Good quality RCA > XLR cables

[Speedskater]

So when making a RCA > XLR cable, is it better to connect pin 1 and 3 at the RCA side (ie, attach both to the RCA shield), or jump them on the XLR side?

'P48' in post #41 details the best connection method.

 

[starfly]

RANE recommends:

RCA Out to XLR In:
2-conductor shielded cable
shield lifted at the RCA and connected to pin 1
common ground from the RCA connected to pin 3

XLR Out to RCA In:
2-conductor shielded cable
shield lifted at the RCA and connected to pin 1, then shorted to pin 3
common ground from the RCA connected to pin 3

Source: https://www.ranecommercial.com/kb_article.php?article=2107

But it probably depends on the circuit of the input.

So reading through that article, with RCA out to XLR in, it looks like I don't attach the shield to anything on the RCA side, only connect the signals, like this:

On the input side it's going to a DIY amp, so again from reading the article they appear to recommend that on the XLR input side, the shield should be connected to chassis ground, not signal ground, as that will give the best results.

 

[Speedskater]

Yep, a correctly installed chassis XLR (be it Male or Female) should have pin 1 (the shield) connected to the chassis with a very short jumper.

But even though this 'Pin 1 Problem' was first documented in 1995, some audiophile equipment still gets it wrong.

 

[Speedskater]

On wiring a DIY project. Note, I won't use the lower case 'ground' it's just to confusing.
1] AC power attach the Safety Ground to the chassis near where the cord enters the chassis.
2] XLR chassis connectors. Each pin 1 to the chassis very near that connector.
3] Audio circuit common. Only one attachment to the chassis.
4] DC supply common. Only one attachment to the chassis.
5] Both of these attachments should be at the same point and it should be near the input connectors.

 

[starfly]

On wiring a DIY project. Note, I won't use the lower case 'ground' it's just to confusing.
1] AC power attach the Safety Ground to the chassis near where the cord enters the chassis.
2] XLR chassis connectors. Each pin 1 to the chassis very near that connector.
3] Audio circuit common. Only one attachment to the chassis.
4] DC supply common. Only one attachment to the chassis.
5] Both of these attachments should be at the same point and it should be near the input connectors.

Thanks, that's very helpful. I was actually wondering how to properly ground all the equipment in my build (first time doing this).

For your point 5, "both of these attachments should be at the same point...", are you referring to the Audio Circuit Common and DC Supply Common? As I will be using a AC>DC converter to provide DC power to the switching power supply for standby power.

 

[Speedskater]

The DC supply that powers the Audio Circuit. Doubt that any other supplies need to be connected to the chassis.

 

[starfly]

RANE recommends:

RCA Out to XLR In:
2-conductor shielded cable
shield lifted at the RCA and connected to pin 1
common ground from the RCA connected to pin 3

XLR Out to RCA In:
2-conductor shielded cable
shield lifted at the RCA and connected to pin 1, then shorted to pin 3
common ground from the RCA connected to pin 3

Source: https://www.ranecommercial.com/kb_article.php?article=2107

But it probably depends on the circuit of the input.

So I finally got around to doing a first test of my amp build with my self made cables. I had built cables for the RCA Out > XLR In path. On the RCA side, the cable shield lifted (not connected to anything), and on the XLR side cable shield connected to Pin 1.

I got this loud buzzing sound as soon as I connected the cables. I didn't have other cables on hand to isolate if it's the cables, but I did have a different source I could use with a regular fully balanced cable and no buzzing on that, so it wasn't something I had screwed up with my amp.

For the cables, someone suggested I should short the cable shield and common ground on the RCA side to fix the issue (i.e. both the common ground and the cable shield should be soldered to the RCA shield).

Would that solve the issue?

