Nord Piano 4 stereo vs mono, balanced vs unbalanced

[diogenes]

Hi, I'm fairly new to recording concepts, learning Logic Pro with a Nord Piano 4 and Focusrite Scarlett Solo interface on Mac.

The Nord manual says that the Left & Right Out are 1/4 inch unbalanced line level outputs. The Nord Piano 4 is a stereo instrument with separate signal paths for left and right audio channels.

Also, for the time being I'll be recording just piano, not synth, so I'll use Stereo mode on the Nord, about which the manual says all sounds are sent to both audio outputs.

Question #1:
In Stereo mode, does this mean that each output contains all sounds in a single channel (mono), or in 2 channels (stereo)? I'm thinking it's probably mono, but want to be sure. Of course, even if it were stereo, it wouldn't help me because Logic Pro only receives one channel per input, and I have only 1 line input.

Question #2:
The manual's use of the term unbalanced output is confusing to me because from my reading I thought that balanced/unbalanced was a cable characteristic, and you can choose to use either cable based on your physical setup. In fact, I've done trials with both a TS (unbalanced) and TRS (balanced) cable, and they both work equally well. So I'm not sure what it means to call an output unbalanced?

Thanks!

[Hlaalu]

Question #1:
In Stereo mode, does this mean that each output contains all sounds in a single channel (mono), or in 2 channels (stereo)? I'm thinking it's probably mono, but want to be sure. Of course, even if it were stereo, it wouldn't help me because Logic Pro only receives one channel per input, and I have only 1 line input.

Hi and welcome to the forum!
No, stereo means that output 1 and 2 carry different portions of the signal - that's why it's stereo. So if you were to use only one of them, you'd have 50% of the sound, and that wouldn't sound very good. You'd have to turn on the mono mode in your P4, but pianos (as many other things) don't sound very good in mono.

Question #2:
The manual's use of the term unbalanced output is confusing to me because from my reading I thought that balanced/unbalanced was a cable characteristic, and you can choose to use either cable based on your physical setup. In fact, I've done trials with both a TS (unbalanced) and TRS (balanced) cable, and they both work equally well. So I'm not sure what it means to call an output unbalanced?

Balanced / unbalanced is not the same as TS / TRS. The first is a way of transmitting an signal, the second is the physical way in which a cable is made (2 or 3 wires, that is connections). To oversimplify a bit, a single (mono) balanced signal needs 3 wires per channel: the ground, the signal itself and a "copy" of the same signal which serves in turn to "clean" any interference, to put it simply. Now, since we said you need 3 wires for this, a suitable cable could be TRS, but can also be XLR, and in fact the latter is often the case.

Now, Nord keyboards, as 99% of the keyboards around, have UNbalanced outputs, which means that the out 1 and 2 you see on the back have only 2 physical connectors in them, the Tip and the Slave (TS). So plugging a TRS wouldn't make a difference since the Ring (R) wouldn't connect to anything. (Incidentally, the reason why most keyboards have unbalanced out is because, when live or in big avenues (which is when you can have interference problems) you'd be putting a DI straight after the outs, which makes the signal balanced, plus doing other nice things depending on the DI model, for example transformer-isolating the signal, shielding also from phantom power in case one worries...))

So: TRS or XLR only tells you how many "paths" there are per connector. What you then do with such paths varies case by case. A TRS/XLR connection could be carrying a mono, balanced signal, or a stereo, unbalanced signal. That's because, as we saw, to carry a balanced mono signal you already need 3 signal paths. But a single TS can only carry an unbalanced mono signal.

Now all the above is from the side of the keyboard. As for the Focusrite Solo, of which I only know what I read on the Thomann page (https://www.thomann.de/gb/focusrite_sca ... UiOiJlbiJ9), it says it has one Line/instrument input, but it doesn't say whether it's TS or TRS. If it's of the TS type, there is no way you can feed it with a stereo signal. If, on the contrary, it's of the TRS type, you'd need a double-TS to one-TRS adapter cable, out from the Nord and straight into it, and you'be sending a stereo signal. This is probably written in the Focusrite manual...

[harmonizer]

Most of the Nord-provided Acoustic Piano sounds are optimized for stereo. So you definitely want to record it in stereo.

[diogenes]

Very interesting! So again, the manual says that in stereo mode, all sounds are sent to both audio outputs. But you're saying that each output carries different portions of the signal. That sounds like a contradiction to me. Is it possible the Nord is sending identical copies of "all sounds" out on both outputs and calling it stereo? It seems weird, but if I also think about the fact that this is piano only, and rest of that manual paragraph says When set to Piano:L Synth:R, Piano sounds are sent to the left output and sample synth sounds to the right., then it doesn't sound that far fetched.

Now if this is crazy, and you are correct that different parts of the piano sound is sent to the L and R outputs, then can you help me understand how it is determined which goes where, given that there are no mics involved? Sorry to ask such naive questions, but I've also read that you can take a mono instrument recording, duplicate it, maybe alter one slightly, and pan one left and the other right to get a wider stereo effect. I know I'm probably going down the rabbit hole, but I just want to understand how this stuff works.

[maxpiano]

Nord Piano library pianos are stereo sampled, so when played back the L sample goes to Out 1 and the R to Out 2. When Piano is routed to a single output or set to Mono, the Nord Piano engine applies an algorithm to combine L and R samples and produce a mono output while trying to minimize the consequent timbre alteration

[anotherscott]

Very interesting! So again, the manual says that in stereo mode, all sounds are sent to both audio outputs. But you're saying that each output carries different portions of the signal. That sounds like a contradiction to me.

It is not a contradiction. By analogy, if you plug earbuds into your phone and listen to music, everything is sent to the left and right ear pieces. If you're listening to a stereo recording, each earpiece will get something different. If you're listening to an old mono recording, each earpiece will get the same thing. But no matter what track you play, it will send something to each side.

