The Junkyard-D'

[dogears]

That is the dilemma. The stack is designed to correctly operate with the lugs connected. However, in PAB mode, the lugs must be broken!! That is why Dumble used a relay. One set of contacts breakes the bass pot from treble pot, and the other set breaks the connection between the input lug and the wiper.

I didn't like how the tone controls worked with that jumper, so I removed it. I found the PAB worked better after that too.

I am having a great time setting that trimmer at the entrance to OD1. Every time I settle with a setting, I find a better one! Maybe I should have put it on the front panel.

[Fischerman]

How does not breaking the bass wiper connection 'screw up' the PAB? I just recently tested this myself and the difference wasn't enough for me worry about. Yes, it sounded a little different (and I never did decide which I thought sounded better...just that they were a little different) and the bass pot affects the PAB but I always keep my bass control within a reasonable range so that was a total non-issue. But freeing up half of the PAB relay so I could use it for something else was such a huge benefit that I felt it was well worth ditching the bass wiper break (it's just hardwired-connected to the CW lug). In the end...after-mod sounds better than before-mod on my amp so I guess I'm curious why I keep hearing how not breaking the bass wiper 'ruins' the PAB? It did anything but on my amp.

[dogears]

For me, the PAB is a bit thin, especially when you only have 150K or so to ground on the bass pot. By breaking the wiper, you raise the resistance from ground up to the full pot value, ie, 500K. This fattens things a bit. Once again, I guess ruin is a bad word, but it fattens and that for me is better, and I am a perfectionist

I had some things I wanted relay control of so I added another relay

How does not breaking the bass wiper connection 'screw up' the PAB? I just recently tested this myself and the difference wasn't enough for me worry about. Yes, it sounded a little different (and I never did decide which I thought sounded better...just that they were a little different) and the bass pot affects the PAB but I always keep my bass control within a reasonable range so that was a total non-issue. But freeing up half of the PAB relay so I could use it for something else was such a huge benefit that I felt it was well worth ditching the bass wiper break (it's just hardwired-connected to the CW lug). In the end...after-mod sounds better than before-mod on my amp so I guess I'm curious why I keep hearing how not breaking the bass wiper 'ruins' the PAB? It did anything but on my amp.

[Fischerman]

For me, the PAB is a bit thin, especially when you only have 150K or so to ground on the bass pot. By breaking the wiper, you raise the resistance from ground up to the full pot value, ie, 500K. This fattens things a bit. Once again, I guess ruin is a bad word, but it fattens and that for me is better, and I am a perfectionist

I had some things I wanted relay control of so I added another relay

Yea...I did some experimenting with it and the resistance values are easy enough to see from the schematic. From my testing; the difference between 150k and 500k there isn't that big...and as long as you are 'sufficiently-above-zero-resistance' there then it doesn't make that much of a difference. I agree that it's a bit thin (that's the problem IMO)...and it is a little bit thinner with the bass wiper connected. But since I wanted to fatten it up (since it is a bit thin even when the wiper connection is broken) and since I feel I can do that much better by using the other half of the PAB relay...then it seemed the better (i.e. more perfect ) solution to was use it that way rather than to have it perform some minor tweek to the PAB (that's already imperfect anyway).

I had considered adding another relay but I really wanted to experiment with the existing relay and exhaust all possibilities there before I did so (something you probably did years ago ). But my amp is young and I'm still pretty green to these amps...not anywhere near as far along in my 'evolution' with these things as you are Scott...so who knows I may add more relays. As you know...my amp is supposed to 'act like and look like' an independant 2-channel amp with separate tone stacks (i.e. panel-mounted HRM tone controls) and only sharing the input Volume control...so my amp is really intended to be run with PAB on in OD at all times (even though you can switch it off if you want). So mine is a very slightly different aminal...more simple actually.