3rd Gen w/PAB

[xk49w]

I am planning a 3rd Gen into a cepedals chassis and want to use the PAB feature. I hadn't seen one of these so I sort blended a couple of schem's and had at it. It seems pretty similar to the #124 schematic but R25 connects to S2A rather than S2 common, which seems to be a standard connection for PAB schematics.

Has there been a 3rd gen w/PAB schematic with which I can compare? Further, any forseen problems with the proposed connection?

-- bradley

[dcribbs1412]

Hi xk49w

http://ampgarage.com/forum/viewtopic.ph ... d&start=15

about half way down 2nd_gen_hybrid pdf
might be something you can use for ideas
recommend the FET on relay

D

[Luthierwnc]

I just did something similar with a 2nd gen. Obviously a jumble of several eras but it works. I do PABs with a tail resistor rather than the lift (little blue 10-turn on the relay board). You'll have your own opinions there.

There are no brights on the loop controls. Kinda offsets the lack of PF loss cables to and from separate units. I did borrow bluesman's MESA series/parallel circuit but I'm in-between reverb units so I haven't tried it out. That's the 25k pot between the send and return jacks.

I used dual masters so the resistance going into the OD relay is much different than the usual Level into an overall master. I removed the clean master bright cap on mine (red) but this design (not by me) keeps that cap from dumping highs to ground when the OD is on because the CM #1 lug feeds into the OD entrance. When the OD is off, it works as usual.

If you're looking, I've never put manual OD or PAB switches on the back. The FET is on the footswitch and so is a mid-boost. Very not 2nd-gen but I can live with the shame. I have a 5meg JPG of the same gut shot in the files. I don't think I can get that into the thread but if you'll PM me with your email address, I'll send it to you. sh

[Phazor]

Luthierwnc, why the elevated heaters? I thought that was only needed with a CF. Does it reduce noise or something?

[Luthierwnc]

the loop has a CF, sh

[xk49w]

I just did something similar with a 2nd gen. Obviously a jumble of several eras but it works. I do PABs with a tail resistor rather than the lift (little blue 10-turn on the relay board). You'll have your own opinions there

That's interesting. And it appears to remove a bit of the the load on V1 caused by the TS compared to the standard PAB connection. Easier too - might try this first.

[Luthierwnc]

Much easier -- and adjustable. Just hit a chord and dial to taste. I didn't want as much of a volume increase as I got with lifting the ground. It also let me hot up the OD for two volume boosts. No need for 22m pop resistors either.

On this one I used a trimmer but you can just hang a resistor off Mid lug #1 to the bus and a parallel wire to the relay. I've seen versions with different resistors for the bass and mid tails. I couldn't tell the difference but there are those who can. sh