Quick question please.
If I have two audio signals from two amps, one swinging entirely above DC and the other entirely below what happens if the active sides are mixed without any earth connection? Both signals are identical and with the same DC offset, but 180 degress out of phase.
I am assuming the net voltage will be zero, but how does this affect the load seen by the amp?
Martin Kane
You forgot to say what you mean by 'mix.' The answers vary depending on that.
NT
You appear to be describing a bridged pair of amplifiers. Such a configuration can be used to deliver larger voltages across the terminals of a higher resistance load up to the rating of the amp.
Isn't great but it has diagrams that might help you phrase your question more clearly.
If you connect them together without a load resistance the power output stages of each unit will attempt to destroy the other until at least one of them is successful or the fuse blows. Possibly both.
Regards, Martin Brown
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-- JF
Without any earth connection on either amp, the two power domains will be driven into audio frequency voltage excursions. Zero signal to the node. It is the common. No problem, no sound.
-- No.
"Mix" in RF means multiply. "Mix" in audio means arithmetic add. Note one cannot "wire or" low impedance outputs like amp outputs. You use a "buildout resistor". probably not a good idea on the output of an amp. Need hi wattage resistors that get real hot. Inefficient. In general, out of phase sine waves will cancel.
Given the nature of the question I couldnt rule that out. Who knows whether the OP meant amp outputs hardwired in parallel, hooked up in series, common ground or separate, speaker between the 2 signal outputs, could be anything.
In general, yes. But in some cases it can get different. If the OP were parallelling the outputs of 2 amps, and one provided much more power than the other, likely the smaller one would cut out and leave the big one to drive the load.
... who knows.
NT
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