Film-Tech Forum ARCHIVE: Remote volume format control for CP-55?

This is topic Remote volume format control for CP-55? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Paul Gordon (Member # 3320) on 02-19-2010, 08:56 AM:

Did Dolby ever make a remote volume format box for the Cp55. I know there is one for the CP200 would that one work? I'm building a home cinema and it would be nice to adjust volume from my seat.

Posted by Demetris Thoupis (Member # 833) on 02-19-2010, 09:07 AM:

There was one. Cat no 122. Check the manual in the warehouse section and you will see about it including components so you could built one yourself.
Demetris

Posted by Steve Guttag (Member # 268) on 02-19-2010, 09:31 AM:

Yeah...the Cat 122 was a tricky one...a 100K pot, an LED and a current limiting resistor!

The Cat 123 is the other one if you are doing changeovers...it has the "brains" to allow one to have the fader follow the projector.

Steve

Posted by Sam D. Chavez (Member # 1841) on 02-19-2010, 09:31 AM:

Either a 122 or 123 will work. It's just a 100K Ohm linear pot inside.

Posted by Gordon McLeod (Member # 33) on 02-19-2010, 09:51 AM:

Sound Associates built a very nice remote for the CP55/CP65 that had remote of format and indicator as well as a changeover control funtction

Posted by Sam D. Chavez (Member # 1841) on 02-19-2010, 11:58 PM:

The current limiting resistor was to keep from blowing up the CP100 fader module and not the CP50.

Posted by Steve Guttag (Member # 268) on 02-20-2010, 07:09 AM:

The current limiting resistor was just for the LED...since it was powered by the 24V rail....there is nothing on the fader itself...just the 100K pot.

The CP100 had its own dedicated faders complete with changeover buttons on top (one normally open, one normally closed).

Steve

Posted by Jean-Marc Toussaint (Member # 4784) on 02-20-2010, 08:20 AM:

As some of the members suggest, going the DIY way seems reasonnable. And it will be considerably cheaper. Dolby being nice enough to include the diagram in the installation and alignment manual, a friend of mine, who's an electronic guru, built a remote (fader + format) for my CP45. It ended up costing less than 1/5 of what Dolby was asking for the official thing.

Posted by Sean McKinnon (Member # 612) on 02-20-2010, 11:03 AM:

AFAIK, And I may be wrong here but I think if you use single pole momentary contact buttons with the ground from the CP on one side going back to the connection you want to switch on the automation terminal on the back of the cp, with a 100k linear pot connected to the remote fader terminal (plus a switch to switch into remote fader) you should be all set. Very simple. As far as adding indicator LED's that would be a little more complicated.

Posted by Sam D. Chavez (Member # 1841) on 02-20-2010, 12:01 PM:

Steve,

You are right as a far as it goes, but no one used a clunky CP100 remote as a portable auditorium fader. Most used a 122 or 123 for previews so the director/mixer could set house level.

This is where the 100K current limiting resistor came in series with the pot so you could not blow up the CP100 fader module and this happened a number of embarrassing times in the early years.

I think I mistook the 100K resisitor you mentioned for the one I was had in mind.

Posted by Steve Guttag (Member # 268) on 02-20-2010, 01:18 PM:

The only 100K anything I mentioned was the POT for the VCA itself. The Current limiting resistor, "R105" is a 2.2K and is only for the LED itself. Which lets the LED have about 10mA if the +24 rail is actually 24V...which, in other threads has been shown, to be anywhere from about 21 to 28V...depending on the processor, loading and power supply condition.

Now you may be meaning the choice of 100K as the pot choice (over say 10K, which is popular in other devices...or even as low as 1K).

Also, I think there is a misunderstanding on the subject matter. The Cat 122/123 are to the CP55 as the Cat 88 remote units are for the CP100.

The fact that the Cat 122 also saw much life as an "Auditorium Fader" is another topic all together.

Now I'm sure you are referring to the 5.6K resistor used on all CP100 faders (in series with the 100K pot) (including the Cat 88s, where the resistor is internal to the faders). Those that want to use the Cat 122 on a CP100 would have to add the 5.6K the resistor themselves to the fader line (I wonder how many do...or did). The Cat 122 does not include it as the Cat 122 was a CP50 product, not a CP100 product.

Steve

Posted by Louis Bornwasser (Member # 3063) on 02-20-2010, 01:37 PM:

Boy! You guys bring back many memories of screenings.

I put a 3 pin XLR socket on my c/n 122 so I could use standard mike cables or house snakes when installed at the director's chair. Louis