Both connections will result in basically the same audio quality. If anything, the line-in connection will probably be more reliable since it is connected directly to one of the speakers. So save your money and connect the turntable to the line-in on one of the Era 300s.

I have a turntable connected to my Era 300

I am using rather expensive Sonos cable

It works okay except

the Sonos speaker is too close to the turntable and can cause feedback

I get a hum that I cannot get rid of.

Dont really hear it when the music is playing but when it stops it is constant.

Also it stays humming hours after I have finished using the turntable.

To fix this I discovered that if I ask Alexa to play something else say from Spotify and then stop that the hum does not come back. It is like it swtiches inputs inside

Steve

Hi Steve, thanks for the reply. Try using a bit longer RCA to 3.5mm cable? Also you MUST use the Sonos in-line adapter short cable. Any other adapters will give you issues. Also check the phono / line in your turntable. All these can cause a hum/buzz. 

If the RCA cable or phono cartridge passes close to a transformer or power supply, hum can be induced. It’s easy to diagnose this because physically moving something will change the characteristics of the hum. Curing the issue might not be so easy.

Another potential hum source can be associated with the orientation of the power plugs in their outlet. Experiment with changing orientations. You may be able to find a combination that reduces hum.

Hello,

I am using the official Sonos cable but I bought the one that ethernet as the other was not available and I could not wait.

I hve tried moving the cables around that come out of the turntable pre amp but it makes no difference.

However I will look at tht again

Buzz. I tried seperating the cables but it makes no difference to the hum whatsoever. The phono pre amp is a few years old and was not being used for the last 3. I cannot rule that out as faulty. I iwll try your other suggetions but I have seperated cables with no chnge to the hum. I would expect it to get quiert when I move it.

Disconnect the turntable and preamp from Line-In. This test would be best performed if the input to Line-In is replaced by two “shorting plugs”. Unfortunately, these are becoming hard to find. You could build your own shorting plugs by cutting open a spare RCA cable and connecting the inner and outer conductors together. The idea is to create a zero input situation for Line-In. Now any residual noise should be difficult or impossible to hear. Next, connect the preamp to Line-In and replace the turntable with the shorting plugs. Again, there should be little or no noise.