Whatever, dude. You be you.
Now getting back to your original question, assuming that's still relevant: For connecting single-ended sources to a differential input I recommend a pseudo-differential cable: https://neurochrome.com/pages/pseudo-differential-cable You can make one easily by chopping the end off of an XLR cable and soldering an RCA connector there. You can also buy the cables ready-made or use adapters as mentioned earlier.
Tom
Now getting back to your original question, assuming that's still relevant: For connecting single-ended sources to a differential input I recommend a pseudo-differential cable: https://neurochrome.com/pages/pseudo-differential-cable You can make one easily by chopping the end off of an XLR cable and soldering an RCA connector there. You can also buy the cables ready-made or use adapters as mentioned earlier.
Tom
Sir Tom is probably too modest to mention it, but for those interested in LDR volume controls I recommend to check out his Tortuga Audio LDR3 testing page.
It well illustrates the myriad issues with this sort of device.
Dave.
https://neurochrome.com/pages/tortuga-audio-ldr3
It well illustrates the myriad issues with this sort of device.
Dave.
https://neurochrome.com/pages/tortuga-audio-ldr3
I was expecting the LDR to be nonlinear ... and it was. The frequency dependence came as a surprise.
Tom
Tom
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I honestly don't think that is a good idea
If both ends are earthed, you will have a loop
If only one end is earthed, you will have a current in the screen which will add to the audio, and this current will depend on the power supply characteristics of the non-earthed device and could be a mess
Brian
You will always have a loop. Even if you connect two RCA cables you have a loop through the shields. Besides, AES48-2005 recommends that you ground the shield at both ends.
If you leave the shield of a pseudo-differential connection unconnected you could end up violating the common mode voltage spec of the differential receiver. Best case this leads to distortion. Worst case you fry the receiver.
Tom
If you leave the shield of a pseudo-differential connection unconnected you could end up violating the common mode voltage spec of the differential receiver. Best case this leads to distortion. Worst case you fry the receiver.
Tom
I agree about the danger of exceeding the common mode spec - been there
For the case where both pieces of equipment are earthed, the method in the Rane paper referenced earlier can be used
For the case where the source only does not have an earth, I have found better performance using the above scheme and adding a separate ground wire from the "ground" on the source to pin 1 of the XLR on the amp. In my case I had many un-earthed sources with a mixture of linear and switched mode power supplies, and an earthed power amp - the current in the cable screen was enough to cause an audible hum with added switching noise. Putting this current down a separate wire made it silent
YMMV and it does depend on what is the main source of noise in any given setup
Brian
For the case where both pieces of equipment are earthed, the method in the Rane paper referenced earlier can be used
For the case where the source only does not have an earth, I have found better performance using the above scheme and adding a separate ground wire from the "ground" on the source to pin 1 of the XLR on the amp. In my case I had many un-earthed sources with a mixture of linear and switched mode power supplies, and an earthed power amp - the current in the cable screen was enough to cause an audible hum with added switching noise. Putting this current down a separate wire made it silent
YMMV and it does depend on what is the main source of noise in any given setup
Brian
Yep. That's the key. And if you build your own equipment or verify what you have before use you can make it work.
Tom
The rule is simple: one and only one path for signal current; one (or exceptionally none) path for shield current; one and only one path for mains leakage current, and these paths must be separate.
This rule is almost always broken to some extent, but if you think in terms of current you won't go far wrong. An often forgotten issue for the usual single ended, common signal ground sources is that noise immunity in a coaxial cable or in a twisted pair only comes when signal current is equal in both conductors, and if both channels of a stereo pair have a common signal ground each channel's signal current "return" travels equally between the two channels' "return" conductors (because they're equal impedances). Very naughty.
All good fortune,
Chris
This rule is almost always broken to some extent, but if you think in terms of current you won't go far wrong. An often forgotten issue for the usual single ended, common signal ground sources is that noise immunity in a coaxial cable or in a twisted pair only comes when signal current is equal in both conductors, and if both channels of a stereo pair have a common signal ground each channel's signal current "return" travels equally between the two channels' "return" conductors (because they're equal impedances). Very naughty.
All good fortune,
Chris
In addition to AN003 that I linked earlier, I also suggest AN004 from Jensen.
https://www.jensen-transformers.com/wp-content/uploads/2014/08/an004.pdf
Unfortunately, the unbalanced interface has dominated in domestic audio gear for many decades, and thus we are left with these potential issues.
Luckily, it's usually not problematic to adapt.
Dave.
https://www.jensen-transformers.com/wp-content/uploads/2014/08/an004.pdf
Unfortunately, the unbalanced interface has dominated in domestic audio gear for many decades, and thus we are left with these potential issues.
Luckily, it's usually not problematic to adapt.
Dave.