Headphone Out vs Audio Out

aarb420 · 2022-12-19T17:25:24.376Z

brucegill:

It’s not an issue though?

It was my version of a polite attempt to point our friend in that direction.
I’d assume Sequential may be better suited to answer their question, perhaps.

The mono synth part makes sense if that’s what @ddiamond84 is experiencing, and I’m not sure why I forgot to consider that very important aspect haha (I just re-read your first post with the routing recommendation).

ddiamond84 · 2022-12-19T19:50:07.454Z

Thanks for all the responses so far!

It wasn’t unique to the prophet 10. I tried it with my Erica DB-01 which only has a mono audio out. I guess I just don’t know why to do mono out to stereo rca in isn’t playing on both sides, but headphone out does.

I’ll keep trying things from this thread. Y’all rock!

zollenz · 2022-12-19T20:24:36.928Z

Judging from the pics, you are using a TRS to dual mono splitter cable from the P10 to your mixer.

This will work when using the headphone out because the P10 is likely just doubling the mono signal on the tip and ring. But when plugging that same cable into the line output, the ring is ignored and you’ll only get a signal on the left (tip) end of the split while the right (ring) will be silent.

Judging from the P10 manual the line out is unbalanced, so you should just use a mono TS cable from the line out to a mono channel on your mixer. I don’t see a reason to use a TRS cable, though @brucegill does state there is some advantage to using TRS. But I could be talking out of my a** here as I don’t have a P10.

In any case I’d say whether you use a TS or TRS cable, go mono from the P10 line output to your mixer/pedal/etc, unless you actually want to get a split mono signal from the headphone out.

See also this recent MW thread on the subject.

brucegill · 2022-12-19T20:31:41.515Z

zollenz:

Judging from the P10 manual the line out is unbalanced, so you should just use a mono TS cable from the line out to a mono channel on your mixer. I don’t see a reason to use a TRS cable, though @brucegill does state there is some advantage to using TRS. But I could be talking out of my a** here as I don’t have a P10.

I’ve had a P10 and then a P5 (both Rev 4). Both needed a balanced cable to sort noise issues out. I can’t find the details but someone at Sequential mentioned it on their forum I think. I know it’s stated as NOT being a balanced output, but it 100% solved my issues and someone else on here also. Very strange!

jemmons · 2022-12-19T20:34:08.736Z

ddiamond84:

guess I just don’t know why to do mono out to stereo rca in isn’t playing on both sides

Well, are you duplicating the mono signal such that there is one for each side? If not, then that’s why.

Mono outs only provide two connections: ground and signal. Stereo ins expect three connections: ground, left, and right. If you try to wire them together, you’ll wire ground-to-ground, and signal-to-left, but realize you’re out of inputs for the right. That’s the mismatch.

An example of this: there’s not really a cable made to go “from mono out to stereo rca in”. Say you have a phono-to-stereo-RCA cable like this:

TRS201-large750×550 29 KB

The first thing to note is this is not mono to stereo. The phono plug is TRS. That is, Tip (left) Ring (right) and Sleeve (ground). That gets directly wired to black (left) and red (right) RCA. If you don’t provide signal on the ring of the phono plug, the cable isn’t going to magically double it for you. It’s going to just play nothing over the red RCA.

And that’s exactly what mono jacks do. They connect to the tip and the sleeve of a plug and completely ignore the ring. So on the RCA side you’ll get sound over the black one but not the red.

Now, why does it work for headphones? Because headphone plugs are also TRS. So if the headphone jack were mono, we’d all only hear sound over the left speaker. This would be beyond annoying. So the P10 does the work of doubling the signal for us, connecting to and sending it out over both the tip and the ring of the phono plug. (it also wouldn’t be a great experience trying to listen to line levels over headphones, so the headphone out also incorporates an amp. More on this in a second)

So you have to options. One, use the mono out, and only plug it into a mono channel of your mixer (or a stereo channel panned hard-left). Two, use the headphone out, which has helpfully doubled the signal for you already.

