Film-Tech Forum ARCHIVE: MOD IIC sound issues

This is topic MOD IIC sound issues in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Richard Miller (Member # 1405) on 01-24-2004, 03:51 PM:

We are having some sound issues with our MOD IIC. We recently hookied up DVD players that run all day through the music board. However, 2 out of 4 theaters now have sound leaking from the music into the other formats (digital, mono, and such). Does anyone possibly know why this is or how to fix it?

Posted by Gordon McLeod (Member # 33) on 01-24-2004, 04:01 PM:

Turn the small white trim pot on the edge of the format board to max and then set the levels with the trim pots on the output card
the music fade circuit has a range of travel and you have exceeded it
there is some discusion else where on the site on this issue

Posted by Oscar Neundorfer (Member # 458) on 01-24-2004, 09:31 PM:

Richard,

There is only a certain amount of attenuation of the music signals when the MOD IIC is in a film format. If the signal level going into the music VCA's on the output card is excessive, then leakage occurs.

Gordon is basically right about setting the levels, although I usually recommend setting the overall music level trimpot to about the 3 o'clock position so that you have a litle upward volume adjustment left. This is the trimpot on the right-hand side of the Format board, visible with the front panel removed.

With the trimpot in the 3 o'clock position, adjust the left and right music input trimpots on the MOD IIC Output Card for the desired level in the auditorium. These are the bottom 2 pots as I recall.

Also, you may want to check for possible grounding problems because this too can cause leakage through the ground side of the signal wiring. You can isolate the music input signals from the DVD players with audio line isolation transformers placed between the DVD players and the MOD IIC music inputs. Sometimes this has helped greatly for this problem. Remember that decent transformers can get expensive. However I believe Mouser has the 42TU016 line transformer really cheap. I used these for years in our music distribution amp, and considering their price, they do a decent job. I no longer use the Mouser part because I have them made especially for us now. But I _think_ they are still available from Mouser.

Posted by Gordon McLeod (Member # 33) on 01-24-2004, 10:05 PM:

I guess the reason I set the main fade trim pot to max is to stop the ease f overpowering the levle of what I deem as preshow nonsynce (abit that may be advertising)
Since the problem didn't appear before and often I have found that DVD adverising has the audio fed through the pre non sync distribution amp I have noticed that many didn't check the relative level sets between those two points just like with the mod 5's they often have the front panel trim at the min and the internal pots up hig