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emperor 22nd April 2006 12:28 AM

Ah Njoe Tjoeb 4000 problem
Hi there

I have owned one of these fine TUbe output CD players for about 4 years now, all was well up until this morning and i would be very appreciative of any insights you may have. I bought a CD, that i played this morning and i could only hear the right channel.

Now stupidly I took the cover off thinking it was the tubes, that one had gone. So i got an old pair of Philips tubes that come with the CD player, and tried them, still no luck!.

on the control board and im no expert at these things, but there are 2 Burr brown opamps, set parralel to one another, i thought one of those might be the problem. There was also another small chip of the same size i think is the DAC chip. I took them out reseated them, changed them round , (only the opamps).

Maybe stupidly the wrong way round, the opamps have 8 pins 1- 4 5 - 8 I turned them round only because I forgot which way they went round. I usually do a little diagram before undertaking such work, but alas i didnt, fool!. Well the thing is it was the bloody Cd that was at fault. Overjoyed when I played my Meddle Album, In perfect stereo, was really happy. But to my horror... now at low levels i get a distortion sound and a slight ghosting of a high pitch sine wave around the 6th octave of a piano.

It cuts out after certain low passages break into higher volume. but ambient music is awash with this distorted tone. I know the tubes all work, I know the fuse is good, Im just wondering if i have damaged the opamps, or the circuit board.

heaven help me if i have , i have to send it back to holland to be fixed if its not a straight replacement

so guys any insight would be much appreciated


sbelyo 24th April 2006 03:46 PM

I don't own one but I could give you some pointers.

If you haven't already put your tubes that were working fine back in, do that.

If the opamp was in backwards you wouldn't get any sound, but if it's not seated in all the way or the legs are bent that may cause a problem.

The opamps that come with that player are the burr brown opa604 I believe. You can replace them with opa627-bp or opa227.

emperor 25th April 2006 05:27 PM

Thanks for your help Sbelyo,

yes spot on i now have a spare pair of opa604 as well, it seems that the opamps, are working as putting in the newer ones doesnt make no difference to the sound.

I actually have replaced the Opamps with some from Im thinking of the top of my head analogue solutions??. and it sounds better. (only for the sakes of soundstage Purposes, still have the same problem) I also have sourced a supplier of the DAC chips, as Its either the board thats not working properly, or i have damaged the DAC chip.

the tubes all work, light up!..2 sets

So i will find out hopefully soon, when the DAC chip comes from Thailand, If it works.

It does still work at mid to high volume, but as ever theres the sibilance and distortion of ambient peices, which Might be The DAC? If that gets put the wrong way round, which i did.

As i say im not a Amplifier DIY hobbyist, but im learning quickly a lot of do nots, any more insight about what could cause it??

Much appreciation

sbelyo 25th April 2006 06:03 PM

I see.. I didn't think that you removed the dac. I suppose that would cause a problem. Those types of chips (opamps too) have a half circle molded into on end of the chip. The socket will have the same half circle showing you how to orient the chip.

I always seem to like the Burr Brown chips rather than the Analog Device chips. The BB's are warmer to my ears. The AD's are more analytical or truer to the ear. I've replaced the opamp in my SACD player with an AD and I have mixed emotions about it.

emperor 25th April 2006 09:24 PM

Yes Im just hoping that it is the DAC. Thing is i usually do a diagram on paper how everything is orientated.

and contrary to my first post i, ahem did change the DAc round. I dont think i could sabotage it more if i tried

I usually can make modifications under instruction, and have fixed a few synths i own. But i buggered this up, hopefully not too badly.

Yes i know what you mean about burr brown, but this opamp sounded really punchy and detailed, its a DP27EP. I just thought i would buy a few that were compatible and this was the best, for my ears anyway.

sbelyo 26th April 2006 02:52 PM

Oh well... stuff happens. I think the dac should fix it.

emperor 28th April 2006 11:21 PM

:) i just hope so, been a week now since i contacted the manufacturers in holland, seems they take a 2 week exodus, and shut the factory down. So looking forward to the DAC from Thailand, i think it is.

I just looked inside my Rotel pre amp, it has about 4 opamps in their, you know what im thinking, "Without any prior clue what im doing", I could upgrade those opamps couldnt i??

What would make it sound better you reckon ?

sbelyo 30th April 2006 02:48 AM

What kind of chips are in there now?

emperor 3rd May 2006 05:18 PM

well theres a mixture.

on the left near the headphone inputs is a JRC 4556D

what seems off the tone controls is a Signetics NE5532AN

and then in the centre just off the volume switch is another one exactly the same

Now near what im sure is the phono preamplifier stage is 2 Signetic NE5534AN, and two TL071CP.

I have from trying different opamps in the Cd player, have these Opamps, spare

BB OPA604AP times 2

BB OPA2134PA " "

BB OPA2604AP " "

AD OP27EP IC " "

Would any of these be of good improvement over the stock ones?

A bit irritating but it wont let me upload the photo of the insides of the Amp:mad: , even though the file is 400KB??

starkeyg 30th October 2007 05:06 PM

Tjoeb opamps

Would add to the list of opamps to try the LME49710. Price is fair and so far I have been pleased with these in a couple of projects.


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