Am I a numpty?

[up the music]

I posted yesterday on how I dug out my old turntable and set up a temporary rig for a few disks. Today I went back to my usual set up but forgot to remove the biwire speaker jumpers. I ended up with 2 runs of cable per channel like a biwire arrangement but with the jumpers still in place.

I had switched on and was chatting to a friend but had not yet put on any music when there was a 'something falling' sound from my equipment rack followed by the click of my amp switching off. I haven't found anything in the rack that might have fallen.

I discovered the amps protection turned it off again every time I tried to switch it on. It was removed from the rack and there's the distinctive aroma of fried circuitry. Removing the lid I can see definite signs that something went explosive in one channels output.

The question? Could this be caused by my failure to remove jumpers? Or did my pre amp do it and that was the 'falling sound'? Or was it the power amp all on it's own? I've checked mains and interconnect cables and they're fine and in the clear.

 

[Anonymous]

I think you might just be a numpty! lol

What did this 'falling sound' sound like? Like a thud or like "Noooooooooo"?

 

[up the music]

Well I was sat immediately in front of the rack about 1 ft away and it sounded like something clattering down hitting things on the way. Like I said though there was nothing out of place. Then the click of death as the amp turned off.

Oh yes, further reading on my part and it's official. I'm a numpty. I'd just got so used to biwire that I forgot that I'd put the jumpers in yesterday and that forgetfullness is gonna cost me.
So it's off to the fixing shop tomorrow.

 

[the record spot]

I think you've answered your own question sadly. No offence and all that...!

(Hope you get it fixed btw!)

 

[chebby]

So the bi-wired cable and the bridge formed loop circuits? (No that cannot be right because one side is +ve and the other -ve.)

Not convinced the biwire caused the problem.

Surely (with the bridge in place) the speaker and the amp only 'see' one cable to +ve and another one to -ve despite there being two.

How is it different (electrically/topologically or whatever) to having two single cables wired into a single banana plug at each end?

Any 'circuit' is still formed correctly between +ve and -ve with the speaker/crossover in between even if you used 10 cables between +ve on the amp and +ve on the speaker.

The only harm I can think of is if you mixed up +ve and -ve by mistake and biwired across them with the bridge in place,

Was the 'clattering' something conductive that may have rested across the amp terminals (shorting them) on it's way down?

 

[jc.com]

If I read this correctly, you have two cables joined at the amp end, going to two sets of terminals at the speakers, and the speaker terminals are bridged, as though mono-wired?

If so, why should this cause problems, assuming you had observed the polarities correctly? Shouldn't it simply be like a thicker mono-wire?

 

[up the music]

My initial thoughts were that it's as Chebby and JC.Com said. It should make no difference. Then late into the night I came upon a page suggesting damage could occur using this wiring. It didn't get technical on how this would happen though. I can't find the page anymore. It may be just part of the mass of incorrect information available on the web. So I've changed my stance, I am a numpty, but I'm not convinced my numptiness killed the output stage.

The idea of something shorting is interesting. The amp didnt get moved and uses air filters whih should prevent ingress of any foreign objects.
Yes, I can see how crossing polarity of one pair of cables would be bad, but I double checked when I put them in initially. I triple checked after my amp went sparky. Polarity was fine.

My other idea of a misbehaving pre amp. Surely this would take out input stages on the amp, not output?

Anyway. Off to the shops now.