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Isolating tone controls from two pickups

Stealth

Stealth

Feb 5, 2008
3,322
113
Zagreb, Croatia
#1
Suppose you had a two-pickup bass, each with its own V/T stack. Considering tone controls commonly interfere with each other if the pickups are later connected into a parallel (turning one will necessarily affect the other as well), is there any way to somehow have each of the tone controls function independently on its respective pickup?
 
#3
Yep, you need to step beyond passive into active circuitry at some point if you want isolation and more definitive control. Whether you do this on the bass or downstream, that's what it takes.

One way a few do it is just to have separate outputs from each pickup, to separate signal chains.
 
#4
certain old danelectro basses had their two single coil pickups in series, at which point the individual tone pots were isolated. it made for a surprisingly useful effect, as since you could kill the highs of just one coil, you could effectively have the low frequencies being heard by both coils (series fatness) and the highs by just one (single coil clarity).
 
#6
I had a two pickup bass set up so each pickup went to its own 6-position rotary switch that went Off, .1, .069, .047, .033, .022.

I thought it would add flexibility by having one pickup bright and the other dark...didn't work all that great. It's one of those ideas that seems a lot better thinking about it than it sounds in real life. I changed it to one switch to select pickups and Off, and the other switch for caps.
 
#7
GlennW said:
I had a two pickup bass set up so each pickup went to its own 6-position rotary switch that went Off, .1, .069, .047, .033, .022.

I thought it would add flexibility by having one pickup bright and the other dark...didn't work all that great. It's one of those ideas that seems a lot better thinking about it than it sounds in real life. I changed it to one switch to select pickups and Off, and the other switch for caps.
Click to expand...

It is a cool idea to roll the highs off the neck and some lows off the bridge when you mix them together, you eliminate some phase cancelations and overlaps, but it doesn't work well passive.

I guess that's why stereo instruments were made.

I was going to stick a preamp with bass/treble for each pickup in one of my basses, but then I used the other preamp in another bass.

I think it's still a cool idea though.
 
#10
SGD Lutherie said:
It is a cool idea to roll the highs off the neck and some lows off the bridge when you mix them together, you eliminate some phase cancelations and overlaps, but it doesn't work well passive.
Click to expand...

It didn't do anything that couldn't be done with a master tone switch and fiddling with the amp a little. All those caps take up a lot of space too.
 
#11
UncleBalsamic said:
This probably wouldn't work, but couldn't you put a diode after the tone pots?
Click to expand...

no...the diode will create a small forward voltage problem to overcome...this could act like a "gate" on your signal and kill your sustain...heck, if the Vf is high enough, the entire signal could be killed.

for eliminating interaction, active buffer is the suitable solution.

sus
 
#13
UncleBalsamic said:
This probably wouldn't work, but couldn't you put a diode after the tone pots?
Click to expand...

A diode might cause a little clipping. That Black Ice Passaic distortion thing is a couple of diodes.

I used to wire up diodes where you would out the tone cap for built in passive overdrive. Jack Bruce had one in his Gibson basses.

A couple of resistors would add some isolation at the expense of reducing the output.
 
#16
Les Pauls also have the problem of one volume control effecting both pickups when you have them both on. If you turn one pickup off, they are both off.

Rics in stereo have separation as long as you have each pickup going into a separate input or two amps.

But really why would you want to remove the highs from one pickup and not the other? It seems like a good idea until you try it and then it doesn't sound all that much different.
 
#17
Well, the wiring layout I made (as a purely mental exercise) was supposed to go mono/stereo. The stereo not interfering with itself makes sense considering the output branches from each of the pickups is split into two channels that aren't connected anywhere...

However, if I have a Mono/Stereo wiring (similar to the [Invalid or Expired Link Removed] diagram on the Seymour Duncan site), am I correct in assuming that I better use an on/off switch for the mono output, because without it even the stereo tone will get mixed and I'll get tone-pot interference due to the fact the signals mix in the mono output branch?

My common sense just isn't tingling these days - ergo the slightly silly question. :smug:'
 
#18
The tone pot shunts highs to ground via the capacitor. You have to have the pickups isolated from each other totally for the tone control to work only on one PUP and not the other. And the way passive electronics work, there aren't many good options for creating that isolation. The original wiring for the Fender Jazz Bass used resistors to isolate the signals, but it also reduced the output level of the system. So for the Vintage Series reissues, they elected not to use the resistors, but the tone controls interact.

They don't on a Gibson style instrument only if the switch is soloing the PUP. That's becasue the switch isolates the control circuit for the bridge PUP from the neck PUP totall- if you have only the one PUP selected. If you put the toggle in the middle, either tone control will cut the highs.

jte
 

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