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Teac CD-Z500 cd player modding advice required

Discussion in 'd.i.y.' started by Chaggy78, May 3, 2014.

  1. Chaggy78

    Chaggy78 pfm Member

    Hi everyone,
    I have just acquired a really nice vintage Teac CD-Z500 cd player that uses two TDA1541A DACs, it sounds really nice in stock form but I would like to do some simple mods to get a bit more out of it like change the op-amps and install new capacitors.
    It uses 2x Mitsubishi M5238L op-amps in the first stage and also 2x Mistsubishi M5238L in the second stage nearer the output rca's, would there be a drop in replacement that would sound better than these ancient op-amps? I would need to buy an adapter though and solder the op-amps onto them.
    Also surrounding the 2x TDA1541A are many resistors which I find strange as there are usually capacitors surrounding them.
    If anybody has any idea's I would be very grateful thanks.
    I have uploaded a few pics of the dac board here:
    http://s1218.photobucket.com/user/Chaggy78/slideshow/Teac CD-Z500

    Many thanks everyone
     
  2. Chaggy78

    Chaggy78 pfm Member

    I just realised that they are not resistors surrounding the dac's they are axial capacitors but have no idea what type or value they are, would it even be worthwhile to upgrade these?
     
  3. davidsrsb

    davidsrsb pfm Member

    The M5238 is a 20V/us, 6MHz jfet opamp, so already rather better than a TL072

    Parts that are much faster than this don't like being on adaptors
     
  4. Chaggy78

    Chaggy78 pfm Member

    Thanks for the info david, very interesting. I have read that some people who modded this cdp used burr brown opa2604 x2 on an adapter but some also used opa2134.
    I was wondering if these would make a vast improvement over the M5238?
     
  5. Chaggy78

    Chaggy78 pfm Member

  6. davidsrsb

    davidsrsb pfm Member

    I think the cheap single layer pcb with no ground plane is the limitation here
     
  7. istari_knight

    istari_knight pfm Member

    Indeed. Unfortunately you can't make a silk purse from a sow's ear :(

    From a brief glance I would suggest upgrading the TDA1541 decoupling caps to some decent 100nF films, M5238 opamps are really bad... Fit LM4562 or OPA2134, snip the muting transistors, add local decoupling caps to the +/- opamp supplies [10uF-47uF tantalum or solid polymer], bypass output coupling caps or replace with MKP.

    Is it worth the effort ? Almost certainly not but it'll be fun & you might learn something so go for it.
     
  8. Chaggy78

    Chaggy78 pfm Member

    Thanks for the advice guys, I will have a go at some of the mods suggested by Istari. Despite being a single layer pcb it does sound quite amazing, it's not that far off beating my Naim CDi and that's no joke! It sounds very dynamic with lots of deep bass and is very natural sounding which is why I like it.
     
  9. Chaggy78

    Chaggy78 pfm Member

    I don't have a schematic and my knowledge is pretty limited, can you point out the muting transistors and which are the output coupling caps please?
    I was also wondering if it is possible to bypass the op-amps at all? Many thanks
     
  10. istari_knight

    istari_knight pfm Member

    Impossible to say for certain without a schematic. I would hazard a guess the coupling caps are C131/C231 & muting transistors are Q202/Q? - Whatever's next to 202.

    Losing the opamps isnt an option AFAIK, DAC's come in two flavours... Either I or V output... Voltage output you can replace the opamps with a simple RCR filter but current output requires the opamps for I/V conversion. You could always add a tube output stage ala Lampizator: http://www.lampizator.eu/lampizator/TDA1541 corner/TDA1541.html

    All good fun :D
     
  11. Chaggy78

    Chaggy78 pfm Member

    I'm just about to upgrade the op-amps to LM4562 to start with and see how it sounds after, will report back.
     
  12. Chaggy78

    Chaggy78 pfm Member

    The new LM4562's are now installed and it makes quite a big difference, the sound is clearer and more detailed which is nice. Not sure if I will try any other mods yet but thanks to everyone for the help and advice.
     
  13. istari_knight

    istari_knight pfm Member

    Its amazing quite how muddy those old Mitsubishi opamps sound isn't it ?
     
  14. Chaggy78

    Chaggy78 pfm Member

    Yes very true, they did seem to block a lot of the detail and did sound muddy like you mentioned. I'm really happy with the sound quality now, big improvement.
    Would you recommend removing the muting transistors and coupling caps?
     

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