Digital Drive: Re: Musical Fidelity X-24K DAC.... ? by bobwire

I've used my moded Cd67 as a front end on several DAC's. Wth all the mods it works well, and has all you want in a front end. I love those direct buttons. Without the mods however it only OK. Here are my mods if you'd like to use them. Good luck, bobwire

Changes to the Cd67 Oct.03, 1999
By Robert Noriega

OK, here we go. Those of you that received my short list of changes will find this similar with only a few additions. I have included pictures of my PC board as well. Study them the schematic and the parts layout carefully. The parts lay out is the most important. It shows the backside of the board and all components.
If you look at it carefully you'll see where the different sections of the player are located. You'll also see how ground and power are run. Those are what most of the changes are about, improving power and ground.
I'll try to break the changes into sections for you. It can be fun to hear how they effect the sound. With each set of changes you'll begin to hear the next even more clearly.
Just after I took the photos of the board and reassembled the player I was studying the board layout and I saw something I hadn't seen before. At the main processor (Q102) I saw that I hadn't gone as far as I might have in improving its power inputs. The 5volts comes in and is split into three, the +5, +5A, and +5B. From those three it goes through some chokes then to .047uF capacitors and into the power pins of the IC. See schematic "B" and you'll see there are five power pins on this IC (Q102). In the past I had changed C114, 120 and the caps on the +5V the feed this power to this IC. I hadn't done anything for the power inside of these inductors going to each pin. The Inductors are L101, 102 and R117, 118.
I now placed 47uF/10V caps across each of the .047 caps. This I was able to do from the top of the PC board by simply tinning the leads of the .047's first. Once tinned the leads from the larger caps soldered right in with no problem. The difference was remarkable! I have a new player all over again.
In resent weeks I had heard coloration in my system that I thought was my power amplifiers. I was wrong! It was the CD67 that I was hearing. This change took away that color and the sound is more open than before. After the change I spent hours listening to my CD's. Hearing what I hadn't heard before or just hearing it better. Never, have vocals been so good! Notes fade out forever!
WOW! I get excited just writing about it.
Like I said before here we go.

Power Supply:

Change to 4700uF/35V
C803, 804

Change to 4700uF/16V
C805, 806, 871

Remove components:

C659, 660
R655, 656

Replace with jumpers:

R651, 652, 653, 654
R613, 614, 615, 616
RD01, RD04
R501, 502, 503
R117, 118

Change to 1000Uf/16V:

C651, 652, 653, 654
C611, 612, 613, 614
C903, 904
C126, 155, 114, 120, 126
Note; C126 is located on the servo PCB.
Capacitors added to PCB: 47uF/10V
C115, 116, 117, 118, 119
Notes:
1. These are the ones I spoke of in the text.

2. Looking at the photos of the back of the PCB you'll note there are many little orange caps. These are .1uF caps added across every large cap I put in. I have never counted them I just put them in. I can't say I heard any difference with them in but I would never take them out!

Look closely at the PCB layout of the servo board. C126 is there as well as C121 and 124. C126 should already have been changed to 1000uf/16V. C121 goes into pin 8 of Q101. Pin nine (9) of Q101 is the HF output that we want to now bring out on a coax. This calls for cutting the trace coming from pin 9. The center conductor of the coax will solder to the pin and the shield of the coax will solder to the ground at the end of C121. Be careful not to short out pin 8! Next remove jumper U101 we will no longer need it. With the trace cut at pin 9 it will no longer be used so we will ground it. On the ground plane next to U101 scrape off the solder mask down to the copper underneath. Solder a short jumper from the unused trace to ground. Next, carefully add a second jumper across jumpers U104 and U107. This makes a better ground and power connections to IC Q101. Last place a .1uF across C126. We're done here for now.
The other end of the coax goes to the main board. We won't attach it until we're all done. This is because it a pain in the ass to separate the two boards after its connected!
Going back to the PCB layout of the main board find R105 that is next to J103 and C114. We want to unsolder the end that goes to J103. This end of the resistor will be left in the air and will be where we attach the center of our coax coming from the servo board. I tuned R105 around 180 degrees so that the coax would come in from the direction of the open space behind C114.
Further study of the layout will show you the places you can double up ground and power jumpers.

