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Need Parallel/Series Jazz Bass Schematics

The issue with passive blend is primarily the interaction of all the impedances in the circuit - the pickups and the pots. The pickups impedances interact with each other, and the other stuff in the circuit affects that as well. Keep in mind that a blend pot is basically two volume pots stacked on top of one another, one of which operates backward, and in a typical blend circuit you also have a master volume..... so a typical blend circuit has 3 volume pots where a typical V-V-T only has 2.

Since these impedances all interact in a passive circuit, it's very hard to predict how well a blend will work with a particular set of pickups. If you try it and it's not working well with a 500K blend pot, you can try it with a 1000k or a 250k and see if it gets any better....... I've got two Bartolini equipped Modulus basses with passive blends that work just fine, but I've found some pickups that just don't work well with passive blend no matter what.

I've never tried it, but I would bet that a passive blend wired up with no master volume would work just as well as a V-V-T......... all I ever use a master volume for is to mute the bass when I'm not playing, so maybe wire in a push-pull pot for the tone control, use the switch to cut output........

Also, just using a preamp does not neccessarily mean you're getting an active blend circuit. In fact, almost all preamps are single channel designs where you do all volume control and blending passively, before the signal ever gets to the pre, so they really don't affect "the passive blend problem" at all, for better or for worse. Aguilar, Sadowsky, Seymour Duncan, and most Bartolini preamps are single channel designs.

EMG "systems" - the ones named "BTS", BQS", etc. - have buffered blend circuits (their various items labeled "controls" do not), Audere pres are two channel designs with active blend circuits, Demeter on board pres have active blend, some of the East pres have active blend, some Bartolini circuits have active blend.

(in case you didn't know, "buffered blend" and "active blend" mean the same thing........ the audio signals being mixed together are electronically isolated from each other using buffers)

You can add an active blend circuit in front of your favorite single channel pre if you want - Bartolini makes a few different 2 channel buffer amps that can be used this way.

Back to the original topic - I don't know absolutely, but I'm 99% sure that your 3 wire split-coil Fralins have a hot wire for each coil so you can run each pickup in series or parallel (just like you might do with a P style split coil), plus a common ground. So you basically sort out how you want to run each pickup first, which leaves you with two wires coming from each pickup to feed into the "master" circuit - which you could then also run in series or parallel. Essentially, you could have a series/parallel switch for each individual pickup, plus a series parallel switch for the overall circuit........ maybe more switches than you want to deal with, so you'd most like want to hard-wire each pickups split coils in parallel and just use a series/parallel switch on the outputs of both pickups.

Hopefully that makes sense to you........;)
 
The issue with passive blend is primarily the interaction of all the impedances in the circuit - the pickups and the pots. The pickups impedances interact with each other, and the other stuff in the circuit affects that as well.

Pickups want to see a high impedance, and anything less will effectively change their output... plus you're leaving out a few very important other impedance sources - the capacitors, and the cable going to the amplifier.

All this stuff hanging off your pickups is basically resistively-damped second-order low-pass filter.

Keep in mind that a blend pot is basically two volume pots stacked on top of one another, one of which operates backward, and in a typical blend circuit you also have a master volume..... so a typical blend circuit has 3 volume pots where a typical V-V-T only has 2.

True, but the master volume pot in a blend circuit is merely an attenuator - although it may form a filter with the master tone control. Also note that any output attenuator (volume control) will interact as a first order RC lowpass filter in combination with the cable impedance.

Since these impedances all interact in a passive circuit, it's very hard to predict how well a blend will work with a particular set of pickups.

Not really - it's a really simple passive circuit to analyze in something like spice... and as long as the pickup output impedance is low enough and the input to the filter circuit impedance is high enough, there shouldn't be any issues.
 
Found this thread. Seems like the right place to ask my queston. So here goes.

I recently acquired a cheap(er) fretless that I'd like to wire up in series parallel. I've got two Dimarzio model J's. Will these work to wire in series/parallel?

If possible I'd like to keep the p bass pup in the neck position, put both jazz in the rear, wire the jazz to series/parallel and put a 3 or 5 way pup selector (whatever is more logical) in to top it off.

I don't even know if this is possible. It would be great if there was a pre-wired harness someplace.

Thanks guys.
 
The issue with passive blend is primarily the interaction of all the impedances in the circuit - the pickups and the pots. The pickups impedances interact with each other, and the other stuff in the circuit affects that as well. Keep in mind that a blend pot is basically two volume pots stacked on top of one another, one of which operates backward, and in a typical blend circuit you also have a master volume..... so a typical blend circuit has 3 volume pots where a typical V-V-T only has 2.

Since these impedances all interact in a passive circuit, it's very hard to predict how well a blend will work with a particular set of pickups. If you try it and it's not working well with a 500K blend pot, you can try it with a 1000k or a 250k and see if it gets any better....... I've got two Bartolini equipped Modulus basses with passive blends that work just fine, but I've found some pickups that just don't work well with passive blend no matter what.

I've never tried it, but I would bet that a passive blend wired up with no master volume would work just as well as a V-V-T......... all I ever use a master volume for is to mute the bass when I'm not playing, so maybe wire in a push-pull pot for the tone control, use the switch to cut output........

Also, just using a preamp does not neccessarily mean you're getting an active blend circuit. In fact, almost all preamps are single channel designs where you do all volume control and blending passively, before the signal ever gets to the pre, so they really don't affect "the passive blend problem" at all, for better or for worse. Aguilar, Sadowsky, Seymour Duncan, and most Bartolini preamps are single channel designs.

