How to convert a XLR - TRS cable to RCA - TRS cable?

[PaperBoat]

A TS input is an unbalanced input. In unbalanced interconnection, the signal is defined by the voltage between the ground/shield and the other conductor.

A TRS input is a balanced input. In balanced interconnection, the signal is defined by the voltage between the "cold" and "hot" conductors. There is a third ground/shield conductor, but it is only used to protect the system against interference and is NOT used to carry the signal.

An RCA output is an unbalanced output, so it only has two conductors and the voltage between them defines the signal. Since a balanced input expects the signal between cold and hot, it makes sense to connect the two unbalanced output conductors to the cold and hot balanced input connectors - conventionally, RCA sleeve to cold and RCA tip to hot (though the opposite would likely also work).

So, now that we know what to do with the balanced cold and hot, what about the balanced ground/shield? Well you have two choices, which are both valid but have implications regarding noise performance. You can tie the ground and the cold together (preferably as close as possible to the unbalanced output), as @sergeauckland suggests. This grounds the shield end-to-end, improving resistance from outside interference. In particular it prevents the cable from acting like an antenna. But it also invites ground loops since the signal path is now tied to the balanced equipment chassis ground (and from there to the mains earth if the equipment is class I etc.). The alternative is to leave the shield connected only to the balanced input ground but leave it disconnected (floating) from the unbalanced output. Depending on which method you choose you will attract noise from different sources, so it really depends on your particular situation and there is no universal answer. In my experience I often get noisy ground loops if I connect the shield to the unbalanced output ground (especially if the source is a PC) so I tend to leave it disconnected, and @sergeauckland apparently has the opposite experience.

The reason for leaving the shield unconnected as in18 is to avoid the possibility of a hum loop between items. However, in my experience hum loops are rare, although certainly can happen. Best to connect the grounds and only start thinking about lifting shields if hum happens. As I said, not that common.

S

WoW! Learning is fun..!

 

[Chrispy]

A cable is the least of your worries with a diy build, tho

 

[PaperBoat]

A cable is the least of your worries with a diy build, tho

I'm going with 6' cables for my iFi Zen Air to JBL 305 unbalanced connection... Is 6' beyond the optimal length for unbalanced connection?

 

[Doodski]

I'm going with 6' cables for my iFi Zen Air to JBL 305 unbalanced connection... Is 6' beyond the optimal length for unbalanced connection?

6 foot unbalanced RCA cables are fine. I've run 2, 25 footers in series through a switchbox and that worked just fine.

 

[PaperBoat]

6 foot unbalanced RCA cables are fine. I've run 2, 25 footers in series through a switchbox and that worked just fine.

WoW! That's sounds great!

 

[Doodski]

WoW! That's sounds great!

Yes, it works good. Just make sure the cables are not those really cheap dollar store types with poor shielding. A decent low budget but decently constructed cable will suffice in a jiffy but something better quality is the top choice if possible.

 

[PaperBoat]

Yes, it works good. Just make sure the cables are not those really cheap dollar store types with poor shielding. A decent low budget but decently constructed cable will suffice in a jiffy but something better quality is the top choice if possible.

My TRS to XLR balanced cables are 24 AWG... Is it enough?

 

[sergeauckland]

My TRS to XLR balanced cables are 24 AWG... Is it enough?

Gauge only matters for cables carrying loudspeaker level signals, (or mains current). Your cables will only be carrying line-level signals, so any thickness will be fine. More important in your case is the quality of the screening of the cable, as your cables are being used unbalanced. With a balanced connection, screening is much less important, except for microphone levels, as balancing removes external interference. In studio installations, many line level audio cables are unscreened, just twisted together, and there's no hum.
When you remove the XLR, you'll see what the screen looks like, it's most likely to be a spiral wrap of thin wires, covering the two signal cables, which will be lightly twisted together. That will be perfect for your needs. It might even have a further foil wrap, which is even better screening and would make the cable suitable also for low-level microphone signals.

S.

 

[PaperBoat]

Gauge only matters for cables carrying loudspeaker level signals, (or mains current). Your cables will only be carrying line-level signals, so any thickness will be fine. More important in your case is the quality of the screening of the cable, as your cables are being used unbalanced. With a balanced connection, screening is much less important, except for microphone levels, as balancing removes external interference. In studio installations, many line level audio cables are unscreened, just twisted together, and there's no hum.
When you remove the XLR, you'll see what the screen looks like, it's most likely to be a spiral wrap of thin wires, covering the two signal cables, which will be lightly twisted together. That will be perfect for your needs. It might even have a further foil wrap, which is even better screening and would make the cable suitable also for low-level microphone signals.

S.

