Alright well I just got my Peavey Ultra Plus head back from the shop, it stopped turning on and I couldn't find anyone to help me so I just took it in. Turns out the main fuse was blown and a couple of the tubes were in bad shape, whatever. So I got it back today - but I'm a little nervous to even plug it in. I want to make sure I have it set up right.

I don't remember specifically if I was messing with the impedance settings when it fried - but I don't know what else it could have been.

So, amp gurus. Am I correct in saying that the source impedance should not be higher then the load impedance? The head just says 4 ohms minimum, and the cab says 16 ohms. So theoretically, does this mean I could set the head at 4, 8, or 16 ohms and it should be fine?

Seems like I should just put it at 16, but I want to check before I start turning stuff on. My knowledge of impedance is.. well, you just heard pretty much all that I know

If the head could be at any impedance and not be higher ohms than the cab, what else could have caused the main fuse to go?

Fast advice please! I'm dying to turn this thing on, but I'm gonna wait until someone who knows what I'm talking about chimes in so I don't have to go straight back to the shop.


Oh, and while we're at it. What's this GND switch with + 0 - ??
Last edited by cm880999 at Jun 9, 2011,
Matching impedance is the way to go. 16 to 16.

It sounds like your power tubes just shorted out. That's not terrifically uncommon, and it's probably nothing you did. A power spike might have done it, so if you'd like to avoid it again, a power conditioner (not a surge protector!) would be a good way to protect your amp.
As a rule of thumb it's best to match head and cab impedance.
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