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  1. #481

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    Quote Originally Posted by SCompRacer View Post
    Wait, I have one! I hope your pics turned out better than mine.....
    That one looks quite artsy, actually.

    Well, after a few(ish) months of foot-dragging I finally made it over to master tradesman SCompRacer's house to start my soldering apprenticeship. I even had most of the parts needed for the mod! I'd been thinking about it for so long I was certain that I had all my caps in hand, but found out at the last moment that I was missing a handful (The 2200uF Nichicon FGs and the 470uF Panny FCs) for the power supply. As such, the full modding will be done in two parts.

    What I did bring to the modding party was a Hakko 808 desoldering device, which has a trigger-actuated pump that removes solder through a hole in the iron's tip. It's a pretty nifty tool, but there were still several holes in the PCBs that weren't easily willing to be cleaned out. Rich has a patient hand, fortunately, and the mod went smoothly if slowly.

    The main difference in our approach compared to the previous documentations (especially those of George and Brock) was how we installed the two "local power supply reservoir" caps for each opamp: Both George and Brock mounted the two 120uF Panny FCs on the underside of the board. Please read and view the description/pictures of Brock's posts 115 & 116 on page 4 of this thread to see how they mounted these caps. I decided to try to do the same task in a different manner, one which Fred (FTGV) suggested would work as well in words/pictures in post 248 of page 9 of this thread. At the time the soldering iron was hot, I was actually working from a months-old recollection of the pictures from that post as the forum disappearing-photo bugaboo was still in effect. The key thing (just as with the other method) is to make sure that the polarity of the two 120uF caps is correct with respect to pin #4 (neg) and pin #8 (pos) of the opamps.

    Here's two shots of the analog board: The first half-completed, the second after completion.






    So how does it sound? Well, in a word it sounds great. Right off the bench it sounded really, really good and I've had it running for 80+ hours and my rig sounds better than it ever has before. I'm super happy to have done this and I'm looking forward to completing the job with the last few power-supply caps that I now have in hand. If replacing them makes additional audible improvement, well, I guess I be that much more happy!

    Special thanks to all those that have made this possible: Rich for his workshop, experience and steady hand (and for razzing me at every opportunity until I committed to a date to get this done), George and Brock for documenting well both how to do this mod and for making it clear how pleased they were with the results; and finally to Fred, for sharing your knowledge and insight--your generosity is noted and appreciated!

    I'll snap a couple pics of the other board when I get around to completing it--don't hold your breath, school starts this coming week!

    Jay

  2. #482

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    No drunk post (regretablely) using phone big thumbs small keys and sometimes to lazy to edit typo's. LOL sorry bout that chief. Will be less lazy in the future!
    Main Rig:
    Krell KAV 250a
    McIntosh MC 2120 bi-amped
    Into JBL L123 drivers
    Rane external crossover.
    MIT exp 1 ic's
    Perreaux SA33 class A preamp
    AQ kingcobra ic's
    ADCOM GDA 700 DAC ( MODDED)
    YAMMY CDC-665
    Marantz 6100 tt w/pickering XV-15/625E cart.
    Monster HTS 3600 power conditioner
    POLK RTA-12C'S W/ RDO194 TWEETS, clarity ESA caps mills risistors (full mod)
    MIT exps2 speaker cable

  3. #483

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    All hail Jay! All hail Jay! Thanks for the kind words but you did great! I've read about them Hakko's, but using it makes me want one to replace my spring operated solder sucker. One handed, trigger control action. Love the tone of the pump changing when you have a clean, cleared out hole in the PCB.

    Some of them solder joints reminded me of working with the RoHS lead free solder. The stuff just didn't want to flow completely out of the hole in the PCB. We ended up adding more solder and having another go with the Hakko 808.



