The Adcom GDA 600 modification thread

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  • FTGVFTGV Posts: 3,654
    edited June 2010
    sm88 wrote: »
    I thought the link that George provided was $50 for a pair of them, so it would actually be two of those sets?
    Since the OPA627 is a single opamp the adaptor must be used to get two of them into the dual opamp config. needed for the 600.So each adaptor assembly contains a pair and two pair are required.
  • george danielgeorge daniel Posts: 11,992
    edited June 2010
    I don't have any complaints at all. I am comfortably satisfied with it--I know there was some chatter about too much bass or something like that,,I tried to hear it on mine,,I could not find it though,,now with the regs,it just seems/feels like it's gotten a tad more musical,,kinda zippy,detail in spades,and the bass is tight,certainly not bloated. Looking back,it's been a very rewarding and worthwhile project.I think that I can finally say that I'm done with this one.In retrospect, I discovered how musical the auricaps can be in some gear,with that said,it would be innaresting to hear them in the Adcom,but I'll live with the sonicaps.One last thing--if you own one of these,,you will never understand what you are missing out on if you do not perform this mod,as it truly transforms this into a whole 'nother animal.Not to mention we have a "resident expert" Fred,who responds quickly--and has yet to steer me wrong,and I say that with the utmost respect,as this man must have the patience of Job,,, after all,,he deals with people like me.;)
    JC approves....he told me so. (F-1 nut)
  • heiney9heiney9 Posts: 24,124
    edited June 2010
    Yeah, it was me who thinks there is more bass and frankly there is almost too much IMO at times. I have been having a heck of a time getting things dialed back in. My old favorite tubes are out of the picture now because there is too much high end detail with those and the dac mods.

    I have 4 pairs of these and they are very expensive; Valvo Hamburg made 6201 gold pins and Telefunken ECC801S. I'm back to Philips/Mullard based tubes to get a slightly rolled off high end to ever so slightly tame the detail in the high end.

    Actually a pair of 1958 Raytheon 6414 black plate, 3 mica w/ "D" getter are sounding absolutely fabulous. Before the upgrade I thought these were just a little too soft up top now they sound great w/ nice bass control and a very lush midrange.

    It's a shame about the Valvo 6201's and the Tele ECC801S, between those 4 pairs of tubes I have over $300 invested and I'm not sure I can use them anymore. I have a pair of MIT Shotgun S2 speaker cables coming (replacing my current MIT Terminator 2's) so I'm sure that will upset everything I've put in place recently and I'll have to re-evaluate everything :D:p. Part of the love/hate thing with this hobby.

    As a side note I replaced the very cheap stock switching power supply on the Squeezebox WiFi server I use with the Adcom dac, with a Bolder Modded ELPAC power supply. The ELPAC is a brick type linear power supply made for computers. Bolder adds hexFred rectifiers, Panasonic and Blackgate caps, a much beefier cable with the proper female plug as well as a beefier power cable. They also disable the 12V section of the PS. All I can say is I'm floored at the difference it makes. Simply floored!!!!!

    I'll borrow a phrase from Madmax.............EVERYTHING MATTERS!!!! The difference is very apparent. I've spent a lot of time listening to 3 different very familiar songs over and over and over plugging/unplugging the stock switching PS vs. the modded ELPAC. I am simply blown away. This hobby never, ever, ceases to amaze me.

    I listened for 4 things specifically...........1) instrument and vocal placement both depth and across the front plane of the sound stage . 2) extension of bass notes and decay of bass notes. 3) decay especially of cymbals and sympathetic vibration of stringed instruments. 4) for anything prominent that wasn't as apparent with one or the other power supply.

    The ELPAC won all these specific tests with the 3 familiar songs everytime and without a doubt. Biggest thing I noticed was even more separation of instruments and vocal, the decay on the cymbals was to die for and bass didn't seem like it hit a wall suddenly, it extended a tad deeper but more naturally rolled off (decay). I noticed a tad better clarity which I think has to do with a slightly less digital, edgy sound. Much less congestion with the ELPAC.

    George, if you find a way or a source for Auricaps that will work in the Adcom let me know............I'm very fond of Auricaps. I'm half thinking about adding them to the high pass of my 1C's when I tear them apart to put Larry's rings and Mortite everything.

