I use 1/4" TS to dual mono RCA cables for hooking monaural devices to my DB4. They’re pretty easily found and the ones I got from 7ball Music were wicked inexpensive.
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Any chance you have a link? 
Seems 7ball has disappeared but these ought to do fine.
EDIT: argh nevermind, brb
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Can I Use a Headphone Out as Line Out?
Don’t worry: the police certainly won’t come knocking on your door with a warrant, but you should know that using the headphone out you are pumping distortion (and noise) into the signal.
Whether this is good or bad is up to you.
Line out signal has a source impedance within the regions of 100 ohms and more. it is meant for driving loads that have high input impedance. Line level out is optimized to produce low noise / distortion when used with high impedance loads.
Unlike line out, headphone outs have a low source impedance. They come with impedance between 16 ohms and 600 ohms.
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Ok. I found this @jemmons
Thank you for this helpful observation! I have observed similar hum issues with my Prophet-10 rev 4 when connecting it to an RME Fireface UFX+ input with a TS cable. The Sequential Owner’s Manual states that the audio output on the Prophet-10 is 1/4" unbalanced. Somewhere I recall reading that the output is actually TRS, but since it is a mono output I always wondered why it was designed this way. After running across your post, I found an article that explains why it works. See page 5 starting at the last paragraph in the article (link below). Essentially, the output circuit is designed to operate both in an unbalanced and balanced manner, by using a clever and inexpensive method. Why the audio output specification is not listed as such in the manual (e.g. balanced/unbalanced), I do not know.
I tried a TRS cable instead, as you did, plugged into a balanced line level input on my RME interface. No more hum!! Magical. I am so pleased.
Regarding your thought about using balanced cables for everything. My sense is that will only work if the output circuitry is designed to operate in this fashion, but would not if the output is unbalanced only. So I guess you could test each device to find out with no potential for harm. Thanks again!
https://mikeriversaudio.files.wordpress.com/2010/12/balanced-unbalanced_revised.pdf
Source:
https://forum.sequential.com/index.php/topic,6084.msg58267.html#msg58267
A little more digging and apparently it’s known as “ impedance balanced output”. I give up though as I’m now looking at Gear Space and that place makes me question why I bother interacting with Humans at all.
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Yeah, impedance balanced is not unbalanced at all. It is, in fact, the very definition of what is meant when something is called “balanced”.
The more extreme kind, where rather than just matching impedance we also include the inverted the signal is properly called “differential signaling”. But for some reason people also refer to it as being “balanced”.
But it doesn’t really matter because you handle both
signals the same way. Just a differential signal tends to be about 6db hotter.
Regardless, if the P10 output is impedance balanced, it is categorically not unbalanced and the manual is blatantly wrong labeling it as such.
I’ve just gone and looked again. I think the “Impedance balanced” has come from some random guy on GS - NOT Sequential. Be good to find out properly from Sequential really.
I’ve emailed support. Will report back…
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So, not really any the wiser:
Thanks for reaching out to Sequential, happy to help with this. You’re correct that the outputs of our synths are unbalanced. There’s no harm using a TRS cable, though if your mixer/interface expects a balanced signal it is possible to run to into a level drop. Hum while using a TS cable is likely due to a ground loop somewhere in your hardware configuration.
You can read more about locating and eliminating ground loops in your system at the following web link (PDF file):
Understanding & Eliminating Ground Loops
If you have any additional questions, feel free to ask. Have a great holiday!
Any extra questions worth asking @jemmons?
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No, that all seems correct to me. To summarize:
- Dude on GS is full of it. The mono out is not differentially or impedance balanced.
- Using a TRS cable is fine because the mono out TS jack on the P10 just ignores the ring.
- Plugging it into a mixer expecting balanced signal is also fine because it just takes the null ring signal, inverts it, and sums it with the tip signal. And nothing + signal = the original signal.
- But if the mixer is expecting differential signaling, it’s expecting to sum two signals resulting in a new signal twice as loud. So if one of those signals is null, it will sound “quieter”, hence “it is possible to run to into a level drop”
Of course the DSI tech could be mistaken, but to go any deeper would require the disassembly of a P10. And I don’t see a reason to doubt them as their explanation seems to account for everything. Back to the original:
If balanced cables plugged into an unbalanced, mono jack are doing something, it’s because there’s a mistake or something is wired horribly wrong.
It sounds like it is, indeed, a mono jack, it is wired correctly, but there was a mistake in the setup that has created a ground loop.
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