Film-Tech Forum ARCHIVE: Audio Wiring Question (DAX-602 / JS-200)

This is topic Audio Wiring Question (DAX-602 / JS-200) in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Jason McMillan (Member # 5542) on 05-09-2016, 02:34 PM:

Hello everyone... I'm looking for some advice on a situation we have on one screen. In our smallest auditorium, we only have a center stage speaker (it's a VERY small room) with stereo surround. We have a GDC SX-2001 with the built-in media block. The AES output on the GDC is connected to a USL DAX-602, which in turn is connected to a JS-200.

Here is the question at hand... since we only have the center channel and no left or right channel, we're trying to decide what is the best way to add the three channels together so we don't lose audio. Inside the DAX-602, there looks to be a jumper (JP2 IIRC) that we can set to add the three channels inside the DAX602 itself. Alternatively, someone suggested that instead, just taking a jumper wire from the L and R output terminals on the back of the JS-200 and connecting them to the C terminal.

So any thoughts on the best way to connect this up? Much appreciated for any advice.

Posted by Marco Giustini (Member # 4544) on 05-09-2016, 02:50 PM:

Wouldn't be better to look into having the Left and Right channels too? You obviously invested into a server and projector, there are small speakers for small auditoria now, why wasting time into missing L and R?

Posted by Jason McMillan (Member # 5542) on 05-09-2016, 03:13 PM:

That is not an option at this time.

Posted by Harold Hallikainen (Member # 5405) on 05-09-2016, 05:54 PM:

The DAX-602 has two jumpers to generate a mono screen channel and/or a mono surround channel. To generate a mono screen channel while keeping stereo surrounds, move JP2 as shown at http://uslinc.com:8888/phpwiki/index.php/CCR-CHGR%20USB%20Cable%20Durability and adjust the LCR output trims as described. The summed signal will appear on the center output. Do not change JP3 since you do not want to end up with a mono surround.

This procedure does a proper mix of LCR to generate a mono signal. You should not connect outputs of the DAX-602 in parallel since the outputs are very low impedance servo driven outputs (similar to floating transformer secondaries). Shorting multiple outputs together will have each output trying to force a particular voltage across the output. One or more of the outputs will overcurrent causing clipping of the audio.

The DAX-602 has mono/surround circuitry built in. For applications where that is not the case, the resistor network shown at http://ftp.uslinc.com/ftp/MultiProduct/MonoSumCircuit.pdf can be used.

Harold

Posted by Jason McMillan (Member # 5542) on 05-09-2016, 08:53 PM:

Thank you, Harold. That's what I was thinking, and I'd surely trust your advice. We're replacing some old Smart Mod 8's that the power supplies died on so this question came up during the change to the JS200 in this one auditorium.

Posted by Marco Giustini (Member # 4544) on 05-10-2016, 03:31 AM:

Hello Harold,

Not sure the first link is correct? It's asking for ID and PW.
Thanks

Posted by Harold Hallikainen (Member # 5405) on 05-10-2016, 08:17 AM:

Oops! Copy and paste error! The link to the manual is http://ftp.uslinc.com/ftp/Products/DAX-602-802/Documents/Dax-602-802%205-9-13%20Single%20Page.pdf#page=14 . Sorry about that!

Harold

Posted by Mark Gulbrandsen (Member # 72) on 05-10-2016, 09:52 AM:

The GDC Server also has audio routing built in. So this is a non issue except I would never come to this screen for a movie! And I thought I had cheapo customers.

Mark

Posted by Ken Lackner (Member # 1002) on 05-10-2016, 10:20 AM:

I don't anticipate ever needing this in the future, but I wish I had known this when I converted an old discount house to digital a few years ago! The four small auditoriums were center/mono surround. I would have pulled four DAX-602's from another site, installed ECI-60's in their place, and moved the DAX's to this site instead of installing resistor networks on the processor outputs.

Harold, any way to do this on an ECI-60?

Posted by Jason McMillan (Member # 5542) on 05-10-2016, 01:54 PM:

quote: Mark Gulbrandsen
The GDC Server also has audio routing built in.

TIL. I didn't even think about that. This is a great example of why I keep coming here and learning from the experts.

quote:
I would never come to this screen for a movie!

Please do understand that it's a small sub-run venue that targets the budget consumer and families that normally couldn't afford a night out at the movies. There is a major first-run 18-plex literally right next door. Seriously, I could leisurely throw a quarter from the roof of the building and hit the first-run venue.

While there are discussions on upgrading this screen, right now, the decision was made to get it back up as soon as possible with what was there already. I think the community served by this theatre would rather have mono/surround than no movie at all. It'll get there in time.

Posted by Marco Giustini (Member # 4544) on 05-10-2016, 02:30 PM:

Doremi have audio routing too but you cannot sum different channels. Can the GDC?

Posted by Sascha F. Roll (Member # 9043) on 05-10-2016, 04:25 PM:

Same with all kinds of Sony Servers.
You can route 1 Input Channel to as many Output as you wish, but (of course) not the other way.

Posted by Mark Gulbrandsen (Member # 72) on 05-10-2016, 04:44 PM:

quote: Jason McMillan
Please do understand that it's a small sub-run venue that targets the budget consumer and families that normally couldn't afford a night out at the movies. There is a major first-run 18-plex literally right next door. Seriously, I could leisurely throw a quarter from the roof of the building and hit the first-run venue.

I service a number of sites just like yours. The promiximity of the first run site is even more reason to try to be better than they are, and honestly... It's not usually that difficult. All my customers have excellent sound and picture, installing L&R channels and a stereo power amp is not a huge expenditure. Especially if you look for clean used cinema equipment. I have customers that were center surround like your screen but what the did was buy speakers and amps we pulled from other nearby theater's during upgrades. You may want to shop around based on what's back screen now and see ify I out can match them up.

Mark

Posted by Harold Hallikainen (Member # 5405) on 05-10-2016, 05:05 PM:

The ECI-60 does not have a channel summing circuit. You can use the resistive network linked to above. What I really like is the JSD-60 where you can mix anything with anything to any output. I'm always pushing for more generic designs here with this sort of approach.

Thanks!

Harold