[ServinginEcuador]

Head-Fi'ers,
Has anyone done any modifications to one of these CDPs? I read a lot about the LC Audio clock replacement, but not sure how much difference it would make in this CDP. I am looking at replacing the OP amps with some better replacements, so does anyone have any recommendations for replacing the output NE5543N OP amps?? Any other mods or recommendations, other than buy a different player please, would be greatly appreciated!!!

Thanks in advance!!!


Lord Bless,
doug p.

 

[puppyslugg]

Quote:

...any recommendations for replacing the output NE5543N OP amps??

I assume you meant NE5534 opamp(?) I just modded my amc cd8b and replaced the TL072's with ad8610/20 with ccs class A bias. If your opamp is a 5534, the ad8610 should work. I would take a look at the psu, too.

One other thing, you should try to get a schematic from Cambridge for you unit.

 

[Budgie]

I know this is not related to your thread, but did you know Quito has a live web cam- http://www.earthcam.com/southamerica/ecuador/quito/

I would (also) recommend you bias the opamps into class A. You could do that to the current opamps, as a quick improvement in sound, while you wait for the new opamps to arrive.(I guess I am repeating what puppyslugg allready said, so consider it as "I second his statement")

 

[ServinginEcuador]

Puppyslug,

Thanks for the response. All i can say is: DUH!! I guess I should have my eyes checked, as the amps are indeed 5534 not 5543 as I had originally written down and posted. This makes it so much easier to find replacements as LC Audio sells drop-in op amps. I am interested in how you switched the bias of your op amps to class A, can you post a little on how you did that? Resistor swaps, cap swaps, etc? Also, how do you rate the swap you did with the new ad8610 amps? Big change, little change, etc. I really don't want to spend more money, but if another $100 in op amps makes a big difference, I am very willing to do so!!!!!!


Budgie,

Thanks for the web cam site and for seconding puppgslug's post!!! My wife and I were looking at it to figure out just where it is located. The trees and park area that predominates the foreground is called Parque Carolina. It is in the northern part of town, with three American style malls surrounding it!! Beautiful park! (OBTW, love that graphic of the smiley face pounding his head into the wall!!)


Lord Bless,
doug

 

[ServinginEcuador]

After doing some looking around, and price shopping, I decided to order a set of AD825's modules from www.upscaleaudio.com They had the best price, $27/pair as opposed to $26.90 PER op amp from www.diycable.com DIY Cable is the main importer of these, and yet they are almost exactly twice as expensive as Upscale Audio. Upscale offers these replacements op amps for the AH! Tjoeb Cd player, and don't normally advertise them as stand alone items for sale!!

I will post some impressions as to how they affect the sound after I get them in and burn 'em in for the recommended 100 hours that Upscale has on their web site. Should make a pretty big difference, and for $92 worth of amps, they had better!!!! This hobby is getting just a bit TOO expensive. Must......stop.....buying....stufffffffff!!!!!!!!! !!


Lord Bless,
doug p.

 

[puppyslugg]

ServinginEcuador,

Read tangent's 'Biasing the Op-Amp into Class A':

http://www.tangentsoft.net/audio/meta42/tweaks.html

The ad8610 w/class A, compared to the tlo72, was a signigicant change: better extension, inner detail, very smooth and airy. Another possibility would be the ad843, a ppl favorite. I've been listening to the ad843 in my Corda and it is very close. Though it may not have quite the detail and air of the ad8610, but not they are bad at all. It's a bit more forward which may sound better with certain music, particulary if you listen to rock, pop, etc. One other advantage the ad843 has is it can run on 15v psu, whereas the ad8610/20 is limited to 13v max. May save you the trouble of having to modify the psu. And they do not require an smd adaptor.

As budgie suggestested, biasing the ne5534 class A would help and will tie your over til your chips arrive. Actually, if you have a couple of (approx.) 4k resistors, tie one end to the output (pin6) and the other end to the negative supply (pin4). Not the best way of biasing class A, but it should improve the sound of the 5534.

Take a look at the input couping caps. If they are mylar films, I would use polypropylene caps. At the output, if there are electrolytics, consider replacing with low esr types, along with the film bypasses. Resistors are one of the last thing I would be replacing. Not that it doesn't make a difference, the return is small compared to opamp, cap changes.

