From: kucharsk@Solbourne.COM (William Kucharski)
Newsgroups: rec.audio.high-end
Subject: Making a Denon 2560 Level 1
Date: 11 Nov 1992 14:48:43 -0700
Organization: Solbourne Computer, Inc., Longmont, CO
Distribution: usa
NNTP-Posting-Host: 129.89.7.4
Originator: tjk@csd4.csd.uwm.edu


Well, I got enough responses that I thought a post was called for.

First, let me start by stating the obvious, that this voids your warranty and
gives you the chance to seriously damage your CD player.  This is called the
disclaimer:

The modification described below should only be attempted by those acquainted
with the safety and ESD procedures required when working with digital
electronics.  Even then, I in no way guarantee that anything stated below
works and don't claim that this mod won't cause your CD player to self-destruct
after 30 seconds of use.

Well, enough a** covering.  Let me state the second caveat, that this mod will
do you precious little good if you don't have a Wadia decoder or aren't
the type to go through some hell for what may (depending upon which decoder
you are using) be negligible results.

OK then...

Parts Needed:
=============
* Service manual for the player involved (or great confidence in your sleuthing
  abilities without a schematic)

* Capacitors:  An assortment of 5-470pf capacitors, all at least 50VDC and with
	       a tolerance of +/- 5%.  NPO parts are preferable.

* Soldering iron, 15-25 watts

* Either a Wadia D/A converter or a calibrated frequency counter good to
  50-80 Mhz with a 10 sec. gate and accuracy of +/- 1 part per million

Summary:
========
The Denon *560 players are driven by a similar chip in each unit (in the 2560
it's the CXD25000).  There are two pins on the chip, pins 53 and 54, which
are wired in a parallel configuration to a crystal running at 16.9344 Mhz
which provides the system clock for the unit and provides the basis for
generation of the clock for outgoing digital data.  The problem in the Denon
units is that Denon did not design the players to be level 1 transports and
thus did not specify the use of high precision (NPO) parts.  The upshot of
all this is that the 16.9344 Mhz crystal may be off by hundreds of parts per
million as it is simply trimmed by two known value capacitors.  Therefore,
depending upon crystal and capacitor tolerances, the clock encoded into the
digital output stream may be off by hundreds of parts per million as well.

(For more information on this, see John Shriver's EXCELLENT article, message
 ID <1drc7iINNl9r@uwm.edu>, "SPDIF jitter.")

A rough schematic for the appropriate section of the DCD-2560:

     |
     |
     *	pin 54  -----------------------------------
     |	XTAO	     	     ______		  |	Capacitor tolerances
C    |			  |  |    |  |		  |	are +/- .25 pf
X    *	pin 53  ----*-----|  |    |  |------------*
D    |	XTAI	    | 	  |  |    |  | 		  |
     |		    |        ------   		  |
2    |	    C212  _____       X200          	_____  C213
5    |	    5 pf  _____     16.9344 Mhz         _____  3 pf
0    |		    |                             |
0    |		    |                             |
0    *	pin 52  -*--*-----------------------------*
     |	Vss      |
     |		 |
     |	       ______
     |	       / / /
		   
The solution to the problem is to replace one of the capacitors trimming the
crystal in order to provide a more accurate crystal frequency resulting in
the generation of a clock signal with significantly less jitter.

The two hardest parts about this mod are detecting when you've got the capacitor
value correct and which capacitor you should change.  For the DCD-2560, the
second part is easy, it's C213.  For other players (or perhaps other 2560s)
you'll need to experiment with changing both C212 and C213, changing whichever
makes the biggest difference.

If you have a Wadia converter with a Level 1 chip, the solution is pretty
simple:  you can "shotgun" your way to the correct value.  Connect the digital
out from the Denon to the Wadia and play a disc.  Put your finger across C213
(skin provides a capacitance of approximately 10pf).  If this allows the Wadia
to "lock on," you know you'll need to replace the 3pf cap with a 10pf cap.  If
this doesn't allow the Wadia to lock, you should try holding increasing value
caps with their terminals in parallel with the 3pf cap (summing the capacitance)
until you achieve data lock.  The X-32 makes this particularly easy, as the
"44.1" LED will glow brighter as you approach the correct frequency, finally
glowing brightest when you achive data lock.  When this occurs, simply remove
the 3pf cap and replace it with a cap of the determined value.  Note that to
get some values you may need to insert one cap in place of the 3pf cap and
"piggy back" another cap in parallel across the pads on the back side of the
circuit board.

Where this gets difficult is if you don't have a Wadia converter.  Then you'll
need the aforementioned frequency counter and a way to monitor the digital
out of the Denon after having first stripped everything from the data stream
but the clock.  Unfortunately this isn't exactly trivial.  You'll basically
follow the same procedure, but you'll replace whichever cap makes a greater
change on the frequency counter and choose a value which minimizes the
jitter present in the clock stream.

Well, best of luck to any of you who actually try this; if you're curious my
player eventually required 16pf of capacitance at C213, but I know of a 3560
owner that needed to replace their 3pf cap with a 470pf, so don't give up if
you don't see results right away.  You'll know you've gone too far if the
CD player itself stops working, since obviously the CXD25000 chip will only
work if the crystal frequency is within a reasonable tolerance of what it
should be.
-- 
| William Kucharski, Solbourne Computer, Inc.     | Opinions expressed above
| Internet: kucharsk@solbourne.com   Ham: N0OKQ   | are MINE alone, not those
| Snail Mail: 1900 Pike Road, Longmont, CO  80501 | of Solbourne Computer, Inc.
| President, "Just the Ten of Us" Fan Club        | "Dittos from Longmont, CO"