Film-Tech Forum ARCHIVE: Dolby Cat. 410 reversion accelerator.

This is topic Dolby Cat. 410 reversion accelerator. in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Stephen Furley (Member # 1277) on 09-03-2013, 02:12 PM:

What exactltly is in one of these? Would it be feasible to build one, since I'm unlikely to find an original one?

Posted by Marco Giustini (Member # 4544) on 09-03-2013, 04:04 PM:

It sounds like the flux capacitor to me! [Smile]

Posted by Brad Miller (Member # 2) on 09-03-2013, 04:28 PM:

I've never had to use one, but it was a DB25 to DB25 box that went in between the DA20 and a CP65 (or similar) to extend the pulse for analog failover. You are calling it a reversion accelerator, so I'm not sure. Someone like Sam Chevez would probably remember.

I've got a couple laying around somewhere. I've never opened one up, but I don't see how it could "accelerate the reversion" since it still relies on the same pulse from the DA20. I thought it was just to ensure the failover cue didn't miss.

Posted by Steve Guttag (Member # 268) on 09-03-2013, 05:35 PM:

It is indeed a reversion accelerator.

The CP65 has a debounce circuit on its format selections to allow for mechanical switches/relays to switch the format. This debounce circuit will slow down the time it takes to revert to SR from Dolby digital in a drop out situation. What the CAT 410 did is to switch out/lower the time constant of the debounce circuit only when the DA20 wanted it to revert.

Posted by Brad Miller (Member # 2) on 09-03-2013, 09:37 PM:

Very interesting. I never knew exactly what it was and never really had a need for it. It was a crazy rare day when an SRD track would have a fallback.

Posted by Stephen Furley (Member # 1277) on 09-04-2013, 01:15 AM:

There's a manual for the thing in the Warehouse, but it gives no indication as to what's actually in it. I will be getting a DA-20 in a few days, though it won't actually be installed for a few months. It doesn't have a Cat. 410. My thinking is that in future running 35 mm is going to be just old prints of films which are not on digital. These prints are more likely to have analogue reversions than new-ish ones, so putting in the Cat. 410.

I've only ever run one show on 35 mm with Dolby Digital, and probably not heard it more than about ten times. Most of the cinemas I used had only analogue sound on film, and many of the films I saw pre-dated digital.

Brad, if you have some of these, would you be interested in selling one? If not, and they're not sealed, could you, or somebody else, take a look inside and see what's there? I suspect that it's just a few simple components, and it would be possible to make one.

Posted by Carsten Kurz (Member # 5396) on 09-04-2013, 07:39 AM:

To my knowledge, the modification bypasses the original reversion delay circuit of the CP65 and introduces a new one with a short delay. It's not a plug and play device, you need to do some soldering/rewiring of the processor. I don't think it's worth the effort for the rare occurence of an SRD->SR reversion. If you're not experienced in such modifications, you might ruin your CAT443 or even more.

- Carsten

Posted by Stephen Furley (Member # 1277) on 09-04-2013, 08:18 AM:

Carsten,

I have experience on component level modifications on similar equipment, but I wouldn't be making them in this case; the technician doing the digital install would.