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Preamps with two main-outs

Question for folks with two separate stereo amps driven by a single preamp. My preamp has two main outputs feeding two separate amps - one stereo and one pair of monoblocks, driving two pairs of speakers in two different rooms. Is it normal to need to turn on all the amplifiers to play any music? In other words, I can't just turn on my stereo amp to listen to music in one room. Its all or nothing. Fortunately the mono amps (MC2200) have volume control and I can turn them all the way down but can't do that for the stereo amp for the speakers in the other room. I was wondering if this is normal for all preamps with multiple pre-outs or its dependent on a particular preamp model. If it matters, the preamp is a NAD C165BEE. Thanks.

P.S. The second main-out has a little knob for gain control but its on the back of the preamp next to the ports and not practical to use for this purpose.

128x128kalali
yogiboy's avatar
yogiboy
5,701 posts
 
Yes it is normal!
onhwy61's avatar
onhwy61
5,229 posts
 
I'd be concerned about out of phase backflow voltages coming from the turned off amp.  The electrons travel down the interconnect and when they reach the turned offed amp they don't know what to do -- they knock on the door, ring the doorbell, go around back to check the backdoor and even throw pebbles at windows to try to wake the amp up.  But once they realize "nobody is home" they straggle back to the preamp.  Once back at the preamp some of the electrons then decide to travel to the other power amp, but by then they are out of phase.  It's actually a little more complicated, but in essence, that's OOP backflow current.  Some people can't hear the effect and other people think the effect is jaw-dropping.  Go figure!
kalali's avatar
kalali OP
1,977 posts
 

Thank you. It would have been nice to be able to select which (or both) main-out you'd like to be active at any given time especially for scenarios like mine where the amps drive speakers in different (but adjacent) rooms. I have a Schiit Sys passive pre that I can insert in the middle to control (or turn off) the volume for my stereo amp but mainly wanted to first make sure if this is normal before resorting to a workaround.

Like onhwy61's theatrical analogy.... makes good sense, I guess.

almarg's avatar
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almarg
9,670 posts
 
Onhwy61, I hereby nominate you for today’s edition of the Wolf_Garcia Award for most amusing post of the day.

I must, however, respectfully disagree with my learned A’gon colleagues who posted above. Kalali, while I’m not certain if what you have described is or is not normal for your particular equipment, it is certainly **very** unusual. The only explanation I can think of is the possibility that the amps short their inputs when turned off, perhaps via a relay. Which would be very unusual, and furthermore I looked at the manual for the MC2200 (as well as the manual for the NAD preamp), and I see nothing that is supportive of that explanation. So I’m baffled.

Best regards,
-- Al

wbs
77 posts
 
I too am baffled.  My Mac C100 has two outs which I use for biamping and if I power down one set of amps the other keeps working.  There is no separate control for individual outputs, both are always going.

Bill
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