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Line level out without disturbing impedance
Line level out without disturbing impedance
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Old 27th December 2019, 06:21 PM   #1
jwags818 is offline jwags818  United States
diyAudio Member
Join Date: Aug 2005
Default Line level out without disturbing impedance

I want to put a device on my amplifier to turn it off if no music plays for 10 minutes. Seems to me I can do this on the signal coming into my amp or the speakers going out. But how to do it so it is not really in the signal path? I was thinking an opamp on the input because opamps do not flow current thru the inputs they shouldn't affect the source impedance. But I really dont like the idea of doing it pre power amp as any artifact will be amplified. Open to suggestions.
Corvallis Oregon
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Old 28th December 2019, 12:49 AM   #2
Mark Tillotson is online now Mark Tillotson
diyAudio Member
Join Date: May 2018
Location: Cambridge UK
Overcome your fear, so long as the opamp is powered up its inputs are not going to disturb a signal, they are multi-megaohm and a few pF only. opamp followers into an envelop detector would be reasonable. An opamp-follower actually bootstraps its non-inverting input anyway so it looks even less of a load. Could add 100k input resistors if you want the device not to clip the audio if its powered-down - use JFET input opamp so input offset isn't large.
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