Unfocused Sound stage

I once accidentally swapped +- on the speaker and my brand new amp blown the whole output stage. Fuse didn't act fast enough to prevent output stage from blowing.
In DC coupled amps DC component of signal is diverted to chassis. Connecting speakers reverse to DC-coupled amp may cause the amplifier damage.

I have never heard of this and don't see how it could occur. I have used DC coupled amps in the past and have reversed wiring many times. Wouldn't a phase reversal switch also blow the amp in your description? My CJ 350 reverses phase as does my Magic pre amp; would I blow the amp if I were to use them together? I must be missing something here but not being an electronics expert have no idea what it is.

Stan,

That one was primitive Creek 4330SE and there was a clear instruction not to swap speaker terminals or kaput.
Your amps have isolated ground most likely.

Stanwal, I too don't understand Marakanetz's scenario unless he momentarily/accidentally shorted the speaker wiring while making a *hot* swap. A speaker's passive (non-polarized) x-over components don't care which polarity feeds them aside from matching phase response to "excurt" like-drivers simultaneously during the same AC cycle half. Beats me!

I second Newbee's comment. The only things I can think of that would account for the symptoms the OP described are a +/- reversal to one (and only one) speaker, or use of a balanced interconnect that has pins 2 and 3 interchanged at one end of the cable in one (and only one) channel.

Regarding the experience Marakanetz reported, I agree with the comments by Stan and Metro, provided that the speaker is purely passive (i.e., it does not contain an amplifier), and provided that a powered sub is not connected to the outputs of the main amp.

If the main amp is connected to the inputs of another amp (either in the speakers or in a powered sub), then it is possible that a +/- reversal could cause damage. That would occur if both amplifiers have 3-prong power plugs, and both have ac safety ground in common with (i.e., connected to) their internal circuit ground. In that situation reversing + and - would short the + output of the main amp to its ground, via a path through the amp in the speaker or sub and the safety ground wiring of the two components.

Regards,
-- Al