The Adcom GDA 600 modification thread

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  • heiney9heiney9 Posts: 24,108
    edited April 2010
    I'll let Fred answer about C124 & C125. I just followed his and George's lead on this. Maybe in my write up I mis-labeled them as 25v. THIS is why I wish we still had the *edit post* feature. If it is wrong I'll try to get a mod to correct 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 | 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: 3,644
    edited April 2010
    He,he,,Fred,, one day you are just gonna have to show me how to do that one
    Now that I can see their actual physical placement in H9's pics I could give more specific directions.:D.
    Guys,,if you own one of these,,you owe it to yourself to do this mod
    I'll be keeping a eye out for a 600 to add to my collection.
    a BIG THANKS to FRED
    Your very welcome,I'm glad I could help.
    dacboy wrote: »
    Hey all! I have a question. In the power supply side, Is there a reason why you did not replace (C124 &C125) with 125uF 25v Panasonic FCs?
    No real advantage doing so and being as they are located ahead of the regulators and depending on the raw DC voltage the 25 volt rating may not be sufficient.
    Also, I see that these caps are listed as 35v and you replaced them with ones rated at 25v?
    If you are refering to the 120 uf 25v caps that replaced the 10uf's, then the 25 volt rating is plenty as they are at the outputs of the 5 volt regulators.
  • dacboydacboy Posts: 23
    edited April 2010
    No real advantage doing so and being as they are located ahead of the regulators and depending on the raw DC voltage the 25 volt rating may not be sufficient.If you are refering to the 120 uf 25v caps that replaced the 10uf's, then the 25 volt rating is plenty as they are at the outputs of the 5 volt regulators.

    Thank you again FTGV!!
  • george danielgeorge daniel Posts: 11,989
    edited April 2010
    SDA2mike-- I'm sending you some caps--please pass on any xtras to the the next polkie that needs any--good luck--keep us posted as to the final outcome,,,and get ready to exercise self control when you hear it.;)
    JC approves....he told me so. (F-1 nut)
  • sda2mikesda2mike Posts: 3,151
    edited April 2010
    SDA2mike-- I'm sending you some caps--please pass on any xtras to the the next polkie that needs any--good luck--keep us posted as to the final outcome,,,and get ready to exercise self control when you hear it.;)

    thanks george! that's why i quit drinking....i never heard me no self-control!:D
    i'll keep you posted!:cool:
  • george danielgeorge daniel Posts: 11,989
    edited April 2010
    he,he,, how does that line go,,Doc Holiday,, "self control got the best of me":)

    Oops,, gotta stay focused,, I'm looking for another one to mod,I'll keep you posted and add to the thread.
    JC approves....he told me so. (F-1 nut)
  • FTGVFTGV Posts: 3,644
    edited April 2010
    I'm looking for another one to mod...
    I hope we don't get into a bidding war for one.:D
  • george danielgeorge daniel Posts: 11,989
    edited April 2010
    If I find one that is reasonably priced--it's yours,, that's the least that I can do after all of the help and support that you have given.:)
    JC approves....he told me so. (F-1 nut)
  • FTGVFTGV Posts: 3,644
    edited April 2010
    If I find one that is reasonably priced--it's yours,...
    Thats very generous of you George but if you find one go ahead and snag it.I have a number of other projects that I would like to try before tackling a 600.
  • heiney9heiney9 Posts: 24,108
    edited April 2010
    I haven't had a whole lot of time lately to critically listen, but the bass just seemed to come around a couple days ago. Initially it was a little lean and now it's full and extended. I am doing something an audiophile shouldn't do; I added new power cables to all my gear so who knows if it's a combination of cables and the dac mod or just one or the other. I probably realistically have about 30-40 hours on the dac mods.

    Wish I had an unmodded 600 to make a comparo.

    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!
  • heiney9heiney9 Posts: 24,108
    edited April 2010
    So who else has done this mod? I know have about 60-70 hours on the new parts. One word that comes to mind is hyper-detail. I'm not saying if that is a positive or negative, just very, very detailed. Not sure how I feel about it. I definitely wouldn't say it's analog sounding like the stock unit leaned. Again I need more listening time to formulate if it's too detailed. Not harsh, or fatiguing, etc. just very detailed.

    The sound stage has improved hugely in both depth and width and space around instruments is superb. Decay and attack has improved as well.

    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!
  • daboyzdaboyz Posts: 4,913
    edited April 2010
    Um,hello?:confused:;)

    heiney9 wrote: »
    I haven't had a whole lot of time lately to critically listen, but the bass just seemed to come around a couple days ago. Initially it was a little lean and now it's full and extended. I am doing something an audiophile shouldn't do; I added new power cables to all my gear so who knows if it's a combination of cables and the dac mod or just one or the other. I probably realistically have about 30-40 hours on the dac mods.

    Wish I had an unmodded 600 to make a comparo.

