2. amps-preamps
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channel separation

Have been doing some preliminary research about possibly moving from a nice integrated to separates.  Was hoping someone could set me straight on a measurement characteristic that has always bugged me:  channel separation.  Just read the Stereophile review of the Prima Luna EVO 400 preamp, which is described as dual mono from end-to-end. Yet, channel separation was measured at only 50 db (at 20 kHz) due to "capacitive coupling."

How can the channels bleed into one another when the entire layout is dual mono?  Why do solid state preamps seem to measure better in this area - is the output device of importance? Most importantly - does this matter? I always imagined that greater separation would mean greater preservation of image and soundstage.  Thanks very much!

batvac2

Showing 3 responses by erik_squires

erik_squires
16,589 posts
 
Interesting. It sounds like channel separation may not be causally related to sound quality,

I wouldn’t say this, exactly, but that 50 dB is a very high amount of channel separation.

As a scientist - but not an engineer - I remain puzzled about how the channels can bleed together at all in an amplifier (not a phono cartridge) if the right and left circuits are truly separated from input to output.

They are galvanically isolated, that is, there is no DC path from one to the other, however electromatnetic (inductive) and electrostatic (capacitive) coupling are quite well understood.

https://en.wikipedia.org/wiki/Capacitive_coupling

Best,

Erik
erik_squires
16,589 posts
 
BTW, I did the math.

Assuming one channel has 1V, -50 dB is about 0.003 volts.
erik_squires
16,589 posts
 
It's just really a matter of how well isolated the audio as well as the power supplies are.

At 20 kHz it probably doesn't matter. 50 dB is pretty good!

It's in my mind the midrange where separation is more important.
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