Film-Tech Forum ARCHIVE: Run a DVD player on JS-200

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Posted by Scott Manley (Member # 867) on 01-24-2004, 04:48 PM:

Would anyone have any idea if you can run a DVD player through a Ultra Stereo JS 200 and have L C R Surr?

Posted by Gordon McLeod (Member # 33) on 01-24-2004, 09:23 PM:

on the JS you would have to connect to the mag input on those units and that would allow you to address the LCRS inputs with no access to the SW
on the latter ones LCRS is addressable on the synth inputs

Posted by Chris Hipp (Member # 1788) on 01-25-2004, 01:22 AM:

I always had an idea to run your audio into the digital/ext input and run it that way. I'm not sure if it would work or not.

Posted by Ray Brown (Member # 1449) on 01-25-2004, 12:14 PM:

This might sound half-assed but it works on our set up. I used the projector 2 input and turned the input level all the way down. I have a toggle switch mounted on the sound rack to control the "changeover" between projector 1 & 2.

Since DVDs and VHS tapes very so much in audio levels and the sound is on the "harsh" side, I have a Yamaha graphic EQ with audio level ouput controls in between the DVD/VCR players and the JS200 to control input level and clean up the sound.

Sound is great and the surrounds work the way they are supposed to. I played the launch scene from Apollo 13 and the balcony floor was vibrating from the subs. [thumbsup]

I use the led meter on the JS200 to check and adjust sound level before I hit the Stereo/SR button.

I'm not really comfortable with the set up but it works and sounds great and we will get by with it untill we come up with something else.

Posted by Frank Angel (Member # 248) on 01-25-2004, 02:18 PM:

You've got an upside to your setup and a bunch of down sides. Upside is you are getting matrix decoding which takes your L,R disk player output and give you the L,C,R,S,plus that nice hefty subass output, with the matrix extracting out-of-phase audio and routing it thru the surrounds; that can give you a nice airy sound to music. The downside is you are mismatching the player output level to the input gain of your processor. Basically you are feeding a line level output into a mic level input which is a no-no big time. That's why you have to turn the fader practically off for it to sound any way normal. This mismatch also introduces lots of distortion (hence your harsh sound). If that is not bad enough, it also is passing the signals through Dolby Noise Reduction while your audio source does not need any NR at all. This will cause a very weird sound with a lot of high end funkiness and pumping. This anomaly cannot be resolved, but for a lot of music, you might feel you can live with it. If you can live with this, the level problem can be solved fairly simply by doing the following:

You must put some resistance between the output of the source and the input to the processor on the source side of your switch. How much resistance -- not easy to tell without knowing how hot your DVD or CD player is putting out....like you stated, levels can be all over the place. Best way is to skip the math and simply either put a) trim pots on the switch, or if you like the idea of a fixed resistor instead (less variables to deal with), b) a fixed resistor. But what value. Ok, do this:

1) insert a resistance substitution box in the signal path of one of the output channels from your player (with the resistance set to its highest value) and connect the output of the box into one of the CP projector #2 inputs

2) set your fader to #7

3) play a disk, and starting from the highest resistance setting simply dial down to lower resistances until the level that is coming out of your house system is just where you feel it is almost loud enough (you are only feeding one channel so when both are playing the sound will be a bit louder).

4) note the resistance that you've stopped at on the resistance substitution box and go buy yourself a few resistors of that value and

4) stick them on the switch (player side, both channels).

That's all there's too it.

Listen to a few disks that you want to play back and see if you can stand the NR processing. You might think it's OK. I wouldn't but it's all a matter of taste and necessity. Now is there a way to disable NR while still using the projector solar cell inputs? I have no idea. There's no way on my CP50 or 55s that I know of except using dummy NR cards to replace the decoding cards, but that pretty much defeats the simplicity you are going for with a single switch.

Posted by Gordon McLeod (Member # 33) on 01-25-2004, 02:55 PM:

the original JS200 chris did not have a digital ext input but had a 4 track mag/external input as there was no access to the suib and no split surround the JSX serries I believed introduced that
Feeding it into the Projector2 is a bad idea since you are adding a tone of distortion due to the impedance mismatch of the cell input and the Noise reduction being in line
On the mother board is a set of straps marked NR out and Matrix in and I usually put a toggle switch there to route an external source directly to the matrix

Posted by Nic Margherio (Member # 273) on 01-25-2004, 06:09 PM:

If you have a JS200 with DIG/EXT inputs, it is quite easy to hook up a DVD player to it in particular if your DVD player has an internal AC3/dts decoder and 5.1 analog outputs as most DVD players do nowadays.

Using the analog outputs, you first need to get three 6 or 12 foot RCA cables from RadioShack or some other electronics store, cut each cable in half (into 3 or 6 foot sections), connect spade lugs to the signal (center conductor) and ground (shield conductor) and connect to the JS200 inputs. Most DVD players' analog outputs are rated at 2v RMS and 10Kohm output impedance, well within the JS200's specs. You should run an audio setup routine on the DVD player (you will need some kind of TV monitor for this) and set all of the speakers to "large" (full bandwith). You can also adjust individual channel levels at this point if you need to without messing with any of the JS200's levels. Most DVD players will even output pink noise (term used loosely-you will find wide variations in the quality of the pink noise source between DVD players)in each channel for this purpose. This method will yeild the best results since you will be able to run 5.1 DVDs (dts or Dolby Digital), DVD Audio, SACD and Dolby Surround sources (via the player's internal Pro-Logic decoder).

The other method, if your player does not have 5.1 analog outputs, or your JS200 does not have 5.1 (6) inputs, would be to run the L/R line out to the non-sync inputs as Gordon has mentioned. In this case the JS200 would perform the 2:4 decode instead of the DVD player and you would not have 5.1 discrete channels.

I have connected both a JS200 and a DFP-3000 to a DVD player using the first method mentioned and have achieved very good results, though the DFP-3000 requires much more work on the interface cable due to the 25 pin D-sub input as opposed to the JS200's terminal strip.

Posted by Steve Guttag (Member # 268) on 01-25-2004, 11:20 PM:

The general rule of thumb of connecting a line-level source to an optical preamp is to use two 47K resistors for each channel. Connect one to the "+" and one to the "-" or low terminal (some use signal ground some have a "neutral." You will normally find that the level is somewhere in your optical preamp's range.

You still have the lack of NR issues if you use the processor's SVA decoder and some extra noise from the total gain structure mismatch.

Steve

Posted by Scott Manley (Member # 867) on 01-26-2004, 04:12 PM:

Ok Steve.......going to give your idea a try....will post later in the week how it turns out.

Posted by Gordon McLeod (Member # 33) on 01-26-2004, 07:36 PM:

Nic I don't think I said NonSync inputs but remove the jumper straps between the NR out and matrix in and put a toggle switch to route the external source directly to the matrix