In this case, "all sounds are sent to both audio outputs" means that, for example, your piano sound AND your layered string sound (or whatever) are both going to be sent to both audio outputs. Any such sound that is stereo will send something different to each side; any such sound that is mono will send the same thing to both sides (though keep in mind that even mono sounds can have stereo effects applied to them, in which case they, too, will be sending something different to each side).

rest of that manual paragraph says When set to Piano:L Synth:R, Piano sounds are sent to the left output and sample synth sounds to the right.

This setting changes the routing so that instead of L and R producing a single stereo output that includes every sound you are playing, it creates two MONO outputs, sending both the left AND right sides of the piano to the left channel output (creating a mono piano sound), and sending the non-piano sound (in mono) to the right channel output (regardless of whether that sound originated as mono or stereo... if the latter, both "sides" of the sound will be sent to the right channel output).

Now if this is crazy, and you are correct that different parts of the piano sound is sent to the L and R outputs, then can you help me understand how it is determined which goes where, given that there are no mics involved?

There were mics involved when the piano samples were created (the keyboard creates its piano sounds by playing back recordings of pianos actually playing those notes). The signal picked up by the left mic goes to the left channel, the signal picked up by the right mic goes to the right channel.

Simplified, but that's the gist.

[harmonizer]

diognese, I suggest you stop worrying about what the wording in the manual says.
When playing one of the Nord-provided acoustic piano sounds, your Nord Piano will be sending a stereo signal out of the L and R output jacks.
(I am assuming you are not pressing the Mono button).
The Nord-provided acoustic piano sounds are optimized for stereo.
Most of them do not sound that good if you try to collapse them to mono, either by pressing the Mono button on the Nord, or by only taking the output from just the L or the R output jack.
So I suggest you just record them in stereo, taking the separate L and R outputs into two separate inputs on whatever device you will be using to record your Nord's piano sounds.

[diogenes]

I finally get it! Thanks to all for patiently explaining, particularly Hiaalu and anotherscott. I'm exchanging my Focusrite Solo for a 2i2 so I can record stereo.

[Hlaalu]

I'm glad we could help!

Just a last note, hoping not to sound too redundant. I think part of the confusion, especially if you are beginning with all this, is because you were in fact dealing with four different "subjects" at once so to speak:

1. Whether a sound material is mono or stereo. To put it shortly, humans only came up with stereo recordings because we have 2 ears. Nothing more and nothing less than that. Whether a signal is mono or stereo depends on the way it's been sampled at the origin. That is, the details about which frequencies are sent to left and which to right is dependent on the exact and unique way they mic'ed the source during sampling. Nevertheless, later transformation from one into the other is possible, but with caveats. What you can always do easily is to collapse a stereo signal into a mono one by merging the two paths. On the other hand, while you certainly can transform a mono signal into stereo, results vary widely in terms of the final quality... Whatever algorithm you use to do that, it will have to "guess" which frequencies is best to put on the L and which ones to the R, and this vary, but one thing is for sure: if you took an originally stereo signal, made it into mono, and then stereo again, you'd end up with something different than what you had started with.

2. Where to route, that is send, our signals. This is what the manual part you were reading was referring to. Now of course, while this is a different concept, it is also inevitably entangled with whether the signal is mono or stereo. As we saw, a stereo signal can't be routed to a single output -- unless that's a TRS / XLR jack, but we're playing over the definition of "one" output here, since such connectors have room for both the L and R at once. With TS (as 99% of the keyboards), you can only send one signal at a time. To have stereo out, you need two TS, there's no way out of that. Now if your sound source isn't stereo but mono however, you can choose to route it to only one jack, or to both, having what's usually called "dual mono" -- even though the word "dual" is somewhat misleading here, since there's nothing intrinsically "double" in this: you can "copy" your signal all over as many outs as you want, or I should say as many as your keyboard physically allows for. The Nord Piano has 2, but for example the Stage series has 4. In this case you could route a mono signal into one, two, three or all four of them. Or, you could route a stereo signal in two, namely 1-2 and 3-4, left-right and left-right.

3. Balanced / unbalanced. This has nothing to do with mono or stereo. Rather, it is an extremely simple and yet extremely clever way of removing unwanted noise in the signal. The caveat here is that, in order for it to work, it requires one added physical pathway for each signal it's going to filter. So if you're filtering a mono signal, which has one pathway, you need two. If you're filtering stereo, you need four (the ground stays one).

4. Which physical connector is suitable for which task. This of course depends on the task, but the source of confusion, for people first learning these things, is that the same physical connector can be used for two entirely different tasks. A single TRS or XLR connection could be used to either carry a stereo unbalanced signal, or to carry a mono balanced signal. Two entirely different concepts, but same connector. Say you need a balanced stereo signal, you'd need two TRS / XLR connectors, and so on.

Of course this isn't the end of the story, because there are all those situations in which one end of the connection expects a certain kind of signal/connector and the other a different one... What happens in such cases varies case by case. But I hope you have at least a starting point...

[diogenes]

Great summary!

And yes, I was partly confused over the tendency to conflate "TRS" with "balanced". For example, https://blog.zzounds.com/2020/05/29/ts- ... rs-cables/ says In a balanced TRS cable, Tip and Ring carry a positive and negative mono audio signal, with the Sleeve functioning as Ground. So when I read that, I thought "oh, TRS cables = balanced." But, sounds like there's technically no such thing as a "balanced TRS cable", rather a TRS cable can carry whatever it is sent, such as balanced mono, unbalanced stereo, or even unbalanced mono, where the "R" part is (hopefully) unused. Better: When a TRS cable is used to carry balanced mono signal, ....