RhinoTime
Joined: 01/04/08
Posts: 192
Loc: West Sussex UK
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My long drawn out building of a new music PC is pretty much complete put I've hit an issue
that I don't understand.
I have an Octopre LE with the optional ADAT board.
I've connected the two lightpipes to the optical connectors on the 1212m. But I can't get
the Octopre to sync to the EMU clock via ADAT. The EMU card will sync to the Octopore
though. I go into the patchmix software and set the clock to external adat it seems
fine.
I've tried swapping cables and it's not having it. The emu is switched to
ADAT not spdif and I can receive the audio via adat.
So I'm left with two
questions:
1. Does it matter that I'm clocking the EMU from the Octopre?
Particularly with reference to sound quality.
2. Am I missing something in my
understanding here?
Thanks for any input.
Grant.
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No, it's supposed to sound like that...
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Ramirez
Joined: 24/10/06
Posts: 197
Loc: Pwllheli, Cymru
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Hi,
There is probably a setting on the Octopre itself that allows you to sync it to
another device's clock. There's a switch on my Behringer ADA8000 to select external sync,
and it works fine with my 1212m.
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Bill Withers while Tom Waits, and Stan Getz
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RhinoTime
Joined: 01/04/08
Posts: 192
Loc: West Sussex UK
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Yes there's a switch, but when I switch to ADAT sync on the Octopre just flashes and the
ADC lock light stays off. (This is with the emu sync set to internal, so the emu is using
it's own clock.)
--------------------
No, it's supposed to sound like that...
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RhinoTime
Joined: 01/04/08
Posts: 192
Loc: West Sussex UK
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Sorry, I've wasted your bandwidth  , problem solved.
I removed all cables and replugged and now it
works!
Ugh!
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No, it's supposed to sound like that...
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Martin Walker
Watcher Of The Skies
Joined: 28/02/01
Posts: 10824
Loc: Cornwall, UK
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Glad you're sorted - isn't it annoying when that happens 
Martin
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YewTreeMagic
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RhinoTime
Joined: 01/04/08
Posts: 192
Loc: West Sussex UK
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Yes, very frustrating.
I still have the question of which device should be the
master for clocking as I now have the choice. Any thoughts?
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No, it's supposed to sound like that...
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Martin Walker
Watcher Of The Skies
Joined: 28/02/01
Posts: 10824
Loc: Cornwall, UK
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The Emu range sound better when run from their internal clocks (the external clock works
OK but jitter will end up higher, even if fed from a lower jitter clock externally).
So, if the Octopre LE incorporates jitter reduction circuitry I'd run that on
external clock from the Emu and rely on it being cleaned up on the way in.
If
on the other hand there's no jitter reduction circuitry mentioned, I'd switch clock
depending on what task I was doing - during recording run the Octopre on Internal clock
and slave the EMu to that to capture the best quality recordings, while during mixdown
switch the Emu to Internal clock for its lowest jitter.
Martin
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YewTreeMagic
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James Perrett
Joined: 10/09/01
Posts: 6280
Loc: The wilds of Hampshire
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Following on from Martin here... As a general rule with modern gear you should use the
most important ADC or DAC as the clock master. The reason is that most modern convertors
have good clocks and are happier working on internal clock than external clock. Internally
convertors use clocks running up to a few MHz. Wordclock only works at a few tens of kHz
so it has to be multiplied up to the required internal clock frequency - usually by using
a phase locked loop. The difficulty is in designing a phase locked loop that has both low
jitter and the ability to quickly lock onto different input frequencies.
Of
course, there are always exceptions to this rule so it is worth trying different clocking
scenarios to see which works best.
Cheers
James.
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JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net
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Martin Walker
Watcher Of The Skies
Joined: 28/02/01
Posts: 10824
Loc: Cornwall, UK
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Quote James Perrett:
Of course,
there are always exceptions to this rule so it is worth trying different clocking
scenarios to see which works best.
...and if you want a quick guide to what to listen for when comparing clock
quality, have a read of this box named 'The Audible Effects Of Jitter' that I wrote for
SOS January 2009:
www.soundonsound.com/sos/jan09/articles/daconverters.htm#10
Martin
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YewTreeMagic
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