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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
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.
grannyring's avatar
grannyring
6,534 posts
 
Have an iec plug installed and use a better aftermarket power cord. It can also be upgraded to a 2500a by CJ with using better quality caps.

You can also install audiophile grade fuses for better sound.
jeffatus OP
42 posts
 
Thanks for the replies. I read a review of the amp on Steroephile and the reviewer addressed the hum with a Shakti Stone. What the heck is that?

"........One note I should make here: when I first connected the amp, it did hum a little. I checked all of my connections and everything was tight. Instead of experimenting with cheater plugs, which I don’t like to use, I put a Shakti Stone on top of the amp, center towards the rear. The hum went right away and all of my listening was done without a trace of hum."

I have already contacted CJ and I am waiting for their response. Anyone have an idea of how much the upgrade to the "A" model costs? I wonder if it's worth it. Should it be given the "once over" by CJ without the "A" upgrade because it is ten years old?

Thanks for your advice.

Jeff
stanwal's avatar
stanwal
3,147 posts
 
I put WBT RCA jacks and binding posts on my CJ 350. No A-B possible of course but I thought it gave a worthwhile improvement. I would change the RCAs at least; they are not CJs strong point. There are several RCAs cheaper than WBT which are still worthwhile upgrades. I second installing an iec plug.
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