Battling Loud Trailers

Tired of the complaints from loud trailers?
Tired of the complaints from quiet features?
Here's the $5.00 solution!

Soldering gun
100K linear taper potentiometer
Short length of small gauge wire
Dolby cat85 pink noise generator (optional)

NOTE:  This trick will only work on Dolby brand processors.  The example below is specific to the model CP-65.  View the diagrams below for reference.
For SDDS installations, see further below.


1. Mount the potentiometer.  We prefer mounting it on the back of the CP-65 processor by drilling out one of the holes in the rear flange, but anywhere it won't be accidentally knocked is fine.

2. Run two wires to the potentiometer (see the drawing below) from TB2 "remote fader A and B" on the back of the CP-65.

3.  Connect a wire from the automation system (which will deliver a momentary pulse) to TB1 "R/L" on the back of the CP-65.  NOTE:  the drawing below lists this connection as "C/O", but is labeled properly on the back side of the CP-65.  For reference purposes, the "R/L" connector is between "S7" and "MUTE" on TB1.

4.  Turn off all power amplifiers, including any self-powered subwoofers.  Disconnect power to the CP65.  Remove the cat #443 card.  On this card is a jumper to enable the remote fader option.  Position the jumper to the "ON" position.  (Dolby ships these cards from the factory in the "OFF" position.)  Reinstall this card and then power everything back up.

5.  Insert a cat85 pink noise generator and read the center channel output at normal feature fader level.  It should be 85db or near it.

6.  Press the "select local/remote" button on the front side of the CP-65, just below the master fader.  Note the red led above the fader will extinguish, signifying the "remote" or "trailer" fader is active.  With pink noise on the center channel still running, set the newly installed potentiometer to 75db (or 10db lower than your normal feature fader level).  NOTE:  this adjustment will approximate the final setting.  A minor adjustment by ear may be desired.

The installation is now complete.

Use the front panel fader to adjust the desired feature level and leave the rear panel fader alone to play trailers.

1.  A cat85 pink noise generator is not absolutely necessary for the installation, but will save time in setup.

2.  Your automation MUST be configured in a way that will allow a momentary pulse to switch the processor INTO remote status at the douser open and OUT of remote status on a cue.  It is a simple "toggle" and there is no logic built into the CP-65 to differentiate between local and remote status.  Ideally, a separate cue alltogether is on the leader and one at the feature or just before the sound demonstration logo.  However that is not always possible.  A common automation design will pulse the Dolby processor into "mono" at the douser open and then into "stereo/SR" at the lights down/feature cue.  If you have such a system, connect BOTH "mono" and "stereo" pulse wires together at the "stereo/SR" input.  Then jump THAT connection to the "L/R" connector.  This will pulse the unit into "remote/trailer fader" and "stereo/SR" at the douser open.  Then at the feature cue, the unit will pulse into "local/feature fader."  It's that simple and as an added benefit, will play the trailers in stereo/SR.

3.  Should the automation miss a cue, a simple push of the "select local/remote" button on the front side of the CP-65 will restore the status.  (Of course, powering down at night will also reset the local/remote status back correctly.)  Remember, the ONLY time the led above the master fader should be extinguished is during the trailers.

4.  The front panel fader will have NO effect on the volume in the theater during trailers.

5.  This wiring trick will NOT work with SDDS units in their typical configuration.  See below for a trick on SDDS.


25 pin female computer cable OR 25 pin female/female gender changer
Short length of small gauge wire.

1.  On the back panel of the SDDS 2000 series decoder, you will see an "automation I/O" connector.  It is a standard 25 pin connect.  Connect your 25 pin cable or gender changer to this so that you have a direct wire lead to pin #13.

2.  Connect your designated SDDS momentary cue from your automation to pin #13.  If you do not have the capability of a dedicated cue, connect the "mono" lead as mentioned above to "stereo/SR" and the original "stereo/SR" cue to pin #13 on the SDDS automation I/O connector.

The installation is now complete.

Use the SDDS fader to adjust the desired feature level and the Dolby fader to play trailers.

1.  The projectionist MUST manually press the "bypass" button on the SDDS decoder before EACH start up.  It can be bypassed during the thread-up process and then left for an automated timer to run the show with no problems.  Should the projectionist forget, the trailers will simply play at feature level in SDDS and the customers will be quick to notify management of the error.

2.  What will happen is, the SDDS decoder will remain in bypass during the trailers until the "feature" or dedicated "SDDS" cue pulses the decoder OUT of bypass mode, allowing the feature to run at the setting on the decoder itself.  Whatever the analog processor is set to will be the volume of the trailers.