How audio/midi interface work?

L

lukasz.jan95

New member
Hey guys,
I did some research about the question above but not clear enough explained for me lol
First of all please forgive me my mistakes, I come from Poland. Please use easier english. I could probably do with more sophiscicated one but the more simple the quicker I get the point. :D

I would like to set up a home recording studio in my bedroom. I've already gathered some info about how it generally works but I have couple of questions to ask about inputs and outputs in interface.

As a example one I will talk about Scarlett 2i4 Which specification's listed below:

Front panel:
2 line/mic/instrument combination inputs - high quality XLR/ ¼ “ TRS Jack Combo
2 line/inst switches
2 illuminating “PAD” buttons
2 Gain knobs
2 Gain halo signal indicators
48V Phantom power switch
MIDI activity LED indicator
USB connection LED indicator
“DIRECT MONITOR” control
“STEREO/MONO” switch for direct monitor
Large monitor level dial (controls headphone and line level outputs)
Headphone output - ¼” TRS Jack

Rear panel:
2 balanced monitor outputs – TRS (channels 1-2)
4 unbalanced outputs – RCA Phono (channels 1-4)
MIDI IO
USB 2.0 Port
Kensington Lock slot

I will put numbers to question so that it will be easier to comunicate.

1. When I plug my M-Audio Keystation to MIDI IN data signal goes through Scarlett to PC. This is clear. Then it 'gets' sound from VST in eg Cubase. Do I hear it through HEADPHNES OUT of my computer or only from foucsrite? Where do I hear it? Monitor output in focusrite or headphones in focusrite? :facepalm:

2. Are monitor outputs (balanced) made only for monitors? What if I want to play live on stage? Can I plug jack jack cable to Scarlett and to stage loudspeaker or mixer input?

3. Why they give me 2 pairs of chinch outs? If count all together I have one stereo output on frontal side, 2 stereo sets of chinch outs and 1 (1 pair) Quite a lot! How they can be useful?

4. The guy at music store told me that I will be not able to play&record live MIDI track during MIDI track being played (eg. I've got a backing track I've recorded in MIDI and audio) Why is it only for play live/record or placback? When I use my USB cable for Keystation Iam able to hear what I play&record live and hear all the midi tracks I recorded previously. How it is that scarlett, much more 'proffesional' gear is not able to give me this possibility?

5. If the problem above actually occurs how can I solve it out? My dream is to have an ability to do homerecording stuff (overdubbing, playing one instrument after another) with acoustic instruemnts, electrc (guitar) and MIDI and perform with this live with an ability to use 2 audio inputs (eg, mic + guitar direct in) and one MIDI keyboard and all of them recorded while playing.
haha, am I asking for the moon? :confused: The guy at store told me that I have to invest more money into that.

Whats your opinion? Which interface will cover my needs?

THANKS A LOT in advance.
Cheers.
 
1. When I plug my M-Audio Keystation to MIDI IN data signal goes through Scarlett to PC. This is clear. Then it 'gets' sound from VST in eg Cubase. Do I hear it through HEADPHNES OUT of my computer or only from foucsrite? Where do I hear it? Monitor output in focusrite or headphones in focusrite?
1a: The Scarlet becomes the computer sound card. In fact it is often better to disable the On Board Sound (usually called AC97 or Realtek)

2. Are monitor outputs (balanced) made only for monitors? What if I want to play live on stage? Can I plug jack jack cable to Scarlett and to stage loudspeaker or mixer input?
2a: No, the outputs are not specialized they can drive almost an other audio device, active speakers, mixer, tape recorder etc.

3. Why they give me 2 pairs of chinch outs? If count all together I have one stereo output on frontal side, 2 stereo sets of chinch outs and 1 (1 pair) Quite a lot! How they can be useful?
3a: Probably just duplicate unbalanced outs. Could feed a pair of "grotbox" monitors.

4. The guy at music store told me that I will be not able to play&record live MIDI track during MIDI track being played (eg. I've got a backing track I've recorded in MIDI and audio) Why is it only for play live/record or placback? When I use my USB cable for Keystation Iam able to hear what I play&record live and hear all the midi tracks I recorded previously. How it is that scarlett, much more 'proffesional' gear is not able to give me this possibility?
4a: Not sure if he is just pumping the bill? See further...