Why use mono out instead of headphone out? Well as mentioned above, the headphone out has an amp in front of it. Maybe you worry about the quality of that amp and want the “purest” unmodified signal right out of the synth to go to your mixer? The mono out provides that.

Personally I don’t feel like there’s any quality issue worth worrying about. For me, it’s all about the convenience of having an amp I can control the volume of independently of the line out so that I can adjust my headphones to taste without throwing off the mix at my mixer. But if you’re monitoring from the mixer and never bump the headphone volume by accident, I can’t think of a reason not to use the headphone out. Just remember, you’re not actually getting stereo. You’re just getting the same signal cloned left and right.

zollenz · 2022-12-19T20:40:55.556Z

@brucegill Right on, can’t argue with experience. Reminds of the OTO Boum thread where it was also found to be advantageous to use balanced cables even though the manual explicitly states that the ins/outs are unbalanced. So I’m also doing that now.

jemmons · 2022-12-19T20:47:36.370Z

I can argue with experience. If balanced cables plugged into an unbalanced, mono jack are doing something, it’s because there’s making a mistake or something is wired horribly wrong. Either way, the best solution is to research where the misunderstanding is, because your setup will be unreliable at best or risking damage to gear at worst.

zollenz · 2022-12-19T21:00:22.075Z

Yeah, my common sense also says no. But when the devs start recommending it (same case for the Boum) it does get confusing.

jemmons · 2022-12-19T21:21:00.746Z

It definitely adds a layer of confusion. But when the devs recommend it, that just helps localize the misunderstanding: either their documentation is wrong or their wiring is. Again, either way it needs to be pinned down and understood or Bad Things can result.

As a for example, I had a used kit-build where (I found out much later) the guy who put it together substituted a TRS jack for an unbalanced out (because he couldn’t find a TS jack or had a TRS one lying around or something? ) so the tip was signal, the sleeve was ground, but the ring was just left floating. It would sometimes get noisy unless I used a balanced cable (I think because that, in effect, isolated the floating bit to the ring channel rather than ground?), so that’s what I did.

But sometimes that floating ring would pick up spikes. And because I ran it to my balance-expecting mixer, these were dutifully inverted and summed — sometimes resulting in egregiously loud pops. This was very intermittent and very different from the noise issue I’d had, so it took me forever to track down.

If I had understood the problem, I could have dealt with it by using a TRS -> breakout cable and leaving the red unplugged. Instead I just randomly plugged in cables until something worked and lost a few good takes and ultimately a cheap pair of monitors as a result.

Be smarter than me!

ddiamond84 · 2022-12-19T21:53:33.656Z

Really awesome responses, thank you all again. I don’t think the DB4 has a mono in, at least from what I can tell.

Annihilation_Squares · 2022-12-19T21:59:55.481Z

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.

ddiamond84 · 2022-12-19T22:12:30.785Z

Any chance you have a link?

Annihilation_Squares · 2022-12-19T22:16:41.345Z

Seems 7ball has disappeared but these ought to do fine.

EDIT: argh nevermind, brb

Annihilation_Squares · 2022-12-19T22:20:11.786Z

reverb.com

Hosa CYR103 CYR103 1/4" TS to Dual RCA - 3 Meter | Reverb

Reverb is a marketplace bringing together a wide-spanning community to buy, sell, and discuss all things music gear.

Crudeliar · 2022-12-19T22:32:19.767Z

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.

brucegill · 2022-12-19T23:57:31.954Z

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:

forum.sequential.com

Ground hum on Prophet-10 rev4

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.

jemmons · 2022-12-20T04:23:22.057Z

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.

brucegill · 2022-12-20T07:47:45.573Z

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…

brucegill · 2022-12-20T17:52:29.997Z

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?

jemmons · 2022-12-20T18:35:08.992Z

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.