2. amps-preamps
  3. 130195-80275

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
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imhififan's avatar
imhififan
2,210 posts
 
it appears that what is most likely a relay is connected directly between the signal pin and the ground sleeve of the RCA input connector on each channel. Presumably when the warmup period concludes a control voltage is applied to the relay which causes its contacts to open up, allowing the input signal to proceed to the input stage. And presumably when the amp is turned off that control voltage goes away and the contacts close, resulting in a short across the input.
A modification may solve the problem:

INPUT         NO
@-------------o
 |                   \              R2
 |                    O--------WWW------
 |                     C
 |---------------o
 |                  NC
 |
V
GND
kalali's avatar
kalali OP
1,977 posts
 

With the amplifiers off, I measure "continuity" at the input ports on the Vincent but not on the MC2200, using my very basic millimeter. Didn't feel comfortable sticking my meter probes inside the ports with the amplifiers turned on. I think we can surmise this is NOT normal behavior and is dependent on the amplifiers' input stage design. Thanks everyone for your help in explaining this behavior.


kalali's avatar
kalali OP
1,977 posts
 
Previous post should read "multimeter" not millimeter. Autocorrect in action...
stanwal's avatar
stanwal
3,147 posts
 
I use to have an unusual set up, 4 monblxks driving the top and bottom ends of a Dutta Signature. Since they were identical I just bought a set of custom Y connectors. Worked fine but I doubt if few have a system like this.
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