chipamp AB testing

jimbo1968 · 14th December 2005, 03:06 PM

If I parallel two amplifiers into some speakers, leave them both switched on, and then switch the input signal from A to B, does the amp without a signal effect the output from the 'active' amp ?

Does the answer depend on whether the amps are nominally the same? or whether they have output resistors?

neutron7 · 14th December 2005, 03:27 PM

i wouldnt do that! it could possibly lead to release of smoke. and definately change and distort the sound by quite a lot.

imagine one amp is trying to stay at 0v because it has no input. while the other one is trying to play music. though a speaker, and throughj another amplifiers output stage.

what happens when the non playing amplifiers feedback circuit sees the signal there it will try and swing the output to compensate. then the playing amplifier will have to do something to compensate for that. and make it even worse. maybe a high power oscillation that blows amplifiers and even the speaker.

switch the output as well as the input for a proper a/b comparison.

if you decide not to switch the input you may or may not have impedance matching problems, which could affect the sound but you wont blow anything up.

tiltedhalo · 14th December 2005, 06:16 PM

I wouldnt do that either, the one active amp will dump current to the inactive amp, poof smoke good by chip

14th December 2005, 03:06 PM	#1
jimbo1968 diyAudio Member Join Date: Nov 2004 Location: UK, bristol	chipamp AB testing If I parallel two amplifiers into some speakers, leave them both switched on, and then switch the input signal from A to B, does the amp without a signal effect the output from the 'active' amp ? Does the answer depend on whether the amps are nominally the same? or whether they have output resistors?

14th December 2005, 06:16 PM	#3
tiltedhalo diyAudio Member Join Date: Sep 2005 Location: Melbourne Florida	AB testing I wouldnt do that either, the one active amp will dump current to the inactive amp, poof smoke good by chip

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14th December 2005, 03:27 PM	#2
neutron7 diyAudio Member Join Date: Dec 2003 Location: Toronto Canada	i wouldnt do that! it could possibly lead to release of smoke. and definately change and distort the sound by quite a lot. imagine one amp is trying to stay at 0v because it has no input. while the other one is trying to play music. though a speaker, and throughj another amplifiers output stage. what happens when the non playing amplifiers feedback circuit sees the signal there it will try and swing the output to compensate. then the playing amplifier will have to do something to compensate for that. and make it even worse. maybe a high power oscillation that blows amplifiers and even the speaker. switch the output as well as the input for a proper a/b comparison. if you decide not to switch the input you may or may not have impedance matching problems, which could affect the sound but you wont blow anything up.

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