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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
sugarbrie
3,854 posts
 
Contact Knut Ryerson at Conrad Johnson. He is always helpful no matter how old your CJ equipment is. He will get you an answer and usually fast if he is in the day you write. His address is custserv@conradjohnson.com
jcbtubes
400 posts
 
811- Sean is probably correct in his assumption that the offset voltage on one or both channels of the pre-amp is just high enough to trigger the protection circuit of the Citation. I'm not familiar with the CJ PF-R pre-amp. If it is capacitively coupled on the output, then it is possible that at least one of the output caps needs replacement. If it is DC coupled on the output, then the driver circuit needs to be adjusted or repaired.

Very low-frequency oscillation can also produce this situation. On one occasion, I had a very odd situation where the input circuit protection was responding to low frequency junk caused by a ground loop in a system. However, this is extremely rare.
Good luck.
say811 OP
27 posts
 
I'm using the Citation to bi-amp my speakers, not bridging it. I've got "Y" cord interconnects coming from the preamp outputs in order to feed all four channels on the Citation. If it was a problem with the interconnects or some other connection then wouldn't the problem show up when I swap out the CJ with another preamp? I've tried two other preamps (the preamp section of a Denon receiver and an Adcom GTP-760 pre/proc) and the problem does not occur with either one, only with the CJ. I'm wondering about the ground loop senerio. I have another Citation right above the other one that is used for H/T. There are certain occasions when this second Citation starts to hum a little bit. This happens very infrequently and stops if I turn the unit off, then turn it right back on. Also, could there be a connection problem that doesn't show up on the other two preamps and only on the CJ due to sensitivity or something of that nature? I can sometimes have the unit on for a half hour before anything happens, sometimes for only five minutes. There doesn't appear to be any ryme or reason, just random occurance. Should I contact the seller (Audiogon member) about the problem? I think he offered a 90 warranty on the unit. I've noticed that this member is selling other CJ equipment on eBay. He had this unit on eBay also, but no-one met his reserve.
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