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Two differing pickups, two separate passove tone controls?

FourBanger

FourBanger

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Sep 2, 2012
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#1
Has anyone ever done or seen this? Where a two pickup bass is wired passively V/V/T/T and utilizing different cap and/or pot values for the tone coming from each pickup?

I was thinking this could be useful in basses with two dramatically different voiced pickups, like MM/S or MM/P so that the values selected for roll-of aren't a compromise.

Thoughts? Is it more common that I am aware?
 
#4
line6man said:
That's the usual way that it is done. Few people use the same capacitance for both pickups.
Click to expand...

You are one of my go-to resources for such matters. So I am literally asking and not arguing.

Would two tone controls not "mess with each other" in the circuit? In other words, by adjusting the tone control on one pickup are you not somehow affecting the whole circuit? Are the caps somehow "isolating" the two pickups and the signals are then combined just before output? I admit I didn't look up any wiring diagrams before "blurting out" my question.
 
#5
two fingers said:
You are one of my go-to resources for such matters. So I am literally asking and not arguing.

Would two tone controls not "mess with each other" in the circuit? In other words, by adjusting the tone control on one pickup are you not somehow affecting the whole circuit? Are the caps somehow "isolating" the two pickups and the signals are then combined just before output? I admit I didn't look up any wiring diagrams before "blurting out" my question.
Click to expand...

In order for two tone controls to work independently, you have to isolate the signal paths with resistors. The problem, however, is that you lose output. This is one reason why this scheme was abandoned 50+ years ago. It just isn't practical. Plus, when you try to cut treble on one pickup, the other pickup usually just brings it back, so there is little value in having multiple tone controls.
 
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#6
line6man said:
In order for two tone controls to work independently, you have to isolate the signal paths with resistors. The problem, however, is that you lose output. This is one reason why this scheme was abandoned 50+ years ago. It just isn't practical. Plus, when you try to cut treble on one pickup, the other pickup usually just brings it back, so there is little value in having multiple tone controls.
Click to expand...

Thanks. That's kind of what I thought. I should have figured resistors rather than caps. Duh.

I guess that's why the stack knob didn't last very long, maybe?
 
#8
So the two tones effect each other even when the only common connection is the output? I guess that's why my electrical expertise extends only to being really good at recreating a wiring diagram with a soldering iron and not seeing how they actually work.
 
#9
FourBanger said:
So the two tones effect each other even when the only common connection is the output?
Click to expand...

Yes!
The best way to take advantage of two tone controls is with a 3-way switch that can turn on one pickup at a time. Then you can set each pickup's tone differently & move between them with the switch.
However, when you have both pickups on, the tone controls will be ganged & not independent of one another.
 
#11
So the two tones effect each other even when the only common connection is the output?
Click to expand...

Yes. But I'd recommend you try my circuit from that thread. The resistors make an almost inaudible difference, but (fwiw!) give you isolated tone pots.

I guess that's why my electrical expertise extends only to being really good at recreating a wiring diagram with a soldering iron and not seeing how they actually work.
Click to expand...

Follow my post through. Try building the test jig. Test the tone pot isolation by tapping the tops of the pickups with a small screwdriver or something similar. Flick the switch to short the test pot. Find the sweetspot for your bass.

This will greatly help your understanding of all this.
 
#13
Looks like the blend pot should keep a resistance sitting between the point where the two pickups sum and help to isolate the tone controls.... I hope.
Click to expand...

It depends on the blend pot. The most common blend pot is an "MN". This only has resistance from the middle going clockwise for one gang, and the middle going anti-clockwise for the other. So with an MN blend in the middle, there's no resistance. The pickups are hard wired together and the tones will interact.

There is a less common blend pot called often called an A/C taper pot because one gang has a regular audio taper (A), and the other an anti-log, or reverse audio taper (C). If this is wired correctly, in the middle there'll be "summing resistance" of around 15% of the pot's value.

For a passive blend pot, don't be tempted to use a dual gang linear pot (B taper). This will give you a big volume loss in the middle.

If you have an MN pot, you can still use a couple of summing resistors as in the other thread.

Personally, If I had a passive bass with two pickups and four holes, I would just go VBT, and perhaps put a rotary series-parallel switch in the spare.

As I said at the end of that thread, having two passive tone pots is pretty useless IME, even when their operation is isolated with those (controversial!) resistors. With a blend pot I guess it sort of makes sense if you plan to say, roll the treble from the bridge pickup so it's nice and middy, but leave the neck pickup with its bright and hollow tone. If your pickups are adjusted well, the blend will sort of work as a mid control in reverse...
 
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#14
Two tone pots with different cap values is not as bad as all that. Everyone seems to be hung up on the fact that with both pickups fully on there is no point because of the way they interact. But both pups dimed is only one of a range of possible settings, and in my case it is probably the least used. Surely the idea of, say, a 0.047uF cap on the neck tone and 0.022uF on the bridge has a certain draw? With both pups on you have the option of either or both. Just because you can't dial in some treble from the bridge makes it pointless? So what, you never could!
 
#16
I've learned a lot in this thread so thank you all for that.

I won't be doing this in the current bass project, the SR400 is having the stock pickups replaced with a combination I know I like better and from there I may or may not experiment with a clone of a MusicMan 2 band as you may have seen me post about elsewhere. For the pickups I like and the tones I like this may be surprisingly good.

Depending on how well I can cop 'vintagey' sounds with that result I might start working on a Precision-based passive PJ around the same pickup set.
 
#17
4StringTheorist said:
Thanks for the thread read!

Going to be setting up my old Warmoth J body as a passive fretless. Four knobs, so I decided to do Vol-Blend-Tone-Tone. Looks like the blend pot should keep a resistance sitting between the point where the two pickups sum and help to isolate the tone controls.... I hope.
Click to expand...

If it is 100/100 at the centre then it will not provide the necessary isolation at any setting as at least one pup is full on all the time, meaning that pup's tone control is always in the circuit. However, with a V/V/T/T setup, all you have to do is back the volumes off a bit, and provided you wire the tone controls between the pickups and their respective volume controls you will get the necessary isolation - with the added benefit of being able to adjust the level of isolation. Of course with both volumes dimed there will be no isolation but you will also have both caps in parallel meaning a lower cut-off frequency, should you need it.
 
#19
Killed_by_Death said:
So essentially, at least one of the pickups will need to be backed off on the volume (or balance) to get any independence out of the two tone controls, unless of course you put in some extra resistance, which I am dead against.
Click to expand...

No, both will need to be backed off a little AND the tones will need to be wired on the pup side of the volume controls. Search Les Paul 'modern' and 50s wiring options to see what I mean.
 

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