Onkyo DX C390 6-CD changer - First CD DIY project - diyAudio
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Old 15th April 2011, 10:46 PM   #1
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Join Date: Apr 2010
Location: In my own world
Default Onkyo DX C390 6-CD changer - First CD DIY project

So, yesterday, I bought my first CD player, to start off in the realm of CD player modding. I had a CD changer at my parents' home, which was a Philips CDC741, which had inspired me to do some digging into quality CD changers for upgrading. I wouldn't think my parents would be happy with a CD player that's missing it's cabinet because of some components sticking out of it . Also, I wouldn't be able to compare the DAC's influence because it doesn't have S/PDIF outputs, just analogue.

Anyway, I bought the Onkyo DX C390, a 6-CD changer, because it was the only CD changer I could find on internet for a good price for quality (well, that is, I read some articles about good sounding CD changers, don't know about the credibility though ).

Once bought, I opened it and checked all the chips inside. And surely, when doing the first basic measurements to the supply lines, I already blew something up . It should not be too hard to fix, though, as now I have some understanding of the inner workings of the unit. I downloaded the service manual, which I found hanging somewhere around the interwebs, for ease of understanding what the hell is going on with all the wires and the copper traces running about an acting all spidery (those Japanese sure like them star grounds!).

Now I noticed there are a few things that can be upgraded. A preliminary list of thing I want to do is as follows:
  • Analogue:
    • Opamps: Now some jelly-bean 4580 from New Japan Radio Company, will probably upgrade to National Semi's LM4562
    • Mute transistor: Will have to go, no non-linear/signal dependant capacitances in my output buffer!
    • Amplifier topology: not much room to do anything there, but this thing looks pretty nasty... Other than that, I might want to change it to inverting in stead of non-inverting for better distortion performance. To Be Pondered Over.
    • Longish cable from DAC to amplifier: Possibly some ferrite beads to reduce common-mode noise/EMI, if needed at all.
    • Supply: New transformer and +/-15V shunt regulators, those poor opamps are starving with only +/-7V.
    • Filter caps: Change to better quality electrolytes, or polypropylene in case of manageable size (and price).
  • DAC:
    • Well look at that: a Wolfson WM8726. Ought to be decent as I heard good things about Wolfson from a dear friend of mine...
    • Supply: Will start off to upgrade the now installed 2905 to a +5V shunt reg.
    • Clock: Will be a Tentlabs XO2 or one of its siblings for low jitter.
      I'm wondering why the MCLK goes through the LC78683E first before going to the DAC, I'll need to think that one over. Luckily, if I want to, there's a non-connected resistor that connects it directly to the DAC. That also seems the case for the I2S lines coming from the CXD3068Q. TBPO.
    • Reference capacitor: May upgrade this to a better electrolyte cap or a polypropylene film cap.
  • S/PDIF output:
    • TBPO
Well, that's about all I think I can manage to actually pull off. Things like transport suspension, CD chip modding, etc. are now a bit out of my league and are therefore outside the scope of this project.

Pictures of the unit and charts of measurements (in a before/after fashion for most of aforementioned steps) will be posted here as the project progresses.

This ought to be a fun ride for a first DIY project of this type.

Cheers,

Lord Le Brand
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Old 17th April 2011, 11:36 AM   #2
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Join Date: Apr 2010
Location: In my own world
It seems that the defect I've caused is more severe than I thought. The IC that handles all the buttons and the display is blown in such way that the input of the stand-by button is shorted to ground . I have already sent an email to Onkyo and a service company, specialized in Onkyo, for information on purchasing a new chip or display PCB, but I don't know for sure if that's going to yield a workable solution. To make things worse, all of the Onkyo service stations are in the Americas, a great distance away from here...
I'm keeping my fingers crossed
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Old 17th April 2011, 01:52 PM   #3
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Join Date: Apr 2010
Location: In my own world
It seems that the defect I've caused is more severe than I thought. The IC that handles all the buttons and the display is blown in such way that the input of the stand-by button is shorted to ground . I have already sent an email to Onkyo and a service company, specialized in Onkyo, for information on purchasing a new chip or display PCB, but I don't know for sure if that's going to yield a workable solution. To make things worse, all of the Onkyo service stations are in the Americas, a great distance away from here...
I'm keeping my fingers crossed
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