Explain PAB Circuits

[LooseChange]

There appears to be a few different PAB circuits.
1. Lifts the MID control from ground.
2. A variation of 1 and adds resistance (partial lift)
3. This one confuses me. Disconnects the treble pot from the Bass pot.

Which version do you use?
Explanation of what is going on in #3?
Thanks!

[heisthl]

There appears to be a few different PAB circuits.
1. Lifts the MID control from ground.!

This works for the common tone stack like you might see in a Fender, by removing the ground you not only raise the resistance away from ground for the signal (gets louder), you also give the lows and mids no path to ground (gets fatter).

2. A variation of 1 and adds resistance (partial lift)!

Same as number one but less in both respects because you are providing some resistance to ground.

3. This one confuses me. Disconnects the treble pot from the Bass pot.!

This one is usually associated with the Skyliner stack which has separate paths to ground for Mid and Bass pots (no common grounding point to lift) It does boost volume by reducing signal path to ground resistance but does not really fatten the tone because Bass and Mids can still get to ground.
For fun you can play around with lifting just the Mid pot or just the Bass pot(or both) on the skyliner style.

Which version do you use?
Explanation of what is going on in #3?
Thanks!

I use #3 for Skyliner and #2 for regular stack types.

[benoit]

I use #3 for Skyliner and #2 for regular stack types.

Is this because you just want loud without too much tone change?

[heisthl]

In the lifted stack case it's because just taking it away from ground is too much of a volume jump. In the skyliner case for non-HRM it's because I tend to like (read build) darker sounding amps and the lack of bass boost in the PAB is a good thing for certain solo sounds. In a HRM most people use PAB anytime the OD is engaged and adjust the OD trimmers accordingly, so again the lack of bass boost is probably not a big deal. I have read compaints of clean and PAB not having enough bass but I've never had these complaints on builds I've sold to others or played myself.

[Structo]

Yes, my amp is heavy on the bass. I usually have the bass pot all the way down and when I flip the PAB switch it is still too much.
This is on single coil strats and teles.
I was kind of surprised at this because I have read more about taming the treble on these amps.

[Tonegeek]

Yes, my amp is heavy on the bass. I usually have the bass pot all the way down and when I flip the PAB switch it is still too much.
This is on single coil strats and teles.
I was kind of surprised at this because I have read more about taming the treble on these amps.

If your PAB works by the method that separates the treble and bass pots and also lifts the bass wiper then you may be able to tame your bass in OD mode by modding your switch to leave the bass wiper connected. This will give you less bass in OD, especially since you keep the control down low. I did this on mine and it helps.

Really since you get too much bass overall, then you may want to change one or more coupling caps to a lower value. I like .01 for the V1b (CL2) coupler. Other caps to look at would be the PI plates (.1 down to .02) and maybe the PI input (I like .02 but have used .01).

[Structo]

Thanks, that may be the ticket.
So would I just run leg 3 to the PAB switch and connect the wiper to the bass cap on the board?

[Deric]

Tom,

Do you have a jumper accross lugs 2 and 3 of the bass pot?

[Structo]

Yes I do, I was in the process of changing that to the non bass mod wiring when I had the problems with the power tube red plating.
Which turned out to be a faulty speaker cable.

So in my effort to retrace my steps leading to the tube problem I wired everything back the way it was.
So I never got to try it without the mod.

[Deric]

On this build I had the pots all mounted and wired when I did a 180 and decided to change a bunch of things. I meant to remove the "bass mod" but forgot untill yesterday. I like it much better without.