[dnewman]

I'm confused (what else is new?) by a specification
in the HagDac manual which states that the S/PDIF
input is "standard S/PDIF (0.5Vpp)".  I thought that
Co-axial S/PDIF is +/- 0.5V and hence 1.0Vpp.  Or,
is this just my confusion between the nominal, *unloaded*
+/- 0.5V versus the approx. +/- 0.25V resulting from the
expected and proper use of 75 Ohm termination?

At any rate, before I play with interfacing a toslink,
I had better first be certain I know what the limits are
for the HagDac inputs.  (Yes, I need to convert from
0/+5V TTL levels.)

Thanks,
Dan

[hagtech]

Yeah, I forget.  Some boards specify unterminated.  The HAGDAC will handle anything from about 0.1Vpp to 2Vpp.  Or something like that.  I never really measured the complete limits.  It was not meant to TTL inputs.  Only 75 ohm style.  A simple 2 resistor pad and cap (to remove dc offset) can do the trick.  Say 1uF into 1k into 100 ohm (use any termination you want, HAGDAC is high impedance).  Tap off the 100 ohm.

jh

[dnewman]

Jim,

Thanks for the followup.  For the TTL conversion, yes I was going to do a
simple voltage divider along with a small cap.  If I have to, I'll toss in
an inverter driving three inverters in parallel (hex inverter chip, so
there's plenty of them).  I'll only do the inverters if there doesn't seem
to be enough current off of the tos link receiver (torx173 or similar).
I'll probably steal a little power from the +8V supply for the HagDac
card to get the +5V for the tos link....  This is all just my experimenting
around and having fun with my two Chimes.

Again, thanks for the great designs!

Cheers,
Dan

[hagtech]

Lots of spare +/-8V current.

jh