Film-Tech Forum ARCHIVE: Strange Voices (problems with dts 6-AD)

This is topic Strange Voices (problems with dts 6-AD) 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=004272

Posted by Peter Schoell (Member # 919) on 12-02-2002, 10:53 PM:

To Karen or anyone else who hears strange voices
As I was watching Harry Potter last night I just could hear strange voices every once and awhile during the quiet moments. Normaly I don't pay attention to strange voices, but this time I reconized them from the screen ads.
The processor is a DTS 6AD, the screen ads are on DVD from USA Productions. The ads are on the non-sync channel and I would have thought they would be isolated from the film.
Where should the DVD signal come in?
Is there something that should be set diferently on the processor?
I imagine I can set a relay in the DVD signal path, but if something can be done with the system as is, that would be better.

Posted by Paul G. Thompson (Member # 655) on 12-02-2002, 11:42 PM:

Supposedly, that should never happen, but I learned along time ago to"Never make a flat statement" in electronics.

It could be a DTS-6AD malfunction in the making. I have four suggestions:

1. Disconnect the non-sync to the input of the DTS and see if the strange voices go away.

2. Use some other source for a non-sync feed such as a cassette, tuner, or maybe even a cd player and see if different strange voices appear.

3. Shut down the DTS and see what happens to the strange voices.

4. Shut down the power amps one by one to see which channel it is sneaking into.

These four suggestions might help you isolate where it may be sneaking in.

I might mention that once I had the low side of the power amp output short to ground through the speaker line in a hunk of EMT. The amplifier broke into some wierd oscillation and acted like a transmitter that radiated enough RF where the A chains in adjacent houses picked it up and played the sound into those theatres.

Posted by Ken McFall (Member # 845) on 12-03-2002, 06:04 PM:

If you could hear the sound from the ads on dvd then clearly the DVD player was still running during the feature. I've never heard of such a system but surely you could just turn off the DVD player during the feature.... or am I missing something else that's going on.

I have heard non sync over a film input before but it was VERY VERY low and you really had to have the fader up high to hear it, way way above normal, so it's never been a problem. It's not there all the time so may be down to simply turning off the processor and it clears itself.

I've never heard of adverts on DVD so what is the advert system you are using.... is it audio only or video as well?

Oh by the way.... you say you don't normally take any notice of strange voices!! Be worried be very worried, they don't go away if you ignore them.... or so I'm told [Mad]

Regards.

Posted by Jon Bartow (Member # 241) on 12-03-2002, 08:12 PM:

I've had this problem with a Kelmar AS-8800 system (admittedly a VERY different beast) and this is what it turned out to be:
When the theater was installed they turned up all of the inputs and outputs of their Smart DA226 (distribution amp for the Non-sync) to max (resulting in a VERY high output level). Then set the Kelmar system's non-sync inputs to minimum. The Kelmar system did not employ relays for the non-sync, it has an electronic fader. The result: non-sync during the movie, only really noticable during quiet scenes. It also took 20 years for this problem to occur.
Solution (I think it's obvious, but here goes) turned down the DA226 levels so that they were appropriate and then turned up the Kelmar imputs. Problem solved. [thumbsup]

Now I'm not familiar with your particular install, but are you going through a distribution amp? You're not using a "headphone" output on the DVD player are you ? [Embarrassed]

Check the grounding of the DVD player and the 6AD. Check the cables from the DVD to DTS (switch them with another house if possible) Possibly switch the DVD players too?

Posted by Peter Schoell (Member # 919) on 12-03-2002, 09:25 PM:

Thanks for the input. The setup on this ad system is handled by the ad company, they supply all the equipment and hook in to my sound systems. They have one DVD player that feeds all three screens, which means the DVD needs to run when there is a break between movies in the other auditoriums.I remember the tech that set up the DVD system had to turn the distribution amp up all the way, in order to get enough volume.
I guess if the problem can be corrected with the DTS unit, it's my responsibility, if the problem comes from the DVD it's the ad companies responsibility.
I'm thinking if the problem stems from leakage, a good old fashioned electomagnetic relay triggered to close when the ads start, should keep any signal from getting through. The ads start anytime the film projector stops.
The techs that install these systems come from companies that setup sound systems for bands, and intercom systems. I'd of thought they would have run into this kind of situation before.

Posted by Paul G. Thompson (Member # 655) on 12-03-2002, 09:52 PM:

You have to determine where the fault is before you can determine who's responsibility it is to fix the problem. It could save you some big money. [Wink]

Did you try some of the suggestions that were made to help isolate the problem?

