ADAT over copper?

[mervaka]

I know it's called ADAT Lightpipe for a reason, but I was wondering if anyone has been successful in cooking up a way of transporting ADAT data over either AES, CAT5/5e/6 or RG59 coax cable?

 

The situation is one where I need to carry a few channels of audio and two return over distances of about 100-150m. Has anyone seen anything for sale that converts Toslink to either XLR, RJ45, or BNC, or have come up with a similar DIY solution? I've already investigated the phantom circuits idea, and I cant say it's a good idea on this occasion, as it's for broadcast!

 

A concurrent post has been automatically merged from this point on.

 

found this, but it's a bit dearer than what I was expecting. it's just a low level link after all..

[dbuckley]

If that's excessively expensive I'll not suggest what I was going to

[mackerr]

It is probably also more expensive than you would like, but AudioRail lets you send 32 channels of ADAT over CAT5. It is a simple optical to electrical converter so it has no signal timing in it, it is just an extender. Using multiple 8ch ADAT signals requires dealing with the WC sync between them.

 

I would almost always prefer converting to a more robust format like AES for transport.

 

Mac

[mervaka]

well I was only after a layer 1 electro-optical bridge, so all it should really need to be in laymans terms is a light triggered driver circuit with an LED at the other end. of course the light sensor and LED would in reality be Toslink Rx and Tx sockets. See why I'm not prepared to pay much for it?

 

this with this is more along the lines of what I'm after, but with the guarantees of it working up to the 15MBit or so that ADAT requires.

 

this bloke seems to be on very similar territory to me, as I'm covering live sport!

[BlueShift]

Hear Technologies make an ADAT extender that works with cat5.

[dbuckley]

It is probably also more expensive than you would like, but AudioRail ...

That's exactly the (probably too expensive) product I had in mind

[dirkenstein]

Yes, this is possible, at least over shorter ranges, using standard Toshiba toslink TOTX/TORX TX/RX units and RS485 transceivers. Make sure you get the faster versions of the toslink transmitters and receivers and use 3.3 or 5v to taste.

 

The circuit is dead simple- basically just use the standard cicuit diagram for the toslink units with their power supply decoupling requirements and connect to the RS485 transceiver with correct hard-coding of send/receive and termination.

 

I breadboarded something like this before deciding to buy a packaged solution after discovering I could never make it work reliably at ranges over 25m.

 

You will need to find a low-jitter RS485 transmitter. The ones I was using didn't cut it over the distances I was trying to go (30m-50m). I suspect I know which ones are used in the appsys products but couldn't bring myself to pump Appsys for more information (and the relevant chips were not available from Farnell or RS anyway).

 

Remember the clock rate will be around 12-13MHz so you'll need to pretty much find the fastest and lowest jitter RS485 transmitters and receivers you can.

 

There are additional caveats involving clock recovery for anything involving using ADAT framers not made by wavefront semi (such as the JetPLL designs and specifically those found on Yamaha my8at and my16at cards)- this means if you intend to generate wordclock at point A, transmit it to point B then return a clocked signal again to point A (where Point A is a Yamaha card) then this may not work. You need to add ADAT clock reframers which makes the whole solution a lot more complex as a homebrew project. The wavefront chips also cost around 4$ each and I'm not sure they are available in any quantity under 1000. Maybe evaluation units.

 

If you're very brave you can also try the usual cheap toslink-->phono converters, phono-->BNC connectors and 75 ohm BNC cable. I tried this variant with cat5 video baluns and also got rather less then 50m out of it.

 

 

Dirk

[dirkenstein]

My original deisgn was 5V and used TOTXTORX177L and TI SN65HVD3088EDG4 transceivers.

 

My suggestion, as yet unconfirmed by an actual working design, would be to use:

 

3.3V design

 

Intersil ISL3179EFBZ (Farnell 1439860) rs485 transceiver, 40mbit/s

 

Toshiba

TORX147L (Farnell 1225768)

and

TOTX147L (Farnell 1225775)

^^ 3.3v, shuttered, with mounting screw.

 

You will need some 100n decoupling caps for the transmitters/receiver and miniature 47uH inductors for the receiver.

[mervaka]

looks like a good idea. I think a lot of the design hurdles could well boil down to making sure impedances are properly matched to the cable used.