D1 questions - AT&T receiver?

[spzzzzkt]

Hi,

Just wondering if anyone knew the part number for the AT&T receiver used in the D1?

cheers
Paul

[hifimaker]

The version I've seen uses the CS8412 as the input receiver.

-David

[spzzzzkt]

I mean the AT&T fiber optic receiver - comments suggest this is the most transparent sounding input option on the DAC, and no - it's not a toslink input

I have a feeling that I may have tracked down the device in question - CTS 1361AAC - unfortunately it's obsolete and seems very difficult to get. The prices I've seen ($60-70US) clearly warrant the statement in the Owners Manual - "It is a very expensive part, and we will charge for its replacement."

I've found a datasheet so I'll leave an empty footprint on the pcb in case I manage to track one down at reasonable cost.

[georgehifi]

Try these
Also this thread should be in the Digital section
Yes I agree it's the most transparent, I can use spidf B&C coax, toslink or AT&T ST glass fiber optical and it is by far the better sounding.
Cheers George
http://www.optekinc.com/viewparts.aspx?categoryID=3

[georgehifi]

Pic of mine in Wadia
Toslink to the left and bnc spdif to the right and more inputs right again out of picture.
Cheers George

[spzzzzkt]

Hi George,

thanks for the pic. It seems that variants of the 1361AAC were made by a number of companies. The implementation shown in the D1 schematic is very similar to the ODL50 datasheet attached, so it seems something ODL50 compatible will work.

My intent is to put together a fairly straight D1 clone (a D1 clone without enhancements?) based on the Rev 1 schematic that Pass Labs had on their site a few years back. Out of respect for Nelson and Wayne I prefer to post questions relating to their work in the Pass Labs forum.

cheers
Paul

[georgehifi]

Thanks for the Data sheet Paul, I've been looking for it.
Please let me know if you find these for sale anywhere as I also would like to use them on my newer dac projects.
Cheers George

[TJF]

Please more ... :-)

Can you explain a little bit more - how the Optek 482 is used (as sender, receiver?). There are many similar looking receivers and transmitters at Optek. Any schematic to test instead of a two pin SPDIF ...?

Very interesting ... :-)

[spzzzzkt]

The optek 482 is a bare photodiode so would need support circuits to output something useful... The RX modules contain a photodiode, preamp and output buffer.

As far as I can determine, you need something that has similar cable interface, and bandwidth specs to the ODL series II - 1mbit/s -50mbit/s transfer rates, compatibility with 62.5/125um optical fibre, plus TTL outputs...

The following is from the ML No31 sales information:

ST-optical digital interconnection was designed by AT&T for computer networking. Though not optimal for audio, it has certain advantages over digital interfaces found on some equipment. ST has a wider bandwidth than the more common EIAJ optical standard (often referred to by Toshiba's "Toslink®" trademark) and the coupling transformers used in most S/PDIF interfaces. It also provides ground-noise isolation often lacking in poorly designed electrical interfaces, and ST generally uses glass-fiber rather than plastic-fiber cables. ST is also recommended when digital-interconnection distances greater than fifty
feet are required.

The ST implementation in the N° 31 uses Hewlett-Packard parts with twice the bandwidth of the AT&T parts, yet is fully compatible with AT&T receivers. This 100MHz bandwidth is less than half that of the AES/EBU and SPDIF circuitry on the N° 31, but it may perform better with processors with poorly implemented electrical inputs.

It doesn't sound like a glowing recommendation for the ST interface.

Based on the "tip" of using higher bandwidth HP parts, it might be worth investigating the Avago HFBR-2416 / HFBR1414 pair.

cheers
Paul

[TJF]

50mbit/s is still oversized... :-) But may be - if you can really hear the benefit of higher bandwidth we should look at SFP-Modules like Finisar (over 4 GB/s). I talked to someone from Finisar. Should work. But I ask myself if it isn't extreme oversized...

I also asked at CTS, what happened with their module... I will post it...