BAXANDALL EQ Question....

[zozoe]

Greetings again~ I've been wondering why my Ampeg GU12' doesn't rock nearly as well as my AC12's.... My GU is wonderfully clean, but NOWHERE as 'Stones'y as the AC's once its NFB is clipped.

THEN, I just now caught a YT video, comparing the 2 amp models, & the only major diff was that the AC's had a NFB loop whilst the newer GU's removed it, BUT the guy furthur explains how ''the 2-band (treb/bass) Baxandall eq curcuit on the GU's has a bunch less gain in the front end than the single Tone circuit on the AC 's, MUCH less!!" AHA!!

Is there anything, including totally altering or replacing the Baxandall with the AC12's 1-tone circuit, in order to re'gain' that lost gain factor that truly disappoints & perhaps is why the GU doesn't kick arse like the AC's (w/NFB clipped!)??
Many thanks~

[Willabe]

Those Ampeg GU12's are supposed to be great amps, as is, stock. No need for any mods. The GU12 is supposed to be 1 of their best guitar amps, in the top 3 at least.   

It is what it is. Not many out there. Why not sell it, and buy an Ampeg AC12? You seem to prefer it much better than the GU12?

David at Tone Quest Report Magazine bought 1 and did a review on it, some years back before he passed. He was over the moon about that amp. And he had bought, played and then reviewed many amps, vintage and new for the TQR magazine.

I thought that was the amp, GU12, not AC12, reported to have been used on the Stones' Exile on Main Street?

I was looking to buy 1, almost did, but the few I've seen the printing on the face plate was pretty bad or some other problem(s). I still might buy 1 some day, if I find 1 in better shape.

I would not change much in that amp, if anything, no mods, just change a bad cap or drifted R, snipping a NFB loop might be OK. It's a PC board, a very good PC board with heavy traces, but still a PC board.

No way would I take out the whole TS, it's a James (passive), not a Baxandall (active). Here's why;

Ampeg used a pre made circuit part back then for some of their TS's. It's the part of the TS with the dotted line around it in Ampeg's schemo. Those resistors and capacitors are inside of a tan/brown package pre wired internally with solder lead legs sticking out. If you mess with it and take it out, and then don't like it and want to put it back in, might be problems. It might fall apart just heating it up and trying to get it to come loose.

Looks like the normal input jack on the GU12 and the accordion jack on the AC12 are the hotter input jacks.