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How to shield RCA to XLR cables from noise (auto power off on speakers won't work)

mrmojo

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Jan 10, 2023
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I had a pair of speakers with XLR inputs connected to my topping DX3pro DAC (RCA outputs). They sound great, but the issue is that the speakers have an auto power off, which won't work when connected to this DAC (even if the DAC is powered off/unplugged from power). Sometimes one speaker will auto power off, sometimes the other will. I was pretty sure it was noise on the RCA to XLR cables which was causing the auto power off function not work (noise is detected as signal by the speakers) so I got the SMSL DO100 DAC with XLR outputs.

Using the SMSL DAC the speakers properly power off, but the SMSL DAC causes all sorts of popping and crackling noises, which I can't seem to get rid of though.

Rather than trying another XLR DAC (maybe the schiit modius) I'd rather get some RCA to XLR cables to use with the DX3pro DAC, which don't pick up noise so that the speakers properly auto power off.

Anyone have any recommendations for cables that might suit my purpose? Is it even possible ot get such cables (the speaker auto powered off correctly when I unplugged the XLR to RCA cables from the DX3pro DAC, but left them connected to the speakers, so it might be noise that's just coming form the DAC).

Thanks.
 
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You could have a ground loop between DAC and speakers with the RCA adapter cable. You may have low level hum even if it isn't obvious. One way to check is to get some of those cheater plugs that let you plug a three prong power cord into a two prong outlet. Use them on the power cord of your speakers. That will lift the 3rd pin ground and break the ground loop.

PLEASE NOTE: This is not an electrically safe condition and therefore not a permanent solution. Just a way to test if breaking the ground loop fixes your issue.

If possible plugging the speakers into the same outlets as the DAC and other gear should eliminate such a loop. If that is doable try that first. Assuming this is not an overload for the electrical outlets.
 
I had a pair of speakers with XLR inputs connected to my topping DX3pro DAC (RCA outputs). They sound great, but the issue is that the speakers have an auto power off, which won't work when connected to this DAC (even if the DAC is powered off/unplugged from power). Sometimes one speaker will auto power off, sometimes the other will. I was pretty sure it was noise on the RCA to XLR cables which was causing the auto power off function not work (noise is detected as signal by the speakers) so I got the SMSL DO100 DAC with XLR outputs.

Using the SMSL DAC the speakers properly power off, but the SMSL DAC causes all sorts of popping and crackling noises, which I can't seem to get rid of though.

Rather than trying another XLR DAC (maybe the schiit modius) I'd rather get some cables, which don't pick up noise so that the speakers properly auto power off.

Anyone have any recommendations for cables that might suit my purpose? Is it even possible ot get such cables (the speaker auto powered off correctly when I unplugged the XLR to RCA cables from the DX3pro DAC, but left them connected to the speakers, so it might be noise that's just coming form the DAC).

Thanks.
You can get RCA to XLR cables but they won't help because the signal is still single ended (unbalanced) not differential (balanced) You need a balanced output into a balanced cable into a balanced receiver to eliminate common mode hum.

You can find active RCA to XLR converter boxes that use amplifiers to generate a true differential output. The converter would have a short RCA cable to the DAC and long XLR cables to the speakers. And the old-school unbalanced to balanced transformers are still available, which require no power but may not have a flat frquency response.

It might be cheaper to buy a balanced Topping DAC though.
 
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You can get RCA to XLR cables but they won't help because the signal is still single ended (unbalanced) not differential (balanced) You need a balanced output into a balanced cable into a balanced receiver to eliminate common mode hum.

You can find active RCA to XLR converter boxes that use amplifiers to generate a true differential output. The converter would have a short RCA cable to the DAC and long XLR cables to the speakers. And the old-school unbalanced to balanced transformers are still available, which require no power but may not have a flat frquency response.

It might be cheaper to buy a balanced Topping DAC though.
Getting the balanced RCA DAC would solve the issue even though the cables would still be XLR to RCA cables and not XLR to XLR?
 
Getting the balanced RCA DAC would solve the issue even though the cables would still be XLR to RCA cables and not XLR to XLR?

No, you need balanced connections - XLR (or TRS) to XLR (or TRS). I'd be more concerned about understanding the ' popping and crackling noises' you hear with the DO100 as this suggest you may have some other issues.

What are you driving the DAC with? You could try isolating the source (presumably a PC) from the DAC by using a USB isolator or switching to an optical connection.
 
For all we know, it could be out of band HF from the DAC that is keeping the auto power off from reliably functioning. i.e. the speakers think there is signal... Auto power off signal sensing circuits are pretty simple and rarely incorporate RFI filtering components.
 
No, you need balanced connections - XLR (or TRS) to XLR (or TRS). I'd be more concerned about understanding the ' popping and crackling noises' you hear with the DO100 as this suggest you may have some other issues.

What are you driving the DAC with? You could try isolating the source (presumably a PC) from the DAC by using a USB isolator or switching to an optical connection.
popping noises from the Do100 seem to be a pretty common issue. i just haven't been able to fix it.
 
Getting the balanced RCA DAC would solve the issue even though the cables would still be XLR to RCA cables and not XLR to XLR?
A balanced DAC will have balanced outputs - either TRS (same as 1/4" stereo headphone jack/plug) or XLR. The Topping D10 Balanced that I linked to uses TRS outputs. You would need balanced cables with TRS plug on one end and XLR on the other, or TRS to XLR adapters and XLR cables.

How do you connect your SMSL DO100 DAC?
 
I'm using an SMSL DO100 and drive a Crown XLS 1500 with it. I heard the pops etc when the source changed on my computer. I have now added a Schiit Magnius between the SMSL and the Crown. That has fixed all my problems and gives me a good analog volume control which I much prefer to the multiple turn digital contol in the SMSL (does anyone actually like using those "spin forever" volume controls?).
 
Another RCA to XLR problem again. Really need to stop praising about this adaptor even you don't have the problem. However, you can check whether it is adaptor problem by disconnecting your speaker and listen to noise. Play the music for a while, then plug out the adaptor. It will create a loud pop. A safer way, it is play music and switch off the DAC and wait for auto power off. Then you don't need to do the first test.
 
A balanced DAC will have balanced outputs - either TRS (same as 1/4" stereo headphone jack/plug) or XLR. The Topping D10 Balanced that I linked to uses TRS outputs. You would need balanced cables with TRS plug on one end and XLR on the other, or TRS to XLR adapters and XLR cables.

How do you connect your SMSL DO100 DAC?
Ah, so if I used TRS to XLR cable with the D10 DAC it shjould resolve my issue? I use just plain XLR to XLR cables to connect the do100
 
Ah, so if I used TRS to XLR cable with the D10 DAC it shjould resolve my issue? I use just plain XLR to XLR cables to connect the do100
Actually the Topping D10B comes with some TRS to XLR adapters included. If you already have XLR to XLR you are set. I prefer the adapter on the other end so on my D10B I use TRS to TRS cables with an XLR adapter at the far end.
 
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