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Any way to "improve" a Conrad Johnson MF 2500

I recently purchased a 10 year old CJ MF2500 amplifier. It is in perfect condition and it sounds excellent, but I noticed a hum coming from my speakers when it is turned on. It got me thinking, since there is no way to upgrade the power cord, if there was a way to "refurbish" or update the amp. I don't know if that is something normal for a solid state amp, but it's sounds so good and is in such good shape that I thought I would see what the rest of you thought. It would be nice to see it work for another ten years.
jeffatus
czbbcl's avatar
czbbcl
1,752 posts
 
Upgrade it to a 2500A if it isn't an A already. The "A" mod improves the amps speed and detail. You have to send it to cj to get the work done but it is well worth it and while it is there they can go through it.

Chuck
jmcgrogan2's avatar
jmcgrogan2
6,346 posts
 
If it's a ground loop hum there is a pretty easy fix. To test if it's a ground loop hum, put a cheater plug on the amp's plug and see if the hum goes away.
roxy54's avatar
roxy54
8,086 posts
 
I have heard of the hum problem with that particular amp, and I believe that it can be fixed. Are you aware that there was an "A" revision also? You should call Conrad Johnson and inquire. That is a great amp. I auditioned it once for a couple of hours, and thought it was extremely musical.
rdavwhitaker
173 posts
 
I used to own a 2500, and I personally wouldn't advocate modding it - it was a great piece to begin with. Incidentally, that hum is probably a ground loop - CJ amps, especially the MF series, are highly susceptible. You can probably kill the hum by using a "cheater" plug to lift the ground. I used one on my amp and the hum disappeared completely - and I continued to use the amp for several years with no ill-effect.
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