One thing I haven mentioned yet was that IC's Q605 and Q606 should have already been changed out for Analog Devices AD827 or Ad828's. I wouldn't use sockets, as these are unlikely to be changed again.
Next find jumper U200, C815, Q8111 (7805). From the layout you'll notice that this 5volt regulator supplies power to the DAC, CPU, and everything forward to the laser. We now want to use a separate regulator for the DAC. Notice all power to the DAC goes through jumper U200! Remove U200 and you have a perfect place for the new regulator.
With U200 out we take our new 5volt regulator and holding it so the leads are towards us and we can read the value (7805), the left-hand lead is the input lead. The center lead in ground and the right-hand lead is the output. We get out input voltage from the same place as Q811, in fact we'll connect a short wire right to the input pin of Q811. Bend the input pin of the new device into the air, then bend the ground lead 90 degrees about half way up its length. Cut a little bit off so the is a small foot made by the bend. This will get soldered to the ground on top of the PCB. The output lead goes through the hole that used to bring power to the DAC. Make sure you use the right hole! We want the one that connects with U203 and goes to the jumper at RD04. Solder the output lead in the hole and the ground lead to the ground plane. (Scrape off the solder mask first!) The wire we soldered to the input pin of Q811 now gets soldered to the input lead of our new regulator. Last we add a 1000uF16V to the input lead as well. From the layout you can see that both Q811 and our new device are feed from C813 which is kind of far away, so that's why we need the extra cap. Now the DAC has its own regulator!
Look at the photos and you'll see I added one more regulator on the bottom side of the board. This one feeds the front end of our player and leaves Q811 to feed only the CPU.
This calls for removing jumper U167. Notice in the photo how I used the input and ground pins of Q811 as my input for the new regulator! I had to use some tape to insulate the backside of the regulator as well. The output of this one goes to the trace where U167 used to be, next to R117. This device gives us regulation for the main processor.
The last regulator is for the servo PCB. This calls for once again the cutting of a trace. At J103 on the layout notice that the 5volts goes into this connector on a trace that tee's off from U182 and C114. On the layout you'll see where the 5volts goes into the eighth pin up from the bottom. We want to cut it lose from C114 and U182. Then attach a wire that wraps around to the topside of the PCB. On the topside we want to make a place for the regulator near where our coax and C114 are located. Bend the input and output leads in the air, then solder the ground lead to the board. Solder a pair of caps (1000uF/16V) to the input and output leads as well. The input of this regulator comes from the same input source as our other devices. A good place to pick it off on the topside of the board is at Jumper U268, located near C813.
The only thing left is to put in any extra .1 caps you feel like adding and extra jumpers across power and ground. In the photos you can see the ones I put in.
Something I haven't done but you might think about is matching components. For instance, the six 120P caps at Q107. These could be matched so they are all exactly the same value. The same might be done for the caps and resistors around the IC's Q605, Q606. These are all 120p, 10K and 27K. Match them all and you might gain a little more fine detail. By matching I mean the same value exactly: 121.7p means all are 121.7p or 10.13k all are 10.13k and so on.
Now, I wish to encourage you to do all this and anything else you might thing of that I haven't! I've loved this player and as of yesterday I love it even more! When you hear what it can do, you'll be like me and be pissed that they don't do it right to begin with! You'll also develop an ear for what the changes sound like as you do them (assuming you do them a few at a time.) this means when you hear a system that has this or that sound you'll know what's causing it!

Please write me and let me know how your baby is doing. OH, and please don't blame me if you find you need to upgrade the rest of you're system. I only had to do with the front end! Have fun and pass it on, who knows, maybe it will find its way all the way to Japan!

Sincerely, bobwire

News Flash! DVD's can get better too!

While I was poking around inside my DVD player I found out a few things. One, I couldn't just add caps to its power supply like I've done to everything else I own. The power supply won't even come up!
Two, I can get around this by using an inductor. I wound four one-inch ferrite cores with twenty feet of wire. These were then installed into the switching power supply of the Sony DVD player. There were four fuse-sistor's in the output of the supply, two for plus/minus 12V and two more for two kinds of 5Volts. I removed these fuses and installed my inductors in their place. You can also put the inductors in series with the fuse-sistors if you like. I didn't measure how much voltage drop this would cause, so you're on your own here. Then on the plus/minus 12V I changed the capacitors from 47uF to 1000uf. By the way, you can leave the fuses in by only lifting one end and putting the inductor in series with it.
The results of this change were not subtle! The sound now has bass and an image! Things were sorted out with more space around everything, not as good as my CD67 but much better. The video was improved as well! I watched The Lord of the Dance, before and after. The video was noiseless and had better contrast. Detail I hadn't seen before because it was blurred was now clean and sharp!
Switching supplies are noisy by nature and don't allow for much capacitance to improve the situation. The inductors I installed filter the noise out very well.
Winding the coils was no fun at all but it was worth the effort. It makes me wonder what else I own that could use some help? Maybe the VCR?
As a further upgrade this evening I added more capacitance to the DAC and output IC's of the DVD. I can't understand how they continue to be so CHEEP! Just a few more Uf's would make such a large difference. After tonight's changes the sound has gotten much better. I could almost live with it, almost. I'll keep after it until it comes around or I brake it! I ordered some sample AD828's in surface mount for the output stage. Stay tuned for a report when I get them.

Once again good luck, bobwire

PPS: the AD828's didn't work due to size! Ah, to bad.