Port analog v digital issues

  • 26 January 2022
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I have a Sonos Port hooked up to my Denon S710W AVR via both analog and digital (co-ax) connections.  I used the included cables that came with the Port to hook up the analog feed and a new shielded coax cable from Amazon Basics  to hook up the digital feed.  I’ve tested both variable and fixed line out settings and issues sound occurs in both setups.

Heres the problem. The sound out of the digital connection is much harsher and more nasal sounding than the analog connection.  This is true whether the output is set to variable or fixed and true even when the receiver “Pure” mode (direct two channel mode, minimal processing).  The analog feed sounds softer and more appealing with a bit wider stereo soundfield.  

When I switch on Dolby Digital surround (which is the way I like to listen when Im moving around doing things) things really get uglty on the digital side.  It sounds echo-ey and harsh in a way that the analog feed run through the same DD processing does not.  I made sure that any EQ settings on the Sonos app are the same in both situations but the digital feed still has a harsh boost in the upper mid frequencies.  Snares and vocals get “turned up to 11” so to speak., in a bad way.

Can this difference in sound really be the difference between using the built in Port DAC versus the Denon DAC?  I don’t get why the digital sound is so harsh.  I used the same receiver DAC to decode music sent over HDMI via an Apple TV for ages and it never sounded this bad.  Ideas?

 


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In Fixed Volume mode the Port digital output is evidently taken straight from the decoder. No EQ, no volume control, no DSP. 

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@ratty so what is happening to the digital signal in variable output mode?  I notice EQ is disabled in fixed mode but not variable.  How does the Port apply EQ to a digital signal that hasn’t been decoded yet?  or is the Port decoding and applying EQ and then re-encoding to digital to send  to the AVR to be decoded a second time?

Also, is there any way to make the background hiss/noise less apparent when using the variable output analog connection?  Because frankly thats the one that sounds the best and give me the ability to control volume with all my other zones (which is important to me).  Variable digital does not have the hiss but it sounds like garbage compared to the analog connection.

@ratty so what is happening to the digital signal in variable output mode?  I notice EQ is disabled in fixed mode but not variable.  How does the Port apply EQ to a digital signal that hasn’t been decoded yet?  or is the Port decoding and applying EQ and then re-encoding to digital to send  to the AVR to be decoded a second time?

I was referring to decoding, from whatever audio format the music arrives in (FLAC, AAC, etc) into PCM stereo. You appear to be mixing that up with DA conversion. EQ in the Port is applied in the digital domain. DA conversion only occurs at the end, for the analog Line Out. 

 

Also, is there any way to make the background hiss/noise less apparent when using the variable output analog connection?  Because frankly thats the one that sounds the best and give me the ability to control volume with all my other zones (which is important to me).  Variable digital does not have the hiss but it sounds like garbage compared to the analog connection.

I’ve never noticed any obvious hiss on the Port analog out. One of mine feeds decent headphones through a headphone amp.. Are you sure the AVR isn’t responsible? 

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@ratty 

I suppose it could be the AVR.  Although the hiss completely disappears when I switch to fixed line out as opposed to variable over the same analog cable.  I do notice having to turn up the receiver to a fairly high volume so that the variable output plays at the same level as the fixed.  Perhaps thats why the hiss is more apparent. 

Well if you keep the Port’s variable output low then it will obviously reduce the signal to noise ratio. After switching to Variable the level defaults to 25%. 

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@ratty Well thats the problem.  To get the same volume that I get with fixed line out and the receiver at 60dB I have to crank the receiver to 85 dB and turn the Sonos volume up to 60-70%% of it’s max. Frustrating that there is so little gain when using variable.

If I recall, the Port’s output is the standard 2V RMS nominal, when volume is Fixed or at 100%. This would be no different from a typical CD player.

Why are you using Variable anyway? 

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I need to use variable because this Port and AVR is just one part of a whole house Sonos system  Nobody in my household will wants to have to go to the living room to manually adjust the volume. And since digital out variable produced such harsh sound, analog variable is my only choice.

With dual in-line volume controls to provide a degree of control on the Sonos side, you’ll have to accept that the AVR volume will need to be inched up to compensate.