Using a GDC SX/SR Server with 7.1 audio with a QSC/USL JSD-60D

Using a GDC SX/SR Server with 7.1 audio with a QSC/USL JSD-60D

It is possible to use a GDC server with an USL JSD-60D processor and get 7.1 audio  and HI/VI output.  It does require a bit of technical sleight of hand to make it work properly.

The issue is that the JSD-60D is an 8 channel audio processor.  It can be configured as 5.1 stereo with a HI/VI output (5.1 channels + HI + VI = 8 channels) or 7.1 (8 channels) without HI/VI.  The processor, as sold, does not have the ability to provide 7.1 with HI/VI.  The workaround is to have the JSD-60 process the 7.1 audio channels and use an external D/A converter to provide analog audio to the HI/VI device.  If you are using a device that requires a digital input, such as the Fidelio, a similar technique may be employed.

DCP provide for 16 channels of metadata, which includes the audio tracks.  The 16 channels are presented as paired AES audio channels.  That is to say that the server outputs 8 AES (digital audio) pairs which contain the 16 tracks.  The wiring is simplified on the newer processors, such as the SX3000, SX4000 and SR1000 by splitting the 8 AES pairs over 2 CAT style cables.  The CAT cable that is plugged into A-TOP carries channels 1-8.  Similarly, the cable that is plugged into A-BOTTOM carries channels 9-16.

Legacy GDC processors used a multi-pin cable to carry the AES audio out.  Dargco manufactures custom adapters to convert the DB style output of the legacy processors to the more contemporary RJ-45 (CAT cable) output.

The JSD-60D processor has a single CAT cable input for AES signals.  It can only "see" channels 1-8.  Likewise the 25 pin connector adjacent to the CAT jack, while theoretically could handle all 16 channels, is only wired to accept channels 1-8.  The standard designation for channels 1-8 is:

Pair 1            Channel 1/2            Left Channel/Right channel
Pair 2            Channel 3/4            Center Channel/Subwoofer channel
Pair 3            Channel 5/6            Left Surround/Right Surround
Pair 4            Channel 7/8            Hearing Impaired (HI)/Visually Impaired (VI)

This single CAT cable in A-TOP carries all of the signals needed for 5.1 playback.

To provide 7.1 sound, a second CAT cable, plugged into A-BOTTOM is utilized.  The back surround left/back surround right signal is carried on Pair 6.

Due to the 8 channel limit on the JSD-60D, in order to process 7.1 audio with it, Pair 4 (Channel 7/8) needs to be removed and replaced with Pair 6 (Channels 11/12) that carry the BSL (Back Sound Left)/BSR (Back Sound Right) channels.  In addition to this, Pair 4 now needs to be rerouted to an external device, either connecting directly to the HI/VI systems (in the case of systems requiring a digital input, such as the Fidelio), or to an external D/A device that would translate the AES audio to analog audio.

While it is possible to use the set up GUI within the GDC processor to remap the AES pairs as needed, it doesn't address breaking out Pair 4 and rerouting it to the desired device.  The easiest way that we have found to achieve this is to use one of several different varieties of breakout board manufactured by Dargco (formerly Odyssey).  With these boards, both CAT cables (channels 1-8 and channels 9-16) are run to the breakout board which is plugged into the DB-25 connector on the back of the JSD-60D.  The board is hard wired to pass Pairs 1-3 directly to the matching pairs on the JSD-60d.    It substitutes Pair 4 with Pair 6 (BSL/BSR) so that the 7.1 audio channels are now going directly into the JSD-60.  Pair 4 is redirected away from the JSD-60 and is presented as a digital signal on either a RCA jack or Phoenix block, depending on the model of Dargco board utilized.

The JSD-60 is set to 7.1 mode and, on the ADVANCED tab, the channel mix is set as shown in the illustration.

If using a SR-1000 server, log in as MAINTENANCE, then go to Configuration->Playback.  About halfway down the page there is a section labelled Audio with a click box called CHANNEL MAPPING.

At the bottom of the channel mapping page, click the button labelled PRESETS.  This will bring up the preset configuration page which should be configured as shown:

Go back to the channel mapping page and adjust as follows:

Download the ISDCF/SMPTE 7.1 Test film.  This is a piece of test stock that should be run to confirm that the channels are assigned properly.  It calls out all of the channels in 7.1 audio.  The test stock can be downloaded from:

If you are using a legacy GDC server, use the following instructions:

1.      From the SMS screen click on CONFIGURATION.  Log in with the MAINTENANCE password.
2.      Click on the AUDIO tab
3.      On the audio tab, click on AUDIO CHANNEL MAPPING.
4      On the tab marked USE DCP CHANNEL ORDER, it as follows:

5. Select the PRESET button at the bottom of the page:

The rest of the instructions are the same as the SR units.

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