How to connect headphone output to a "balanced" monitor speaker?

Question

It seems complicated to connect a digital piano's headphone output to a monitor speaker which takes a "balanced" input. How is it done?

It seems what a "balanced input" is, is to use 3 wires to send a signal, so that no matter how long the cable is (such as 25 feet), the noise can be canceled out. Some info here, here, and here.

So then, if we get one of these speakers, such as the Yamaha HS5 or HS8, then how do we connect a digital piano's headphone output to it? There are TRS to XLR cables that connect Tip and Ring together... but will it work? (because if one signal is subtracted from another, then it becomes 0). If we use the "pure" TRS to TRS or TRS to XLR cables, is it true that it won't work? Or do we need a mixer to do that, because if we do, it may seem like the easiest way is to use a regular computer speaker pair. Also, the cable I use is merely 5 foot long, so it is not like it really needs a "balanced" connection. One possible way a cable can work is, if the ring is totally disconnected, then when the "balanced" signal is obtained, the positive is subtracted from the negative (which is always 0), and we still get the positive signal to output to the speaker. (but so far I have not seen such cable being sold on Amazon). If we connect Tip and Ring, then they subtract to become 0 and should not work. (Amazon does sell cables that connect Tip and Ring together).

The question is, what if we want to connect the digital piano's headphone output to a studio monitor like the Yamaha HS5 with balanced input, how is it done? (and is it a good choice to do that?)

Answer 1

1. Yamaha HS5 has both balanced and unbalanced input, you can simply use the latter.

2. If you're looking for other devices, some of them have a "combo" inputs, which may seem like XLR at first, but in fact allow also to connect an unbalanced 1/4" jack. Check your device spec sheet.

3. I agree, piano headphone or line output should be quite strong and should work fine with an unbalanced connection. Give it a try. The worst thing I can think of are ground loops which may add some noise.

4. As you wrote with a properly made cable you can connect an unbalanced output to a balanced input, but the connection will be still unbalanced. It might be good enough for you.

5. For a truly balanced connection you indeed need to convert the signal. You could use a mixer, as you proposed, but a more typical tool for the job is a DI box.

Answer 2

If you can convince your keyboard to pan everything hard to the left (namely with the right channel being silent), you get output that is pretty suitable for a balanced input by just using a normal balanced TRS cable (the difference to a stereo cable is subtle: a balanced cable has a defined twist of both signal wires): a balanced input works by interpreting the difference between its two inputs, and the difference to a signal that is zero is just the non-zero signal. How does this differ from an unbalanced connection? For one, the shield is not running signal current. For another, the source impedances of both "signals" are the same since they are from the same headphone circuit.

Some balanced outputs are actually implemented that way (with a matched resistor pair from ground and a low-impedancy output connecting to return and signal wires) while the "proper" way is sending an inverted signal on the return wire. That gives a higher SNR ratio but otherwise is indistinguishable on a balanced input and may get better results on an unbalanced input.

Answer 3

If the piano is mono, then the signals on the Tip and Ring will be the same.

If you connect either the Tip or Ring to one of the balanced lines, then the Sleeve to both the other balanced line and the ground, then it should work.

Turn the headphone output volume down to a moderate volume to ensure it's not above normal line levels. The most appropriate approach would be to set the speaker to a moderate volume level, then adjust the volume at the headphone output.