Film-Tech Forum ARCHIVE: A-chains and B-chains

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Topic: A-chains and B-chains

Stephen Furley
Film God

Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002

posted 09-23-2007 05:13 PM

quote: John Hawkinson
No.
To restate what Gordon said:

There is an A chain for optical.
There is an A chain for mag.
You could even argue there is an A chain for digital sound alignment, though that terminology is not typically used.

That actually isn't too far off what I said; the A chain is the part where the various sources are handled separately (perhaps I should have said 'chains'), but the B chain is common to everything.

quote: John Hawkinson
I still don't understand why there's interest in trying to shoehorn so much stuff into these definitions. A chain typically refers to the optical sound setup, B chain to the EQ (and post), and if you try to fit other things into these definitions, you are likely to just confuse people you are talking to.

Probably true.

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Monte L Fullmer
Film God

Posts: 8367
From: Nampa, Idaho, USA
Registered: Nov 2004

posted 09-24-2007 01:08 AM

quote:
Where would one place the Digital Reader alingment!!? A or B Chain!!! ???

you're key word here is "alignment"- being optical magnetic, digital...as what Louis said before .. anything before the fader is "A" chain - any source before it hits the "target" preamp section.

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Jeffry L. Johnson
Jedi Master Film Handler

Posts: 809
From: Cleveland, Ohio, USA
Registered: Apr 2000

posted 09-24-2007 03:29 PM

SMPTE 202M

quote:
A-chain (transducer system): That part of a motion-picture audio system...extending from the transducer to the input terminals of the main fader.

B-chain (final chain): That part of a motion-picture sound reproduction system...commencing at the input terminals of the main fader and terminating in the listening area...at which sound pressure measurements are taken.

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Ken Lackner
Phenomenal Film Handler

Posts: 1907
From: Atlanta, GA, USA
Registered: Sep 2001

posted 09-24-2007 05:38 PM

Now I'm confused. I thought the EQ cards (or EQ section, in a digital processor) were part of the B-Chain, but I also thought said section was before the fader. Also, by common practice, isn't the optical tube part of the A-chain, and yet it is before the transducer? [Confused]

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Louis Bornwasser
Film God

Posts: 4441
From: prospect ky usa
Registered: Mar 2005

posted 09-25-2007 10:04 AM

In the olden days, the fader was post preamp and pre output amp. In the Dolby the fader has moved over to the point after the EQ, probably for noise reasons.

I would consider all "common to all formats" areas as the B chain in a processor. I would consider the A chain to be each individual format: Dolby optical; magnetic, Dolby Digital, etc. Louis

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Viktor Marosi
Film Handler

Posts: 1
From: Budapest / Hungary
Registered: Sep 2007

posted 10-26-2007 02:00 PM

A chain:

CAT 240A
CAT 222 or CAT 350 Dolby® SR/A
CAT 150 2:4 Dolby® MP

B chain:

CAT 64 EQ
CAT 441 surround + LFE card (Ls, Rs, SW)
CAT 242
CAT 443
CAT 249, CAT 250

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