume control (A) wired on the 'cold' side and another volume control (B ) wired on the 'hot' side. Turn both controls up full and you get max volume. Turning down either vol A or vol B will reduce the volume - ie. they both do [u]exactly the same thing[/u] so one is effectively redundant.[/quote]

Thanks. I kind of understood this. I'm not entirely sure what you mean by "cold" side and "hot" side - do you mean the two wires coming out of your pickup? If so, then I see your point and agree.


[quote name='ikay' post='1096428' date='Jan 20 2011, 03:04 PM']Now imagine the same setup with one twin coil/humbucking pickup replacing the single coil pickup. Exactly the same is true. Both vols do exactly the same thing and one is redundant.[/quote]

Ok; we're still treating the pickup as a single electrical device, with two wires coming out from it, right? If so, then, yes, I agree.

[quote name='ikay' post='1096428' date='Jan 20 2011, 03:04 PM']Wiring two jazz pickups in series is the same as having one twin coil/humbucking pickup. The only difference being that it's a very wide aperture humbucker (the two coils are some distance apart).[/quote]

Well, yes, ok, but I don't see the connection.

The two pickups in a jazz bass have four wires between them. If I put a volume control on each of those pickups then I can reduce the signal coming from each of them. If I then take those reduced signals and put them in series then both volume controls will affect the result. In particular, reducing the volume on the bridge pickup will give me less high frequencies overtones. So in the combined (series) signal there will be, relatively, more low-frequencies. Conversely, if I lower the neck pickup volume, I'll get relatively more high-frequency tones. The two volume controls are having different effects.

People seem to be saying that with parallel wiring it's good to have independent volume controls, but with series, the volume controls can't work independently. But I just don't get this - it seems to me that they work the same in both cases - affecting the overall volume and the balance between the pickups. I wish I understood :)

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[quote]The two pickups in a jazz bass have four wires between them.[/quote]

I think this is where the confusion is creeping in. Imagine a humbucker with two coils hard-wired in series. There's only one wire going in and one coming out like this:

(cold) wire >> into '-' [COIL 1] '+' >> connected to >> '-' [COIL 2] '+' >> (hot) wire

Two single coils wired in series look exactly the same. Sure there are more complex ways of wiring this up via switches etc but in effect there's only one wire going in and one coming out. When in series they act exactly as if they are two coills of a hardwired humbucker.

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Yep, that I understand. It's a more complex circuit that I'm trying to get my head round, but I just don't seem to be able to explain my question, so I'll go and think about it some more and see if I can either understand it, or explain it better! Thanks for your patience :)

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[quote name='mart' post='1096498' date='Jan 20 2011, 04:03 PM']Yep, that I understand. It's a more complex circuit that I'm trying to get my head round, but I just don't seem to be able to explain my question, so I'll go and think about it some more and see if I can either understand it, or explain it better! Thanks for your patience :)[/quote]

The jaz bass circuit isn't any more complicated IIRC it just happens to have a physical separation between the coils (linked by the pickup wires). Having two separate volume controls won't allow you more control, it just means you have two physically different points in the circuit performing identical function. If you drop either one you end up shunting the combined series output from both pickups to earth - as soon as you enter series mode you no longer have control over the contribution of each individual pickup.

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[quote name='mart' post='1096498' date='Jan 20 2011, 04:03 PM']Yep, that I understand. It's a more complex circuit that I'm trying to get my head round, but I just don't seem to be able to explain my question, so I'll go and think about it some more and see if I can either understand it, or explain it better! Thanks for your patience :)[/quote]

Don't worry I sometimes think I'm going mad as well :). I know what you're getting at. The idea of tweaking the amount of signal from each coil to get different flavours of harmonic content is seductive but I think in practice doesn't work. Even if it does, attenuating the signal from one coil when it's in series will affect the overall signal volume to such an extent that subtle change in harmonic content would probably be lost anyway.

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Hmm, ok so I've just re-read all the earlier posts, and I'm kinda confused again :) I know it's a lot to ask, but is there any chance someone could draw me a diagram, or explain to me, how I would wire this all up? The earlier diagrams for the S1 don't seem to be for the push/pull pots, don't I need to wire them in a certain way for them to work like an S1 switch? If not, then how do I make the second (bridge) vol work as a in/out of phase switch, considering I'm going to be using the same type of pot as the first? Also, don't I have to ground each pot?

Perhaps I'm just being extremely thick here, but I'm completely baffled!

Just want to make sure I can do all this with 2 push/pull pots (2 of these: [url="http://cgi.ebay.co.uk/Fender-Tone-Volume-Push-Pull-250K-Pot-CTS-Split-Shaft-/140499251084?pt=Guitar_Accessories&hash=item20b6686f8c"]http://cgi.ebay.co.uk/Fender-Tone-Volume-P...=item20b6686f8c[/url] ), a 250k pot for the tone, a 0.047uF cap, and a switchcraft jack.

Cheers!
Jack.

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Here are two wiring diagrams. The first I have drawn from scratch, the second is my attempt at correcting the Seymour Duncan circuit I posted earlier, with a phase switch wired in. I've re-wired a few basses and guitars in my time, but my electrical qualifications consist solely of an O level. So I will quite understand if you don't trust these circuits. In fact, I'd hope they can be a basis for further discussion and improvement in this thread.

The first circuit uses both volume controls in their traditional roles: one for each pickup. Some posters seem to suggest that the two controls will both act as master volumes; I believe they will adjust the balance between the pickups. But I haven't used the circuit so I don't know whether to believe me or everyone else! :) Although I have drawn the pots separately from the DPDT switches, any push/pull DPDT pot can be wired according to this diagram.


The second circuit, I think, uses one control as a master when in series mode.


Sorry about the poor quality of the diagrams - I was never very good at technical drawing, and now it seems I can't even get the scanner to take colour images! But I think the only colours that matter at all are the wires from the pickups and the connections to the jack socket. For the pickups the upper wire is the white one, and the lower one is the black. For the jack socket the upper tag is the hot one (the tip), and the left one is the ground (shielding).

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To the original OP, try googling it internet is your friend!!! I can see no reason why you can't use push/pull pots, the only thing i would suggest is if you do/can go down that route buy the solid shaft pots so you can screw the knobs into the shaft, if you use spilt shaft you could pull the knob clean of the pot!!

Other than that two small switches would be good but you will have to drill the control plate. I can't confirm that the above diagrams are correct, I think the second one is something more like you want.

If in doubt speak to a local luthier :)

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  • 4 weeks later...

Hmm, over a month since I posted this? well bugger me, didn't think it was that long ago!

Anywho, so I've got the parts now, but a couple of things are bugging me, I can find plenty of diagrams with the S1 switch, but none with the push/pull pot. I'd assume that you could just wire the 6 extra tabs on the pot like you would the switch, but I'm not 100% sure about this.
Also, on every diagram I've seen, you always need to solder directly onto the bottom of the pot, but on the push/pull, there's no room! The bottom of the pot is taken up by the big square thing with the 6 tabs on it. Is it ok to solder onto the side of the pot instead? I'm guessing this is just for earthing issues, in which case I don't see why it wouldn't be ok, but again I just want to make sure :)

Thanks again and sorry for being a moron about this stuff, I'll learn eventually haha.

Edited by SignsOfDelirium_bassist
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  • 1 month later...

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