Film-Tech Forum ARCHIVE: Amps with digital input

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Posted by Antonio Marcheselli (Member # 373) on 08-25-2004, 07:11 PM:

Hi everyone

Are there amplifiers with digital inputs?

Bye
A

Posted by Andrew Jefferson (Member # 2565) on 08-25-2004, 07:34 PM:

Yes, Crown Audio's "I-Tech" Is a digital amp that cas PC monitoring over a LAN. Also there is QSC Audio's DCA Series.

Posted by Antonio Marcheselli (Member # 373) on 08-25-2004, 07:37 PM:

DCAs has Digital inputs? I didn't found on the specs...

Bye
A

Posted by Andrew Jefferson (Member # 2565) on 08-25-2004, 07:50 PM:

Yes, DCA means Digital Cinema Amplifier, as far as I belive if you have a QSC Digital Cinema Monitor Then the whole A and B Chain will be digital with the exception of the run from your amps to the speakers.

Your wiring would be like this: Digital out from the Processor, into the Digital in on the monitor. Digital out from the monitor, into digital in on the amps.

quote:
QSC's Digital Cinema Monitors provide signal processing and monitor functions in a single integrated system. Designed to be used with QSC's Digital Cinema Amplifiers (DCAs), DCMs optimize loudspeaker performance while simplifying cinema sound system wiring and configuration. Three models--the DCM-1, DCM-2 and DCM-3--cover cinema systems ranging from six to eight channels configured for bi-amp or tri-amp operation. DCMs are also compatible with all cinema processor formats including Dolby Surround-EX.

Digital Signal Processing
The DCM's digital signal processing capability outperforms traditional analog crossovers for optimized speaker performance. Crossover frequency, parametric equalization, polarity and gain can be precisely adjusted for each speaker in your system. Digital delays, adjustable in 20 microsecond increments, assure proper acoustical time-alignment of loudspeaker drivers for smooth frequency response, especially critical in three-way systems. A passive emergency bypass crossover is also included for fail-safe operation.

Less Wiring, Faster Setup
DCMs greatly simplify system wiring and set-up, significantly reducing installation time and labor cost. Input to the DCM is provided via a standard DB-25 cable from the cinema processor. Connections to DCA amplifiers for input and monitor signals are made through a single VGA-style cable. All traditional XLR and barrier strip terminations are eliminated.
DCMs also simplify set-up by using a menu-driven, PC-based software program for configuration. The program includes a speaker data file that lists default parameters for popular cinema speaker models. Commonly used configurations can also be saved on a disk, allowing you to quickly load them on other DCMs.

Advanced Monitor Functions
In addition to audio monitoring of amplifier inputs and outputs, DCMs include QSC's exclusive "Load Fault" detection. DCMs monitor all amplifier outputs and indicate opens and shorts in the speaker system and wiring via LED "load fault" indicators, providing confirmation that all amp outputs are functioning properly.

Posted by Pete Naples (Member # 761) on 08-26-2004, 01:11 AM:

Not quite.

The DCM input is analogue. It's a DSP crossover/monitor unit, so it digitizes the input signal, processes it, then converts it back to analogue. The DCA amplifiers are analogue input. There is status and load monitoring going on between the DCA/DCM, all via the VGA cables used to link them.

Personally I reckon the whole Digital Cinema Amplifier / Monitor nomeclature is misleading, that said they are very good amplifiers / crossovers / monitors.

Posted by Frank Angel (Member # 248) on 08-26-2004, 03:00 AM:

Seems like this is adding lots of added complexity just to eliminate input wires. And what is so convenient about "VGA-style cable?" It's not nearly as easy to work with as regular XLRs on standard analog shielded cable -- seems to me that six Belden shielded pairs is no big deal to wire compared to a big fat uncooperative VGA monitor cable with a DB25 connector.

And I would imagine that unless you can have your "single VGA-style cable" custome ordered to the exact length you need for neat and compact wire dressing, would you have to make up your own cable which HAS to be much more difficult than cutting Beldon shielded pair to the exact length you need and wiring up XLRs on the ends or spade lugs, whichever are required. Ever try doing your own DB25 cables?

Posted by Antonio Marcheselli (Member # 373) on 08-26-2004, 06:31 AM:

Andrew

I have DCMs and DCAs all over my theater and it is as Pete says. The input of the DCM is analog and the input of the DCA are made by using a VGA style cable but I do not know if they're really in digital mode or not, I do not think so.

"digital" for DCA are referring to the fact that thy're switching amplifiers, commonly named "digital".

Beside the I-Tech are there cheaper amplifier on the market with digital inputs?

Bye
A

Posted by Mark Gulbrandsen (Member # 72) on 08-26-2004, 08:43 AM:

"DCA are made by using a VGA style cable but I do not know if they're really in digital mode or not, I do not think so."

They are analog input but are just facilitated with the VGA style input to make crappy/e-cheapo/quick wiring jobs out of a rack full of nice equipment. Several other manufacturers have put this facility on the backs of theor equipment as well. Even the best VGA cables are junk compared to good Belden 8451.

Mark @ CLACO

Posted by Andrew Jefferson (Member # 2565) on 08-26-2004, 06:00 PM:

Thanks for clearing that up, I was always skeptical of the DCA's, hence I said, "As far as I belive...".

I've seen the I-Techs in action at an Entertainment Technology Expo (Entech) recently here in Sydney. They use RJ-45 connections and i'm pretty sure these ARE digital inputs.

RJ-45 is ALOT easier than both XLR and VGA to connect ends to, all you need is a crimper!

Posted by Steve Guttag (Member # 268) on 08-26-2004, 09:23 PM:

Frank, I make D-sub cables up all the time. What's the big deal? In fact, I think I can make one up faster than most could make up and dress even phoenix style connectors.

Check this out...for Dolby Digital...we generally pull in the reader cable off a spool and make both ends (Dsub on one, Molex KK on the other).

Phooey on RJ45...I never liked the RJ series of connectors...glory be that is the choice of Ethernet...heck since Cat 5/UTP (and now Cat. 6) is so cheap...people seem bent on figuring new ways to use the UTP cable for just about everything. With Cobranet one can send ordinary audio lines over great distances with just a stinkin Cat 5 cable. Wanna connect a laptop computer to a video projector that is oh, say 500-feet away...well there is this Cat. 5 adapter that will let you do it (for a price).

As to the VGA cable thing...yes QSC does make/sell the VGA cables in 1-foot increments up to something like 10-feet. For quick installations....a singe VGA cable lets QSC connect up two channels to an amplifier, complete with pre and post amplifier monitoring (Audio) plus have load monitoring. Do I like it? Nope, I pretty much agree with Mark G on this one though I use Belden 9451 or Belden snake cables. I have other technical reasons for not using the VGA cable method too but I not want to go into that here.

Steve