    Sorry for the long post but I have spent quite a bit of time listening to the main rig primarily evaluating the Dac mod............I love it and would highly recommend it to everyone. My minor complaints can be remedied by tube rolling and next up for me after I get the MIT Shotguns in place will be room treatments. I admit I have a pretty live room and that contributes to some of the issues I'm having

    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 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
  • FTGVFTGV Posts: 3,654
    edited June 2010
    ,, after all,,he deals with people like me.;)
    Nonsense George it's a pleasure helping out one of the good guys like yourself,and I in turn appreciate your generosity in sending me the fabulous cable and connectors(which have'nt arrived yet).
  • george danielgeorge daniel Posts: 11,992
    edited June 2010
    FTGV wrote: »
    Nonsense George it's a pleasure helping out one of the good guys like yourself,and I in turn appreciate your generosity in sending me the fabulous cable and connectors(which have'nt arrived yet).

    waaaaaaa--- yes I know-- all in good time,, all in good time,, they'll be there soon.:)
    JC approves....he told me so. (F-1 nut)
  • FTGVFTGV Posts: 3,654
    edited June 2010
    waaaaaaa--- yes I know-- all in good time,, all in good time,, they'll be there soon.:)
    Yep it takes a 1.5-2 weeks so I should see em this week.
  • george danielgeorge daniel Posts: 11,992
    edited June 2010
    FTGV wrote: »
    Yep it takes a 1.5-2 weeks so I should see em this week.

    Hmmm,,, raised an eyebrow with that wire eh?
    JC approves....he told me so. (F-1 nut)
  • FTGVFTGV Posts: 3,654
    edited June 2010
    Hmmm,,, raised an eyebrow with that wire eh?
    Sorry not sure of the question?
  • george danielgeorge daniel Posts: 11,992
    edited June 2010
    Brock,,since I have never mastered the multiquote,here goes,, after my Adcom mod,,I was re-thinking my tube selection in my Belles,,as it's typically dark sounding, so I put some JJ goldpins e somethings(12au7 type)to liven it up,,, enter the Adcom,,,not wanting to roll more tubes,,I popped 4 Clarity MR series caps in it(go figure),blame it on the heat,,,so I'm kinda' in the same boat as you are,,and since we never get out of the boat,,he,he,,I might just roll some RCA cleartops back in,,just listen to us,,lol.God,,I love this hobby and the folks that come with it.


    Think I'll change something.


    Never get out of the boat.
    JC approves....he told me so. (F-1 nut)
  • george danielgeorge daniel Posts: 11,992
    edited June 2010
    FTGV wrote: »
    Sorry not sure of the question?

    My attempt of sayin',,,Innaresting wire ain't it? :)
    JC approves....he told me so. (F-1 nut)
  • FTGVFTGV Posts: 3,654
    edited June 2010
    My attempt of sayin',,,Innaresting wire ain't it? :)

    Ah gotcha,it sure does and I'm anxious to give it a try.Thanks again.
  • davide256davide256 Posts: 50
    edited June 2010
    Relief, got the replacement burson regulator, all is now working fine, voltages where they should be, no sibilance. Does anyone know, how good are the resistors used in the DAC? Was thinking about replacing the stock resistors closest to the analog output (530, 531) and a few others. I'm actually impressedwith the stock ones, measured a couple of pairs, the ohm values are spot on but I have no clue who made them..
  • FTGVFTGV Posts: 3,654
    edited June 2010
    davide256 wrote: »
    Relief, got the replacement burson regulator, all is now working fine, voltages where they should be, no sibilance.
    Excellent.
    Does anyone know, how good are the resistors used in the DAC?
    They look like regular .25 watt 1% metal film's like Roedersteins or the Yageo's available at Digi-key.
    Was thinking about replacing the stock resistors closest to the analog output (530, 531) and a few others.
    While I'm skeptical replacing a couple of resistors will make much of a difference, if you are going through the effort then you might want to try Caddock MK series precision metal film's or Vishay's bulk foils.
  • heiney9heiney9 Posts: 24,124
    edited June 2010
    Probably going to be awhile until I have time to install the new Burson rectifiers. Is there a way to test them outside the circuit. With davide256 having a defective one I don;t want to get stuck in a couple months when I finally install them.