 

[jsm]

sounds like a ground loop, you make a quick test by isolate just one "cold" (black) RCA pin side by tapping temporarely the external rca connector, and unsolder this if it fix the buzz . Most of my RCA cable run like this without any troubles

 

[AnalogSteph]

So I finally got around to doing a first test of my amp build with my self made cables. I had built cables for the RCA Out > XLR In path. On the RCA side, the cable shield lifted (not connected to anything), and on the XLR side cable shield connected to Pin 1.

I got this loud buzzing sound as soon as I connected the cables.

So for the record, your cable was as follows:
RCA ground --> hot --> XLR pin 3
RCA signal --> cold --> XLR pin 2
(open) --> shield --> XLR pin 1
Correct?

That should work as long as both sides are grounded somewhere (e.g. PC to active monitors, both IEC Class I devices with PE connection). If one end is floating, change to
RCA ground --> hot --> XLR pin 3
RCA signal --> cold --> XLR pin 2
RCA ground (2) --> shield --> XLR pin 1
instead, as suggested. This will provide a ground connection for the floating side.

"One side floating" generally means that there is some capacitive coupling to mains through either the mains transformer (several hundred pF) or filter capacitors (nF). This may mean that your balanced input with its high input impedances ends up being subjected to tens of volts of common-mode AC superimposed on the signal, driving it into clipping or at least giving its CMRR a lot to do (and a basic balanced input won't have more than 40-60 dB of CMRR on tap). Once the mains leakage currents are given a low-impedance path to ground, the voltage between floating side ground and the grounded side (and hence common-mode voltage) will be substantially reduced - possibly by as much as 80 dB.

If both sides are grounded, the cable with shield connection also works but may be somewhat prone to ground loop issues if either the balanced side suffers from a Pin 1 Problem or the connection from RCA ground to star ground on the unbalanced sided isn't quite as low impedance as it could be. It should still be better than unbalanced though.

 

[starfly]

So for the record, your cable was as follows:
RCA ground --> hot --> XLR pin 3
RCA signal --> cold --> XLR pin 2
(open) --> shield --> XLR pin 1
Correct?

That should work as long as both sides are grounded somewhere (e.g. PC to active monitors, both IEC Class I devices with PE connection). If one end is floating, change to
RCA ground --> hot --> XLR pin 3
RCA signal --> cold --> XLR pin 2
RCA ground (2) --> shield --> XLR pin 1
instead, as suggested. This will provide a ground connection for the floating side.

"One side floating" generally means that there is some capacitive coupling to mains through either the mains transformer (several hundred pF) or filter capacitors (nF). This may mean that your balanced input with its high input impedances ends up being subjected to tens of volts of common-mode AC superimposed on the signal, driving it into clipping or at least giving its CMRR a lot to do (and a basic balanced input won't have more than 40-60 dB of CMRR on tap). Once the mains leakage currents are given a low-impedance path to ground, the voltage between floating side ground and the grounded side (and hence common-mode voltage) will be substantially reduced - possibly by as much as 80 dB.

If both sides are grounded, the cable with shield connection also works but may be somewhat prone to ground loop issues if either the balanced side suffers from a Pin 1 Problem or the connection from RCA ground to star ground on the unbalanced sided isn't quite as low impedance as it could be. It should still be better than unbalanced though.

Yeah, shorting cable shield and ground on the RCA side fixed it. Did that last night and now it works perfectly.

It connects my Yamaha AVR (unbalanced) to my power amp.

 

[AnalogSteph]

Minor correction:

So for the record, your cable was as follows:
RCA ground --> hot --> XLR pin 3
RCA signal --> cold --> XLR pin 2
(open) --> shield --> XLR pin 1
Correct?

That should work as long as both sides are grounded somewhere (e.g. PC to active monitors, both IEC Class I devices with PE connection). If one end is floating, change to
RCA ground --> hot --> XLR pin 3
RCA signal --> cold --> XLR pin 2
RCA ground (2) --> shield --> XLR pin 1
instead, as suggested. This will provide a ground connection for the floating side.

This should have read:

RCA ground --> cold --> XLR pin 3
RCA signal --> hot --> XLR pin 2
(open) --> shield --> XLR pin 1
Correct?

