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  #1  
Old 02-05-2000, 10:16 PM
shaggy shaggy is offline
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Default Weird offset spikes record onto audio channels.

ADAT optical to 001

Tried setting session rate to 16 rather that 24. Still spikes appear (single sample) however much less often. Anyone else get this?

[This message has been edited by shaggy (edited February 06, 2000).]
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  #2  
Old 02-06-2000, 03:13 PM
mitcho67 mitcho67 is offline
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Default Re: Weird offset spikes record onto audio channels.

shaggy,

yeah, I still get that too. I've heard it's because PT is not receiving clock, but I can't make any sence of it. Are you getting good sync from ADAT to PTLE?
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Old 02-06-2000, 06:44 PM
jampro jampro is offline
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Default Re: Weird offset spikes record onto audio channels.

I've had the same problem. Dumped 8Tracks Adat through pipeline. It sounded like rice krispies. Digi any suggestions or comments?
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  #4  
Old 02-07-2000, 07:49 AM
shaggy shaggy is offline
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Default Re: Weird offset spikes record onto audio channels.

They are single samples (one half of the waveform (pos or neg value) in PCM modulation)-PT's displays them as v's.

Of course my first run was with PTs set at 44.1k- Rice Krispies in a microwave. Then 48k but 24 bit session rate (16 bit adats). Less snap, crackle, and pop. But no chipmunks. Converted ok except too many of those blasted anomalies. Lastly 48k and 16. Just a sporadic assortment here and there.

I didn't notice any improvement on vocal tracking at 24 bit. But boy, did I notice how bad those adats sound.

Oh. I've been doing the two pop. Works like a charm. Now I've got simpte on a track in PT's. Kind've useless. But I could still get midi back onto it later- if I really need it.
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Old 02-08-2000, 10:47 AM
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Default Re: Weird offset spikes record onto audio channels.


This is a clocking problem between the Adat the and 001.

When two or more digital devices are used together, there must always be one and only one clock source.

If you are recording from an Adat to the 001 you must not only select the correct inputs but you must also put Pro Tools software (and therefore the 001) in digital sync mode and tell it to look at the optical inputs for it's clock source. If you do not, you will get the exact symptoms you have described.

You can set these settings in the "Session Setup" window in Pro Tools. Sync mode = digital, input = Optical.

Jon Connolly
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Old 02-08-2000, 03:19 PM
dsmalls dsmalls is offline
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Default Re: Weird offset spikes record onto audio channels.

John, I did an ADAT transfer a couple of days ago and had no audio problems, but it seemed like the sync was off a bit. Xfer was 16 tracks (2 tapes synced).
We took the SMPTE off of the BRC and fed it thorough my Micro Express to convert to MTC, then slaved PT to it. I believe sync in session setup was digital. obviously track inputs were digital.

Is this the correct way to do a multi tape transfer? or would you just skip the SMPTE - MTC part all together and just let the optical input do it all for you?

Thanks for your response.
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Old 02-08-2000, 03:37 PM
lwilliam lwilliam is offline
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Default Re: Weird offset spikes record onto audio channels.

Jon's right on top of it...

I've done a couple of ol' blackface transfers into the 001. I maybe got 2 spikes (that I noticed) out of 20 minutes worth of transferred music - and they could've been there already from the original recording (no way to tell).

I did have the clock source set to the external ADAT optical, however.

The only glitch I had was that PT kept switching back and forth between telling me "receiving sync", and "not receiving sync", until I started the ADAT (very confusing), so I just backed up the tape a few seconds from where I needed to record, started it, and it worked great.

...Shaggy...you're right. It is SOOOO obvious the difference between those ADAT recordings and the new 24-bit stuff. Even my cat can tell the difference .

..uh, Jon, just realized...with an ADAT transfer, is there any problem (sound-wise) with the 001 just adding zeros to the last 8 bits in a 24-bit session? As I understand it, you only need to dither when getting RID of bits, not adding them, correct?

------------------
LW

[This message has been edited by lwilliam (edited February 08, 2000).]
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Old 02-08-2000, 09:25 PM
shaggy shaggy is offline
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Default Re: Weird offset spikes record onto audio channels.

Thanks.

Now does anyone know whether the stereo mic inputs can handle 600 ohm mics (Earthworks) or 50 ohm FETs? And is this really a Focusrite Stereo channel?

Jon. Did you win the coin toss?(loser gets LE)
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Old 02-08-2000, 09:28 PM
jampro jampro is offline
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Default Re: Weird offset spikes record onto audio channels.


Thanks Jon

Problem solved. No more rice krispies,

Jampro
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  #10  
Old 02-09-2000, 12:24 AM
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Default Re: Weird offset spikes record onto audio channels.


lwilliam,

You're correct, no dithering is needed when adding bits. If you are in a 24 bit session, Pro Tools will add 8 "empty" bits to the 16 bit Adat files coming in. Since they're empty, these extra bits will not add or take away from the sound quality of the files.


Shaggy,

I'm not sure about your 600/50 ohm microphone question, I'll have to look into that one and get back to you...

The mic pre's in the 001 are NOT actually focusrite.

No, I didn't lose the coin toss for the LE User Conference section, if that's what you mean. I hang out here because I love it so much!!

Jon
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