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From: Dirk Bruere at NeoPax on 7 Jun 2010 18:10
There are a number of circuits on the Net to do this. For example:
http://sound.westhost.com/project85.htm

In Fig 5 should that IC be a 74HC04 as stated, or 74HCU04?


--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
http://www.blogtalkradio.com/onetribe - Occult Talk Show
From: Winfield Hill on 8 Jun 2010 07:13
Dirk Bruere at NeoPax wrote...
>
> There are a number of circuits on the Net to do this.
> For example: http://sound.westhost.com/project85.htm
>
> In Fig 5 should that IC be a 74HC04 as stated, or 74HCU04?

That's a simple AC signal to DC logic conversion,

.. | \
.. AC ---||---+---| >O--+----
.. | | / |
.. | |
.. '---/\/\---'

I'd say, yes, in the absence of any signal, an HCU04 gate
would do a better job of settling at 1/2 Vcc, and perhaps
do so with less class-A current, but in the absence of a
signal, who cares what happens? In practice, S/PDIF lines
have a continuous AC signal, so this simplified circuit's
feedback RC node should find the average of the incoming
data stream. Also, the continuous huge signal means the
gates won't have a class-A rail-rail current problem.

s/pdif data doesn't have a 50% duty cycle, which gives me
pause, but Andrew Kilpatrick, Randy McAnally and ESP =
Rod Elliott swear by it, so it must be adequate. :-)

http://www.andrewkilpatrick.org/blog/?page_id=215
http://www.andrewkilpatrick.org/blog/wp-content/uploads/2008/07/spdif_circuits.gif

OTOH, you can get official s/pdif receiver connectors and
ICs for a few bucks, and that seems a bit more professional.


--
Thanks,
- Win
From: Winfield Hill on 8 Jun 2010 07:22
Winfield Hill wrote...
>
> s/pdif data doesn't have a 50% duty cycle, which gives me
> pause, but Andrew Kilpatrick, Randy McAnally and ESP =
> Rod Elliott swear by it, so it must be adequate. :-)

Check that, s/pdif's biphase mark code is more than
close enough to a 50% average for good RC coupling.
http://en.wikipedia.org/wiki/Biphase_mark_code


--
Thanks,
- Win
From: Grant on 8 Jun 2010 07:51
On 8 Jun 2010 04:13:59 -0700, Winfield Hill <Winfield_member(a)newsguy.com> wrote:

>Dirk Bruere at NeoPax wrote...
>>
>> There are a number of circuits on the Net to do this.
>> For example: http://sound.westhost.com/project85.htm
>>
>> In Fig 5 should that IC be a 74HC04 as stated, or 74HCU04?
>
> That's a simple AC signal to DC logic conversion,
>
>. | \
>. AC ---||---+---| >O--+----
>. | | / |
>. | |
>. '---/\/\---'
>
> I'd say, yes, in the absence of any signal, an HCU04 gate
> would do a better job of settling at 1/2 Vcc, and perhaps
> do so with less class-A current, but in the absence of a
> signal, who cares what happens? In practice, S/PDIF lines
> have a continuous AC signal, so this simplified circuit's
> feedback RC node should find the average of the incoming
> data stream. Also, the continuous huge signal means the
> gates won't have a class-A rail-rail current problem.
>
> s/pdif data doesn't have a 50% duty cycle,

Averages 50% in the longer term, that's why it's an AC coupled signal.

> which gives me
> pause, but Andrew Kilpatrick, Randy McAnally and ESP =
> Rod Elliott swear by it, so it must be adequate. :-)
>
> http://www.andrewkilpatrick.org/blog/?page_id=215
>http://www.andrewkilpatrick.org/blog/wp-content/uploads/2008/07/spdif_circuits.gif
>
> OTOH, you can get official s/pdif receiver connectors and
> ICs for a few bucks, and that seems a bit more professional.

Yes, but there's more to life than doing everything efficiently ;)

Grant.
--
http://bugs.id.au/
From: M.Randelzhofer on 8 Jun 2010 07:53

"Dirk Bruere at NeoPax" <dirk.bruere(a)gmail.com> schrieb im Newsbeitrag
news:87592cF9ouU1(a)mid.individual.net...
> There are a number of circuits on the Net to do this. For example:
> http://sound.westhost.com/project85.htm
>
> In Fig 5 should that IC be a 74HC04 as stated, or 74HCU04?
>
>
> --
> Dirk
>
> http://www.transcendence.me.uk/ - Transcendence UK
> http://www.blogtalkradio.com/onetribe - Occult Talk Show

In the following schematics page 17 upper left corner, you see a working
solution (I have the eval board, its working nicely in coax SPDIF mode).

http://focus.ti.com/lit/an/slea035a/slea035a.pdf

MIKE

--
www.oho-elektronik.de
OHO-Elektronik
Michael Randelzhofer
FPGA und CPLD Mini Module
Klein aber oho !
Kontakt:
Tel: 08131 339230
Usst.ID: DE130097310


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