Distorted sound through port line-in - CD player not turntable

  • 19 March 2023
  • 7 replies

I’ve set up my Port to play line-in output through to a One-SL pair in a different room. I want to be able to select between two sources for that - turntable or CDplayer.

I’ve done this by connecting my Port to an analogue (Marantz PM5005) amplifier. I’ve connected the Port’s line-in RCAs to the amplifier’s Recorder-out RCA ports. My turntable (Pro-ject Essential III) is connected to the Phono-in RCAs in the amplifier (i.e.there’s a built-in pre-amp in the amplifier). I also have a  (Marantz) CD player connected to my amplifier via CD-in RCAs.

Both CDs and vinyl sound great on my analogue wired speakers.

To get digital output on my One-SLs in another room I select line-in input on my Sonos App. I play vinyl by selecting Phono on the analogue amplifier. This all works perfectly. However, when i select CD on the analogue amp, the sound through the One-SLs is hugely distorted.

Does anyone have any idea why this happens?  The phono signal has gone through pre-amp so the signal power shouldn’t be that different. Maybe I need attenuators for the CD-in cables? The other factor is that I don’t want to lose the ability to listen to CDs in analogue mode so I need any solution to keep this possibility.

Just to say too that I previously tried a different approach, using the headphone jack as output source by connecting through a jack to RCA line-in for the port, but this produced distorted sound for both turntable and CD player. I’ve also tried plugging the CD player RCAs directly into the Port – I still get the distortion so it seems like the problem is more likely to do with CD player/Port compatibility than anything amplifier-specific.

All ideas/thoughts much appreciated.


Best answer by buzz 19 March 2023, 21:16

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7 replies

Userlevel 7
Badge +17

What’s the volume setting of the Line in?

It’s set to 10 - should I try 2 ?

Thanks for your help 106rallye - I did that and it’s definitely improved … it’s probably still not as clean as the phono signal though, but it is much better. I’ll run Trueplay to improve the room sound. Is there anything else worth trying - eg lower signal to level 1 / reduce maximum volume to less than 100%?


CD players tend to have high output while Phono’s tend to have relatively low output. If you set PORT to accommodate the CD input, Phono will likely be low. The ultimate solution will be an attenuator in the CD connection. Meanwhile you can adjust PORT’s Line-In sensitivity. Feel free to experiment with the Line-In sensitivity.

Userlevel 7
Badge +22

Sounds like the CD’s output is a bit high, try 1 first but then look to see if your receiver offers level adjustments on the CD input.

If not you could consider adding a volume control, like a passive mixer, or the attenuator you mentioned between the CD and receiver to drop the levels.

thanks all, there is a level adjust dial on the CD player but not on the amplifier - adjusting this doesn’t seem to make any difference to the analogue amplified signal but I’ll see if that makes any difference to the signal into the Port. Setting line-in to level 1 does help reduce the CD distortion but sets up a volume imbalance between turntable and CD - not a huge deal but I’d prefer to avoid this if possible. If not, I’ll find attenuators - I’m assuming those sit between the CD player and CD-in RCAs to dampen the signal. I’ve only seen these as female to female interconnectors so would also need to get additional RCA leads if I go this route, unless female to male versions exist which can plug in directly?




Userlevel 7
Badge +22

I’d go adjustable with something like this in the CD to reciever link, it lets you fool with levels and get as good a match to your other signals as possible.

They do make attenuators like you asked about but being non-adjustable you’d likely have to try several levels of cut to find the right match. I’m also NOT fond of these as if bumped they can easily destroy your equipment jacks.