Precision Electronics

[Belva]

I recently accuired a Precision Electronics PA head that has been converted for guitar use. Tube lineup: 7868 X 2, 6EU7 X 2 & 6c4 X 1. My question concerns speakers & impedance. This has a speaker strip allowing 4, 8 & 16 ohm loads. Would I cook my OT by hooking a 4 ohm speaker & an 8 ohm speaker to this strip at the same time? Each one with pos to the appropriate screw & both to the common. Just curious as I have one of each in my collection of junque. BTW this is a master volume amp & really has a good sound. Kicks holy pooper too!

[mike42]

My little resistance ruler says the total load that the amp will see is around 2.7 ohms, so the appropriate question may be, "are you feeling lucky today?' Seriously, I wouldn't try it.

[Belva]

Thanks. That's kinda what I thought. Think I'll get another 8 ohm speaker & just build a cab that I can run at either 4 or 16 ohms. I wasn't sure if the amp would see 2 different loads. I'm a tube noob.

[mike42]

Yeah, that's an interesting question, and I have wondered if there may some big PAs that have multiple isolated output taps where you could do that. But I think anything with just a single "common" is probably coming off the same transformer, or output stage. Maybe somebody else knows more?

[Belva]

Exactly what I'm trying to find out. I know it only has one OT & one PT. Finding a schematic will be tough if not impossible. My guess is it's something like a Bogen CHA 35. It was cheap & works well so I intend to keep it as is.