Film-Tech Forum ARCHIVE: Updating digital audio processor to Datasat AP20

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Posted by Peter Castle (Member # 1997) on 04-05-2014, 12:59 AM:

Well, after over four years of digital cinema, we've decided to buy a new audio processor to replace our CP500. I feel that the AP20 seems to fit all our requirements. I would, however, like to seek advice regarding some options.
I've held off updating, hoping that one day we might use 35mm again - not so far. We've a Kinoton FP25E. But I hate to see us lose the ability. Our audio chain at the moment is CP500 with either analog, DTS or Dolby Digital, with the output being passed through an SDDS processor finally to our THX crossovers.
Could we feed that output somehow into the AP20 via its analog 8-channel input?
With the AP20 doing the theatre EQ, what happens with the CP500 and the SDDS EQ?
Should I continue to use the THX crossovers or use those in the AP20?

At least we'll be able to go to 7.1 - our surrounds are ready for that.

Posted by Dave Macaulay (Member # 813) on 04-05-2014, 01:29 AM:

Yes, you can pass the film sound system analog output into the 8ch AP20 analog input and keep film available.
Having several arguing equalizers is rarely a great idea. Without studying the AP20 book, I don't know if you can have a flat eq option and use the eq from the CP500/SDDS but I think it has selectable eq presets so probably you can. I would set the CP500 and SDDS eq to flat and do eq in the AP20. though. Just calibrating the output levels from the CP500 and SDDS processors will be enough of a challenge - trying to do EQ as well...? The AP20 is a digital processor and proper analog input level is critical to maximize headroom and avoid overmodulation.
The THX monitor crossovers were good in their day and have some faithful fans... but the AP20 is also a monitor, it has crossovers built in, and adding another (obsolete) processing block would be a mistake in my opinion.

Posted by Ian Freer (Member # 1940) on 04-05-2014, 05:46 AM:

Dave is correct.
The AP20 can be set up in a couple of different ways in this setup. The AP20 can indeed have multiple EQ and channel profiles (routing and x-overs) saved into it and recalled as part of any given preset.
So if you are really happy with the setup of the current 35mm equipment, the output of the CP500 could be fed into the AP20's 8ch analogue input into a preset with flat EQ etc, or you could flatten off the CP500 / SDDS EQs and just level balance them correctly into the AP20.
The choice is yours...

Posted by Marco Giustini (Member # 4544) on 04-05-2014, 05:53 AM:

I would definitely remove the SDDS and the THX monitor and feed the CP500 output with the EQ flat in the AP20. The AP20 will be used as a crossover as well and has an output for a small active speaker to be used as a monitor - even though the monitor screen is slow. You may want to keep the THX monitor if you like the touch of it, but I would not use it as a crossover - unless maybe it's the digital version?

The AP20 has the option for a "film card" which I don't know much about. I would be happy with the CP500 into the AP20 to be honest.

Posted by Ian Freer (Member # 1940) on 04-05-2014, 06:20 AM:

The optional film card enables the AP20 to reproduce analogue optical 35mm film sound formats: Mono, A-type and SR.
I've installed a couple in sites that wanted to keep basic 35mm functionality when they converted. They work well, (but I don't claim to have done any critical listening tests, as they are hardly being used).
In the OPs case, if SR-D is required, the CP500 will still be required anyway, so the film card is probably not necessary, but it is certainly useful for basic 35mm audio if replacing a processor in a site that was analogue only (CP65/JS105 etc) or has a DA20 which could be fed into the 8ch input. The AP20's automation functionality can be programmed to handle fall-back from DA20 to the optical film card...

Posted by Carsten Kurz (Member # 5396) on 04-05-2014, 07:28 AM:

When we converted to digital, we fed our CP65/DA20 analog outs to the AP20 8ch analog in and set the CP65 EQs all flat. As some have noted, no problem to have many EQ settings in the AP20 attached to any given format, so you can even compare both CP500 and AP20 EQ options. I'd too go with CP500 flat and AP20 main EQ and crossovers.

- Carsten

Posted by Harold Hallikainen (Member # 5405) on 04-05-2014, 12:02 PM:

I like the idea of settinf the CP500 flat and doing auditorium eq in the AP20. The CP500 becomes the A chain, and the AP20 the B chain.

What are people typically using multi-channel analog inpt for? How much use is it getting?

