Capacitor on a Blend Pot......What does it do?

[dkelley]

Plus, adding a Master volume with a bleed cap might create a flux capacitor. Possible time travel implications...

Well hell. Now you HAVE to try it!

 

[fig]

Well hell. Now you HAVE to try it!

I DO try it. We've had this conversation 14 times now.

Weird.

Feels like having amnesia and deja-vu at the same time.



Actually, I won't be testing this LOL. Blend knobs and treble bleeds aren't for me. Had blends in the past, just prefer separate volumes. Volume treble bleeds are a good idea for players who wanna keep the high end. Other players, like me, like dialing the volume control back a bit to take off some high end. Kinda like a secondary tone control, I suppose.

 

[dkelley]

I DO try it. We've had this conversation 14 times now.

Weird.

Feels like having amnesia and deja-vu at the same time.



Actually, I won't be testing this LOL. Blend knobs and treble bleeds aren't for me. Had blends in the past, just prefer separate volumes. Volume treble bleeds are a good idea for players who wanna keep the high end. Other players, like me, like dialing the volume control back a bit to take off some high end. Kinda like a secondary tone control, I suppose.

yea LoL

 

[fig]

ZTR&R! Zombie Thread Revival & Review, 1 year 8 months later.

This concerns the pot labeled 'Blend' in original Bill Lawrence diagram. I think some folk (me included on first look) figured the word 'blend' means volume blend, which this isn't. With the cap attached, it's a standard tone control that we'd ID'd earlier in this thread.

Yeah, I know I already commented on it, but I found a little extra concerning that pot, also from Bill Lawrence, that some of ya'll might find interesting. And I'd like to relabel 'Blend' to something more appropriate, please LOL

Original Bill Lawrence diagram (from post #1):

Here's a schematic for it, showing what it does with the J Bridge pot wiper arm (2) at both extremes. A better name, in my opinion, is Bridge Tone Control.:

This next one is one simple mod from original circuit. Remove the cap and connect Bridge pot wiper arm (2) directly to ground. A Bridge Volume Control.:

So, in a loose interpretation, the Bridge tone or volume can be blended (hence, the 'blend' name) with the neck pickup. I just see it a bit more specifically and less confusing.

If you wanna get fancy, add a 1Pole/2Throw switch off the Bridge pot wiper arm (2) to combine the above two circuits, making each selectable. Select either Bridge Tone or Bridge Volume function.:

Anyway, thought this was interesting and maybe useful to someone.

 

[sikamikanico]

Thanks, good stuff! I figured something like this may be going on with this circuit, but never tried it. In a way, this uses the same trick that G&L OMG does - with two coils/pickups in series, you can load one of them with a cap so that it blends/mixes in the lows to the other coil/pickup.

Perhaps what is less intuitive to me is why you would add the cap on the bridge pickup - I would reverse that, do it on the neck pickup. I tried it on a J-style bass and you can get a pretty cool tone, basically a soloed bridge J sound with bass boost.

One idea/thought: in your last schematic above, you use a switch to go from bridge tone control to bridge volume control. Could you use two pots in parallel to have both controls at the same time?

 

[Bassamatic]

2 tone controls make no sense to me. Without some isolation resistors, they are essentially in parallel and when in use both are rolling of the highs of both pickups. If either of them is at the extreme, it is killing the highs for both pups. It is all going out the same mono output jack! I have a new Jaguar that was wired VTVT - it was quickly changed to a much more functional VBT.

 

[sikamikanico]

2 tone controls make no sense to me. Without some isolation resistors, they are essentially in parallel and when in use both are rolling of the highs of both pickups. If either of them is at the extreme, it is killing the highs for both pups. It is all going out the same mono output jack! I have a new Jaguar that was wired VTVT - it was quickly changed to a much more functional VBT.

That's true when pickups are in parallel, the most common configuration. But if they're in series, you can have separate tone controls.

 

[fig]

2 tone controls make no sense to me. Without some isolation resistors, they are essentially in parallel and when in use both are rolling of the highs of both pickups. If either of them is at the extreme, it is killing the highs for both pups. It is all going out the same mono output jack!

As sikamikanico said, with the pickups in series there will be a constant and permanent isolation of the two tone controls by the internal resistance of the pickup. That internal resistance is called DCR (DC Resistance). The tone controls will be isolated for all time, even until we pass to the Great Stage beyond LOL.:

In a typical parallel VVTT circuit, there is no permanent resistance for isolation. With both volumes max'd, the tone controls are directly connected to each other. So backing off of one, or both, volumes will provide a variable degree of tone isolation. Or adding two resistors (a permanent isolation) will cure that, like you said.

One idea/thought: in your last schematic above, you use a switch to go from bridge tone control to bridge volume control. Could you use two pots in parallel to have both controls at the same time?

So, the bridge pickup with a tone control pot and a volume control pot? If that's what you mean, then, sure. It's a feature of the series connected Danelectro bass pickups, which has been around since the late 50's (don't quote me on the date LOL). Each pickup has it's own tone and volume control.

Besides the Danelectro method, there's another connection method called a Shunt method where each pickup also gets it's own tone and volume control.

 

[fig]

Found another Bill Lawrence schematic. He's one of those folk who can combine simplicity with knowledge and creativity. This one again deals with a series circuit.

Here's original:

Here's what it does and how it works, first with the ground selected by the 1pole/2throw switch, then with the cap selected:

Anyway, thought it was cool and creative.

 

[mrperkolator]

Found another Bill Lawrence schematic. He's one of those folk who can combine simplicity with knowledge and creativity. This one again deals with a series circuit.

Anyway, thought it was cool and creative.

Am I the only one staring at this wondering if a standard Push/pull could be added to make it series / parallel.... still with vol/blend.

