Hi all,
I wanted to mod my players with a coaxial digital output so as to connect it to my DAC.
I got this circuit from the web.
I tried it on my old Sony CD (model CDP 590) player which uses a CXD2500Q chip, on pin 60 (digital out) but there is no sound output from the DAC.
I tried it on my old Pioneer LD (model CLD-D580) player which uses a Sanyo LC7868 1K chip, on pin 43 (digital out), again there’s no sound.
I don’t think is the thin copper wire that I used between the output resistor & the RCA connector.
Anyway if anyone have done this mod (that is moding your player with a digital output so as to connect it to an external DAC), if u don’t mind do share with me your knowledge & experience.
Thanks!
I wanted to mod my players with a coaxial digital output so as to connect it to my DAC.
I got this circuit from the web.
I tried it on my old Sony CD (model CDP 590) player which uses a CXD2500Q chip, on pin 60 (digital out) but there is no sound output from the DAC.
I tried it on my old Pioneer LD (model CLD-D580) player which uses a Sanyo LC7868 1K chip, on pin 43 (digital out), again there’s no sound.
I don’t think is the thin copper wire that I used between the output resistor & the RCA connector.
Anyway if anyone have done this mod (that is moding your player with a digital output so as to connect it to an external DAC), if u don’t mind do share with me your knowledge & experience.
Thanks!
An externally hosted image should be here but it was not working when we last tested it.
Yes, I've done that with a Hitachi VIP-RX8 (guts built by Pioneer) laserdisc player. It used the CXD2500AQ chip, and had traces and locations on the board for a Toslink output. Since at the time it was hard to get Toslink devices, I put in a little buffer board and an RCA jack output. I think the circuit I used was a lot like yours.
Maybe the output has to be enabled? Pin 59 is the "Digital Out On/Off Control"; High for On, Low for Off.
CXD2500AQ at Alldatasheet.net
Maybe the output has to be enabled? Pin 59 is the "Digital Out On/Off Control"; High for On, Low for Off.
CXD2500AQ at Alldatasheet.net
Pin 59 could be connected directly, or through a resistor (10k or so) to the same supply voltage the chip uses, probably 5V. The datasheet should explain what is OK to do.
If I remember, maybe I will open up the player and take some pictures (I didn't have a camera with macro at the time I did the mod.). I've got a sketch someplace of the board layout, or maybe I can get a shot of the backside of the board if I didn't mount it too permanently.
If I remember, maybe I will open up the player and take some pictures (I didn't have a camera with macro at the time I did the mod.). I've got a sketch someplace of the board layout, or maybe I can get a shot of the backside of the board if I didn't mount it too permanently.
Hi Dangus,
Thanks! I can see u are using HC14, what's the different between it & the HC04?
U didn't mentioned about enabling pin 59 on the CXD 2500Q chip.
So i guess that is not needed.
Here's another TTL to SPDIF circuit -
So confusing now, wonder which circuit will really work?
Thanks! I can see u are using HC14, what's the different between it & the HC04?
U didn't mentioned about enabling pin 59 on the CXD 2500Q chip.
So i guess that is not needed.
Here's another TTL to SPDIF circuit -
An externally hosted image should be here but it was not working when we last tested it.
So confusing now, wonder which circuit will really work?
Hi,
The 14 is a Schmitt trigger type, probably the best choice but the 04 should work fine.
I have seen it mentioned somewhere that some DAC inputs use a 0 - 5 volt logic level.
I can't see anything wrong, and when I last experimented with something similar ( adding an optical output ) I found it not critical at all. Whether the circuit inverts or not didn't matter.
The 14 is a Schmitt trigger type, probably the best choice but the 04 should work fine.
I have seen it mentioned somewhere that some DAC inputs use a 0 - 5 volt logic level.
I can't see anything wrong, and when I last experimented with something similar ( adding an optical output ) I found it not critical at all. Whether the circuit inverts or not didn't matter.
Mooly said:
Probably doesn't make much difference in this application since the inverter is driven by a good square wave, but hysteresis is implicated as a major contributor to jitter in spdif applications.
Spdif has a specific range of amplitude levels that work (well) above that range things can get very funky with receiver chips latching, etc. Below a certain level most receiver front ends won't lock properly.
400 - 500mVpp with everything properly terminated is a good number to aim for. (See my posts in the shigaclone thread for much more detail on this issue.)
Hi,
Some questions -
1) Is the digital GND very important? I saw pin 12 & 52 labeled as Vss (GND) on the CXD 2500Q chip, I’m using pin 52 as the GND.
2) I suppose I can't use the chassis for the digital GND?
3) Agree, 0.5Vpp is what I should be aiming for. Without a scope, only a digital multimeter, will I be able to check for this 0.5Vpp at the RCA output? What should I be seeing if the circuit works? The reason being I do not want to connect the output to the DAC & damaged it.
Thanks!
Some questions -
1) Is the digital GND very important? I saw pin 12 & 52 labeled as Vss (GND) on the CXD 2500Q chip, I’m using pin 52 as the GND.
2) I suppose I can't use the chassis for the digital GND?
3) Agree, 0.5Vpp is what I should be aiming for. Without a scope, only a digital multimeter, will I be able to check for this 0.5Vpp at the RCA output? What should I be seeing if the circuit works? The reason being I do not want to connect the output to the DAC & damaged it.
Thanks!
