Hi all,
I am in a position to get used CD player Denon DCD-700AE in fantastic condition for cheap. Only problem is it has optical out instead of coaxial S/PDIF that my DAC has.
Looking at the attached schematic I`m a bit confused. I can see digital out from the DSP chip TC94A14FA and then to 74WHC157 multiplexer before it meets TC7SHU04 (inverter/unbuffer-powering led diode?).
At what point (and if it`s even possible) to tap a spdif signal and route it through 75Ohm coax? I actually want to use BNC connectors for this, but that is beside point here.
Unfortunately I am not an expert in digital electronics or S/PDIF protocol so your help would be greatly appreciated, thanks!
I am in a position to get used CD player Denon DCD-700AE in fantastic condition for cheap. Only problem is it has optical out instead of coaxial S/PDIF that my DAC has.
Looking at the attached schematic I`m a bit confused. I can see digital out from the DSP chip TC94A14FA and then to 74WHC157 multiplexer before it meets TC7SHU04 (inverter/unbuffer-powering led diode?).
At what point (and if it`s even possible) to tap a spdif signal and route it through 75Ohm coax? I actually want to use BNC connectors for this, but that is beside point here.
Unfortunately I am not an expert in digital electronics or S/PDIF protocol so your help would be greatly appreciated, thanks!
Would you consider an external converter?
https://www.amazon.co.uk/LiNKFOR-Bi...vlocphy=&hvtargid=pla-4584482462120827&psc=1#
https://www.amazon.co.uk/LiNKFOR-Bi...vlocphy=&hvtargid=pla-4584482462120827&psc=1#
I'm out of my lane here, it's been awhile since I've thought about spdif. I think it's less complicated than you outline. the optical part of spdif takes a normal electric spdif and converts it to optical. so I believe all you'll need to do is tap into the line that feeds the optical (called torx??). probably need some additional passive components, a pulse transformer (though that may be on the receiver side only).
do some searches on older adc/dac chips, the inexpensive ones. iirc they have sample circuits for the Dout pins.
again, I could be way off base so what I said will need confirmation.
do some searches on older adc/dac chips, the inexpensive ones. iirc they have sample circuits for the Dout pins.
again, I could be way off base so what I said will need confirmation.
Thanks Galu for looking this up - I was aware of the product and is a good simple solution, but I still wanted to avoid additional boxes that will probably add more jitter in the signal path and clutter in my gear rack. Also there is an element of tinkering that might lead to learning something, simple plug in and
enjoy solutions are sort of unlawful around here 😉
A much better solution is to add an optical converter to SP/DIF to the existing DAC. You will thus benefit from the almost perfect galvanic isolation provided by the optical fiber and reduce the noise injected through the GND connection.
You just need to use something like this and ensure a 5V or 3.3V power supply for it (filtered locally with a ferrite and 1-2 capacitors, ceramic + electrolytic).
You just need to use something like this and ensure a 5V or 3.3V power supply for it (filtered locally with a ferrite and 1-2 capacitors, ceramic + electrolytic).
Thanks for chiming in... my DAC (Gustard R26) has optical input. The thing is this input is already taken by the TV and I consider coaxial
IMO slightly superior regardless of the inherent galvanic isolation. Introducing two more conversion stages cannot benefit signal integrity which
is analog carrying digital signal at this stage.
Btw, there is an input transformer in my DAC that offers galvanic isolation, so benefit of galvanic isolation would be arguably surpassed by the introduction of jitter.
IMO slightly superior regardless of the inherent galvanic isolation. Introducing two more conversion stages cannot benefit signal integrity which
is analog carrying digital signal at this stage.
Btw, there is an input transformer in my DAC that offers galvanic isolation, so benefit of galvanic isolation would be arguably surpassed by the introduction of jitter.
I don't want to get into the endless jitter-related discussions, but the jitter problem is very, very exaggerated for commercial reasons.
Show me a discussion about how serious the jitter is in the case of video signals, and there it really matters because you have a much wider frequency band.
Show me a discussion about how serious the jitter is in the case of video signals, and there it really matters because you have a much wider frequency band.
My spdif switch project Whazon will perform well. But since you'd rather not having an extra box, there are other ways of doing it. If you are willing to add a BNC outlet to the CD player, the attached circuit will do it well. R1 taps off the TX feed to the existing optical output module. The logic buffer NC7Z125 and all the parts around it can be arranged on a small PCB attached to the back of the BNC connector. C3 and C4 should be placed near the power supply pin on the buffer. R4 and R13 make an equivalent output Z around 75R. If not needed, the BNC can be put where the transformer primary winding is.
Attachments
For what it's worth, here's what I did to add coax S/PDIF out on a Hitachi VIP-RX8EX laserdisc player (rebadged Pioneer).
https://www.diyaudio.com/community/...-coaxial-output-need-help.130129/post-1616739
https://www.diyaudio.com/community/...-coaxial-output-need-help.130129/post-1618227
https://www.diyaudio.com/community/...-coaxial-output-need-help.130129/post-1616739
https://www.diyaudio.com/community/...-coaxial-output-need-help.130129/post-1618227