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)


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
Three possibilities that come to mind...

One, your preamp may be passing D.C. This is a bad thing and if it turns out to be the case, it is a good thing your amp has protection circuits since this is a great way to blow things up in a most spectacular and amusing fashion. It is the least likely problem, but potentially the worst. CJ makes a good product, so this is the least likely scenario.

The second potential problem off the top of my head would be a bad output jack with an intermittant ground connection. If you are running the Citation bridged, then it is particularly sensitive to this (Also, if you are running bridged, double check the bridging connectors...if they get knocked loose, the amp will do exactly what you are seeing). Try swapping the interconnect cables you are using and see if that alleviates the problem. You might try some contact cleaner for giggles. I would also check to make sure there isn't a short in the speaker cables that may have been triggered when you moved things around to hook up the CJ.

Third, your new preamp could be overloading the input of the amp...but that would usually only happen at higher volumes. If the amp only shuts down when you start to turn things up...see how long it will run at low volumes. There may be a way to adjust the output gain on the PFR...I'd contact C.J.

The Sound Broker
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.
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.
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.
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
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.