Film-Tech Forum ARCHIVE: Frequency response between Analog and Digital

This is topic Frequency response between Analog and Digital in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=005279

Posted by Paul Konen (Member # 41) on 09-02-2003, 12:48 PM:

Processors: CP-500 and USL DSP-60 (not stacked)
Amps: QSC
Speakers: JBL
Analog Reader: Dolby on a Christie P35-GPS head.

Problem: When in analog mode, Stereo SR, the sound is flat with seemingly more low end than in Digital Mode.

New Analog LED's installed and A-Chain ran with Dolby Tone Loop.

Is the main problem the focus on the analog reader or just a limitation of the analog soundtrack?

Paul

Posted by Brad Miller (Member # 2) on 09-02-2003, 02:33 PM:

Sounds like a full A-chain was not performed. Simply running tone loop does very little. Nothing less than an RTA and scope with all of the test loops and a little bit of time is required to get that sounding near-digital quality. The reader itself is not at fault though. Even just changing out that led would have thrown the alignment off. Those readers if aligned properly will sound extremely good.

Posted by Dave Macaulay (Member # 813) on 09-02-2003, 04:08 PM:

I think you have a focus and/or azimuth problem with the analog scanner.
You should hear little difference between a good SR setup and digital. The biggest audible difference comes from having the digital sound's discrete surround and sub-bass channels. Digital will sound a bit better on the screen channels but not "night and day" except for the dynamic range you'll notice on explosions et al.
Like Brad says, a Dolby tone loop isn't enough; it doesn't do anything except set Dolby level so the processor can decode the Dolby encoding properly. You also need at the least a pink noise loop, X-Y scope, and good ears to get the azimuth and focus close to correct. With an illumination uniformity loop, a buzz track loop and an RTA as well you can set up the A chain properly.

Posted by Edward Jurich (Member # 1787) on 09-04-2003, 09:47 AM:

Using a scope is a must to be sure you have good phase alignment, otherwise the surround will not decode properly.