Info on shunt caps for Adcom GFA-545?

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nadams
nadams Posts: 5,877
edited February 2009 in DIY, Mods & Tweaks
Can I do the shunt cap mod on my GFA-545? If so, what type of caps do I need? I'm very familiar with capacitors on computer motherboards, as I've replaced scores of bad ones. Audio caps, on the other hand, baffle me. :confused:

See here for pics of a 555 with shunt caps installed - http://www.polkaudio.com/forums/showthread.php?t=76378

Thanks in advance,

Noah
Ludicrous gibs!
Post edited by nadams on
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  • ben62670
    ben62670 Posts: 15,969
    edited February 2009
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    You can easily do the mod. All you need is some 100v or better film caps like you would use in an XO. Now what values you use are controversial. I like either 12uf, or a combo of 20uf, and 1uf paralleled. I will be doing this mod soon. I had a 555 with the mod. I take a look at the schematic to see if there are any input caps that should be replaced. Shoot me a PM if I don't post an answer by this evening.
    Ben
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
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  • nadams
    nadams Posts: 5,877
    edited February 2009
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    So then, I'm looking for something like this, right? - http://www.parts-express.com/pe/showdetl.cfm?Partnumber=027-430

    Would I need 2 or 4?
    Ludicrous gibs!
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  • fredv
    fredv Posts: 923
    edited February 2009
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    4, one by pass per main filer cap.
    I did this before I shipped my pair of GFA-555's the new happy owner.
    This is a low cost way to give a little more helping zooom to the old caps. If you don't mind to spend a little more, replace the main filter caps with new low ESR caps will give you a better improvement. Of course, you can do both :-)

    Have fun!!

    -fredv-
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  • nadams
    nadams Posts: 5,877
    edited February 2009
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    If I could find replacement 10,000uf 100v caps in audio grade, I might entertain the thought of replacement. But I can't find a source for them!
    Ludicrous gibs!
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  • Face
    Face Posts: 14,340
    edited February 2009
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    nadams wrote: »
    If I could find replacement 10,000uf 100v caps in audio grade, I might entertain the thought of replacement. But I can't find a source for them!

    EPCOS

    http://www.alliedelec.com/Search/SearchResults.aspx?Ntt=10000uf+100v&Ntk=Primary&sid=11F8E16DDA28&i=9&Pst=10000uf+&N=0&sw=y
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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  • nadams
    nadams Posts: 5,877
    edited February 2009
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    Ooookay... I won't be spending more for the caps than I did for the amp just now. Maybe if it dies :o
    Ludicrous gibs!
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  • heiney9
    heiney9 Posts: 25,630
    edited February 2009
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    If I could find replacement 10,000uf 100v caps in audio grade, I might entertain the thought of replacement. But I can't find a source for them!

    Nelson Pass swears by computer grade Panasonic filter caps, have you looked into those? Many DIYer's use his suggestion for their projects.
    "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 Labs XA25 | EE Avant Pre | Holo Audio Cyan 2 Dac | MIT Shotgun S1 | Puritan Audio PSM136 Pwr Condtioner & Classic PC's | Legend L600 | Roon Nucleus 1 w/LPS - Tubes add soul!
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  • fredv
    fredv Posts: 923
    edited February 2009
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    heiney9 wrote: »
    Nelson Pass swears by computer grade Panasonic filter caps, have you looked into those? Many DIYer's use his suggestion for their projects.
    Ditto, I am quite happy with Panny. Digikey:
    http://search.digikey.com/scripts/DkSearc/dksus.dll?Detail&name=P10038-ND

    -fredv-
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  • nadams
    nadams Posts: 5,877
    edited February 2009
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    fredv wrote: »
    Ditto, I am quite happy with Panny. Digikey:
    http://search.digikey.com/scripts/DkSearc/dksus.dll?Detail&name=P10038-ND

    Except I need to have screw terminals - http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=338-1265-ND which of course quadrupels the price.
    Ludicrous gibs!
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  • fredv
    fredv Posts: 923
    edited February 2009
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    How about this?
    http://www.diyaudio.com/forums/showthread.php?s=&threadid=135652
    Pretty good price. Of course, this is still almost 3X of the Dayton .... But imagine you still can hear the music for 1 min after you turn off the power :-)

    -fredv-
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  • rabies_70
    rabies_70 Posts: 47
    edited February 2009
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    fredv wrote: »
    4, one by pass per main filer cap.
    I did this before I shipped my pair of GFA-555's the new happy owner.

    That's ME!!!! I have 5 555's in my HT rack now. The two from fredv have the mod. The other 3 soon will have it done. I just added the new cap to my CS350ls, now I'm opening up my Adcoms. Do it. The sound is noticeably improved. Thanks again Fred
    Center- (2) CS350ls
    Mains - Rti12 Biamped
    Sides - Fx1000
    Rear - LSi/fx
    Amps (5)Adcom GFA-555
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