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-   -   what's the best way to convert SPDIF into CMOS level? (http://www.diyaudio.com/forums/digital-source/35172-whats-best-way-convert-spdif-into-cmos-level.html)

banana 1st June 2004 02:57 PM

what's the best way to convert SPDIF into CMOS level?
 
Hello all,

I'm working with DIR1701 as receiver. However, it's D_in only accept CMOS level, I need to convert SPIDF signal into CMOS level.

TI (on DEM-DIR1701 instruction manual) suggest using a two stage 74HCU04 buffer to do the level convert. Is there a better way to do it? Or are there any "low jitter" gates for building the buffer??

http://siuhungfa.homeftp.net/diy/Ban...ad1853pcb3.jpg

Thanks in advance.

Guido Tent 1st June 2004 03:23 PM

Hi,

Treat SPDIF as it where analog. I'd suggest a decent opamp like AD811, with 5 times gain or so.

regards

till 1st June 2004 03:46 PM

thread "CS8412 or AD1892?"
posting#41

banana 1st June 2004 06:22 PM

Thanks Gudio and Till.

ADM1485 looks like a good fit. But I have no idea how it would compare to 74CU04, in terms of clock skew.

And about using Opamp..... How do I ensure the Opamp's output is 0~5V? Does it mean running the Opamp with +5V single supply?

andrei 1st June 2004 10:58 PM

Use a specialized RS-485 receiver, like LTC1685 (or ADM1485).

Guido Tent 1st June 2004 11:05 PM

Quote:

Originally posted by andrei
Use a specialized RS-485 receiver, like LTC1685 (or ADM1485).

be careful, they all sound different !

Guido

Bricolo 1st June 2004 11:08 PM

Guido, why a gain of 5 for the opamp?

Isn't SPDIF 0-0.5V and CMOS 0-5V? So a gain of 10 would be required.

till 1st June 2004 11:10 PM

"be careful, they all sound different !"

yea, and donĀ“t forget the stone on your transport.

carlosfm 1st June 2004 11:14 PM

Quote:

Originally posted by Guido Tent
Hi,

Treat SPDIF as it where analog. I'd suggest a decent opamp like AD811, with 5 times gain or so.

regards

What about the LM6171? :up: or :down: ?

5 times gain?
Shouldn't it be 10x?:scratch:

Guido Tent 2nd June 2004 10:55 AM

Quote:

Originally posted by Bricolo
Guido, why a gain of 5 for the opamp?

Isn't SPDIF 0-0.5V and CMOS 0-5V? So a gain of 10 would be required.


Yes, in theory, but I like to reduce the amplitude in order to reducce the RF current entering the receiving. A tradeof between slope and amplitude

You can play around with it, ofcourse

regards


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