RCA to XLR trouble

[KSTR]

I'm not sure this is relevant to my point, or even accurate. The situation being discussed is taking an un-balanced signal and wiring it into an XLR. My entire point is that this isn't ideal, you get no benefit from it and may even have some issues.

Of course you get a benefit, all stray currents that normally pollute the GND/Shield of the unbalanced connection are diverted away from the signal path, solving gound loop hum/buzz issues.
There are no issues... with the exception of some gear that pretends to have balanced input but actually don't, like some Topping amps.

==> if you have a proper balanced input then connecting it to an unbalanced output works, always, 100% guaranteed and solves any hum/buzz issues.

 

[rcstevensonaz]

In my world as an analog and audio systems designer all equipment should have simple balanced inputs and balanced cabling. Impedance-balanced outputs are sufficient. (emphasis added)
...
We'd see zero threads dealing with "ground-loop" hum and buzz issues.

I originally missed a subtle significance of the last half of @KSTR's comment regarding devices that support proper balanced inputs.

If I read this right, it means there is no need to worry about the device itself being internally balanced. Rather, just that the output connector would be impedance-balanced — e.g., with the entire audio signal on one wire, and the other wire with zero voltage but the same impedance — so that the next device in the audio stream can in turn remove any external noise introduced into the interconnect from external source.

Repeat along the entire audio chain so that all interconnects are properly balanced; regardless of whether any devices are internally balanced (since their internal noise floors are quite negligible).

 

[somebodyelse]

I'm not sure this is relevant to my point, or even accurate. The situation being discussed is taking an un-balanced signal and wiring it into an XLR. My entire point is that this isn't ideal, you get no benefit from it and may even have some issues. In my opinion, and that of anyone who works with and services these systems would say, the OP should just stick with all balanced or unbalanced gear.

Repeatedly stating the same error doesn't make it any more correct. Refer to Jensen Transformers' AN007 section 3.7 - Unbalanced to Balanced Interfaces for details including rejection vs. frequency plots for different cable and transformer arrangements. Wiring as in #100 gives between 20dB and 30dB of rejection for typical balanced inputs, rather than 0dB for purely unbalanced, or for unbalanced to balanced using coax. For inputs using the THAT 1200 series balanced line receivers it could be considerably better.

 

[KSTR]

In practice the impedance balance requirement is not that important unless your hum/buzz issue is really severe. An imbalance of 100Ohms with a standard 4x 10kOhms subtractor circuit will reduce common-mode rejection to still better than 40dB (assuming 0.1% precision values for the 4 10kOhm resistors). That is usually way enough to solve any hum/buzz issue, even 20dB already go a long way.

 

[TehMowat]

Repeatedly stating the same error doesn't make it any more correct. Refer to Jensen Transformers' AN007 section 3.7 - Unbalanced to Balanced Interfaces for details including rejection vs. frequency plots for different cable and transformer arrangements. Wiring as in #100 gives between 20dB and 30dB of rejection for typical balanced inputs, rather than 0dB for purely unbalanced, or for unbalanced to balanced using coax. For inputs using the THAT 1200 series balanced line receivers it could be considerably better.

This is a direct quote from the Jensen AN007 section 3.7. Tell me how I am wrong. Im not repeating the same error over and over. I clearly stated converting an RCA to XLR connection is not going to give you any benefit, and that the OP should just stick with all balanced or unbalanced gear/connections. If you want tell me Im wrong because it goes on to state: "The alternate hookup, using shielded twisted-pair cable, takes advantage of the noise rejection available from the balanced input.", coooool, but that isn't relevant to the OP who is simply wants to use a converter to turn RCA into XLR. That Jensen article clearly states you need to use cabling that isn't typically found in RCA cables, and most of the people on this forum aren't going to go out and source specialty cable and then solder it on to connections.

 

[somebodyelse]

You state repeatedly that converting an RCA to XLR connection is not going to give any benefit. This is demonstrably untrue when done with a shielded twisted pair, to the tune of ~20-30dB of CMRR. The OP asked about cables not an adapter. People posted the correct cable connection necessary to get the benefit, and some sources that sell them ready made.

 

[Devnull]

This is a direct quote from the Jensen AN007 section 3.7. Tell me how I am wrong. Im not repeating the same error over and over. I clearly stated converting an RCA to XLR connection is not going to give you any benefit, and that the OP should just stick with all balanced or unbalanced gear/connections. If you want tell me Im wrong because it goes on to state: "The alternate hookup, using shielded twisted-pair cable, takes advantage of the noise rejection available from the balanced input.", coooool, but that isn't relevant to the OP who is simply wants to use a converter to turn RCA into XLR. That Jensen article clearly states you need to use cabling that isn't typically found in RCA cables, and most of the people on this forum aren't going to go out and source specialty cable and then solder it on to connections.

So shielded twisted pair cable is a specialty cable? I don't think so considering that that's the kind of cable used in XLR to XLR audio cables and numerous other applications. Buy XLR to XLR audio cable and cut one end off. Then solder or crimp or screw connect pin 2 to the center of an RCA. Then connect pins 1 and 3 to the RCA shell. Done! This isn't rocket science.

 

[TehMowat]

So shielded twisted pair cable is a specialty cable? I don't think so considering that that's the kind of cable used in XLR to XLR audio cables and numerous other applications. Buy XLR to XLR audio cable and cut one end off. Then solder or crimp or screw connect pin 2 to the center of an RCA. Then connect pins 1 and 3 to the RCA shell. Done! This isn't rocket science.

I think you are greatly over estimating the desire/capabilities of the vast majority of not just audio enthusiasts, but of the members of this forum. If the dude was asking about how to convert RCA to XLR, do you think he really knows how to source the correct cables and then modify them to achieve what you are describing? I gave simple, sound advice, and people have repeatedly told me Im wrong. It's not rocket science, but it is way outside of the knowledge and experience for the overwhelming majority of audio enthusiasts. To further my point, the OP bought adaptors that while technically combine pin 1 and 3, it happens at the XLR conversion. Meaning, the entire cable is still just a basic RCA cable which then converts to an XLR path the speaker, thus it doesn't have the shielded twisted pair required to get the benefit. Some high end RCA cables do come this way, but I doubt that is what he is working with. So again, all of your telling me I'm wrong and blah blah blah, the dude probably stopped paying attention to this thread and went with one of the easiest options, which offers no noise reduction benefits.

 

[olds1959special]

I use a miniDSP 2x4 HD which has unbalanced RCA outputs and have no problems connecting it to my studio monitors that only have XLR inputs. I used a combination of RCA to XLR cables and standard XLR cables (25 ft star quad). I just used short RCA 0.5ft cables into adaptors to make it work. I used XLR gender changers as well. You can see the miniDSP in this picture with the Velcro on it, attached to an RCA distributor, and then short RCA cables connect to the XLR cables which you can see at the bottom.