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TBKK 19th November 2011 10:55 AM

Static or digital sound by using DAC
I got an problem;

i hear an digital sound looks like static sound when connected the
digital output to an DAC i have convert the SPdif TTL to COAX
does anyone knows this problem

madtecchy 19th November 2011 11:15 AM

I was always under the impresion that SPDIF was a coaxial connection. Maybe you mean you converted a Toslink or other optical to coaxial.
Please forgive me if i am wrong.

Regards Ian

TBKK 19th November 2011 12:53 PM

I only hear this with using THE digital output
Of THE dvd rom to be sure i have converted THE ttl
To normal voltage use for coax

DF96 19th November 2011 01:28 PM

How did you convert the voltage levels? What voltage do you end up with?

TBKK 19th November 2011 02:03 PM

Spdif digital from CDROM = 5 v ttl
I have this with capacitor and two resistors
And THE DAC Locked good.

SoNic_real_one 19th November 2011 02:15 PM

"Two resitors" - that's your problem.
The coax SPDIF is a 75 ohm input. In order to build a passive divider you need to end up with the same impedance at the source - so your divider should be 75 ohms to ground.
That would overload any CDROM digital output, since those are made to work with 1 kohm loads.
If you do a divider with unmatched impedance (1 kohm), you will have "reflections" of the signal on the connecting cable (especially if it is short) and you end up with noise.

TBKK 19th November 2011 08:35 PM

Do you have an schematic for so i can try
I have use also with 100 nF PE65612 paralel 75 ohm to ground same problem
Use several DAC and dvd-rom and CDROM players

TBKK 19th November 2011 08:48 PM

Can i messure the reflection?

SoNic_real_one 19th November 2011 10:01 PM

jaycee 20th November 2011 09:34 AM

You'll find most DAC inputs are 5v tolerant - you should be able to connect your TTL input directly to it.

SPDIF is a bitstream protocol, and can be passed over any medium. TTL is just 0-5v square wave. "Coaxial" is 75 ohm transformer coupled, 0.5v peak-peak. AES/EBU is a balanced 100 ohm signal. TOSLINK is an optical transmission system.

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