In the psu, things to consider:

-replace diode bridge with shottky's with film bypasses
-beef up the input and output caps with the fattest ones you can fit with low esr types and use bypasses.

And if budgie make a recommendation, I would pay attention. He has a good idea of what he's doing.

 

[antness]

puppyslugg,

the AMC CD8B uses TL072? I thought it was just NE5534....anyway, I used to have the complete service manual for that CD player when I owned it. Complete schematic and parts list! I'll try to find it. You might find it useful if you don't have it anyway.

I might have to get another one of those CD players and mod it..

 

[puppyslugg]

Hi antness,

The amc cd8b uses tlo72's. I just removed them from my second cd8b yesterday.
Quote:

I used to have the complete service manual for that CD player when I owned it. Complete schematic and parts list! I'll try to find it. You might find it useful if you don't have it anyway.

Please find it!! I've been trying to get a copy from AMC for a long time now. They are really tight a**es about selling me one. Now that the cd8b are out of production, I thought they would. No such luck.

Anyway, if you can find your copy........

Quote:

I might have to get another one of those CD players and mod it..

I was lucky and found one here at the marketplace(?) a couple of months ago. No HD, SACD, etc. just a good, solid performing unit...better after 'mods', of course.

 

[ServinginEcuador]

AAAAAAAGGGGGGGGGHHHHHHHHH!!!!! Bought the chips, bought the chip puller, got the CDP open, and lo and behold, the chips are soldered in!! Now I have to have the PCB removed, desolder the chips, and have some good IC sockets put in their place to facilitate the chip changing!! Man, the nightmare just won't end.


Lord Bless,
doug p.

 

[puppyslugg]

How did you know what chips were in there without opening the unit?

 

[ServinginEcuador]

Puppyslug,

Didn't look close enough when I opened the thing. It looked like they could be lifted out from the PCB, but when I looked closer to lift out the Ic's, not a chance - they're soldered directly to the PCB. But, on the positive note, I found a good professional company here that is going to remove the 5534s and solder in 4 sockets for about $25. Now I can pull and replace these things to my hearts desire. Easily! I am looking at trying some Burr Brown OPA627s next. That is unless I like the sound of the AD825s.


Lord Bless,
doug p.

 

[Dev]

Wow, cdp tweak - mine pet subject

.

I've make thread in russian forum when I tweak my Sony cdp-ce335 device. It's "lamer guide" for all (and I asked there lamerly too) and it is enough popular in .ru internet.
http://forum.ixbt.com/0012/019317.html
So, anybody can translate this great thread to english?

Yeah it's just a joke

. I can give you some advices and some directions of cdp tweak, if you want... Internal parts and sheme design of our cdp (my Sony and your Cambridge) maybe different, but main principles of cdp tweak is similar.

 

[ServinginEcuador]

IC sockets in place, AD825s burning in, and Burr Brown OPA627APs on their way!! After about a week of burning in these different op amps I will post some listening results to see how they compare against each other. Hopefully this is all worth the money I am inversting!!!!!!


Lord Bless,
doug p.

 

[ServinginEcuador]

For anyone with a multi meter and a Cambridge Audio D500SE: what is the voltage supplied to pin 4 of the output 5534 op amps?? It would help to know as I don't want to overbias the output stage by putting in too small of a resistor across pins 4 and 6.

The article found here: http://www.audioasylum.com/audio/twe...ges/31186.html talks about making sure I don't more than double the output current, so I need to know the input voltage to the op amps so I can figure out what size resistor to put across them.


Thanks and Lord Bless,
doug p.

 

[ServinginEcuador]

For those interested in running a Burr Brown OPA627 in this unit, I would reconsider and try another chip. At first everything went well once I inserted these chips. But whenever a really loud or dynamic passage would hit, the sound would get so "scratchy" and noisy sounding that I had to turn off the CDP to get it to come back. After the second time of this happening I pulled these chips out and put my AD825s back in - and haven't had a problem since.

Seems I read somewhere online that these chips are voltage hungry, and tend to get unstable when used in a circuit with too little voltage. Seems this proved totally true in my case.

Next up is an attempt to try some AD843s and see how they sound. So far I am very impressed with the sound of the 825s, so I really look forward to trying out some of the more dynamic and highly rated 843 chips!!!!!


Lord Bless
doug p.