Marantz CD63 & CD67 mods list

[Fidelity Audio]

whoops me bad

Sorry miss read it. lol

[6h5c]

Brent,

You got me thinking though....

Do all the Audiocom regs have max. 24V input, including the 12 and 15V types?
If so, it might be a good idea to lower the +/-12V windings a bit, to the original 17V. This should still enable the use of a two-stage regulator.

My CD63 measures almost +/-24V before the 12V regs in stop mode. That's a bit high compared to what the manual says. Funny thing is, my CD67 measures correctly.

Ray.

[Fidelity Audio]

Ray

Yes they are all +24 or -24 volts.

My KI measures 20V to 21V same as the manual to the regs

I am running the +/- 20V direct to my op amp regs.

But if you calculate 17.6 volts * 1.4 = 24.64V (un loaded)

[6h5c]

There's some voltage drop over the diodes, and some ripple maybe, but it gets close to 24V
But fortunately there's always some current draw....
So I guess we'll make these windings about 17V then

Regards,

Ray.

[6h5c]

How about using this configuration to get a quote?
What do you think Michael?

Ray.

[DJNUBZ]

Ok well I took the cover off of my cd 53 and I recognize a few things. This first time through I am going to start with the mutting trasistors and the DC blocking caps. From looking at www.diyparadice.com it looks like I can disable the mutting trasistors by jumpering the 100ohm resistors. Is this right? if so will it sound the same as pulling them out? If I have to pull them do I just pull them out or do I have to reconnect anything?

I have a similar question about the DC ouput caps, can I leave them in and just jumper their leads or do I have to pull them out and up a jumper in?

I also am curious if anyone has considered moving the opamps into class A.

http://tangentsoft.net/audio/opamp-bias.html

Would the tecniques on this site work on these op amps?

When I replace the opamps will these be a straight drop in?

http://cimarrontechnology.com/index....PROD&ProdID=31

[poynton]

Originally posted by DJNUBZ
................. From looking at www.diyparadice.com it looks like I can disable the mutting trasistors by jumpering the 100ohm resistors. Is this right? if so will it sound the same as pulling them out? If I have to pull them do I just pull them out or do I have to reconnect anything?

I have a similar question about the DC ouput caps, can I leave them in and just jumper their leads or do I have to pull them out and up a jumper in?

I also am curious if anyone has considered moving the opamps into class A.

http://tangentsoft.net/audio/opamp-bias.html

Would the tecniques on this site work on these op amps?

When I replace the opamps will these be a straight drop in?

http://cimarrontechnology.com/index....PROD&ProdID=31

Hi.

We do seem to have stuck on the design of a tx for the '63. However, that is a good thing as many threads seem to deteriorate into a farce of name-calling, etc. Something positive may result from this thread!!!

Remove the muting transistors - disabling will not result in any improvement.

You could jumper the caps but it would be better to remove them too. Use the holes in the pcb for the replacement jumper.


BrownDog adapters are dropin replacements.



I did ask the question re: Class A, earlier in the thread (around page 24 I think) but it has not progressed. Perhaps now the Tx issue is almost resolved, we can pick up on it.?

Andy

[6h5c]

Hi Andy,

I think the configuration for the tranny is almost set. We should be able to close on it the coming week. Maybe it's a good idea to set up a new thread for this one, and start ordering if we reach, say, ten pieces? I don't want to wait another six weeks or so before anyone else turns up that's interested, I don't know how you feel about it?

I also want to experiment with class-A opamps, but I haven't had the time yet (too busy with some transformer...)
The simplest way is putting a 3k6 resistor on the output to -12V, like described, to make the opamp draw a few mA.

I read the other thread that you started, about HDAM in class-A, good idea. Should be possible if you change the DC setting of the two FET's at the output. You'll have to separate the gates and create a voltage drop between them.

Regards,

Ray.

[poynton]

Hi.

I wait with baited breath for a price on the Tx. It can be offered in the Trading Post section if it will reduce the price (to the thread starters contributers?)

I really want to try Class A myself. Unfortunately, I recently moved house and I just cannot get to anything in the garage/workshop!!!!!!!!!!!!!! I even bought a bunch of 2N5484 fets (although in retrospect CR Diodes may be neater.).

On the subject of the HDAM ( which I don't want to go into too deeply here since I have started the other thread), I just feel that Marantz were on the right lines with a discreet 'opamp' but should have gone Class A !! The FET output is pure Class B !! I have been thinking of going ALL discreet along the lines the circuit shown here :-

http://ultranalog.com/cdenhancer/sacdenhancer/

But like I said .. at the moment...


Andy

[6h5c]

Well...

I couldn't imagine that Marantz made a class-B HDAM....

so I couldn't resist taking a look at the datasheets of the FET's, and it seems that you're wrong

The FET's are of the 'normally-on' type, so with an Ugs of 0V there will be a current flowing, somewhere between 6 and 12mA (?) for the BL version. Fweew....

Regards,

Ray.