I think I'm halfway there..... not sure if this will help.

@ctmullins what do you think.

Edit: a push/pull rerouting the "JB 1 N" black wire to ground should change from V/B series to V/V parallel correct? Not that such a switch is super usable

 

[fig]

I'm not ctmullins, but I play one on TV.

Edit: a push/pull rerouting the "JB 1 N" black wire to ground should change from V/B series to V/V parallel correct?

It'll go parallel, but not a regular VV. The Neck will be full-on to the Master Vol. The Bridge, in parallel with the Neck, is the only one with an adjustable volume, as expected in VV. I drew this circuit, per request, in another thread recently. The switch represents 1 of 2 sets of contacts on a push/pull.

 

[mrperkolator]

I'm not ctmullins, but I play one on TV.


It'll go parallel, but not a regular VV. The Neck will be full-on to the Master Vol. The Bridge, in parallel with the Neck, is the only one with an adjustable volume, as expected in VV. I drew this circuit, per request, in another thread recently. The switch represents 1 of 2 sets of contacts on a push/pull.
View attachment 4841006

What if you used the other half of the push/pull to move the output of bridge vol to the wiper of the master (output of that pot in this case). That way when you pull (or push) it sends neck neg to ground and moves the output of the bridge vol to output of neck vol. Then that should make a vv right?

Edit 1: also... I played with the idea of using a rotary switch to make all of this happen, and It was not near as clean as this. and didnt work.

Edit 2: red line (sorry working quick) is what I meant for other half of push/pull

 

[fig]

Thanks for drawing the red line in your diagram. I'm a visual kind of guy LOL. That being said, your text descriptions are better than many, too.

What if you used the other half of the push/pull to move the output of bridge vol to the wiper of the master (output of that pot in this case). That way when you pull (or push) it sends neck neg to ground and moves the output of the bridge vol to output of neck vol. Then that should make a vv right?

Unfortunately, no.

The Bridge will still remain adjustable (one V of VV). The Mast Vol will still be a Mast Vol, adjusting both pickups.

When switched to parallel, both pickups need to come out identically connected to both pots for true VV, like this:

Back to the circuit under discussion, the Bridge comes out fine in parallel, so ignore it.

But the Neck pickup output needs to connect to the Mast Vol wiper arm, and that pot's output needs to change from the wiper arm to the top of the pot. The former Mast Vol (in series) is now a Neck Vol in parallel. Then both of the separate outputs (from the top of each pot) need to come together for final output.

 

[ctmullins]

Just wanna say, @fig , you’re amazing!

 

[mrperkolator]

Thanks for drawing the red line in your diagram. I'm a visual kind of guy LOL. That being said, your text descriptions are better than many, too.


Unfortunately, no.

The Bridge will still remain adjustable (one V of VV). The Mast Vol will still be a Mast Vol, adjusting both pickups.

When switched to parallel, both pickups need to come out identically connected to both pots for true VV, like this:
View attachment 4841681

Back to the circuit under discussion, the Bridge comes out fine in parallel, so ignore it.

But the Neck pickup output needs to connect to the Mast Vol wiper arm, and that pot's output needs to change from the wiper arm to the top of the pot. The former Mast Vol (in series) is now a Neck Vol in parallel. Then both of the separate outputs (from the top of each pot) need to come together for final output.

If outputs of both vol are connected in parallel with each other, it shouldn't matter which leg is on the wiper. but perhaps it has to do with ground....

... for sake continuing the modification of this circuit.... If you take bill's original diagram and swap the input and output legs of his master volume, it should work the same. Such that the output is opposite of the ground, and input (Neck hot and "blend" output) is on the wiper.

Then add your switch. Should still funciton as you designed. Add my edit of moving output of bridge to move at the same time as your switch to the output of the "master volume" and it should function as a VV in parallel right?

 

[mrperkolator]

This is what I mean in previous post.

The highlighted areas are the switch that would be push/pull. I broke it up to make it easier to see. Red is the hot/positive path. I had to use a dotted line on the schematic to the right to keep it from looking like those wires touch.... I like using multiple colors in a real program instead of pens...

Edit: Oh sorry... forgot to put the bridge pickup leg to ground. pretend it's there.

Edit 2: If I was doing this, I'd use a bridge pot that had a center detent....

 

[fig]

You did it!

By you changing the Neck pu output from the top of the Mast pot and putting it on the wiper arm in your newest diagram made the difference. It forced the Master Vol from staying a Master Vol. The Mast is now a Neck Vol control when switched to parallel.

Anyway, here's how it works out. With more pretty colors, too

For those passing thru that may not understand why, when in parallel, the input and output to each control pot is critical, this diagram might help. Even if only one pot is mis-wired, it will be a Master Vol control to both pickups. Not necessarily a bad thing if the player wants it that way. Just showing how that happens.:

 

[mrperkolator]

You did it!

By you changing the Neck pu output from the top of the Mast pot and putting it on the wiper arm in your newest diagram made the difference. It forced the Master Vol from staying a Master Vol. The Mast is now a Neck Vol control when switched to parallel.

For those passing thru that may not understand why, when in parallel, the input and output to each control pot is critical, this diagram might help. Even if only one pot is mis-wired, it will be a Master Vol control to both pickups. Not necessarily a bad thing if the player wants it that way. Just showing how that happens.:
View attachment 4842623

Cool. In my estimation, this is a more usable series/parallel mod using one push pull than the typical one that renders the second knob obsolete in series. Particularly on a P/J platform this would be perfect since most people are playing P and adding J. I tend to play neck biased on my mix, so this would work for me on a J too. I'll make a pretty version of this someday soon as both a diagram and schematic and post it here....might be a lil bit though.