    H9
    HT - Polk Lsi9, Lsi7, LsiC, Marsh A200s, B&K ST-1430, Pioneer Elite BDP 62FD, Marantz SR7008, Martin Logan Dynamo, NHT CS-10, Mogami 3103 speaker wire, Mogami 2534 IC

    mini HT - Samsung 46" 3D TV + 3D Blu ray player, HK AVR 254, Infinity SL40, Audioengine B1
  • ALL212ALL212 Posts: 1,116
    edited April 2010
    daboyz wrote: »
    Um,hello?:confused:;)

    Didn't you read the "We don't like Dave" thread? :p
    Aaron
    Enabler Extraordinaire
  • heiney9heiney9 Posts: 24,108
    edited April 2010
    daboyz wrote: »
    Um,hello?:confused:;)

    Hi ;). So you will let me borrow your 600 for a few weeks? Actually we were thinking in an upcoming RAS meet having a DAC listening session. The PS Audio, Stello, modded an unmodded Adcom's, LITE, etc.

    If we can all be quiet for a few hours while we listen :p

    H9

    P.s. My prior post doesn't mean to imply that the mod isn't desirable, just putting some impressions out there. My impressions aren't fully formulated yet and may take a few months of listening for the final verdict. So far I LIKE what I hear.
    "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!
  • daboyzdaboyz Posts: 4,913
    edited April 2010
    ALL212 wrote: »
    Didn't you read the "We don't like Dave" thread? :p

    At least my dogs love me.:D
    HT - Polk Lsi9, Lsi7, LsiC, Marsh A200s, B&K ST-1430, Pioneer Elite BDP 62FD, Marantz SR7008, Martin Logan Dynamo, NHT CS-10, Mogami 3103 speaker wire, Mogami 2534 IC

    mini HT - Samsung 46" 3D TV + 3D Blu ray player, HK AVR 254, Infinity SL40, Audioengine B1
  • heiney9heiney9 Posts: 24,108
    edited May 2010
    At just around 100 hours of break-in this thing has really settled in. It sounds fantastic. I can't get over the detail and soundstage is just huge. Bass extension is nice as well especially at lower levels.

    If you have one of these and have the skills this is really a no brainer and worth every penny.

    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!
  • george danielgeorge daniel Posts: 11,989
    edited May 2010
    Good to hear,,guys,,of all the mods that I have ever performed,(not that many),this is the most significant,sucessfull ,bang for the buck tweak that I have EVER done (thanks Fred,again) If you own one of these,,you owe it to yourself to get this one done.It is that good.Rock on.:)
    JC approves....he told me so. (F-1 nut)
  • heiney9heiney9 Posts: 24,108
    edited May 2010
    Ok, the final verdict is this modd is fu*king fantastic. My rig has never sounded better. Better dynamics, detail, bass, clarity, microdynamics and all still leaning towards the analog side of the scale. Biggest improvement has been the sound stage, noticeably deeper and wider as well as better delineation between instruments and vocals.

    Listening to Rod Stewart's - Stay w/ Me last night I kept hearing a cymbol crash way back in the mix behind the speakers.............never heard that before. Well, I've heard the crash before, but mostly in the same plane as the rest of the cymbol's. It's this kind of stuff, which you have to notice and listen for, where the largest improvements and enjoyment comes from for me.

    Highly, highly recommended. The work is a bit tedious because of the wave soldered board and smaller parts. But, with patience and some soldering knowledge and the proper tools it's not too bad.

    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!
  • dacboydacboy Posts: 23
    edited May 2010
    Just received the first batch of parts! FineGolds for the power supply and I'm going to try the Amtrans AMCH Series Film & Foil .pf caps for to replace the Wima (C545 & C542) Will prob do the same to (C553,C552) too. And then Sonicaps (Gen II) for (C561,C560,C544,C543, C540,C541) Oboy! Oboy! :D
  • heiney9heiney9 Posts: 24,108
    edited May 2010
    dacboy wrote: »
    Just received the first batch of parts! FineGolds for the power supply and I'm going to try the Amtrans AMCH Series Film & Foil .pf caps for to replace the Wima (C545 & C542) Will prob do the same to (C553,C552) too. And then Sonicaps (Gen II) for (C561,C560,C544,C543, C540,C541) Oboy! Oboy! :D

    Cool :cool:. Why C553, C552? Do you know something the rest of us don't? That wasn't part of the initial mod. Please share your ideas :)

