Adding SPDIF and other mods to Yamaha CDX 480 - diyAudio
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Old 22nd August 2005, 01:57 PM   #1
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Question Adding SPDIF and other mods to Yamaha CDX 480

Hello all, this is my first post so bear with me please

I got a Yamaha CDX 480 for free a few days ago, and I did not like the fact that it does not have a coax digital out,
so I was searching for CD player mods and i stumbled across here, been lurking for a few days but registered finally to be able to see the attachements

Anyway, i've been busy digging up datasheets on the various chips on the board, and i've found the most important ones, some i cant find though.
This CD player has a LSI that takes care of most of the functions needed for playback and DAC. The LSI is a matsushita (did i get that right ) MN66271RAM.
I here is a picture from the datasheet:
Click the image to open in full size.

And the block diagram:

Click the image to open in full size.

My question is really this: if i want to add a SPDIF output to my machine, do i need to connect it to pin 6? (TX)
What pin should be used for ground? Or can i just use any ground point?

Would it be wise to buy a service doc for this player, or isn't it worth the 25-30 euro's ?

Also, I'd like to change the matsushita caps for either black gates or panasonic FC, which would be the sensible choice?

Last but not least: I'd like to change the opamps, the player has a
JRC/NJR 2068DD dual opamp for the main channels datasheet

I have a AD8620, a BB OPA2132, 2604, 2227 and a 2228.

which one would be best? I think the 8620, any idea's?

Lots of questions from this new user, thanks in advance for answering them
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Old 22nd August 2005, 06:27 PM   #2
tubenut is offline tubenut  South Africa
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The 9inherent tonal balance of this unit is such that I would probably use the 2604 op amp. I think it would suit best. Jm2c

Damping the chassis of this player and the typical PSU upgrades like soft recovery diodes and better caps.

I would not worry about SPDIF... I doubt the unit will make a great transport and I believe better results will be had modding and using what you have in the box.

If the unit has a toslink out you could pick up the spdif there and put it through a suitable RC network to make a co ax output if you must...

G
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Old 22nd August 2005, 06:55 PM   #3
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Quote:
Originally posted by tubenut
The 9inherent tonal balance of this unit is such that I would probably use the 2604 op amp. I think it would suit best. Jm2c

Damping the chassis of this player and the typical PSU upgrades like soft recovery diodes and better caps.

I would not worry about SPDIF... I doubt the unit will make a great transport and I believe better results will be had modding and using what you have in the box.

If the unit has a toslink out you could pick up the spdif there and put it through a suitable RC network to make a co ax output if you must...

G
Thank you for your reply,

The point is that i like to experiment with DTS cd's that I encode myself, so the need for a digital output is clear. The unit does not have toslink, if it had it would not be a problem because my receiver still has 4 toslink inputs unused.

The problem is that it does not have a digital output at all, and i thought about adding the output just for the hell of it , so could you or somebody else please confirm my thoughts of using tx as spidf? or do I need a special encoder or something?

Also, upgrading the caps with black gates may be too expensive, I thought panasonic FC's would be a nice alternative (low ESR and all).

About the opamps. i'll just put a socket in there (gold plated of course ) and see what sounds best.

This unit has a single 6800 uF 16v matsushita cap for the psu, among others, i was browsing thru the digi-key catalog and i saw that he panasonic FC 8200 uF was about half the price as the 6800.

I always thought that a bigger capacitance for the psu is better, is this right? if so, i'll just use the 8200.
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Old 22nd August 2005, 10:57 PM   #4
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Yes, pin 6 to a female RCA should work. You could put a buffer somewhere to protect the IC, but you should test it directly in a coax input to see if it's SPDIF(If not, you will not damage anything anyways).

If you use SPDIF, I don't think that changing opamps is really useful, no?

About panasonic FC, look at the original caps specs, Panasonic is matsushita so maybe you'll end up with the same caps. Putting a bigger cap in the PSU should work, just don't put a too big one(15000+ F)

Putting Schottky diodes instead of the current ones should help too.
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Old 22nd August 2005, 11:05 PM   #5
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Quote:
Originally posted by DragonMaster
Yes, pin 6 to a female RCA should work. You could put a buffer somewhere to protect the IC, but you should test it directly in a coax input to see if it's SPDIF(If not, you will not damage anything anyways).

If you use SPDIF, I don't think that changing opamps is really useful, no?

About panasonic FC, look at the original caps specs, Panasonic is matsushita so maybe you'll end up with the same caps. Putting a bigger cap in the PSU should work, just don't put a too big one(15000+ �F)

Putting Schottky diodes instead of the current ones should help too.
Thanks, thats what I wanted to hear,

about the opamp, i have opamps lying around anyway, i just wanna experiment a little, if i break it, it wont matter because the cd player was free.

I know matsushita is panasonic, however I'm pretty sure these caps arent panasonic FC's, those look very dissimilar (i have them in my mint headphone amp).

Do you think i can use a BUF634U for a buffer in there? I have it left over anyway.

TIA
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Old 23rd August 2005, 12:10 AM   #6
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If you judge it better than a 7407, then it's OK. A protection is useful only if an internal CDP or wire short occurs. Commercial SPDIF equpt. use optoisolators to protect themselves, so it can't damage the CDP.

I'm still not advanced enough to know if your buffer is OK but it's clock is a multiplier of 5 so it should be OK. Trying it is the best way to know IMO.
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Old 31st August 2005, 07:12 AM   #7
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well, took me a while (had to order browndog adapters) and after a big solder splash goofup on one of them

I just installed my dip socket and started to experiment with the different opamp, and i have to say: WOW, the 2604 is a great improvement over the NJR 2068DD, now im gonna try some different ones that are in my first post, thanks for all the help guys.
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Old 31st August 2005, 03:41 PM   #8
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You could try TI samples of some OPA2134.
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Old 13th September 2005, 06:04 PM   #9
popoing is offline popoing  Finland
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Quote:
Originally posted by mace1337
I just installed my dip socket and started to experiment with the different opamp, and i have to say: WOW, the 2604 is a great improvement over the NJR 2068DD, now im gonna try some different ones that are in my first post, thanks for all the help guys. [/B]
Have you tried different op amps yet? Have you upgraded caps?

I'm waiting results. I have Yamaha cd-player and thought I could do some modifications too.
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Old 13th September 2005, 06:42 PM   #10
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Quote:
Originally posted by popoing


Have you tried different op amps yet? Have you upgraded caps?

I'm waiting results. I have Yamaha cd-player and thought I could do some modifications too.
Heh, sorry my friend, i've been quite busy with my studies, so i havent been able to order caps (had to buy new books and all that )

But about the opamps, i definately hear improvement, im still in the process of selecting the final opamp that i will be using, but im leaning more and more towards the AD amp, i just like the sound of it.

I hear improvements in detail, and in placement, the sound seems wider too, but I sadly havent had the time to do extensive listening.

If i get the $$ for some nice pots, i'll post again
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