You won't harm it with only 5 volts max input to play with. The values in post 1 give around 1.1 volts pk/pk. Just ohms law, even though it's a square wave. When it goes high you have 5 volts on top of the two resistors. Try increasing the 100 ohm to 220 ohm and see what happens. You really need a scope to see what's going on. Other than that you can only chack the gates statically applying first a 1 and than a 0 and seeing the output of the final gate toggles correctly.
Should there be a transformer at the output technically ? to give a true floating output.
Should there be a transformer at the output technically ? to give a true floating output.
My written notes mention the pin 59 enable thing, but don't say anything about having to do anything about it. Since the board was laid out for a Toslink output they may have just hard-wired pin 59 to be pulled-up all the time.
I took power and common from the holes for an unpopulated bypass capacitor C205, and used one hole of JA8 (the unpopulated Toslink transmitter) for the signal. I'll see if I can get the player out and have a look inside tonight.
No normal stand-alone DAC should require 0-5V input, but a DIY-er might choose to use a 5V link (maybe RS485) instead of the lower S/PDIF levels. Some of the Creative Labs sound cards are rumored to put out 5V levels.
I took power and common from the holes for an unpopulated bypass capacitor C205, and used one hole of JA8 (the unpopulated Toslink transmitter) for the signal. I'll see if I can get the player out and have a look inside tonight.
No normal stand-alone DAC should require 0-5V input, but a DIY-er might choose to use a 5V link (maybe RS485) instead of the lower S/PDIF levels. Some of the Creative Labs sound cards are rumored to put out 5V levels.
dangus said:
Quite true, spdif levels are much lower than this and CS8416 and some others actually may malfunction if presented with 5V spdif signals.
I had an NEC cdrom that also had a 5V digital output.. Both my Asus mobo have a connector with 5V digital on it that an accessory slot based breakout card can be plugged into - this has both an RCA jack (or two) and the necessary attenuation.
Hi guys,
I just want to be sure with my pin connection, i have re-attach the photo with the pins' connection
I hope u can let me know if there's any connection mistake.
I have not try increasing the 100ohm to 220ohm yet.
My DAC is using a CS8416 chip, seems like my SPDIF output is too high. So adding the resistance to the 100ohm might help?
Thanks!
I just want to be sure with my pin connection, i have re-attach the photo with the pins' connection
I hope u can let me know if there's any connection mistake.
I have not try increasing the 100ohm to 220ohm yet.
My DAC is using a CS8416 chip, seems like my SPDIF output is too high. So adding the resistance to the 100ohm might help?
Thanks!
An externally hosted image should be here but it was not working when we last tested it.
One thing... unused inputs on a chip should not be left floating. It's better to tie them high or low, or just use them.
I pulled the unit out last night and looked inside. The trace from pin 59 wanders off with a bunch of parallel traces which aren't easy to follow; maybe I just measured to see if it was enabled, or figured I'd just hook up the output board and worry about it later if the output didn't work.
Here's views of the top and bottom of the board. It's mounted to the back panel with a single hex standoff. The audio board on this LDP is conveniently a separate board on the side, so the solder side was easily accessible.
I pulled the unit out last night and looked inside. The trace from pin 59 wanders off with a bunch of parallel traces which aren't easy to follow; maybe I just measured to see if it was enabled, or figured I'd just hook up the output board and worry about it later if the output didn't work.
Here's views of the top and bottom of the board. It's mounted to the back panel with a single hex standoff. The audio board on this LDP is conveniently a separate board on the side, so the solder side was easily accessible.
Attachments
Hi guys,
Thanks for all your time & guidance, I finally got it right.
I did what Dangus recommended, tied up the other 2 unused inverters into the circuit & at the same time I found the GND to my 74HC04 was not properly soldered.
I have a few more questions –
1) I noticed there’s clicking sound on my DAC whenever I press the start/stop buttons on my LD player. Is this normal? Any harm?
2) The exact value of the 2 resistors are 313ohm & 98.1ohm, that works out to be about 74.69ohm. Is there any other thing I can do on this circuit to improve the overall sound output from my DAC?
3) Lastly, if I intend to use my player as a transport, will it make sense to do the Kwak clock mod on my player?
Any suggestion is greatly appreciated.
Thanks for all your time & guidance, I finally got it right.
I did what Dangus recommended, tied up the other 2 unused inverters into the circuit & at the same time I found the GND to my 74HC04 was not properly soldered.
I have a few more questions –
1) I noticed there’s clicking sound on my DAC whenever I press the start/stop buttons on my LD player. Is this normal? Any harm?
2) The exact value of the 2 resistors are 313ohm & 98.1ohm, that works out to be about 74.69ohm. Is there any other thing I can do on this circuit to improve the overall sound output from my DAC?
3) Lastly, if I intend to use my player as a transport, will it make sense to do the Kwak clock mod on my player?
Any suggestion is greatly appreciated.
Hi,
Point 1. Dunno really
Is it harmful, not unless it's that loud it's damaging to speakers etc. Does the data stream contain a mute command ? Don't think so ! The original player itself will mute by other means. You can get "clicking" when the PLL in the DAC is on the point of losing lock but that would be there all the time.
Point 2. The resistor are in series not parallel.
Point 3. Can't answer that one. I suspect not worth doing -- others may disagree.
Enjoy
Point 1. Dunno really
Is it harmful, not unless it's that loud it's damaging to speakers etc. Does the data stream contain a mute command ? Don't think so ! The original player itself will mute by other means. You can get "clicking" when the PLL in the DAC is on the point of losing lock but that would be there all the time. Point 2. The resistor are in series not parallel.
Point 3. Can't answer that one. I suspect not worth doing -- others may disagree.
Enjoy
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