My TRS to XLR cables inner core ↓

 

[sergeauckland]

That's very good, excellent construction. You should have no problems with that at all.

S.

 

[PaperBoat]

That's very good, excellent construction. You should have no problems with that at all.

S.

Is it possible that use the sheild/ grounding wire connect to somewhere else and make it interference sheild without connecting to the TRS shield or RCA sleeve? Just wondering...

 

[edechamps]

Is it possible that use the sheild/ grounding wire connect to somewhere else and make it interference sheild without connecting to the TRS shield or RCA sleeve?

I guess if you can find a way to connect it to the chassis ground of the unbalanced equipment, that would be a good option. But note that in order to do this perfectly you will need to make sure the whole assembly is encased within the shield with no gaps. Simply running a wire won't be as good.

I would strongly recommend not worrying about this though. Audible EMI-induced noise is rare. Just connect it in the easiest way and then listen to the noise floor. Can you hear noise/interference? If not, there is no problem and there is no need to "improve" things further.

If you're an irrational perfectionist and really insist in doing this in the cleanest way (audibility be damned), the correct approach is not to mess around with cable assemblies, but to use a balanced source so that the whole system is balanced end-to-end.

 

[Zek]

Is it possible that use the sheild/ grounding wire connect to somewhere else

Connect it on XLR/TRS side and leave it free on RCA side.

 

[PaperBoat]

irrational perfectionist

"irrational perfectionist

use a balanced source so that the whole system is balanced end-to-end.

I had a Topping D10 Balanced... But unfortunately, it was a defective one... I couldn't get a replacement because it was out of stock...

 

[sergeauckland]

I guess if you can find a way to connect it to the chassis ground of the unbalanced equipment, that would be a good option. But note that in order to do this perfectly you will need to make sure the whole assembly is encased within the shield with no gaps. Simply running a wire won't be as good.

I would strongly recommend not worrying about this though. Audible EMI-induced noise is rare. Just connect it in the easiest way and then listen to the noise floor. Can you hear noise/interference? If not, there is no problem and there is no need to "improve" things further.

If you're an irrational perfectionist and really insist in doing this in the cleanest way (audibility be damned), the correct approach is not to mess around with cable assemblies, but to use a balanced source so that the whole system is balanced end-to-end.

A pair of decent Sowter transformers and the whole thing can be balanced. Never mind the cost, feel the good vibes!

S.

 

[sergeauckland]

Is it possible that use the sheild/ grounding wire connect to somewhere else and make it interference sheild without connecting to the TRS shield or RCA sleeve? Just wondering...

Can't help feeling you're overthinking this. It's a perfectly normal unbalanced to balanced connection using a decent piece of cable, so just remove the jack and put a RCA plug on the end, plug in and enjoy.

S.

 

[edechamps]

A pair of decent Sowter transformers and the whole thing can be balanced.

I tend to stay away from transformers ever since I measured a dirt cheap one a few years back and… well:

I had no idea a simple transformer could mess up the signal so badly. (From what I understand it's called "transformer saturation")

I guess more expensive transformers would likely do a better job, but why go through the trouble when you can get a state-of-the-art balanced DAC for $139?

 

[PaperBoat]

Can't help feeling you're overthinking this. It's a perfectly normal unbalanced to balanced connection using a decent piece of cable, so just remove the jack and put a RCA plug on the end, plug in and enjoy.

S.

Okay...

 

[sergeauckland]

I tend to stay away from transformers ever since I measured a dirt cheap one a few years back and… well:

View attachment 217539

I had no idea a simple transformer could mess up the signal so badly. (From what I understand it's called "transformer saturation")

I guess more expensive transformers would likely do a better job, but why go through the trouble when you can get a state-of-the-art balanced DAC for $139?

Transformers have the great benefit of complete galvanic isolation, so avoid any possibility of ground loops and can very easily balance unbalanced sources and destinations. As to distortions, good ones have very little. The Sowters I use have nothing measurable (i.e well below 0.01% with my generator) down to 20Hz at voltages up to 2V or so (+8dBu), and no more than 0.1% at 20Hz at up to 8v (+20dBu), so totally transparent especially between a DAC and a pair of active monitors, or pre to power amp where the voltage will normally be a lot lower than that at normal listening levels.

I agree that with a SOTA DAC now being available for less than the cost of a pair of Sowter transformers, it's somewhat pointless, but there are times when transformers have benefits, especially if one already has them.

S.

 

[Chrispy]

I'm going with 6' cables for my iFi Zen Air to JBL 305 unbalanced connection... Is 6' beyond the optimal length for unbalanced connection?

Mine are around that length....it's a small room. I'd not worry about unbalanced until a much more significant length is involved (like 25' or more)