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Author Topic: 4 Track Recording With 2 UA-5's?  (Read 1436 times)

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Offline cybermansrev

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4 Track Recording With 2 UA-5's?
« on: May 11, 2006, 05:16:37 AM »
Is this possible? Has anyone done it?
As I have a laptop and a UA-5 already I was thinking about a way of doing a soundboard and set of mics matrix, whilst I know you can use the 4 inputs on a single UA-5 to do this in real time to 2 track, is it possible to have 2 UA-5's connected to my laptop via USB and record 4 tracks? Or will the laptop/software only recognise one UA-5?
Also is there any way to keep two UA-5 clocks in-synch?
The reason I ask is that I have an opportunity to pick up a second UA-5 at a reasonable price.
Thanks

(I posted this in computer recording acouple of days ago but wondered if I'd get a better response over here)

Offline Nick Graham

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Re: 4 Track Recording With 2 UA-5's?
« Reply #1 on: May 11, 2006, 05:20:30 AM »
Unless you had some type of USB splitter, I don't know how you'd do it.

I guess using 2 seperate USB inputs would work, but you'd likely run into Buffer issues, plus you'd need 2 seperate recording programs.
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Re: 4 Track Recording With 2 UA-5's?
« Reply #2 on: May 11, 2006, 05:28:19 AM »
Spark E can comment.

Ill tell him to have a look. He was just talking about this.


Offline cybermansrev

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Re: 4 Track Recording With 2 UA-5's?
« Reply #3 on: May 11, 2006, 09:23:01 AM »
I guess using 2 seperate USB inputs would work, but you'd likely run into Buffer issues, plus you'd need 2 seperate recording programps.

This kind of was what I was thinking that there'd be a combination of hardware conflicts and I'd have difficulty finding a single program prepared to recognise 2 "soundcards".

Spark E can comment.

Ill tell him to have a look. He was just talking about this.

Thanks he's normally very knowledgeable but I hope he gives an idiot speak translation for my less technical mind!

Offline SparkE!

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Re: 4 Track Recording With 2 UA-5's?
« Reply #4 on: May 11, 2006, 10:36:16 AM »
Yeah, I've been looking at how to add connectors to two or more UA-5's that would allow them to share the same reference oscillator.  There's a crystal oscillator in each UA-5 that is ultimately the timing reference for everything else that happens inside that UA-5.  It's the difference between individual crystal oscillators that causes the timing skew that you see between the recordings from separate UA-5's.  I'm pretty lucky because the UA-5's that I currently use have crystal oscillators that are pretty close to each other as long as they are in good thermal contact with each other while the recordings are being made.  On the other hand, I'd like to remove the timing skew altogether so that each of them will take audio samples at exactly the same rate.  That way when I line up the recordings with each other at one spot, they are lined up all the way through.    The ideal situation would be to start recording before the set and then use a single beat of the kick drum to line up the two recordings at one spot.  Then because each recorder had recorded at exactly the same rate, the recordings would line up with each other for the entire overlapping duration of the recordings.

Anyway, what I'm thinking about doing is making a small line driver board that could take its signal input from the crystal oscillator's output and send that signal to a connector that's installed into the rear case.  Then I'd run an external cable from that connector to an input connector on the other UA-5.  The input connector on that box would accept the crystal oscillator signal from the original box so that both UA-5's would essentially share the same crystal oscillator.

I've figured out several ways that the mod could be done, but I want to make sure that the mod does not affect the units' ability to boot up (need to make sure that the crystal oscillator starts up reliably after the mod has been made).  I also would like to have the ability to hot plug the clock cable between the units without worry that it will damage either unit.  I'm pretty confident that I can do something to share clocks where you plug the cable in, then turn the units on and everything will work, but I'd rather make it so that you can simply plug the cable in, no matter whether the units are already "ON" or not.

And I want to make it so you can daisy chain more than 2 UA-5's together.  Need an 8 channel recorder? Then connect 4 UA5's together with clock cables.  Need 21 channels?  Connect 11 of them together and leave one channel unused.
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Offline poorlyconditioned

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Re: 4 Track Recording With 2 UA-5's?
« Reply #5 on: May 11, 2006, 11:10:39 AM »
Yeah, I've been looking at how to add connectors to two or more UA-5's that would allow them to share the same reference oscillator.  There's a crystal oscillator in each UA-5 that is ultimately the timing reference for everything else that happens inside that UA-5.  It's the difference between individual crystal oscillators that causes the timing skew that you see between the recordings from separate UA-5's.  I'm pretty lucky because the UA-5's that I currently use have crystal oscillators that are pretty close to each other as long as they are in good thermal contact with each other while the recordings are being made.  On the other hand, I'd like to remove the timing skew altogether so that each of them will take audio samples at exactly the same rate.  That way when I line up the recordings with each other at one spot, they are lined up all the way through.    The ideal situation would be to start recording before the set and then use a single beat of the kick drum to line up the two recordings at one spot.  Then because each recorder had recorded at exactly the same rate, the recordings would line up with each other for the entire overlapping duration of the recordings.

Anyway, what I'm thinking about doing is making a small line driver board that could take its signal input from the crystal oscillator's output and send that signal to a connector that's installed into the rear case.  Then I'd run an external cable from that connector to an input connector on the other UA-5.  The input connector on that box would accept the crystal oscillator signal from the original box so that both UA-5's would essentially share the same crystal oscillator.

