PAB Mod

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nickm57
Posts: 127
Joined: Thu Jun 05, 2008 6:00 am
Location: sydney australia

Re: PAB Mod

Post by nickm57 »

Something I noticed today when I was playing my amp.

For some reason, the boost in clean mode is huge.
When I step on the PAB in overdrive it hardly boosts it at all, more of a tonal shift.

I have the two resistors on the PAB relay but I can't remember the values.

I know I didn't go with the 22M ones because that hadn't been posted before.

Can anybody tell me why the PAB would be so huge on the clean channel but not on the OD channel?
That is where I would prefer the boost to be for soloing.

So mine is wired this way but the resistors on the PAB relay are smaller, maybe 10M.

I am also considering adding a tone control for the OD channel.
Not HRM but a single knob tone control just for the OD.

The boost is pre OD. The OD by its nature compresses/clips the signal .So no matter how much you drive (push more signal) to it you will see no db increase.
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greiswig
Posts: 1002
Joined: Wed Jun 20, 2007 8:19 pm
Location: Oregon

Re: PAB Mod

Post by greiswig »

I put an extra 250k small pot on the face of my amp, which is wired in series between the MV and ground. Normally it's shunted by an unused section of the PAB relay. When engaged, it opens that connection, letting me adjust my PAB volume relative to everything else.
-g
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Structo
Posts: 15446
Joined: Wed Oct 17, 2007 1:01 am
Location: Oregon

Re: PAB Mod

Post by Structo »

nickm57 wrote:
Something I noticed today when I was playing my amp.

For some reason, the boost in clean mode is huge.
When I step on the PAB in overdrive it hardly boosts it at all, more of a tonal shift.

I have the two resistors on the PAB relay but I can't remember the values.

I know I didn't go with the 22M ones because that hadn't been posted before.

Can anybody tell me why the PAB would be so huge on the clean channel but not on the OD channel?
That is where I would prefer the boost to be for soloing.

So mine is wired this way but the resistors on the PAB relay are smaller, maybe 10M.

I am also considering adding a tone control for the OD channel.
Not HRM but a single knob tone control just for the OD.

The boost is pre OD. The OD by its nature compresses/clips the signal .So no matter how much you drive (push more signal) to it you will see no db increase.
That sort of makes sense but it also seems if you goosed the signal before OD then it would boost that as well.
There has to be a work around for this.

The thing that sort of confuses me is why HAD would design it this way.
Why not have an adjustable boost, especially for the OD?

greiswig,
That is a good idea but I really don't want to drill more holes.
Perhaps I could do it with a stacked pot with concentric knobs.
Tom

Don't let that smoke out!
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