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My pre-amp overloads my amp

I just bought a used Conrad Johnson PF-R pre-amp. I hooked it up to my Citation 7.1 amp and everything was fine for the first 10 minutes or so. Then my amp clicked off, the red protection indicator light glowed, then the amp came back on. After a while the same thing happened. I stopped playing music and the same thing happens even when no music is playing. Tried it again the next day (not playing anything) and the same thing happens, the amp goes off, then comes back on. The amp works fine with both my other pre-amps so I know the problem is with the CJ. There are no switches or adjustments of any kind that I can see other than the input and output jacks. I'd like to get some idea as to what is going on before I call the seller (Audiogon member)

Thanks,

Steve
say811
sean
6,231 posts
 
I wonder if the preamp is passing DC into the amp ? This could cause the amp's protection circuitry to trigger, giving you the aforementioned problem. Anybody else got any ideas ? Sean
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drtmth58
66 posts
 
I agree with Sean. The fact that the problem with the CJ occurs even when there is no music playing suggests excessive DC offset; or some other oscillation related difficulty that is triggering the amplifier's protective circuitry. One other possibility, though admittedly a very remote one, is that some exotic and/or poorly designed interconnects might have electrical properties that, in combination with the preamplifier, are also the cause of the oscillation. Obviously, trying a new pair of interconnects is a fairly easy thing to do.
newbee
4,767 posts
 
sean may well be right. i don't know if your amp will pass dc. some ss units do. if your unit does, or if you put in another amp that does, you could pass dc thru to the speakers and fry them! i'm not familar with your pre-amp but if its tubed it could well be that a failing tube is causing a dc offset.
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