S/N ratio Balanced input vs. Unbalanced input


Hi, is it normal that signal to noise (S/N) ratio at rated output of balanced input (XLR) is lesser than unbalanced input (RCA) ?

eg. Accuphase E280 , S/N ratio balanced is 96dB, unbalanced is 107dB.

 

Also E280 , at preamp stage , dB gain : balanced/unbalanced to pre output is 18dB gain, power amp stage dB gain : 28dB, total of 46dB.

What about other integrated amplifiers specs for comparison ? 

S/N ratio (balanced) :

S/N ratio (unbalanced):

Preamp gain :

Poweramp gain: 

 

auronthas

I wouldn’t worry about it but I would be curious. Even if not so loud, the hiss should not be there. I am allergic to anything that gives more digital glare, and the hiss may be a suspect, even if not much notable by itself when playing music in the listening position. So I would wonder, why does this happen. Does the DAC behave that way with other amps also? Are you sure other sources into the amp don’t give the hiss? You’ve said its the same from xlr and single ended inputs. If you have switchable inputs between sources on your amp - the same across these, also? The fact that the hiss does not vary with the volume level makes me pause. Something wrong in the DAC? Or mismatch, amp / DAC?

I just tested in my secondary system, with a Ming Da integrated amp, with a few small DACs including the Fiio x3 and Huawei p30. Aurum Cantus speakers, with top notch ribbon tweeters well able to tell me what goes on. No hiss, but some hum. Varying with volume. Below the "worry" border, though - only heard clearly at max volume.

since hiss is not volume cntrl dependent, you may deal with EMI issue. 

adding "Cable Clamp Clip RFI EMI EMC Noise Filters “ to analog bal/unbal cable, close to the amp inputs,  sometimes helps.

Are you sure other sources into the amp don’t give the hiss?

@o_holter Ya, I tried my old Sony CD player which connect to integrated amplifier via RCA, I did not notice any hiss near tweeter.  I will do fast "switching" from balanced input (Ares II DAC) and RCA input (Sony CD player) to test the hiss noise.

adding "Cable Clamp Clip RFI EMI EMC Noise Filters “ 

@westcoastaudiophile my audio equipment are connected to a good power conditioner of Novaris brand.  I would think EMI issue shall not be the case, wouldn't it ?

@auronthas The reason your amp is noisier with the balanced input is that the amp itself has a single-ended input; its not internally balanced. So the balanced input goes thru a separate circuit which adds noise.

IMO/IME this is a sloppy way of doing things since the balanced operation is more of an afterthought whereas again IMO it should be the star of the show.

Normally if the internal circuitry were balanced-differential, the single-ended input would be noisier as there would be less noise cancellation.

This also explains why there is less noise when the balanced DAC is connected; the opamp that does the balanced to single-ended conversion is able to pick up noise with no input load.

@atmasphere What you said make sense. I will leave it if this not a defect, just not perfect.  Thanks