2. amps-preamps
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Why is my conrad johnson mf 2500 overheating?

I need some help! My cj mf2500 which is 240 watts @ 8 ohms is overheating. It overheats when you run it over 1/3 volume for an extended period of time. It is running magnepan 3.5r speakers thru stealth speaker cables. My cj gets so hot the thermal protection circuit shuts it down. Also I blow more then my fair share of speaker fuses. Any help sure would be appreciated.( I had no problem with amp until I bought these speakers. Do I need a bigger amp?) Thanks Kyle
128x128hifihutch
sean
6,231 posts
 
What preamp are you using ? If running a tubed preamp or an SS model with phenomenally high gain, 1/3 of the volume control might actually be driving the amp to rated power and / or beyond. Sean
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cytocycle
1,043 posts
 
Stupid Question: How is you amp ventilated? is it in a rack? try putting it on the floor with nothing above it.

Are you using the magnepan external crossover box? or are you bypassing it (which will cause fuses to blow)?

The constant 4ohm load will cause the amp to run hot but shouldn't thermal.
hifihutch's avatar
hifihutch OP
1 posts
 
Cytocycle My amp is in a rack with all sides open & about 10" of clearance above it. I am using magnepan's external crossover boxs. My prior speakers were 1.4 maggies & my amp actually ran cool. I do not have a dedicated electric line to the unit. Could that be the problem? maybe the crossovers? This is my first " nice " hi-fi system any help would be appreciated Kyle
rwwear
2,871 posts
 
Something is shorted somewhere. Check all connections and get a meter to check impedence starting at the speaker cables at the amp end.
sean
6,231 posts
 
With more information provided, it sounds like something is haywire in the speaker system, causing the amp to oscillate, run hotter than normal and blow speaker fuses. If possible, try to simplify the speaker installation as much as possible using very basic cabling.

I don't know what is involved in using the internal or external crossovers, but if you can use the internal crossovers with something along the lines of Monster cable, see what that does. If it works okay, then swap in your Stealth cabling. If everything is good there, reinstall the external crossovers. If it things go haywire, leave in the external crossovers and substitute the Monster cable for your Stealth's. If things work okay here, the combo of the Stealth's and the external crossovers present a load that the amp doesn't want to see when hooked up to the Maggies. If things are still goofy with the external crossovers and the Monster's, the external crossovers are defective. You have to track things down by process of elimination in a situation like this. Sean
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