Harold

Posted by Steve Guttag (Member # 268) on 04-05-2014, 01:06 PM:

Since we have several theatres that will continue to run film (e.g. the AFI/Silver), we are often now putting a "DCinema" processor of sorts in and feeding legacy format into it as a source. Some of our site, again the AFI/Silver have extensive switching systems due to the whole complexity of the project so to rewire the world would be not only impractical, it would yield no benefit.

Thus far, in all of the situations, we have put the DCinema processor after the legacy equipment (whatever brand or model) and fed the DCinema processor (again, regardless of brand/model) as a 6 or 8 channel source, as the case may be. The legacy equipment had its EQs either flattened, bypassed or removed (one can cut down on the noise if the card is removed or bypassed...one benefit of processors like the Panastereo CSP1200...the modules no longer used may be bypassed and the cards removed even to be less drain on the power supply.

Thus far, we have normally set the new processor to jump the fader to reference so that the film processor's fader is still used for film. Thus, if you have the AP20, you would have it go to 7.0 when on the film format. For this to work, when you tune your room with the new processor and get it all balanced up, then go back, while the mics are still out and set the levels of the film processor to also be at reference. The net result is if they were running their films at "6.0" before...they still will. Nothing really changes from the film standpoint. This has worked out well for our clients.

I never like having more than one fader in a system but I also don't like the idea of feeding my nice new uncompressed LPCM DCinema audio through some 10-30 year old processor whose noise specs were just fine for optical film but are far noisier than most any of the DCinema processors (or other DSP solution)...also, why have the aged processor that now is only needed for film be the potential source of failure?

Ideally, I'd prefer to use a DSP solution that would have sufficient inputs, controls to select EVERYTHING as a source and provide it with suitable b-chain facilities like fader(s), EQ...etc. With some of these expandable DSPs that is certainly possible though not always cost efficient. However that is starting to change with things like QSC's Q-Sys and Rane's HAL and other examples of current DSP technologies. There is no need for a born-digital audio to ever turn to analog until it is heading to the speakers.

Harold...for the most part, our multi-channel audio ports are now being fed from a BluRay player. We are a dealer for the Oppo brand of BluRays and they provide an analog 8-channel output that will decode all of the current tracks.

Posted by Ken Lackner (Member # 1002) on 04-07-2014, 10:56 AM:

quote: Steve Guttag
Thus far, we have normally set the new processor to jump the fader to reference so that the film processor's fader is still used for film.

Why not just select the proper film format on the legacy processor when running film and use the fader on the digital processor as you would for any digital format?

quote: Steve Guttag
Ideally, I'd prefer to use a DSP solution that would have sufficient inputs, controls to select EVERYTHING as a source and provide it with suitable b-chain facilities like fader(s), EQ...etc.

CP-650? JSD-80?

Posted by Steve Guttag (Member # 268) on 04-07-2014, 11:39 AM:

Because...thus far there has been exist remote faders by each projector where they have established fader values. For DCinema, the fader level is set, more often than not, via cue rather than a person twirling a knob. Thus, if you let the film processor handle film volume and the DCinema processor handle DCinema volume, nobody gets really confused because it is all automatic and the familiar controls remain the familiar controls.

Neither of those processors are particularly input laden with much. I don't trust the CP650's CAT790 module to handle DCinema (too many instances of Robosound...thus far no problem with CAT778 though) and the JSD80...well...um....NO! Plus both of them can only handle one port open on their Ethernet ports (if the JSD model you are working with even has an Ethernet port).

By DSP with inputs...I mean something like a Q-Sys, Basis, HAL, BiAmp...and the list goes on. On something like those, you could get up to silly amounts of inputs/outputs. The idea is to have it be big enough to handle the job and perhaps have room for growth.

Posted by Scott Norwood (Member # 30) on 04-07-2014, 04:35 PM:

Steve--what do you do for video (tape/disk/etc.) in these installations? Do you use the film processor or the digital one (I assume the latter...)?

Posted by Steve Guttag (Member # 268) on 04-08-2014, 05:35 AM:

I generally like to minimize the audio path for any source. If there was an established audio path before, I don't disturb it (normally there isn't time anyway to rewire the entire world on a DCinema conversion or addition). If it is new...then I select a processor that allows for both film and A/V audio to have their own inputs into the system.