I've figured out several ways that the mod could be done, but I want to make sure that the mod does not affect the units' ability to boot up (need to make sure that the crystal oscillator starts up reliably after the mod has been made).  I also would like to have the ability to hot plug the clock cable between the units without worry that it will damage either unit.  I'm pretty confident that I can do something to share clocks where you plug the cable in, then turn the units on and everything will work, but I'd rather make it so that you can simply plug the cable in, no matter whether the units are already "ON" or not.

And I want to make it so you can daisy chain more than 2 UA-5's together.  Need an 8 channel recorder? Then connect 4 UA5's together with clock cables.  Need 21 channels?  Connect 11 of them together and leave one channel unused.

This sounds too difficult.

But I'm thinking of using a UA5 and a DMIC20 together.  The DMIC has a clock input, and that input could come from the RCA SPDIF output of a UA5.  I haven't tried this yet, even though I own both pieces of equipment.  So far, I just bring my laptop + presonus firepod if I need to do four or more tracks.

  Richard
Mics: Sennheiser MKE2002 (dummy head), Studio Projects C4, AT825 (unmodded), AT822 franken mic (x2), AT853(hc,c,sc,o), Senn. MKE2, Senn MKE40, Shure MX183/5, CA Cards, homebrew Panasonic and Transsound capsules.
Pre/ADC: Presonus Firepod & Firebox, DMIC20(x2), UA5(poorly-modded, AD8620+AD8512opamps), VX440
Recorders: Edirol R4, R09, IBM X24 laptop, NJB3(x2), HiMD(x2), MD(1).
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Offline cybermansrev

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Re: 4 Track Recording With 2 UA-5's?
« Reply #6 on: May 11, 2006, 12:03:00 PM »
Thanks for replying, I was kind of hoping there would be an easy dirty solution like initally feeding the digital signal from one UA-5 to the other put the clocks insych but obviously thats not the case.

I'm pretty lucky because the UA-5's that I currently use have crystal oscillators that are pretty close to each other as long as they are in good thermal contact with each other while the recordings are being made.
How can one tell how close the oscillators are? Do you just record the same source and see how out of skew they are, or is there another way of calculating this?

Anyway, what I'm thinking about doing is making a small line driver board that could take its signal input from the crystal oscillator's output and send that signal to a connector that's installed into the rear case.  Then I'd run an external cable from that connector to an input connector on the other UA-5.  The input connector on that box would accept the crystal oscillator signal from the original box so that both UA-5's would essentially share the same crystal oscillator.


If you do crack this i'd love to see your solution although it sounds a wee bit harder than a digimod.
It sounds like you have run two UA-5's before, are you going into 1 laptop? and if so what software or are you using two recorders?



But I'm thinking of using a UA5 and a DMIC20 together.
Funnily enough Richard I remember you say this a while ago hence my question?


Offline SparkE!

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Re: 4 Track Recording With 2 UA-5's?
« Reply #7 on: May 11, 2006, 01:39:43 PM »
I'm pretty lucky because the UA-5's that I currently use have crystal oscillators that are pretty close to each other as long as they are in good thermal contact with each other while the recordings are being made.
How can one tell how close the oscillators are? Do you just record the same source and see how out of skew they are, or is there another way of calculating this?

Yes, just record the digital output of both boxes for an hour, line them up with each other at the beginning of the recording in your favorite editor (I use Audacity) and see how much they've drifted apart at the end of the recording.  That way you know how many milliseconds per hour of timing skew you will see.

I don't like to ever see more than about 4 ms of skew between two sources in the mix at any given spot.  Some people claim you can't hear the skew until it's over 20 ms, but I don't believe that.  At 4 ms of skew, you can get notches in your spectrum at odd multiples of 125 Hz, so even that can be noticeable.  At 20 ms of skew, you can get notches in your spectrum at odd multiples of 25 Hz, so the notches are much more tightly packed.  If you don't want the potential for any notches below 15 kHz, you'd have to line them up to within about 1 1/2 samples at 44100 kHz or 3 samples at 96 kHz.  So, if you have any skew at all, there is the potential for it to be audible, especially if the same sound is present in both recordings at the same level and the mix is equal parts from each source.

I got really burned one time when I tried to mix a PCM-M1 recording (from mics) and a DA-20 recording (from SBD) in post.  There was so much timing skew that I had to make edits every 6 seconds or so through a 2+ hour show.  The result was a mix with the sources within about 4 ms of each other, but it took hours and hours to do the editing.  I think I had almost 25 hours in the project.
If you do crack this i'd love to see your solution although it sounds a wee bit harder than a digimod.
It sounds like you have run two UA-5's before, are you going into 1 laptop? and if so what software or are you using two recorders?
If I ever get this done, I'll definitely start a thread about it.

When I run two UA-5's I'm just recording to NJB3's, one per UA-5.  Then I line up the recordings in post.  I don't currently have a way to do 24/96 in the field, although I've done it into my desktop machine at home.  I've never tried two UA-5's over USB at once, but I wouldn't be surprised if the drivers will only support one at a time per computer.  I'm betting that you'd need two computers if you really want to do 24/96.
How'm I supposed to read your lips when you're talkin' out your ass? - Lern Tilton

Ignorance in audio is exceeded only by our collective willingness to embrace and foster it. -  Srajan Ebaen

 

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