EMG "systems" - the ones named "BTS", BQS", etc. - have buffered blend circuits (their various items labeled "controls" do not), Audere pres are two channel designs with active blend circuits, Demeter on board pres have active blend, some of the East pres have active blend, some Bartolini circuits have active blend.

(in case you didn't know, "buffered blend" and "active blend" mean the same thing........ the audio signals being mixed together are electronically isolated from each other using buffers)

You can add an active blend circuit in front of your favorite single channel pre if you want - Bartolini makes a few different 2 channel buffer amps that can be used this way.

Back to the original topic - I don't know absolutely, but I'm 99% sure that your 3 wire split-coil Fralins have a hot wire for each coil so you can run each pickup in series or parallel (just like you might do with a P style split coil), plus a common ground. So you basically sort out how you want to run each pickup first, which leaves you with two wires coming from each pickup to feed into the "master" circuit - which you could then also run in series or parallel. Essentially, you could have a series/parallel switch for each individual pickup, plus a series parallel switch for the overall circuit........ maybe more switches than you want to deal with, so you'd most like want to hard-wire each pickups split coils in parallel and just use a series/parallel switch on the outputs of both pickups.

Hopefully that makes sense to you........;)

Umm...kinda. :atoz:
 
So!

Here's what I want to do.

Can anyone help me out? I have no idea how electronics work inside.
I know how to make em work for me though...

Split noiseless jazz pickups (2)

neck volume - pickup series parallel on a push pot
bridge volume - pickup series parallel on a push pot
master tone - master series parallel on a push pot

is this difficult? I am open to a separate 2 way switch for master s/p but would like to avoid it.
 
Doesn't sound too difficult, no.

Go for it!

As for how to do it, does the Split J's have four wires from them? If so, searching for "series/parallel wiring" on Google or whatever will give you a schematic for a regular (guitar) humbucker - wire each J to its switch according to that.

Then, you have two output wires from each switch; you'll want to wire them to the pot next, and then to the final, "master" s/p switch. You can either do it the usual way (shared on a scribbled picture on the first page of this thread), or the one above, that retains individual volume control - I haven't tried either, to be honest, but the latter does sound nifty.

And then, finally, wire it to the tone pot/cap. A standard J wiring diagram'll show you the way.


Oh, and sorry, but I'm too lazy to draw up a diagram for you.

Oh right, another thing: there are two different wiring schematics for s/p swich floating around on the 'net - one where the "top" two lugs are connected with a jumper wire, and another where the "left" centre lug is connected to the "top right" lug, and then to one of the pickup wires - the two are, AFAIK, functionally identical, so don't be confused if you happen to see both. Choose whichever you like.
 
Sorry for the size....this way you can print with detail.

BL-Wiring-diag1.jpg



do i understand that this wiring with the extra cap on the blend stops the volume drop when both pickups are on full???

found this diagram for a blend,vol,series parallel push pull tone setup
where abouts on the blend pot would the extra cap go??
anybody find the right cap value to use?
hoping to do this with SD 1/4's for a p/j bass. :D
thanks to Yvarg for his diagram!! http://www.talkbass.com/forum/showthread.php?t=414769

[Invalid or Expired Link Removed]

great thread!
thanks
aL
 
I've changed my plan...

I want to go with a 3 pickup setup...

DarkStar on stacked vol/tone
2 split jazz pickups with Series/Parallel Pushpots
4 way rotary selector/tone:
j's in series, in series with darkstar
j's in parallel, in series with darkstar
j's in series, parallel to darkstar
j's in parallel, parallel to darkstar
3 way toggle between j's and darkstar
phase switch

Anybody else doing this?
 
I've changed my plan...

I want to go with a 3 pickup setup...

DarkStar on stacked vol/tone
2 split jazz pickups with Series/Parallel Pushpots
4 way rotary selector/tone:
j's in series, in series with darkstar
j's in parallel, in series with darkstar
j's in series, parallel to darkstar
j's in parallel, parallel to darkstar
3 way toggle between j's and darkstar
phase switch

Anybody else doing this?

you floored me...... boggles the mind. i can honestly say i have no idea what that just meant. i thought i was being all smarty with mine, back to start of the learning curve for me!!! :p
 
I am really tired of reading this old bullcrap regarding passive blend.
With a proper circuit and proper pots it does not cut signal in any way and delivers full signal in middle position, strictly like dual volumes would do.
If your pickups have a humbucking effect, such as a pair of single coil Js, you will get slightly less volume in middle position. This is perfectly normal and you will experience it just the same with dual volumes.
 
I am really tired of reading this old bullcrap regarding passive blend.
With a proper circuit and proper pots it does not cut signal in any way and delivers full signal in middle position, strictly like dual volumes would do.
If your pickups have a humbucking effect, such as a pair of single coil Js, you will get slightly less volume in middle position. This is perfectly normal and you will experience it just the same with dual volumes.


cool i can work with that! nice one, but ill hold you to it......
 
From what I've been told, passive basses do not work well with blends. When you center the blend, the overall volume will be much lower than when you dial it either way. As you turn it toward one pickup of the other, it will get even louder. That is why Fender has never put a blend control on a passive jazz bass. That is also why preamps are used. Preamps have active buffers that isolate the pickups from each other so that will not happen. So, it's not entirely "non-doable", but the results may not be what you had in mind.

I know this is a very old post, but it is worth to say that sometimes we think we are discovering something new while people in the past already tried those options, blend pot on passive basses doesn't seems to be good enough after all