    I didn't hear it before but it was a great sounding modded DAC in the retro rig downstairs and in the main rig upstairs!
    Last edited by SCompRacer; 08-18-2012 at 01:24 PM.
    Make yourself necessary to someone. Ralph Waldo Emerson

    Salk SoundScape 8's
    Krell KRC-HR Class A Pre w/ Reference Phono
    Krell Class A KSA-250
    Harmonic Technology Pro 9+
    Squeezebox Touch / Welborne Labs PS / I2S Out Mod
    Denon 3910 w/I2S/DSD Out
    Twisted Pear Buffalo III Dual Mono ESS Sabre32 DAC
    Sennheiser HD650
    Heavy Plinth Lenco L75 Idler Drive
    AA MG-1 Linear Air Bearing Arm
    AT33PTG/II & Denon 103R
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  4. #484

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    well, as i posted, it's back i had some lengthy sessions friday and saturday..it's a huge improvement! like going from a redbook cd to a well-done re-master! it is not sutble! i was pushing some serious current into my 2btl's and i think my ears were the weak link;) the bass now has incredible slam and depth!that's on all recordings...not just when it feels like showing up, like before;) the drum sounds are great! snares sound like snares....you can almost se the wires in the snare drum...pianoes sound better than ever...and the SDA???? holy schnikeys! active alive and all over!! this is a must do upgrade! thanks to george daniel for this thread and for doing the surgery! i couldn't have done it! the parts he sent back are TINY:)

    mike

  5. #485

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    Pretty serious upgrade, eh. It's been so long since I did mine that obviously it still sounds fabulous but I forget what the stock unit sounded like by now. It would be nice to compare the stock unit again.

    All I know is I grin from ear to ear with my rig. Finally have things dialed in where I like them as far as cables, tubes and gear, etc.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

  6. #486

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    with the stock unit, i thought i'd reached the pinnacle of what my system could do...it was depressing when i took it out of service to send to george...veiled, digital and lifeless..now, there's things jumping all around the room!

  7. #487

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    The Adcom dac's were very, very good for their day especially the BB PCM-63 chipset. Add a modern, better Op-amp and better caps in the signal path and beef up the PS section with new caps and Viola', you have a superb sounding updated DAC that sounds excellent, for a fraction of the cost of something comparable, new.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

  8. #488

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    Great job Rich and Jay.

  9. #489

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    Quote Originally Posted by sda2mike View Post
    well, as i posted, it's back i had some lengthy sessions friday and saturday..it's a huge improvement! like going from a redbook cd to a well-done re-master! it is not sutble! i was pushing some serious current into my 2btl's and i think my ears were the weak link;) the bass now has incredible slam and depth!that's on all recordings...not just when it feels like showing up, like before;) the drum sounds are great! snares sound like snares....you can almost se the wires in the snare drum...pianoes sound better than ever...and the SDA???? holy schnikeys! active alive and all over!! this is a must do upgrade! thanks to george daniel for this thread and for doing the surgery! i couldn't have done it! the parts he sent back are TINY:)

    mike
    Took me long enough Eh Mike?-- I'm glad that you are happy with it.
    JC approves....he told me so. (F-1 nut)

  10. #490

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    well worth it George! Thank you!

  11. #491

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    Dangerboy (AL) just bought a GDA 600 so I bumped this for him.

    Still interested in Jay's and Mike's thoughts now that you've had some serious time with it.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

  12. #492

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    H9, it's still a must-do upgrade...it hasn't 'worn on me', the effect of the upgrade, that is...see post #484, that sums it all up..thanks

    mike

  13. #493

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    I'm still exceptionally happy I both a) got the DAC (thanks, Dave!) and b) did the George/Fred modding (thanks, Rich!). When I first got it, I could toggle between my CD player's analog outs and the Adcom via my preamp's remote, and the sound via the modded DAC was clearly better--quieter background, more spacious & airy soundstage, and more... Now that I've upgraded my preamp to the Manley Shrimp, I've lost my ability to toggle back and forth, but I'm still offering the Adcom pride of place in my rack. Super happy with my current sound.

    I promised some months ago I'd add a shot of my power supply board once I got the Nichicon FGs soldered in, so I'll take the opportunity to do so now...


  14. #494

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    Quote Originally Posted by agfrost View Post
    I promised some months ago I'd add a shot of my power supply board once I got the Nichicon FGs soldered in, so I'll take the opportunity to do so now...

