Film-Tech Forum ARCHIVE: Academy filtered SR on a CP65?

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Posted by John Hawkinson (Member # 1135) on 11-11-2006, 09:48 PM:

Tonight we had one of those occasional prints with a damaged analog soundtrack that sounds better in mono than SR (Who Killed The Electric Car). There was physical damage on to the soundtrack making SRD unreadable, and SR had continuous repetitive "ticking" sounds.

Dolby A and Dolby SR both sounded bad, but mono sounded passable (still occasional ticks, but not continuously).

Is there a straightforward CP65 modification to turn on the Academy filtering (and maybe even the mono summing?) with SR noise reduction?

Or is there a good postprocessing filter that is useful for these situations?

Thanks!

--jhawk

Posted by John Hawkinson (Member # 1135) on 11-15-2006, 04:14 PM:

No takers? Steve? Gordon? Sam?

--jhawk

Posted by Louis Bornwasser (Member # 3063) on 11-15-2006, 04:35 PM:

Might be easier to use format 01 and switch on the sr. Louis

Posted by Steve Guttag (Member # 268) on 11-15-2006, 04:42 PM:

Whats it worth to ya?

Out of curiosity...do you have real SR or the dreaded 222SR/A....it would have particular problems with this sort of noise.

As to the Academy filter...it is not done as it was on the earlier units (on the Cat 109 card). The Academy filter resides on the Cat 242 and is POST Cat 150 decoder and as such is only on the Center channel.

Furthermore, the Cat 242 treats Mono as a separate input on the Muxes. You can get 3-channel mono from that by removing the inhibit diodes on the Cat 443 board.

To get the filter on just the center could be done with some PCB alterations. It would require the removal of R140 (disable the regular Center channel audio) and then placing a jumper from Pin 4 to Pin 5 on the Center channel mux (IC5). You would then have to contend with mono-gain trim.

In short, it isn't something that you really should do...the CP65 just does not have the means to deal with the problem. You'd be better served to take the audio outboard via the optical preamp outputs ...perform some miracle on the audio....then bring it back in via say Non-Sync and do the 2:4 decode from there.

BTW...how are those cue markers coming?

Steve

Posted by Charles Greenlee (Member # 3856) on 11-15-2006, 06:43 PM:

Oh, I was thinking using an external SR decoder. We have one, sitting around for some reason. All it does is apply the SR noise reduction, does not do any matrixing.

Posted by John Hawkinson (Member # 1135) on 11-15-2006, 10:57 PM:

Cue markers...a continuing sad embarassment on my part [Frown]

No 222 SR/A here. I can never rember the card number though, 300-series...the 350 I guess. It does sound not-worth-doing
if it would be adding 2+ switches to make it happen.

I dunno about miracles. I had hoped to get the benefit of SR noise reduction. Perhaps pulling signals after noise-reduction,
summing them (on the theory that mono has better SNR), then piping them into the miracle box, and straight to the center EQ+amp.

Any suggestions on what such a miracle box should do?

I suppose I have an RPM26z to play with to pull off miracles. Of course, this print is long gone. The question is whether to have some sort of "canned solution" on hand for the next blue moon.

I suppose it's not likely to be worth it.

--jhawk

Posted by Steve Guttag (Member # 268) on 11-16-2006, 08:26 AM:

If it is just ticking...try to find an SAE impulse noise suppressor. They were around in the 70s/80s for use with record players. No doubt in this digital era there are means for doing it in software but there may be a timing issue introduced then since one will want to remain in lip sync.

Steve

Posted by Gordon McLeod (Member # 33) on 11-16-2006, 04:28 PM:

Also a Burwin DNR type of NR would help