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Advice for Naim CDX2 with problems

P

Pedro D

Member
Hi All,
I also posted this in audio section, but maybe better here. I have a Naim CDX2 (first model, no digital output) that a few months ago started with a big diference in volume between the channels. I took it to the shop where I bought it (2nd hand), a well known place for audiphile gear in Lisbon. After a few weeks they told me that they could not diagnose the problem and that the unit had to be sent to Naim UK, with a shipping cost of at least €200 on top of whatever problem Naim would find (maybe). Following the advice of another friend that works in the area, and to avoid the cost and damage risks associated with shipping to the UK, I resorted to another shop here locally Lisbon. They fixed the problem by changing the 2 Burr Brown PCM 1704K. Initially, only 1 was defective, but the other also broke while they were trying to fix the first one so they end up changing both, at a cost of around €300 total.

So now both channels are playing at the same volume, which is great. However, the volume is now much lower than before this intervention. To have the same output levels (perceived, by listening) that I had with the pre-amp (Linn Kolektor) at 50-55% of total volume, I have now to to put the preamp volume at 75-80%. Also, I sense a lot more bass and less highs than before, which I can also try to correct in the Kolektor, but for sure something is still wrong. I opened the unit for inspection and I could see one of the DACs that was substituted and this is a Burr Brown PCM 1704J, not K as the ones that were previously in the unit and that I still have. I could find that J and K are classifications of the dynamic range of the dac with K being better than J, but could that justify should a big difference in volume level ? Is there any way to change the voltage regulation of the PCM 1704J to correct the perceived differences in sound ? Should I send it to Naim UK and ask them to put 2 new Burr Brown PCM 1704K ? Ask Naim UK to install digital out (bypassing the internal DACs - I would have to buy a separate DAC which I do not have at the moment) ?
Any advice is welcome, thanks.
 
Are the replacement DACs fitted exactly the same as original? Sounds to me like they’re not…
 
The fitted dac was BB PCM 1704J, because BB PCM 1704K is not available anymore. Even Naim is now fitting BB PCM 1704J, and according to them the difference is negligible. I took a picture of the motherboard with the BB PCM 1704J, but I could not figure out how to paste it here.
 
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Hmm - is it a single DAC chip for both channels, or one per channel? At the end it can only be a faulty DAC chip, a different fault introduced by replacing the DAC chips or a completely unrelated fault (& I don’t really believe in coincidences :)).

I’m not familiar with the PCM DACs - Id start downloading data sheet and checking voltages around the chips.

oh, there’s a FAQ on how to post photos - you need to host them outside of PFM and link to them.

good luck
 
It is 1 dac chip per channel. They are mounted on each side of the board, I think.
I sent the picture of the mounted chip to Naim UK. They said it is impossible to be sure but it seems real.
I will try to put the picture here too.
 
I’m not familiar with this chipset, but solder of the 1704 looks fine. My comments would be;
- c152 by the left hand opamp looks like it may have been touched at the top by a hot soldering iron, I have killed such capacitors in the past by doing same
- why is the left hand opamp socketed? Naim never used chip sockets to my knowledge. How many opamps are there it total - are those 2 just for this DAC chip, or do they serve the other one too

If the low volume and distortion is affecting both channels, it must be something common to both channels (unless they are indeed fake chips you had fitted*) - I’d check the voltages at the opamps as a first step - should have plus/minus 12 or 15v feeding each one - check opamp data sheet for which pins (I can’t see model numbers of opamps in your photo).

* To rule out fake 1704s, I’d either find a reputable source and buy new again, or check https://www.dutchaudioclassics.nl/the_complete_d_a_dac_converter_list/ for a donor player with same chips and use them (a complete bastard of a job as they’re surface mount chips…unless you have the right tools)

But a question - why not just return it to the place that swapped out the 1704s? It came back faulty, they should fix it?

good luck!
 