That should work as long as both sides are grounded somewhere (e.g. PC to active monitors, both IEC Class I devices with PE connection). If one end is floating, change to
RCA ground --> cold --> XLR pin 3
RCA signal --> hot --> XLR pin 2
RCA ground (2) --> shield --> XLR pin 1
instead, as suggested. This will provide a ground connection for the floating side.

How silly. No biggie, switching the leads of a twisted pair around at both ends would have made zero difference electrically, it's just a matter of convention.

 

[Plastic Jeezus]

Yeah, shorting cable shield and ground on the RCA side fixed it. Did that last night and now it works perfectly.

It connects my Yamaha AVR (unbalanced) to my power amp.

I know this thread is kind of old, but would you say that the way you wired your cable to eliminate the hum followed this diagram I see on the Ghent website for their cables?

Thanks

 

[starfly]

I know this thread is kind of old, but would you say that the way you wired your cable to eliminate the hum followed this diagram I see on the Ghent website for their cables?
View attachment 102244

Thanks

On the RCA side it's correct yes, shield (black) and ground (gray) are in the same spot. Don't remember what I did exactly on the XLR side, but it looks right in this diagram.

 

[Matias]

Just got my 6 RCA to XLR cables custom ordered from Design a Cable (UK), based on the product linked below: Van Damme star quad cables with Neutrik XLR and Switchcraft RCA. I asked for the RCA ground (2 conductors in a star quad configuration) and shield to be connected to the RCA plug ground (as per Hypex datasheet), and also asked for different colors.

https://www.designacable.com/studio...e-xlr-lead-pair-van-damme-starquad-cable.html

 

[ReciprocalSpace]

I agree, China is far... but the value for money of Ghent audio products is excellent. BTW they also sell nice enclosures for class D amplifiers.

Another vote for Ghent audio, I bought Ghent XLR to RCA, Monoprice XLR to RCA cables and Neutrik XLR to RCA adapters. Monoprice worked great, though the cable is thicker than it's gauge would suggest and the RCA head is also large, which may cause issues routing and plugging in if spacing is tight. Neutrik adapters also seem to work fine, but opted for the Ghent in my system. Like the feel of the cable, the small RCA head and the color options.

 

[DuncanDirkDick]

Minor correction:

This should have read:

RCA ground --> cold --> XLR pin 3
RCA signal --> hot --> XLR pin 2
(open) --> shield --> XLR pin 1
Correct?

That should work as long as both sides are grounded somewhere (e.g. PC to active monitors, both IEC Class I devices with PE connection). If one end is floating, change to
RCA ground --> cold --> XLR pin 3
RCA signal --> hot --> XLR pin 2
RCA ground (2) --> shield --> XLR pin 1
instead, as suggested. This will provide a ground connection for the floating side.

How silly. No biggie, switching the leads of a twisted pair around at both ends would have made zero difference electrically, it's just a matter of convention.

I know it's an old post. Any advantages of using a mic cable (2 signal + shield) over rg174 and splitting the shield on the xlr?

 

[Speedskater]

for a RCA output to an XLR input a Shielded Twisted Pair (STP) is always better than a coax cable.
'mic cable' is a sub-set of Shielded Twisted Pair (STP)
it is optimized for robust construction, flexibility and low handling noise.
for an interconnect it has no advantages over other STP cables.

 

[DuncanDirkDick]

for a RCA output to an XLR input a Shielded Twisted Pair (STP) is always better than a coax cable.
'mic cable' is a sub-set of Shielded Twisted Pair (STP)
it is optimized for robust construction, flexibility and low handling noise.
for an interconnect it has no advantages over other STP cables.

That's what I've found as well, care to elaborate on the reasoning behind that?

 

[d3miller]

Blue Jeans will do this for you as well. Very reasonable prices. High quality.

 

[Ricardus]

Just putting it out there. I make cables for my studio and for people in general if anyone needs anything made.