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I've got an 8 ohm 5 watt head, and a 30 watt 16 ohm 110 cab.

This is a complete newb question, but I've never actually mismatched impedence. I'm usually a snob about this, but these two random pieces seem like they should be together.

Can this be done? Will this work?

EDIT: warning shortscale - the below fact is totally higgledy piggledy.

Wrong way round - big amp into little cab is OK, but not vice-versa.

Valve or solid-state amp?
In general, solid-state amps will drive anything from 4 ohms upwards (but usually there's somethng to tell you) and, usually being voltage amplifiers, the lower the ohms the more the watts.
With valve amps an impedance mismatch isn't quite so easy. More ohms on the speaker than the amp is generally OK, but some people say there's a higher chance of a transient causing a flashover in the tube. Personally I'd try it.

Re: amp watts and speakers - since I fried a Fane 20W and a Goodmans 20W with a 100W amp back in the day I've never been a believer in having a cabinet rated lower than the amp. It may give you that cone-break-up-mode distortion but bakes your voice coils. These days voice coils may be built for more abuse (e.g. tape wound on aluminum formers with high-temperature epoxy), back then a transient could knock the voice coil off its former once you'd baked the lacquer to uselessness.

I've run a 4 ohm Bassman into an 8 ohm cab for ages without any issues, but then it's vintage and i've heard/read that they made better transformers in the olden days that can handle mismatched ohm-age.

4 ohm amp into 16 ohm cab OK!
16 ohm amp into 4 ohm cab NOT OKAY!

So whatchu talkin' about benecol?

The way this works (I believe) is that you have less ohms on your cab, the cab wont be taking the FULL LOAD and you can blow things up. Alternatively when you have the amp powering a cabinet with higher ohms the amp has to work twice as hard, so you wear out your tubes faster.

Correct me if I am wrong anyone?

Someone here knows what they're talking about...

http://forum.orangeamps.com/viewtopic.php?t=37029

5 watt tube amp

Ben79 wrote:Someone here knows what they're talking about...

http://forum.orangeamps.com/viewtopic.php?t=37029

I'm not convinced that he does in all areas. For example, he's probably right that the tubes will go before the transformer into a low load. My acquaintance Kevin ran his Dual Rec 100W head into 2x 8-ohm cabs for years on the 8 ohm setting until the PCB gave up - and took the tubes and the output transformer with it. However, the talk about the "flyback voltage" killing the transformer is a bit worrying; IMHO if you have a properly-designed Zobel network in there to dampen transients you shouldn't get a "flyback voltage". Some designs include a resistor in parallel with the output to provide a minimum load at any frequency.

What Ian said, 8 ohm amp into 16 ohm cab is fine. Never go the other way around though, 16 ohm amp into 8 ohm cab is bye bye transformer town.

benecol wrote:Wrong way round - big amp into little cab is OK, but not vice-versa.

This is wrong, as ev'ryone has said.

You want your load to match or exceed what the amp requires; preferably match it when we're talkin' toobz.

benecol@jagstang wrote:Wrong way round - big amp into little cab is OK, but not vice-versa.

NEWB!

Do you know what, Doog? Not only am I going to concede that you're right, I'm going to edit my original post* so that no one mistakes it for a pearl of wisdom.




* I'll even leave the original mistake in, so that people can see that I'm fallible.

... in fact, what this situation needs is a handy aide-de-memoir; I'm proposing this one:

"Just remember, the cab is always bigger than the head!"

... or equal to

Taking it on the chin, like a true gent.

*insert mucky photo*

Doog wrote:Taking it on the chin, like a true gent.

*insert mucky photo*

This thread is treading into dangerous waters, first with discussion of loads and now to "taking it on the chin"??

Ian wrote: The way this works (I believe) is that you have less ohms on your cab, the cab wont be taking the FULL LOAD and you can blow things up. Alternatively when you have the amp powering a cabinet with higher ohms the amp has to work twice as hard, so you wear out your tubes faster.

Correct me if I am wrong anyone?

Ian's Hitting the nail firmly on the head here!...you can knacker your amp up either way, unless your impedence is matched between head/cab..
Speaker wattage is another bugger to get your head around too!..either match/exceed the amp/speaker watts output ratio, or risk the speaker blowing...but then lower wattage speakers breakup earlier, giving you that tasty overdriven noise...aarrrrggghhh!!! Confusing ain't it!!....