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Topic: DTS in headphones

Antonio Marcheselli
Phenomenal Film Handler

Posts: 1260
From: Florence, Italy
Registered: Mar 2000

posted 03-02-2001 07:24 AM

Hello,

I'm trying to identify a problem in my DTS6 unit: I have a little hiss in front left and left surround speakers.
Karen told me that it is very strange since that channels are generated by two different cards. The hiss start ONLY when the unit goes in DIGITAL. You cannot hear the hiss with CP500 on "format11" and DTS on but not playing.
Since we have some problems with RF interference (we have a radio near the cinema) our tech said that perhaps the ribbon cable is picking up the RF signal ONLY when a signal is running on it.
I would like to test the audio output with a headphone. Is it possible? Can I connect the audio output from DTS-6 directly to an headphone?

Thanks for any suggestions!
Antonio

Josh Jones
Redhat

Posts: 1207
From: Plano, TX
Registered: Apr 2000

posted 03-02-2001 10:48 AM

You could use headphones, but the level would be quite low. and also, the phones have a lower impedance than the DTS unit would like to talk to, so your EQ might be off

Josh

Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 03-02-2001 10:48 AM

You could unplug the unit from the CP500 and see if you get a hiss when you select that format with no input and that would tell you if it id the DTS or the CP500 input card
If it isn't there then plug the cable backito the CP500 and unplug it from the Dts and see if the cable is the antena

Scott Norwood
Film God

Posts: 8146
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99

posted 03-02-2001 01:15 PM

I assume that you aren't using the THX booth monitor? It has a headphone connector, although there are a lot of electronics between it and the DTS unit, so it might not help you, anyway.

One option might be to get a headphone amp (or anything similar that has a line-level input and a headphone output with gain control...a small PA mixer would be fine). Connect the output from the DTS unit to the headphone amp and then listen. If you don't hear the hiss, then the problem is not in the DTS unit, and you can start troubleshooting the CP500, amps, wiring, etc.

Antonio Marcheselli
Phenomenal Film Handler

Posts: 1260
From: Florence, Italy
Registered: Mar 2000

posted 03-02-2001 07:37 PM

Hello everyone

No, the problem is not the Dolby.
You can hear the hiss (very low!) ONLY when the DTS goes in "DIGITAL". If you select "format 11" on Cp500 and set volume to 10, with DTS ON but not playing, no hiss can be heard. Only when the relais into the DTS6 connect the audio you can hear the hiss.
Is it possible that the audio cable is taking up some RF interferences ONLY when the DTS is playing something?

I'm in contact with Karen and she is helping me, as usual. However I appreciate any suggestions you can offer!

Oh, and let me thanks again DTS for its availabilty.
bye
Antonio

Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 03-02-2001 08:31 PM

I could be wrong, but the output jack of the SCSI CDROM drives don't have enough OOMPH! to drive low impedance head sets.

Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 03-02-2001 08:39 PM

There is no audio on the cd's for the headphone jack on the drives to reproduce
The disks contain DOs files only

Scott Norwood
Film God

Posts: 8146
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99

posted 03-02-2001 09:11 PM

Antonio -- couldn't there still be an issue with the input card on the CP500? I'm not intimately familiar with the CP500, but others who post here are. Maybe someone else could confirm or reject that this would be a possibility.

Antonio Marcheselli
Phenomenal Film Handler

Posts: 1260
From: Florence, Italy
Registered: Mar 2000

posted 03-03-2001 05:23 AM

Scott,

Yes, perhaps. But why the little hiss is present ONLY when sound (or silence!) is reproduced?
For better understanding, let me explain the test I make to hear this "hiss".
I put a test disk in the CD (usually the empirical test) and go into the theater, under a surround speaker.
After few seconds the DTS unit goes in Digital. In that moment, in the theater I can hear the "hiss" plus more background noise of the recording.
No "digital", no "hiss".
So I don't think that the Dolby input card could be responsible.

Ciao
Antonio

Stefan Scholz
Expert Film Handler

Posts: 223
From: Schoenberg, Germany
Registered: Sep 1999

posted 03-03-2001 06:11 AM

Anybody know of a battery operated mid quality headphone amp? It was a problem with the headphone jacks on the SDDS 2000 with its low levels.
We were shopping around, but unsuccessfull. Either there were high end devices, or extremely low quality products.
I was looking for a device that could be used as a general purpose level amplifier to drive a pair of headphones, either with phone plug input or two wire leads.
Currently my Testjig No.1a (600 Ohm/high impedance telephone from 1960's phone co. stock) that works great to test out signal flows, but is anything than HiFi.
Does anybody know a solution, or has a source?

Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 03-03-2001 10:22 AM

Antonio,
Its possible that you could be hearing hiss generated from the 6 track master that has gotten through fomr the mixdown. This can happen. The DTS system can certainly reproduce any if it is there.
Mark @ GTS

Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 03-03-2001 02:19 PM

Radio Design Labs makes a line of products called stickon and one of them is a headphone driver

Antonio Marcheselli
Phenomenal Film Handler

Posts: 1260
From: Florence, Italy
Registered: Mar 2000

posted 03-03-2001 02:55 PM

Mark,

I don't think. I can hear the hiss with ANY disc. I know what do you mean (I've heard some "digital" soundtrack with too much background noise) but I don't think that this is my case.

Bye
Antonio

Jon Bartow
Master Film Handler

Posts: 287
From: Massachusetts
Registered: Nov 1999

posted 03-04-2001 08:07 PM

Antonio, I don't know if you have another DTS unit or not, but if you do you could try switching the DTS cables (one at a time) to see if you have a bad cable. And if you do have another house try switching the DTS units. (Switch them back before show time of course) If you don't have another DTS unit but you do have another house, try hooking the DTS unit up to another processor (anything with a 6 channel input) and see if the problem remains.
BTW it is a "hiss" (kind of like the hiss from a cassette tape) and not a "hum" (like the hum from a flourescent light bulb), right?

Antonio Marcheselli
Phenomenal Film Handler

Posts: 1260
From: Florence, Italy
Registered: Mar 2000

posted 03-05-2001 06:09 AM

Jon,
Thanks for your help. In this days I'll try my DTS unit in another theater to see what happen.
However I dont' think that it is a RF interference because yesterday night I made some tests with "empirical test" disk. Do you know the "listen to my voice moving from channel to channel" test?
Ok, I was in the booth listening to the booth monitor set to "left
surround". When the voice reaches the left surround channel the "hiss"
change in frequency. When the voice goes to another channel the hiss come
back to the original frequency.
The "hiss" change in frequency also when the DTS changed the track.

And yes, it is not a "hum" but a little "hiss" like the one you can hear on some AM radio station.

Bye
Antonio

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