Curious Peavey impedence jacks

[Randall]

Refurbed a Peavey VT Classic 212 combo, and among other things like a rodent chewed AC cord, it had a faulty speaker plug/cable. I replaced that, but when I was set to plug it back in I noticed the two speaker jacks are labled Main 8 ohm and Aux 4 ohm. The cab is loaded with two Peavey 8 ohm speakers in parallel. The manual states the OT has two difference taps for a wide range of possibilites, and cautions against mis-matching impedences.

If the main jack is 8 ohms, and the cab is loaded at 4 ohms, what were they thinking here? Also, the Aux jack is a switching jack, so I don't think it works by itself, but I didn't try it.

[The Dude]

The schematic is here: http://www.adrsoundsense.co.uk/techn...assic%20VT.pdf

The Aux jack is a switching jack, but it doesn't ground the OT secondary like traditional Fender amps. It switches OT taps. When something is plugged into the Aux jack, it switches to the 4 ohm OT tap. So, if you have 2 separate 8 ohm cabinets, you'd plug one into each jack. If you have a single 4 ohm load, you'd plug into the aux jack. And of course, a single 8 ohm speaker would go to the Main jack.

[Randall]

It's just weird that the 4 ohm jack is labeled Aux not Main, isn't it? Unless something is amiss with the speaker setup, but it looks stock to me.

[The Dude]

Nope. That's stock. It's a little unconventional, but they are also labeled 4 & 8 ohm as I recall. I don't remember the factory speaker configuration, so maybe somebody replaced speakers at one time or another.

[Randall]

So, 4 ohm Aux is what the 2x12, 8 ohm parallel internal speakers are meant to be connected? The math makes sense, the logic does not, not to me at least.

[The Dude]

So, 4 ohm Aux is what the 2x12, 8 ohm parallel internal speakers are meant to be connected?......

Yes. Maybe the cabinet used to have 16 ohm speakers in parallel and they then went to the main jack. But, as it stands, they should go in the Aux jack.

[Enzo]

The Classic VT had 70777007 speaker stock, 12810PA or 12820PA. Look for those numbers on it. They are 8 ohms wired in parallel.

This 4 ohm load plugged into the MAIN jack meant for 8 ohms. It won't hurt anything. The AUX jack switches the whole thing to the 4 ohm tap.


Yes, it was never "right" from the factory.

[Randall]

Just like beans and rice, I knew Enzo would appear! The speakers actually have 12820PA and 67-7844 printed on them.

[Enzo]

Eminence 1978

Yours have the larger magnet. The 10 and 20 in those numbers refer to magnet weight in ounces.


Am I the beans or the rice?