Loss of Sound Quality when both systems are ON

Hello All You Good People

I have come to somewhat of a dissapointment in my setup. I'm hoping it's an easy fix. Over the years i have listened to a good number of amps and speakers. I have come to a personal conclusion on what i like my stereo setup to sound like. I bought two pairs of tube amps, four speakers and run them through a preamp with 2 sets of outputs. When i use each set separately, everything sounds beautiful, bass is full, mids and highs are excellent on each system. But...when i use 2 sets at the same time, the sound coming out from my speakers are dull, almost no bass, lost mids, as if there is not enough power coming to the speakers. I have tried separate electrical circuits, no luck.


This problem is fixed when using amp/preamp's own power, and output 2 (external amps). Both output 1 and 2 are on and they sound great. But as soon as i wire the system so output 1 and 2 are external amps only, the sound they produce is faulty when both outputs are on at the same time.

Here is my system.

McIntosh MA6600 amp/preamp 200w/channel 2sets of outputs
Pair of Cary SLM-100 mono blocks 8ohms 103W Liniar Mode
Pair of Cary SLM-100 mono blocks 8ohms 60W Triode Mode
Pair of Klipsch Chorus II 100W nominal power 8ohms
Pair of Klipsch KG5.2 100W nominal power 8ohms
Is this dual system in the same room or divided into different rooms?
My guess would be that one of the two pairs of Cary amps inverts phase but the other does not. So when you run the two pairs of external amps, the two pairs of speakers are running out of phase relative to each other (i.e., the cones of one pair are moving out while the cones of the other pair are moving in). That would produce the partial bass cancellation and apparent lack of power that you describe.

To fix that, you would have to reverse the plus and minus (red and black) connections to the left and right speakers of ONE of the two pairs of speakers.

Hope that helps,
-- Al
This 'problem' may be a result of the design of the pre-amp. My ARC SP10 does exactly the same thing. I can not use two outputs to drive two systems at the same time. Connecting a seperate system to the second set of outputs 'loads' the other. Almost like the gross effect of having way too much impedence output from an amp or in speaker wires. But its gross! The only way I can successfully drive two different amps, etc, with it is to use a Y signal splitter from one output. Before you waste a lot of time trying to solve something that is unsolvable, call McIntosh and ask them about their design.