    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: 3,644
    edited May 2010
    dacboy wrote: »
    ... Will prob do the same to (C553,C552) too.
    The stock caps (C552,C553) used in the feedback loop of the I-V convertor appear in the posted pics to be ceramics.Upgrading this pair to films certainly won't hurt but I wouldn't expect big gains.IMO the Lions share of improvements comes from the use of a better opamp.Are you planning to use the OPA627 also?
  • dacboydacboy Posts: 23
    edited May 2010
    Hey all! Well, FTGV corrected me on what I thought was a feedback resistor, but was part of the deemphsis circuit. I was planning on doing some resistor upgrades, then after spending a lot of time looking at the board and schematic I kept trying to pick and choose. Since I was replacing the resistors, I might as well do the parallel caps too... So, I've decided to replace everything. I think FTGV is right, the opamps will make the biggest difference, my plan is probably an act of diminishing returns. But I've heard of people getting good results from upgrading the feedback resistor. So we will see. I do plan to use the OPA627, but later. Since the resistors will cost me bit, and the OPA627s are the biggest expense, I'm going to use some OPA2132's that I have left over from another project. I'm using some in a JVC xl-z1010 and I'm really happy with them in that application. No doubt, the OPA627 is better, that's the consensus. I will add those last once I get a feel for the sound. That's my plan at this point.:D
  • dacboydacboy Posts: 23
    edited May 2010
    Kim wrote: »
    I took my mod a little further and removed coax 1 input inductor (L-200) and also replaced input coupling caps (C-220 and C-312). I am still scratching' my head in disbelief and enjoying the tunes. My Marantz SACD player doesn't get used much anymore. Brothers In Arms never sounded soooo good.

    Hey Kim, can you share more about what you did here? Did you remove (replace) the input caps or did you upgrade them to a different kind/size of cap. What was the idea behind removing the inductor/s since the signal is digital here? Can you post pics and more about your mods? :)
  • dacboydacboy Posts: 23
    edited May 2010
    Vishay high speed soft recovery diodes arrived today! (P/N SBYV28-200 -E3/51) Yes I know 200v is overkill but it was the only value Mouser had ready to ship. The SBYV28s are suppose to be the hot setup. 20ns! :D
  • heiney9heiney9 Posts: 24,108
    edited May 2010
    dacboy wrote: »
    Vishay high speed soft recovery diodes arrived today! (P/N SBYV28-200 -E3/51) Yes I know 200v is overkill but it was the only value Mouser had ready to ship. The SBYV28s are suppose to be the hot setup. 20ns! :D

    So you're again going away from the plan? The hot set-up for what? You really should spend the bulk of your $$$ on the OPA627 that's where 90% (in my estimation) the improvement is. So far you haven't done that, but hey it's your project. :)

    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: 3,644
    edited May 2010
    dacboy wrote: »
    Vishay high speed soft recovery diodes arrived today! (P/N SBYV28-200 -E3/51) Yes I know 200v is overkill but it was the only value Mouser had ready to ship. The SBYV28s are suppose to be the hot setup. 20ns! :D
    You'll have to be abit creative installing these in the small foot print of the stock bridges.Are you adding small snubber caps across them?
  • davide256davide256 Posts: 50
    edited May 2010
    I did the update as decribed by Heiney9 in 2 stages and have encountered a 60 cycle hum problem. First stage was the power supply changes, noticed about a 6-9db improvement in gain with no signal hum problems although an increase in transformer hum was noticeable with the case off. Second stage audio circuit done as described by heiney9, had one dead channel but after much rechecking with NTF I moved the working Opamp to the other channel and found that both channels worked and I had a bad Op amp (replacement on order). But hum is noticeable between song cuts and while I can hear the tonal improvement in singers and complex passages its masking the fine details I would like to hear. Anyone have suggestions, thoughts? Note that I did remove the output filter capacitors and inductances as described in after cap and op amp replacement. Also tried running the ground wires for the op amp caps away from the transformer, no effect
  • george danielgeorge daniel Posts: 11,989
    edited May 2010
    hmmm,, mine is dead quiet--can you post some pic's?Hopefully Mr Fred will chime in,,as he is the brains behind this mod.

    How did you ground the caps that you used on/with the opamps?
    JC approves....he told me so. (F-1 nut)
  • dacboydacboy Posts: 23
    edited May 2010
    davide256 wrote: »
    I did the update as decribed by Heiney9 in 2 stages and have encountered a 60 cycle hum problem. First stage was the power supply changes, noticed about a 6-9db improvement in gain [...] But hum is noticeable between song cuts and while I can hear the tonal improvement in singers and complex passages its masking the fine details I would like to hear. Anyone have suggestions, thoughts? Note that I did remove the output filter capacitors and inductances as described in after cap and op amp replacement. Also tried running the ground wires for the op amp caps away from the transformer, no effect

    This is curious... I don't think what you did to the power supply (1stage mod) should have any affect to the gain of the output. Unless, the new caps lowered the noise floor making it "seem" like a 6-9db improvement. So, the 60 cycle hum started after the 2nd stage mod? Both channels? Were there any washers that were moved or left out from the between the chassis posts that support the circuit board? Use a meter to see of you have A/C coming off the chassis. It must be some kind of grounding issue.
  • FTGVFTGV Posts: 3,644
    edited May 2010
    I concur with dacboy that in all likelihood it is a ground issue.Also as he mentioned there should be no change in gain with any part of the mod,other than maybe apparent lowering of the noise floor.Did anything else in the system change at the same time you reinstalled the DAC.
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