Terminate (dummy load) temporary unused power amp inputs?

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syn

Well-known member
Joined
Oct 11, 2005
Messages
653
Hi

        I'm building DAW to power amp selector. It will have one input (output from DAW)  and  two outputs, 1 to power amp  /  2  to a pair of active monitors.
        Inputs and outputs are balanced.
        Is it a good idea to dummy load temporary unused power amp inputs  (I will listen to one or another, not both at the same time obviously) so that unused power amp sees some (dummy) load at its input like resistor from each leg to ground? Like 1k? I read that some power amps like to go into ultrasonic  oscillation when left with no load at input and that can hurt tweeters (?).

Thank you
 
Most (all?) decent power amp designs will be stable with no input termination.

A resistive termination may reduce clicks when switching from leaky capacitors.

JR
 
Thank you, what value of resistor would you recommend then?  Inputs to amps are 10k per a leg so I tought something like1k would be OK - or less?
 
I would go low, to swamp-out stray signal on the unused cable. Even a short; why not? If there is a Why, then 100r or 1K.

Unused guitar-amp inputs routinely use shorts to keep them quiet; but g-level is 100X smaller than power-amp level.
 
Thank you PRR,                         
                                          yes,  that was my original  idea,  to use lower value resistors .  Good to know it would work.
I think 1k is a good compromise here ,  it will terminate properly,  it  will  "swamp-out stray signal on the unused cable" and it will
"reduce clicks when switching from leaky capacitors".
 
You may very well short unused input to ground, that´s very common/useful in a noisy environment.

In any case, and as said above, NO decent amplifier should be unstable with open input, although poor wiring/shielding/grounding/decoupling may cause problems ... but then it´s not exactly an amplifier problem, is it?  ;)
 

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