5. If the problem above actually occurs how can I solve it out? My dream is to have an ability to do homerecording stuff (overdubbing, playing one instrument after another) with acoustic instruemnts, electrc (guitar) and MIDI and perform with this live with an ability to use 2 audio inputs (eg, mic + guitar direct in) and one MIDI keyboard and all of them recorded while playing.
5a: If you have your backing tracks set up on the computer you can certainly play those out of the AI. Yes, the MIDI can trigger sounds and the MIDI data will be recorded. The two audio inputs will be recorded as well. However, to HEAR the two live inputs you will have to use the AI's output and that will incur some delay, latency. This might not be acceptably low for your purposes. The Focusrites are excellent interfaces but do not have the lowest latency you can get by quite a margin.

But in any case, although what you want CAN be made to work it is a brave man that would usde such a rig live!
am I asking for the moon? The guy at store told me that I have to invest more money into that
 
lukasz.jan95 said:
Sorry I didn't catch the 5. explaination. Can you give broader explaination? What you mean by AI?
Click to expand...

Sorry, lazy moir! Audio Interface, i.e. the Scarlet.
So, as I understand things you want to play an existing backing track which would be on the hard drive of the computer and loaded into whatever software you intend to use,ok?

Next you are playing in MIDI data (and I would suggest using the DIN MIDI connectors on the Scarlet) which will trigger sounds in the software host. The software can also have a MIDI track recording the data.

Lastly you want to feed in guitar and vocals, have those reproduced and recorded?

This is all quite possible and I am pretty sure that interface could handle it..But!
In order to hear the MIDI sounds and the backing track you will have to use PC monitoring, that is you cannot use "zero latency" monitoring as you normally would for the two mic inputs. Using the PC sound will cause a delay, latency and this might be bad enough to render the system invalid for live use.

Unfortunately there is no way to predict how good or bad the set up will be. Latency depends largely on the interface and especially its drivers. The PC can be a factor but almost any modern machine should cope, certainly anything dual core or better.

The fastest, i.e. lowest latency interface known to me of reasonable cost (£190, you must convert!) is the Native Instruments Komplete Audio 6. That is a usb device like the Scarlet. If I were attempting this brave project I would find a modest desktop PC and fit an M-Audio 2496 sound card, faster than almost any external AI except the KA6 which is its equal.

Hope that is clearer? DO come back if not, I am fully retired now!

Dave.
 
So the guy at shop wasn't right?
I think I got it but to smooth it out:
I will give an example:
I've got 3 MIDI tracks (eg drums, strings, bass) already recorded. I push play with selected 4th track wchih I'm going to record now piano on top of these 3. Do I hear all, 4, of them while playing? I plug the monitors out to speaker an all of these go through that? And through headphones too?
Sorry for digging again into this but I'm not sure If I explained it the way I wanted to be. And the guy was so rude to me that even when I asked for advise politely he exploded with fury that I'm not gonna achieve all of these without having the 8i6 model.

And of course thanks for answer! You help me a lot.
And the latency comes when playing live and playing recorded tracks (the 3 I used as an example) at the same time?
 
Yes you have it.
Just to be sure? You say "three MIDI tracks recorded" I shall assume you mean these are now actually audio tracks, i.e. .wav audio data tracks? This is important because you do not want the computer to have to process too much MIDI to audio data on the fly, that is, in "real time" because this demands a lot of processing power and that will make low latency even harder to achieve. Also, any effects you might use on the tracks, do that and save the effected track because again, running reverb plugins say, eats up CPU power.

The guy in the shop got angry and rude (we have the word "stroppy" here) because you had tested him to the limit of his knowledge. Such people should not be selling complex electronic equipment but then I know the shops pay peanuts so you get monkeys.

No, you don't need the 8i6 (in fact I cannot see how they can claim 8 inputs?) and if you were going to spend that sort of money go for the NI KA6. It comes with Cubase which many say cannot be bettered for MIDI work.

