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Old 3rd January 2012, 02:20 PM   #1
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Default Adcom gfa-5400 mods?

I have an Adcom GFA-5400 v1.0 and I am interested in modifiying or upgrading it. Does anyone have any suggestions? Or am I limited to what I can do with this design?
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Old 4th January 2012, 02:02 PM   #2
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Im thinking about upgrading some of the components. The caps are from 1998, so they have to be needing replacement. There are 12,000uf 63v caps in there now and I was thinking about replacing it with these:

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Last night I was adju8sting the bias and have decided I hate the pots and want to replace them with the more accurate kind, but can not find the exact value. There are 4 4.7k pots and I was thinking about replacing them with:

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Im also thinking about upgrading the bias caps too to better quality.

Any thoughts?
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Old 5th January 2012, 12:20 AM   #3
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I have recived severial caps from that seller and all have been very fine quality. I just got some polycarbonate caps from him a few weeks ago and they were a fraction of the price from Mouser. So far, no fakes, just takes time to get to the US.
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Old 5th January 2012, 12:33 AM   #4
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Just seen the post on the trimmer replacent. They look like Bourns knock-off's. Anyway, would just go with realy good single turn cermet by Bourns ect.. The bias adjustment moves too much to take advantage of a ten turn pot. Just my 2Cents"
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Old 5th January 2012, 12:41 AM   #5
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Check out Apex Jr. in the Vendor's Forum for Adcom caps too.
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Old 5th January 2012, 05:11 AM   #6
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Thanks for all the responses. I am an amateur when it comes to this stuff, but too poor to afford the good stuff. So I am looking to improve what I have. I have learned to adjust the bias and have it adjusted perfectly. Those pots are so touchy.

Is it OK for me to go from a 12000uf 63v cap to a 15000 63v cap? I figure I am just increasing the capacity and keeping the voltage the same. The kendeil caps are going to make it sound so much better.

I also have a Rotel pre that has a left channel a little muted. I read somewhere on this forum it could be the caps, so I took it apart and found the primary caps the tops are pushing up which is a sign. So I ordered new ones as well(same better quality).

This should be a noticeable improvement on the sound.
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Old 5th January 2012, 12:42 PM   #7
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Changing the caps from 12k to 15k should be no problem. Just be sure that the size of the cap is close to the same. If the cap is PC mounted check you clearance on the board, a few mm can be a deal breaker in dia.
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Old 8th January 2012, 04:41 AM   #8
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Should I upgrade the bridge rectifier's with the added cap capacity?
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Old 19th January 2012, 04:20 AM   #9
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Some cap upgrades. Still waiting on 6 more.

Amp: Adcom GFA-5400

Pre: Rotel RC-1070
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Old 19th January 2012, 04:30 AM   #10
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Very nice. I also like the Super Through and Gold caps. As long as you have the room, why not. Keep up the good work!
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