Thanks Dowser,
I have low volume, but not distortion. In fact, if in the Linn Kolektor preamp I increase the volume to 80% and treble to Max (7), the sound is similar to what I remember.
But still not the same. In fact, I now prefer to listen to Airport Express (internal DAC), even streaming (from Radio Paradise). If I play an Apple Lossless file, then is even better. It should't be. Naim CDX2 is supposed to be very good cd player.

Meanwhile I got some advice form the "official" Naim shop in Italy. They think the 1704J installed are good (from the pic), but there should be something else wrong. They say it would have been much better to change the whole board. That is what they usually do in these case (for around €600). They also change the tantalum capacitors in the analogue output stage. They predicted these new 1704J will also break soon, because other components in the board are old and that should have been the reason why the old ones broke.

Yes, I emailed the shop where the repair was done, but got no reply in the last 3 weeks.
 
Dowser said:
- c152 by the left hand opamp looks like it may have been touched at the top by a hot soldering iron, I have killed such capacitors in the past by doing same
Click to expand...

Me too, just a slight touch with an iron (it happens) and mine was s/c. i wonder if that is it?
 
Pedro D said:
Thanks Dowser,
I have low volume, but not distortion. In fact, if in the Linn Kolektor preamp I increase the volume to 80% and treble to Max (7), the sound is similar to what I remember.
But still not the same. In fact, I now prefer to listen to Airport Express (internal DAC), even streaming (from Radio Paradise). If I play an Apple Lossless file, then is even better. It should't be. Naim CDX2 is supposed to be very good cd player.

Meanwhile I got some advice form the "official" Naim shop in Italy. They think the 1704J installed are good (from the pic), but there should be something else wrong. They say it would have been much better to change the whole board. That is what they usually do in these case (for around €600). They also change the tantalum capacitors in the analogue output stage. They predicted these new 1704J will also break soon, because other components in the board are old and that should have been the reason why the old ones broke.

Yes, I emailed the shop where the repair was done, but got no reply in the last 3 weeks.
Click to expand...

low volume is one thing - needing to adjust treble something completely else :)

Replacing the PCB will fix it, and probably means you’ll get the higher grade 1704 DACs as well…but it’s a bit extreme and not very eco-friendly! And the Naim stores statement is misleading at best, but to be expected unless they have access to a decent engineer - basically, fixing someone else’s mess is never a nice task.

I had a quick look online - CDX2 is a 2 PCB design, with the output stage on a separate PCB. It looks to me like those 2 opamps after DAC are shared between both channels. Therefore if that is a solder burn mark on c152 it could easily be the cause of your fault. I’m still concerned by the socketed opamp though! If it were me, before spending another €600 on it, I’d at least test the cap to see if it is short circuit - do you have the skills to open it your self? And a meter?

Where in Italy are you? If you could get it to me in Zurich I’d be happy to take a look.

Richard
 
I am in Portugal, not Italy. I got advice from Naim shop in Italy via email.
I can open the unit but I don't have a meter or other tools.
Even Naim is using the 1704J since the K run out.

c152 is the silver/red cylinder, right ?
 
Pedro D said:
I am in Portugal, not Italy. I got advice from Naim shop in Italy via email.
I can open the unit but I don't have a meter or other tools.
Even Naim is using the 1704J since the K run out.

c152 is the silver/red cylinder, right ?
Click to expand...

ah, OK, sorry. Yes on c152. Any electronics repair place should be able to open machine and check/change it, but maybe you’re better biting bullet and replacing whole board (whole boards probably still use best chips), but remember Naim themselves would not swap the whole board for this repair, they’d find what’s wrong. Mind you, that is an assumption - I hate repairing stuff someone has been inside of beforehand..you never know what you’ll find (like, why is that opamp socketed?!).
 
I finally got the information from the repair shop that the PCM1704J were bought from ASWO, a reputable german company in this area, they say.
 
After a couple of weeks, the repair shop call me saying they managed to repair the cdx2.
Did not tell me the specifics, but the output was at 400 mV and now is at around 2 V.
I will pick it up Friday.
 
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