Adding SPDIF and other mods to Yamaha CDX 480

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jwb

jwb

Member
Joined 2002
Don't ground the shield of the digital output to the chassis if you are using S/PDIF and coaxial cable. You should use a pulse transformer on the output instead, and isolate the cable shield from everything else.

Of course you could use optical cable instead.
 
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bocka

Member
Joined 2003
synertronixx.de
Don't ground the shield of the digital output to the chassis if you are using S/PDIF and coaxial cable. You should use a pulse transformer on the output instead, and isolate the cable shield from everything else.
Click to expand...

But wouldn't then the cable radiate a lot? Why not use a cap of about 10nF after the transformator to break the ground loop and ground the shield for high frequencies?
 
G

Guido Tent

Member
Joined 2001
TentLabs.com
jwb said:
Don't ground the shield of the digital output to the chassis if you are using S/PDIF and coaxial cable. You should use a pulse transformer on the output instead, and isolate the cable shield from everything else.

Of course you could use optical cable instead.
Click to expand...

Optical is the best route for worse sound, unless you get rid of cheap fibres and improve transmitters and receivers - not my cup of tea.

Obviously the shield of the coax should be connected to the chassis (both ends) as to assure the common mode currents do not run through the cabinet but close their ways outside. If you are afraid of LF ground loops, you may ground the shield RF wise by using a capacitor (say 10nF)

The pulse transformer should be inside the cabinet to provide high impedance for the remaining (small) part of the CM current.

If you do not ground you will have to rely on the shunt capacitance of the transformer, signal wise, and the RF radiation will be MUCH worse.........

best
 
H

havar

Member
Joined 2007
I know it's an old thread, but maybe...

Now I've got one of these CD-players to tweak to death... just for the fun.

I've also got a no-name XO-unit from Asia, but I can't find out how to do the "trick"...:rolleyes:

The original XO has three connectors, and I've never seen that before. Not that I have lots of experience, but anyhow...

If you can help me, please do...:)

All the best!
 
G

Guido Tent

Member
Joined 2001
TentLabs.com
havar said:
I know it's an old thread, but maybe...

Now I've got one of these CD-players to tweak to death... just for the fun.

I've also got a no-name XO-unit from Asia, but I can't find out how to do the "trick"...:rolleyes:

The original XO has three connectors, and I've never seen that before. Not that I have lots of experience, but anyhow...

If you can help me, please do...:)

All the best!
Click to expand...

the middle leg is likely to be grounded

did the Asians specify the jitter ?

best
 
H

havar

Member
Joined 2007
Thank you for replying!

I can't remember if they did, but when I bought this it was a DIY-set, without the XO itself. I also bought a TCXO-unit to make the set complete. I intended to use this set in an old TEAC, but I never got that far...

OK, possibly ground in the middle, but the two other pins then..? The unit I've got is just like most other units, with powercord, ground and signal. Usually one does remove one or two caps, plus the old XO, and then mount the new kit. On this player I cannot identify which parts to remove, and it seems like the two pins on each end of the original XO is conneted to two different pins on the chip/IC underneath the PCB.

If I can provide a good drawing and/or pictures (or even better, the service-manual), would it be possible to get some further help..?
 
G

Guido Tent

Member
Joined 2001
TentLabs.com
havar said:
Thank you for replying!

I can't remember if they did, but when I bought this it was a DIY-set, without the XO itself. I also bought a TCXO-unit to make the set complete. I intended to use this set in an old TEAC, but I never got that far...

OK, possibly ground in the middle, but the two other pins then..? The unit I've got is just like most other units, with powercord, ground and signal. Usually one does remove one or two caps, plus the old XO, and then mount the new kit. On this player I cannot identify which parts to remove, and it seems like the two pins on each end of the original XO is conneted to two different pins on the chip/IC underneath the PCB.

If I can provide a good drawing and/or pictures (or even better, the service-manual), would it be possible to get some further help..?
Click to expand...


this may be of help

http://www.tentlabs.com/Products/cdupgrade/xo2xo3/assets/XO23mounting.pdf

best
 
M

mace1337

Member
Joined 2005
Whoa, talk about resurrecting a old thread.

I haven't been modding this thing very much, I moved on to other things, a few years back I really didn't take the time to complete projects, and I still have tons of 90% complete stuff sitting around waiting to be completed.

Anyway, I did end up adding a SPDIF output, by just connecting the aforementioned TX pin to a TOTX-something toslink transmitter.

The one I used was already buffered, so all I had to do was to tap off some 5v and GND somewhere and connect the TX pin to the TOTX module and I was set.

I think I have some pictures, I'll dig them up if anyone's interested.
 
H

havar

Member
Joined 2007
mace1337 said:
This is the only one I could find.

It ain't pretty, but it works perfectly!

http://i16.tinypic.com/549t7oo.jpg
Click to expand...


Thanx! I think it was very pretty..! ;)

Maybe you can remember where you got the parts as well?

The opamp; is it AD8620, or another? As I've dismanteled my unit totally, I cannot measure the voltage over the opamp. I do know that the 8620 can take only 27 volts (not 32V as OPA2604), so if the voltage is low enough I can change the opamp before I put it all together again.
 
M

mace1337

Member
Joined 2005
revintage said:
Remember I have one in the closet. Why bother with additional OP-amps? It must be better to take the signal via a couplingcap directly from the LSI. The level is probably lower but the std 2V is seldom needed.
Click to expand...

That's not a bad idea actually. I might try that.

Again, I did these mods 2,5 years ago, and I've learned alot since then. It's acutally kinda fun to look at this old mod of mine, since it shows how I did things back then and how differently I'd do them now.
 
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