Dave.
 
No, I meant to leave the backing track only MIDI, not converted. And what about computer issues? If I will have additional SSD, 4 core processor, minimum 4GB RAM? Will it reduce the latency? Or is it only in audio/midi interface hands?
 
lukasz.jan95 said:
No, I meant to leave the backing track only MIDI, not converted. And what about computer issues? If I will have additional SSD, 4 core processor, minimum 4GB RAM? Will it reduce the latency? Or is it only in audio/midi interface hands?
Click to expand...

Well you could try leaving the backing as MIDI data but it would be giving the machine a lot of work to do so why not render it to audio?

But yes, that PC specification is several times better than you need. After a certain, quite modest PC power, latency is almost all determined by the interface and the driver.

Dave.
 
ecc83 said:
Well you could try leaving the backing as MIDI data but it would be giving the machine a lot of work to do so why not render it to audio?

But yes, that PC specification is several times better than you need. After a certain, quite modest PC power, latency is almost all determined by the interface and the driver.

Dave.
Click to expand...

OP - TO Dave's point, you can keep it MIDI and play a VSTi (MIDI instrument on your computer/DAW) if you find your computer struggling, you may want to "send" the audio from the MIDI track and record to an analog track. But you can keep the MIDI while recording on a new MIDI track. As Dave pointed out, your computer may struggle if you are playing too many MIDI instruments on your computer.
 
Thank you David.
To be honest, if I were doing this (yes! I HAVE gigged!) I would not use a PC for backing tracks, well, certainly not the one doing the VSTis and the recording!

I would copy my tracks to another medium. Because I have two machines and a zillion discs I would use Mini Disc but you could use CD or an i"thing". Shoot! You could even use Compact Cassette! For live use the quality of my Sony Dolby S machine would be a vast overkill! (Yeah! Footswitch muting the PA feed, headphones for PFL cuing..Ha! getting into this!)

Dave.
 
"This is all quite possible and I am pretty sure that interface could handle it..But!
In order to hear the MIDI sounds and the backing track you will have to use PC monitoring, that is you cannot use "zero latency" monitoring as you normally would for the two mic inputs. Using the PC sound will cause a delay, latency and this might be bad enough to render the system invalid for live use."

I have to go back to this post. Does it mean that AI oparates the sounds with no latency but only for one use - live or playback? To my understanding it triggers between these two. And when I want to use front panel inputs live, the playback which runs have to go through another audio device which is my computer's sound card what gives me latency? and the troubles I may have are that when I play live I hear the latency occuring in playback? I would be a nonsens because when I play live to whatever I have I don't care about it's latency because it just goes on. A latency on the input would be a boundary because I play the sound but it is heared a bit late and not in the rythme of playback. Am I right?
 
lukasz.jan95 said:
"This is all quite possible and I am pretty sure that interface could handle it..But!
In order to hear the MIDI sounds and the backing track you will have to use PC monitoring, that is you cannot use "zero latency" monitoring as you normally would for the two mic inputs. Using the PC sound will cause a delay, latency and this might be bad enough to render the system invalid for live use."

I have to go back to this post. Does it mean that AI oparates the sounds with no latency but only for one use - live or playback? To my understanding it triggers between these two. And when I want to use front panel inputs live, the playback which runs have to go through another audio device which is my computer's sound card what gives me latency? and the troubles I may have are that when I play live I hear the latency occuring in playback? I would be a nonsens because when I play live to whatever I have I don't care about it's latency because it just goes on. A latency on the input would be a boundary because I play the sound but it is heared a bit late and not in the rythme of playback. Am I right?
Click to expand...

Not sure of other DAWs but Ableton handles that by adding an offset so that it accounts for the latency (i.e. plays earlier so it plays in time). Depending on what you are DAW you are using that might do that. You could also do that manually, but I would think it would be a difficult task.

I get a pretty decent latency through my card (64) which is good, but CPU takes a big hit. Another option, (now you are getting into advance stuff) is the notion of Freezing a MIDI track (either through software or record it to analog) so you can reduce the load on the computer. Just layer your MIDI tracks, either Freeze (if you have that feature) or record them to a track as Analog, disable the original MIDI and now you have just analog tracks. Analog doesn't require as much CPU usage.

