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I have a Focusrite Scarlett 18i20. The USB interface has 4 balanced mono outputs and 2 unbalanced stereo headphone outputs.

I want to output a mono balanced signal on the unbalanced stereo headphone output.

Is there software to generate a balanced signal on two channels? I can then route those two to L and R of the stereo jack and should have a balanced mono output. Or is there a flaw in this approach?

Thanks!

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    I think the major flaw is in thinking a line out really needs to be balanced. Sure, some line outs, especially if you're running to huge internally-amped monitoring, can benefit from it in noisy environments, but you don't really need it for anything else at those levels.
    – Tetsujin
    Jun 28 at 10:17
  • Thanks for your answer! Wouldn't it be best practice to use a balanced signal when you run long distances, say more than 10 meters?
    – kn0
    Jun 28 at 15:02
  • 10m, the length of a decent guitar lead… nope, I wouldn't bother balancing one of those & certainly not output level signals. I can't think of any studio I've ever worked in that used balanced line-level, only mic. I've seen patch panels with TRS jacks, but they tend to be multi-purpose, can push a guitar one way, headphones the other, without being too fussy about which socket to use.
    – Tetsujin
    Jun 28 at 15:49
  • thanks for the helpful examples. at what length would you say one should start thinking about switching to balanced cables for line-level signals? it probably also depends on the environment?
    – kn0
    Jun 29 at 11:32
  • Stage to FoH, which is an area I've never really worked in. Always been a studio engineer, occasionally helping out with live, but I never did the rigging.
    – Tetsujin
    Jun 29 at 11:57
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If you just output a signal on the left headphone channel and keep the right channel at zero, you have a balanced signal. Balancing really is about having the same impedance on both lines and evaluating the differential at the receiving side. Many balanced outputs are done in that manner (rooting the voltage-only signal and signal ground through a matched resistor pair for hot/cold) rather than using an inverted signal for the return: this has the advantage that you don't have ±6dB changes when using unbalanced cables/targets that short the cold line.

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  • Nice! I clearly haven't tinkered enough with electronics, because I could only think of the plus/minus thing that was explained in a text book 30 years ago. :) (A+noise)-(-A+noise)=2A, but (A+noise)-(0+noise)=A, so you still get A without noise. Or maybe this "hack" was explained there and I just remembered half of what was said in the book. Jun 28 at 11:36
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    i don't have the electronics background to analyse this properly, but to me that ends up with a huge DC offset I can't think around.
    – Tetsujin
    Jun 28 at 12:56
  • Thanks a lot for the answer. I can follow the math that leads to A or 2A, but how does the receiving side know, which method was applied? And if by default 2A is expected, wouldn't this result in 1/2 A = 0.5 A ? This may be the DC offset Tetsujin refers to?
    – kn0
    Jun 28 at 15:00
  • @tetsujin I think the way around is given by the decoupling capacitors which are usually located on inputs and outputs of audio systems (and responsible for the pop on powering on as they equilibriate). Their main goal is to remove any DC component of the signal so it is likely that this DC offset won't be propagated anywhere...
    – Tom
    Jun 28 at 15:24
  • I was only looking at it as a math equation. Maybe a question or search on Electrical Engineering is in order electronics.stackexchange.com Jun 28 at 15:25

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