    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 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
  • FTGVFTGV Posts: 3,654
    edited June 2010
    heiney9 wrote: »
    Is there a way to test them outside the circuit.
    To test the regulators you would need a dual voltage power supply.
  • george danielgeorge daniel Posts: 11,992
    edited June 2010
    Brock,,just do like the rest of us did and pop em' in there and experience a few moments of anxiety;)
    JC approves....he told me so. (F-1 nut)
  • george danielgeorge daniel Posts: 11,992
    edited June 2010
    JC approves....he told me so. (F-1 nut)
  • FTGVFTGV Posts: 3,654
    edited June 2010
  • Poee7RPoee7R Posts: 903
    edited June 2010
    Ive emailed the guy selling that dac, but I believe sm88 is trying to work out a deal on it. If he doesnt, Im gonna jump.

    Also, just got the mods done on mine and playing the first cd as I type this. No smoke yet, and both channels are going. Definitely a veil removed, most definitely. Bass is at another level, great mod so far and only 10~ mins on it. Cant wait til everything warms up and things break in.

    Also modded my speakers with new xover component's a few weeks ago, so lots of break in gonna be needed. But such a difference so far.

    Fred, George... you guys rock. Thanks for the guidance and confidence. First class all the way.


    Dave
    Once again we meet at last.
  • george danielgeorge daniel Posts: 11,992
    edited June 2010
    pic's we want pics or at least a descriptive overview of the mods--sounds like you stayed in the boat ;)
    JC approves....he told me so. (F-1 nut)
  • FTGVFTGV Posts: 3,654
    edited June 2010
    Good stuff Dave.I was wondering if you had yet set hot iron to that 600 of yours.Did you get the regulators installed as well?
  • george danielgeorge daniel Posts: 11,992
    edited June 2010
    FTGV wrote: »
    Good stuff Dave.I was wondering if you had yet set hot iron to that 600 of yours.Did you get the regulators installed as well?

    damn,,I like that,,, "set hot iron to it"
    JC approves....he told me so. (F-1 nut)
  • Poee7RPoee7R Posts: 903
    edited June 2010
    Ill shoot some pic's once I install the reg's.

    I held off on installing them just to see the difference it would make.

    As far as mods, I did the opa's and adapters, Sonicaps, Relcaps, Panasonic's w/metal stacks for the opa's resevoir, Nichicons, Muse and Panasonic's in the ps. Pretty much everything in this thread with the exception of the regs, which im figuring a week or two before I install. Hell may be tomorrow with the patience I have.

    And yes Im in the boat, with two oars thankfully. Talk about being nervous when I plugged it in haha.


    Dave
    Once again we meet at last.
  • Poee7RPoee7R Posts: 903
    edited June 2010
    I must mention, the solder sucking pump deal, was great for oh i dunno... the first 6 or so pumps, then it didnt get hot enough to melt the solder. I ended up using a wick, which wasnt so bad. The solder points arent that small, so it worked well actually. All the time involved is in removing parts, installing was a breeze.

    George that solder worked great, Ill have to order some, almost out with all the mods Ive been doing lately.

    Also If anyone else in interested in doing this mod I have left over metal stacks and Panasonic 120uf 25v that George graciously sent me, and Ill pass them along, just send me a pm and Ill getem out to you.


    Dave
    Once again we meet at last.
  • george danielgeorge daniel Posts: 11,992
    edited June 2010
    Great to hear thar Dave,,congrats on the mod.
    JC approves....he told me so. (F-1 nut)
  • FTGVFTGV Posts: 3,654
    edited June 2010
    Poee7R wrote: »
    I held off on installing them just to see the difference it would make.
    Good idea.
    Talk about being nervous when I plugged it in haha.
    I know that will it be exhilaration or agony feeling well.:)



    Atleast you didn't need your fire extinguisher.
  • george danielgeorge daniel Posts: 11,992
    edited June 2010
    Okay-- last pic's before I button her up--anything else to be done?
    BTW--this is the original mod version,I think I'll name it "In the Boat" ;)
    JC approves....he told me so. (F-1 nut)
  • FTGVFTGV Posts: 3,654
    edited June 2010
    ... before I button her up--anything else to be done?
    Other then maybe upgrading the RCA con's to some nice Vampires (or similar) then it's time to sit back and enjoy the fruits of your effort.
  • george danielgeorge daniel Posts: 11,992
    edited June 2010
    somehow,,I knew you were gonna say that,, should I get pcb mount or chassis,,;)
    JC approves....he told me so. (F-1 nut)
  • FTGVFTGV Posts: 3,654
    edited June 2010
    somehow,,I knew you were gonna say that,,
    hehe
    should I get pcb mount or chassis,,;)
    Chassis mount,then just use some short lengths of hook up wire.
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