You are going to have to experiment somewhat, and re-think the problem. Just because it started out MIDI doesn't mean it has to stay that way. If you have a DAW, you don't need 20 MIDI parts going at once. Back in the days of sequencers, but not today.
 
Morning Lukaz.
Let's try to nail this thing?

An audio interface outputs the audio from its inputs in two ways..
First by converting it to digital, sending it into the computer and then back for conversion back to analogue. This take a tiny but finite time called latency. How short this delay is depends upon the AI, MOSTLY its drivers and to a limited extent, the power of the PC but the shorter the delay, the harder everything has to work.

Secondly, almost all interface have what is called "zero latency" monitoring.
In this mode the input signals are routed directly from the inputs to the outputs, no computer intervention so "zero" delay. But!

If you want to hear previously recorded tracks from the PC, by definition you MUST have the monitoring turned to the first condition. Thus analogue input signals will be delayed. You want to add to the PC load by having it render MIDI data in realtime. If you THEN ask it to convert MIDI recordings as well, you are going to have a problem I feel.

The system COULD do all that I am sure but you would have to set a large buffer and live playing would be impossible most likely.

As David said, experiment. Can you get acceptable latency playing live MIDI? If so try that with one backing track (preff' audio!) if still ok move on to input sources but my feeling is things will start to get scratchy.

Dave.
 
ecc83 said:
You want to add to the PC load by having it render MIDI data in realtime. If you THEN ask it to convert MIDI recordings as well, you are going to have a problem I feel.

The system COULD do all that I am sure but you would have to set a large buffer and live playing would be impossible most likely.
Click to expand...

So 'zero latency' is only for analogue inputs? Because MIDI has to go to PC and from there go back to AI? Then If I turn on my backing track (I don't have to leave them MIDI actually, I may record them to analogue, I guess I still have a control over them because I can edit everyone of them separatly, or I may freeze them to reduce PCU's work even more) it's tracks all together play with latency (btw, how big latency may occur?.. with let's say NI Komplete Audio 6 and fast computer which additionaly runs with SSD) but what happens when I add live e.g guitar plugged via jack to AI? Is the sound of the guitar zero latency? I would not be that nice, because I want the sound go through the PC eg when using mic to add compression and little reverb. Can I switch between zero latency and 'going through PC' mode?

Is the MIDI live playing a problem that makes the latency to occur? Eg If I have 30 MIDI track in DAW all set with different VSTis and effects will the computer struggle eventhough I'm not playing my MIDI keyborad live?
 
"Zero latency" is used for inputs where you are happy to hear the "dry" un-effected signal from a guitar or mic (in headphones for the latter!).

If you wan to apply some software FX, some distortion to guitar or "ego" reverb to a mic say, you will have to use the delayed signal from the PC. However, since you don't usually need the WHOLE signal "FX'ed" there is usually a mix control whereby you have some direct sound, for timing, and a bit of reverb (say) "wash" to keep the vocalist happy (fat chance!) .

But 30 MIDI tracks??? Can we have a bit of a reality check here?! This is all for LIVE performance? So, the end result will go into at best two channels (and tho many PA rigs LOOK stereo, often they ain't) .

But I mentioned some time ago bravery? Running JUST a keyboard live on stage is something many musicians would not want to risk. At least if a guitar amp fails you can have a back up running in seconds. If a PC crashes, good night Vienna!
Yes, I know many bands DO run a laptop system but I doubt many ask as much of that system as you seem to be doing?

Dave.
 
Like I said, I can convert tracks to analogue but all of them have to be separate.
I have to consider all these things.. Well, I'm not going to play in sort of a super professional live shows I suppose, If something brakes down it will not be such a big issue.
Anyways, what is your techinque to capture sound in lossless quality live on stage?
I've just though that I may have a playback from differen device.. But how match it to the thing I recorded live afterwards? It would be a lot of work probably. Any suggestions?
What is your live performance experiance? Is it possible to achieve good mix on stage which was set at home studio with monitor speakers?
 
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