newbie stereo/mono question

[sigh]

I recently fried up this shitty combo amp I have, and I can't figure out why.

I was using a peavey 412ms, pictured here.



I used a crate gx212 as a slave.
Stats:
Output Power Rating 115 watts RMS @ 5% THD, 4 ohm load
Speaker Size and Rating GX-120: Custom Design 12”, 4 ohms
(2) GX-212+ Custom Design 12”, 8 ohms

Additional info is on page 5 of this acrobat file:http://www.crateamps.com/pdf/manuals/GX120212+.pdf


So I ran it in mono, because I was only using one amp and one cabinet?
After about 45 minutes I smelled smoked, and turned around just in time to see the red light fade away forever. Fuse seems ok. The cab is fine.

The warning on the cabinet seems to indicate it has something to do with the switch, but I wasn't using a "stereo configuration." At least I didn't think I was?

Am I missing something?

[Enzo]

If you were using a stereo amp into the cab and flipped the switch to mono, it would short the two channels together. That's all the warning means.

You either overloaded the amp or the amp just coincidentally picked now to fail.

[sigh]

Thank you so much for the response!
This prompts me to ask two follow-up questions.

1. Am I wrong to assume that Crate 212 is not a stereo amp?

and 2. What does "overloaded" mean? Is that a possible result of using a stomp box with the level too high?

Thanks again, I'm hopeless.

[Enzo]

Overload has nothing to do with WHAT you amplify. it is about hanging too low an impedance on the output. That can happen if you connect too many speakers or speakers with too low impedance ratings. It can also occur when the speakers are not connected properly or when the speaker cable is either faulty or not really a speaker cable. never use guitar cords for speakers.

The Crate amp is not stereo, it is a basic amp.

ANy amp that really is stereo will be telling you that in no uncertain terms. it will say "STEREO" somewhere on it, or the name will be something like STereo CHorus 100.

Stereo amps means amps that have TWO separate power amplifiers in them

[Steve Conner]

When you say "used as a slave" do you mean that you plugged the speaker output of one amp into the instrument input of another? That's a pretty good way to fry the slave amp.

[sigh]

I used a legit speaker cable and did nothing with multiple amps.
I simply ran a cable from the combo amp's "ext. speaker" output (jack #19 on that pdf) to a 412ms input. The switch was set at mono.

Here's another image of the one I had in my first post:


I just noticed that mono talks about 16 ohms. Stereo talks about 8 ohms.
If my amp's manual says "Output Power Rating 115 watts RMS @ 5% THD, 4 ohm load," does that mean that it was only a matter of time, and the amp and cabinet are simply not compatible because my amp operates in 4 ohms?

Enzo, I guess I don't understand your explanation. Does this situation ^^^^^ sound like a jacked up impedance situation, in which an overload can occur?

Thanks for helping. This is the first cabinet I've ever owned. I know nothing.

[Enzo]

The Crate amp is solid state - that means transistors instead of tubes. As such, it has a minimum impedance load rating, which means you can connect speakers all you like as long as th total impedance does not go below the rated amount. If your amp is rated for 4 ohms, that means you cannot go below 4 ohms. But anything higher is fine. SO a 4, 8, 16 ohm load is fine.

Set for mono use, your 4x12 cab is a 16 ohm cab. The amp will be happy as a clam with that.

Your combo speakers total 8 ohms. SO when adding an external speaker, you cannot go below 8 ohms there. 8 ohms and 8 ohms combne to make 4 ohms. Your cap is 16, so that is fine. 16 is a little less work for the amp.

So NO it does not appear the amp was overloaded.

Of the potential scenarios I mentioned above, I'd go with the second: Your amp coincidentally picked now to fail.