PA 2000 output transformer impedance

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tommytutone
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Joined: 2010-07-13
PA 2000 output transformer impedance

I just picked up a PA2000 tube head (these thing make awesome guitar amps btw) and 2 4X12 towers in vintage 70's Black tuck and roll. The cabinets are 4 ohms each.

Anyone know what the output transformer impedance is? The schematic on schematicheaven.com indicates a 15ohm 'safety' resistor to keep the transformer from running 'open' when no load is attached, indicating the output load should be 16 ohms. But the output jacks are in parallel..........meaning if one hooks up Four 4 ohm cabinets, the output should be a whopping one ohm.

Also, anyone have any idea who the speaker OEM was? There are no markings on the speaker magnets.

Any body have any input?

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pyramid_eye
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Joined: 2011-01-27
hey guys, has anyone made any

hey guys, has anyone made any headway on this? i picked up two plush congress heads recently and have no idea what to plug them into and as old as they are (and poor as i am) i'm scared blind to try anything. really looking forward to plugging in.

i haven't seen a schematic but i e-mailed a guy who was selling a pa2000 to ask the impedance load and he claimed it was 8ohms. is this maybe some misinformation? or maybe the two 4ohm towers are meant to be rigged up in series? (2 x 4ohms in series = 8 ohms? it's brick simple but i go mathematically dyslexic when trying to figure this out.)

i wanna drive a single cabinet, or maybe two smaller cabs, cuz as cool as those towers are, even if were able to track down a pair, who wants to drag those around.

and a side note, i saw that plush also made some 3x12 towers like these as well. they must have really loved those old kustoms.

aldersmoke1
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Joined: 2008-05-07
According to my tech, the

According to my tech, the output for a single cabinet is 4 ohms (plugging into the "Use First" output jack). I use 1 4x12 Marshall cab for my PA 2000. Unfortunately I do not know enough about the mysteries of resistance to be able to tell you what the rating is for 2 cabs; however, I know the PA2000 head was sold as a package with the two 4x12 towers, so I know they're all supposed to play nice together.

And yeah, it makes a fantastic guitar amp. Every bit as awesome as the G2000, with the added flexibility of a Master volume. I actually have 2, although the other is the Plush version, the Congress IV. These heads stack up against some of the big vintage names and hold their own for a fraction of the cost.

Very cool that you found the cabs as well. I'd love to have the full set-up, but the practicality of transporting those suckers to gigs has led to my current compromise.

tommytutone
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Joined: 2010-07-13
the towers are cool, but not

the towers are cool, but not very practical to lug around. I'll prob use a small 4 x 6 cab I built (btw, cheap car speakers make some awesome guitar speakers), especially at small places.

I agree with your tech and see on the schematic exactly what he is talking about, but two 4 ohm cabinets in parallel equals a 2 ohm load (look up ohms law if you'd like to learn how the math works). Ask him what he thinks what load the transformer wants to see.

Awesome that you have the Plush version. And most people don't know the are Fender Twin/Showman copies at a fraction of the cost.

Have you modified yours in any way? I'm about to make a 4 channel head (bassman/plexi, dumble, clean, high gain), foot switchable and mixable.

Lerxst2112
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Joined: 2010-12-22
Mods

Tommy, I own a Congress IV head and I am intrigued by your suggestion for (I am assuming) a PA2000 to modify the independent 4 channels for independently different sounds. That sounds like a really great idea and I (and I'm sure others) would like to know how you are going about doing so if you are willing to part with that information.

Thanks!

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