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RCA L+R Shorting Out/Buzzing at 3.5mm (Turntable to Sonos)

sleevel

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Oct 25, 2023
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Hi all,

I’m having a strange issue where my turntable to preamp to active speaker works (albeit with a hum) if a single channel is connected but with both channels connected the audio seems to “cancel itself out” for lack of a better description.

Specifically, I am connecting my turntable via preamp (since one is not integrated) to my Sonos Era 100 powered speaker. (ClearAudio Concept with AudioTechnica MM cartridge) RCA L/R with ground wire to phono preamp (Graham Slee Era Gold) RCA L/R to a RCA L/R to 3.5mm adapter to a 3.5mm to USB-C Sonos proprietary input.

The grounding wire does appear to be working because with it disconnected the hum is VERY loud. When connected it’s reduced but still very audible. With both channels connected, the sound is ghost-like. If I disconnect either channel, the sound is remarkably louder and clearer (though the hum is still audible). Reconnecting the second channel, it drops back out to ghost sound.

When I connect this same setup to a traditional combo amp to passive tower speakers, there are no issues. Crystal clear sound and no hum. Using the exact same cables and arrangement.

Curiously, if I use my iPhone as a line input to the Sonos speaker (lightning to 3.5 mm dongle to 3.5mm to 3.5mm cable to 3.5mm to USB-C dongle to Sonos) it sounds crystal clear and very detailed. So the speaker is capable of taking a line in input but for some reason, not my turntable setup which works just fine with a traditional combo amp and passive speaker setup.

So I’m wondering if there’s some sort of shorting of the two channels occurring. Or maybe some electrical interference occurring. Or because the iPhone is a digital output versus my turntable is analog (though the signal is still analog, either RCA or 3.5mm, if my understanding of audio is correct).

So does anyone know what could be occurring and how to fix it?
 

Sokel

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Too many adapters to narrow.
Have you tried the 3.5mm to USB-C both ways? (I mean the USB-C plug)
Can you try to ground your phono with Sonos? (a simple wire between the two touching some bare metal on each of them) .
 

restorer-john

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It sounds like you may have a polarity issue causing cancellation. It can happen with a lifted ground in a three conductor stereo wire.

It could also be as simple as the cartridge wiring on the headshell being reversed in one channel.

Or the phono stage could have a single RCA wired incorrectly.
 

Philbo King

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Hi all,

I’m having a strange issue where my turntable to preamp to active speaker works (albeit with a hum) if a single channel is connected but with both channels connected the audio seems to “cancel itself out” for lack of a better description.

Specifically, I am connecting my turntable via preamp (since one is not integrated) to my Sonos Era 100 powered speaker. (ClearAudio Concept with AudioTechnica MM cartridge) RCA L/R with ground wire to phono preamp (Graham Slee Era Gold) RCA L/R to a RCA L/R to 3.5mm adapter to a 3.5mm to USB-C Sonos proprietary input.

The grounding wire does appear to be working because with it disconnected the hum is VERY loud. When connected it’s reduced but still very audible. With both channels connected, the sound is ghost-like. If I disconnect either channel, the sound is remarkably louder and clearer (though the hum is still audible). Reconnecting the second channel, it drops back out to ghost sound.

When I connect this same setup to a traditional combo amp to passive tower speakers, there are no issues. Crystal clear sound and no hum. Using the exact same cables and arrangement.

Curiously, if I use my iPhone as a line input to the Sonos speaker (lightning to 3.5 mm dongle to 3.5mm to 3.5mm cable to 3.5mm to USB-C dongle to Sonos) it sounds crystal clear and very detailed. So the speaker is capable of taking a line in input but for some reason, not my turntable setup which works just fine with a traditional combo amp and passive speaker setup.

So I’m wondering if there’s some sort of shorting of the two channels occurring. Or maybe some electrical interference occurring. Or because the iPhone is a digital output versus my turntable is analog (though the signal is still analog, either RCA or 3.5mm, if my understanding of audio is correct).

So does anyone know what could be occurring and how to fix it?
Sounds like you have a stereo connecter feeding a balanced input, which would give you a L-R (stereo difference signal AKA as Side as in Mid-Side)
 
OP
S

sleevel

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It sounds like you may have a polarity issue causing cancellation. It can happen with a lifted ground in a three conductor stereo wire.

It could also be as simple as the cartridge wiring on the headshell being reversed in one channel.

Or the phono stage could have a single RCA wired incorrectly.
Thank you. But these would happen regardless of speaker/amp used, right? It seems to only happen on the powered active (Sonos) not the combo amp to passive towers.
 

Philbo King

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Thank you. But these would happen regardless of speaker/amp used, right? It seems to only happen on the powered active (Sonos) not the combo amp to passive towers.
That depends on the individual input circuitry for each device you connect it to.
 
OP
S

sleevel

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I did some more investigating. If I have all 4 RCA cables (L / R into preamp and L / R out of preamp into Sonos) I get the low quality sound and buzz. If I only disconnect either the L or R from the output of the preamp it sounds good. While staying in this single channel output (two channel input) mode, if I disconnect one of the input channels (either L or R, doesn’t matter) the sound degrades substantially.
 
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