what's the best way to convert SPDIF into CMOS level? - diyAudio
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Old 1st June 2004, 02:57 PM   #1
banana is offline banana  Hong Kong
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Default 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??

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Thanks in advance.
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Old 1st June 2004, 03:23 PM   #2
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Hi,

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

regards
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Old 1st June 2004, 03:46 PM   #3
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thread "CS8412 or AD1892?"
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Old 1st June 2004, 06:22 PM   #4
banana is offline banana  Hong Kong
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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?
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Old 1st June 2004, 10:58 PM   #5
andrei is offline andrei  Canada
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Use a specialized RS-485 receiver, like LTC1685 (or ADM1485).
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Old 1st June 2004, 11:05 PM   #6
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Quote:
Originally posted by andrei
Use a specialized RS-485 receiver, like LTC1685 (or ADM1485).

be careful, they all sound different !

Guido
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Old 1st June 2004, 11:08 PM   #7
Bricolo is offline Bricolo  France
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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.
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Old 1st June 2004, 11:10 PM   #8
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"be careful, they all sound different !"

yea, and donĀ“t forget the stone on your transport.
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Old 1st June 2004, 11:14 PM   #9
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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? or ?

5 times gain?
Shouldn't it be 10x?
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Old 2nd June 2004, 10:55 AM   #10
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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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