Film-Tech Forum ARCHIVE: external fader for non-sync on CP50

This is topic external fader for non-sync on CP50 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=010358

Posted by Jeff Else (Member # 4063) on 03-02-2010, 10:44 PM:

how would one go about adding a more robust external fader to control non-sync level on a CP50? i have a film festival coming up with mostly local, DVD based stuff. The levels with such things tend to be all over the place and its annoying using a tweaker. I would love to have the fabled Cat 223 daughterboard but it seems there are none to be found...

Posted by Jean-Marc Toussaint (Member # 4784) on 03-03-2010, 02:37 AM:

Why not trying a small DJ mixing console? If this is temporary, for the duration of your festival, it should do the job.
I have rerouted the NS1 input on my CP to the front of the sound cabinet, adding RCA connector so I can basically hook any kind of audio, from tape player to super 8 projector...

Posted by Jim Cassedy (Member # 4115) on 03-04-2010, 12:02 AM:

Another soloution is the simple circuit below.
I've got one of these on the input of a mono
sound system at at theater to control the level
of the pre-show CD player and give the capability
to fade the music up & down. I beleive I used a
100kOhm "audio taper" potentiometer which I got
at Radio Shack. If you need to control a stereo
source you'll need to get a dual "stereo"(ganged)
pot and connect each channel as you see here:

You can build one of these for less than $10.00

I even have a "portable" version I built using a couple
of RCA audio cables and an empty band-aid box.
(The metal box provides shielding & a place to mount
the volume control)

Posted by Cameron Glendinning (Member # 3516) on 03-04-2010, 12:32 AM:

I've built and used Jims style of box and recommend it! works well and does a first class job. I got my bits from Jaycar.

Posted by Ian Parfrey (Member # 5122) on 03-04-2010, 01:22 AM:

I'm guessing the "audio taper" is a log pot as opposed to a linear?

Posted by Jeff Else (Member # 4063) on 03-04-2010, 02:15 AM:

i like jim's idea, but i would like it to control all four input channels. could i remove the trimpot on the 113c and solder wires to an external potentiometer? if i did this, what type of potentiometer would i use?

Posted by Jim Cassedy (Member # 4115) on 03-04-2010, 10:53 AM:

Well, of course you can do anything you want, but that doesn't
necessarily mean it's a good idea.

If you want to control more than one source, than I'd try to find a
small mixer, like Jean-Marc suggested in the first reply.

A couple of years ago, I bought a small 4-Channel mixer from
NADY systems.
You Can See One Here
You can set it up for either mono or stereo ins & outs.
Inputs are unbalanced. Output can be balanced or unbalanced.
All connections are via 1/4in plugs & jacks, so I bought
some cables & adapters. (Since I HATE having adapters
hanging directly off of the back of pieces of equipment)

This thing works great!
Radio Shack used to sell a similar unit. I'm not sure if they still do.

I also have a trusty old SURE M-267 mixer I got cheap on e-bay.

Which mixer I use depends on the needs of the partciular show I'm doing.

Yes, all this stuff cost me a little out-of-pocket cash, but it makes
it so much easier for me to do a professional job.

Posted by Tony Bandiera Jr (Member # 2365) on 03-04-2010, 11:17 PM:

Jim's trim pot idea is the simplest, most cost-effective and will work very well.

Another good accessory to have on hand is a ground-loop isolator or a pair of "direct boxes" to help prevent any hum issues.

Posted by Jeff Else (Member # 4063) on 03-05-2010, 02:32 AM:

i need it to control all four input channels, so the mixer would need to have four outputs... at this point i'm looking at a costlier mixer, and it would be easier operationally to have everything on one control. if one were to remove the nonsync level trimpot and solder wires to an external potentiometer, what type would be used? what kind of trouble am i getting myself into?

Posted by Sean McKinnon (Member # 612) on 03-05-2010, 09:54 AM:

Why do you need to control the levels for all 4 channels? You should be able to take LT and RT right out of the dvd player thru the mixer and into the non-sync input?

Posted by Scott Norwood (Member # 30) on 03-05-2010, 10:18 AM:

He must have an external box that decodes the L/C/R/S signals from the DVD.

Two thoughts:

- you can use a 4-gang pot to control the gain of all four unbalanced channels

- you will get better sound quality out of non-sync on the CP50 by using the cat. 112 manual switch card rather than the 113C automation card; the manual card connects the NS inputs directly to the amps, so you will need an external gain control

Posted by Frank Angel (Member # 248) on 03-05-2010, 11:32 AM:

Unless the DVD player decodes internally and outputs 6.1 in which case he still needs a multiple gang pot or small mixer.

Posted by Jeff Else (Member # 4063) on 03-06-2010, 02:11 AM:

i have a bluray/DVD player with RCA outs for all 6 channels. a 4 gang pot sounds like the way to go. good to know about the 112, i do happen to have one kicking around. how does the 113c affect the NS sound?

Posted by Marin Zorica (Member # 1716) on 03-08-2010, 05:54 PM:

Jeff, if you have 113C than is easy, because 113C uses TDA ic which regulates 4ch input level, so remove non sync level trimmer which is on 113 board near MONO switch and put it somewhere outside, as CP50 don't have front panel fader I did added it one time, also did use stereo pot, so one side is for main fader, other for non-sync (instead that trimmer) so with one know I do control all levels....

Posted by Scott Norwood (Member # 30) on 03-08-2010, 05:55 PM:

The cat. 112 gives you a direct path to the amps. The 113C has some electronics on it (the aforementioned gain pot) that will degrade sound quality.

Posted by Marin Zorica (Member # 1716) on 03-09-2010, 06:05 AM:

TDA1074 is for regulation used on 113C....didn't know why it should get any degradation, since IC is mentioned to be used with audio?

Posted by Gordon McLeod (Member # 33) on 03-09-2010, 07:22 AM:

The TDA 1074 is the VCA used on many DOlby products over the years and should not degrade the sound

Posted by Marin Zorica (Member # 1716) on 03-09-2010, 07:29 AM:

That's is what should I think also....