Posted by Jon Bartow (Member # 241) on 12-04-2002, 08:16 AM:

Peter,
"Band" sound systems and intercom systems are much different from theater sound systems. Having worked extensivly on both sides I can tell you than most "Audio" professionals, while excellent at what they do would be lost in a theater sound system. [Confused]

I'm not trying to bash them, they just don't have the experience.
I refuse to believe that he(she?) HAD to turn up the distribution amp all of the way. The 6AD wants a standard 300mv signal. DVD and CD players do a VERY good job at obtaining that signal level. Implying that the distribution amp shoud have been set more or less at unity across the board for proper level.
First, check cables and grounding (switch cables around if possible).
Perhaps the DVD player is set to 5.1 output and only the L and R outputs are being used?
Look at the Non-Sync "trim" levels in the 6AD (reference page 8-8 or section 8.4.3 in the manual) The factory setting is -3dB. Parhaps someone somewhere along the lines lowered the "trim" level? If so, either you (only if you are comfortable) or your tech should correct the error.
Try just hooking up a CD player to the problem house for a couple of screenings (I'm sure the ad company has a contract with your theater that would prevent you from disconnecting their ads for a couple of regular shows). If the problem is still there with the CD player, then you know it's in the processor. If not, then it's outside the processor.
Jonathan [Smile]

Posted by Karen Hultgren (Member # 395) on 12-04-2002, 02:01 PM:

Peter,

You can use the NONSYNC input. Set the audio input level for 300mV RMS adns stereo. There is no input for video.

If the stereo signal is matrixed, you can set the NONSYNC to playback for that format. Normally, NONSYNC is plain stereo but you can still program where to output the sound on the DTS-6AD. Go into the MENU and select SYSTEM SETUP - OPTIONS - NEXT - NEXT you should ndow be in the NONSYNC programming menu. Select output choices. More info can be found in the manual in section 8.3.3.

OR

You may use the EXTERNAL input and be sure to pulse to that format when the DVD player runs. This imput also wants to see 300mV RMS signal.

Karen at DTS
khultgren@dtsonline.com

Posted by Karen Hultgren (Member # 395) on 12-04-2002, 02:16 PM:

Intercom systems !!! I used to work for RTS before I was at DTS. I know intercom very very well! I worked at RTS for 14 years in test and customer tech support. It was a grest place to work!

Karen at DTS

Posted by Jon Bartow (Member # 241) on 12-04-2002, 03:54 PM:

Paul's comment about electronic things that should never happen reminded me of something that happened to me years ago:

It was a church sound system using a self-contained 6-channel mixer/100w amp combo with all of the mic and speaker lines permanent in the walls. Somewhere along the line someone had spliced into the right speaker channel line and put another speaker in the nursery. (don't get me started about changing the ohm load etc, that was the least of their problems) Well, they used 24awg thermostat wire for this add-on speaker... Someone later on (presumably an HVAC guy) took a bunch of thermostat wires from the old heating system that were all under the stage and spliced them all together. (it was ugly, I think I counted 10 different pairs. Why he was splicing them together [Confused]

) And you guessed it, the add-on speaker wire was spliced into this rats nest. [Eek!]

The end result: No sound in the nursery unless the heat was set at 62deg or higher and no heat unless the master fader was set to at least -15dB. Go figure. Needless to say this one took me quite a while to figure out.
Jonathan

Posted by John Eickhof (Member # 323) on 12-04-2002, 07:58 PM:

Peter, Is the DTS the analog and digital processor? Or do you have a Dolby or Ultra Stereo as the analog? I have customers in N. Dakota that have I believe the same adv. supplier, and when they hooked up, they fed the center channel output of the analog processor, thus if their signal was too high, it would bleed past their own built in electronic fader. They finally had to return and install a relay to disconnect their signal from the system as well as hook their system up to the 'non-synch' as it should be. (I then had to hook up the automation to control the non-synch switching as well as their relay. The 'ghost voices' are now gone. Have fun!

Posted by Peter Schoell (Member # 919) on 12-04-2002, 10:47 PM:

The theatre where I have the "voice" problem is in another town and I havn't been able to get there yet. I plan, providing a worse fire dosn't pop up in another town, to check it out Thurs. I will try the differn't things you've all suggested. Thanks

Posted by Paul G. Thompson (Member # 655) on 12-05-2002, 01:49 AM:

After you set the level to Karen's recommendations, let us know if your strange voices go away. [Big Grin]

Posted by Peter Schoell (Member # 919) on 12-30-2002, 11:30 PM:

I corrected the "voices" problem with a relay controling the hot and neutral leads. The ads were setup with left, right & common leads comming into the non-sync inputs of the DTS 6AD unit. I thought I could run the right and left leads through the relay and leave the common connected, but I still had bleed through. The only way I could get it to work was by controlling the left and the common with the relay and forgetting about the right lead alltogether. The thing I don't understand is, before having this DVD ad package, I had a CD player with background music and never had any problems.
Thanks for your input.

Posted by Gordon McLeod (Member # 33) on 12-31-2002, 09:44 AM:

That tend to make me think there is a grounding issue involved.
Does the theatre use a distribution amplifer to send the signal to each screen

Posted by Paul G. Thompson (Member # 655) on 12-31-2002, 11:30 PM:

I have a tendency to agree with Gordon.

Get some isolation transformers form Radio Smack or a good electronics parts house and place them in the circuit. I found out through the years that it eliminates lots of problems, including the type you are having.

Posted by Peter Schoell (Member # 919) on 01-02-2003, 01:27 PM:

Yes Gordon there is a distribution amp.
do you and Paul think I should do something more than just the relay?

Posted by Gordon McLeod (Member # 33) on 01-02-2003, 02:20 PM:

What you have is a possible symptom of a bigger problem namely a grounding or a wireing issue that some one who can actually see it attempt to solve