Confused by DB25 pinout of MTRX Digital IO

[paulo m]

It´s really simple, although a bit confusing at first look.

DB25 connectors on analogue channels provide 8 balanced channels of either inputs or outputs. Each mono balanced line takes 3 pins, so 8x3=24. Pin nº 13 is not used. So 8 mono channels take the whole connector.

On AES EBU, the corresponding 3 pins of it´s analogue counterpart carry 2 channels of digital signal, so a pair. So, to carry 8 mono ins and 8 mono outs, the DB25 is maxed out at 4 pair ins and 4 pair outs of AES signals, which equals to 8 mono ins and 8 mono outs.

The MTRX has 16 mono channels of AES EBU, so it´s 8 pairs of digital I/O, 4 I/O pairs per each connector.

In fact it´s the label on the back of the MTRX that is misleading, as it could have been labelled AES/EBU 1-8 and AES/EBU 9-16. 😁

Please note that this works for regular DB25 to XLR breakout cables. But if you need to connect the MTRX AES/EBU DB25´s to another unit that has DB25´s AES/EBU connectors, the pinout is different on both ends of the DB25 connectors, as digital ins need to feed digital outs and vice versa so some pins are swapped on ends. Regular DB25 to DB25 don´t work at all.

Hope it helps

[ScottyD]

Yup. Wasn't confused about how AES works. Just confused on how Avid documented it in their manual.

[RobertDorn]

The thing I find more confusing in the MTRX manual is the wiring scheme, where on the Tascam site, the wiring is displayed as output 7-8 5-6 3-4 1-2 and then input 7-8 5-6 3-4 1-2, the MTRX manual says 4-8 3-7 2-6 1-5 for output and input pairs. I guess that's not actually the case, is it?:):)

[LukeHoward]

Originally Posted by RobertDorn

The thing I find more confusing in the MTRX manual is the wiring scheme, where on the Tascam site, the wiring is displayed as output 7-8 5-6 3-4 1-2 and then input 7-8 5-6 3-4 1-2, the MTRX manual says 4-8 3-7 2-6 1-5 for output and input pairs. I guess that's not actually the case, is it?:):)

I never looked at the pinout, I just use Tascam wired breakout cables and they work fine.

[RobertDorn]

ok cool, good to know. So the channel pairs are just 1-2 3-4 5-6 7-8 for the outputs and the inputs I assume.

Originally Posted by LukeHoward

I never looked at the pinout, I just use Tascam wired breakout cables and they work fine.

[JFreak]

TASCAM pinout is what DigiDesign/Avid have always used, and it goes like this:

• I 1-2 = DB25 pins 25-12-24
• I 3-4 = DB25 pins 11-23-10
• I 5-6 = DB25 pins 22-09-21
• I 7-8 = DB25 pins 08-20-07
• O 1-2 = DB25 pins 19-06-18
• O 3-4 = DB25 pins 05-17-04
• O 5-6 = DB25 pins 04-16-03
• O 7-8 = DB25 pins 02-14-01

All pins ground-cold-hot, respectively. This is pretty clever as adjacent channels' pins are as far away as possible.