    Kewl! Good job Jay! It looks and sounds great!
    Make yourself necessary to someone. Ralph Waldo Emerson

    Salk SoundScape 8's
    Krell KRC-HR Class A Pre w/ Reference Phono
    Krell Class A KSA-250
    Harmonic Technology Pro 9+
    Squeezebox Touch / Welborne Labs PS / I2S Out Mod
    Denon 3910 w/I2S/DSD Out
    Twisted Pear Buffalo III Dual Mono ESS Sabre32 DAC
    Sennheiser HD650
    Heavy Plinth Lenco L75 Idler Drive
    AA MG-1 Linear Air Bearing Arm
    AT33PTG/II & Denon 103R
    Shunyata Hydra (Original)
    NHT B-12d subs
    GIK Acoustic Treatments


    CP Showcase

  15. #495

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    congrats!
    JC approves....he told me so. (F-1 nut)

  16. #496

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    Hi guys!
    Sorry for wakening this thread up :-)
    Life goes on and I've just got my GDA-600. Actually I like it's sound, but I'm mad about mods.

    I've ordered OPA627 and going to order caps for replacement.

    Read all 17 pages carefully. Everything is clear except .1 bypass film caps.
    May be there is name for it? I can't get which one to order.

    Appreciate for your help.

  17. #497

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    They are Panasonic V series stacked films. Digi Key part# http://www.digikey.ca/product-detail...P4525-ND/13790

    When/if installing try to keep lead lengths as short as poissible.

  18. #498

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    Thanks!

    I've unsoldered original OpAmps.
    Installed Dip8 socket and have tried 2 OpAmps: LM4562 and AD8599.

    LM4562 sounds too sharp and flat, but very dynamic. Didn't like it actually.
    AD8599 is very good, but it sounds just like original Adcom 7AA OpAmp (which I like a lot BTW).

    I also biased OpAmps into class A.
    Just soldered 3,3 kOhm resistor to 1 and 4 leg of socket, and another 3.3 kOhm resistor to 7 and 4 leg.
    Seems like it made OpAmps sound more tight.

  19. #499

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    Gl with the mod, did my 700 and have been thrilled with the results, my tech did a 600 also for a friend and is was fantastic. Big diff. Enjoy
    Main Rig:
    Krell KAV 250a
    McIntosh MC 2120 bi-amped
    Into JBL L123 drivers
    Rane external crossover.
    MIT exp 1 ic's
    Perreaux SA33 class A preamp
    AQ kingcobra ic's
    ADCOM GDA 700 DAC ( MODDED)
    YAMMY CDC-665
    Marantz 6100 tt w/pickering XV-15/625E cart.
    Monster HTS 3600 power conditioner
    POLK RTA-12C'S W/ RDO194 TWEETS, clarity ESA caps mills risistors (full mod)
    MIT exps2 speaker cable

  20. #500

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    Quote Originally Posted by kind View Post
    I also biased OpAmps into class A.
    Just soldered 3,3 kOhm resistor to 1 and 4 leg of socket, and another 3.3 kOhm resistor to 7 and 4 leg.
    Seems like it made OpAmps sound more tight.
    There is already provision for a resistor or optionally a fet for biasing the stock op-amp into class A.I don't have a schem handy so not sure of the value.3.3 k seems low and may be pulling excessive current through the opamp's output stage.

    The OPA1602 also looks like an interesting option.It's an SMD part so an adapter would be required.

  21. #501

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    I don't have a schem handy so not sure of the value.3.3 k seems low and may be pulling excessive current through the opamp's output stage.
    Neither do I. :-)
    OpAmps are warm but not hot. So current seems to be ok.
    15V / 3300 Ohm = 0,0045A.
    Diyers experiment with lower and higher values.

    The OPA1602 also looks like an interesting option.It's an SMD part so an adapter would be required.
    I'll keep that in mind, thanks.
    AD8599 is SMD as well. I soldered it to extra dip8 socket. In fact I don't have skills in that, so that was funny :-)

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