rplace Posted May 8, 2006 Share Posted May 8, 2006 I picke up a used Conrad Johnson PV 7 Preamp and it has lots of noise out of both channels. It is a Hissy or static sound, not a hum or buzz. No matter what the setting (Phono, Tuner, Aux, Tape 1 or Tape 2) and no matter what the volume, even turned all the way down; it has the static. Equal out of each channel even when you turn the balance knob all the way left or all the way right.It does not get louder as the volume is turned up. I even tried both output channels with the same result. All other parts of the system remain the same except for the change of the preamp. Any ideas? Quote Link to comment Share on other sites More sharing options...
rplace Posted May 8, 2006 Author Share Posted May 8, 2006 Thanks Mark...when I finally get my "real" peramp it will be your BBX for sure[] This is sort of a step in the right (hopefully) direction. I figure I can get most of my money back down the line since CJ has a pretty solid following. Can you offer up any suggestions on which tube this might be given the info supplied by CJ at this link http://www.conrad-johnson.com/It_just_sounds_right/a-PV7.html Thanks for any and all help. I am pretty much a novice when it comes to things under the hood. Quote Link to comment Share on other sites More sharing options...
rplace Posted May 8, 2006 Author Share Posted May 8, 2006 Swapping out the V3 and V5 tubes made no difference...still noisy. Next I swapped out, one at a time, each of the 12AX7 with each other. Same result each time. Finally I removed one tube. Every time it was just as noisy except when the V5 was missing, then it was dead quiet. I tried playing my CD player, line not phono, it would play but very, very quietly and it sounded like it had no guts or power behind it. Any other ideas? Quote Link to comment Share on other sites More sharing options...
rplace Posted May 9, 2006 Author Share Posted May 9, 2006 Thanks for the suggestions. A little history on the preamp acording to the seller. No reason to doubt him, lots and lots of fantastic feedback on Agon. Anyway, one owner purchased in Virginia close to the CJ factory. A few years ago it got a new tube set direct from CJ, shortly after that put into storage. Reason for selling cleaning out old gear. Of course all was checked out and fine before he offered it up for sale...all but the phono stage that is. If you turn the volume up to get beyond the noise it actually sounds very nice. I dig the sound that I do hear. Physically it looks very clean, no signs of abuse. Inside was clean when I opened it up to play with the tubes. Nothing obviously loose or strange inside. If I am not too concerned with the performance of the 12AT7 tubes and just want to get a new set for testing where should I look. Will any place locally like a radio shack have them or do I need to order on line from a tube place? Thanks again for the help! Quote Link to comment Share on other sites More sharing options...
shload Posted May 9, 2006 Share Posted May 9, 2006 Best local place for a quick fix with tubes that I have found in my area are local guitar shops. Most have used ones and also new. Not super quality or matched, but gets you by. Joe Quote Link to comment Share on other sites More sharing options...
LarryC Posted May 9, 2006 Share Posted May 9, 2006 Rich, is this through your K-horns? If so, please remind me what your amps are, and do you know the sensitivity (voltage required to drive how many watts at full output). Quote Link to comment Share on other sites More sharing options...
rplace Posted May 9, 2006 Author Share Posted May 9, 2006 Larry, yes it is through the khorns. The amps are Dynaco MK IIIs. Craig and Gary's old pair. I believe they are in the 60 watt range. I don't know the sensivity answer. That is sort of greek to me, please explain. Maybe MaxG can help [] Quote Link to comment Share on other sites More sharing options...
LarryC Posted May 9, 2006 Share Posted May 9, 2006 Ah, I'd forgotten. The original specs indicate a pleasantly low-sensitivity amp (1.6 v. for 60 watts out) and Gary didn't have a problem either, so scratch that idea. My understanding is that, for example, a sensitivity of say 0.8 v. for 60 out would increase preamp noise through the speakers by 6 db. I've sometimes have had to juggle preamps vs. amplfier sensitivity with K-horns. Quote Link to comment Share on other sites More sharing options...
rplace Posted May 9, 2006 Author Share Posted May 9, 2006 Best local place for a quick fix with tubes that I have found in my area are local guitar shops. Most have used ones and also new. Not super quality or matched, but gets you by. Joe Thanks for the tip! I just called a few stores within driving distance and tracked down 2 12AT7 tubes. Don't know the details, but something is better then nothing. They are open till 9:00PM so I can still pick em up after work...The saga continues. Should I pick up at least one of the other tubes as well, if they have them? There are only two different types and if I am going to replace the 2 12AT7s then having one of the others seems smart. There is no way they can all go bad at the same time can they? Quote Link to comment Share on other sites More sharing options...
rplace Posted May 10, 2006 Author Share Posted May 10, 2006 Still no joy. [] I replaced the two 12AT7 with brand new ones (some Russian tube with Fender logo on them). I also picked up one 12AX7. I replaced both 12AT7 first with the same static noise present. I then swapped out my new 12AX7 in place of each old ones one at a time. Same result. Hissssss, is still on all output modes and does not get louder as you turn the volume up. It is loud enough that you can hear it right away and in any location in the room. You can even here it outside the room. About as loud as listening to TV quietly at night. If I put on a CD or LP and turn the volume you can overpower the hiss, but that is not practical. Any more suggestions? Quote Link to comment Share on other sites More sharing options...
Guy Landau Posted May 10, 2006 Share Posted May 10, 2006 C-J has a great customer service and were very helpful when I needed assistance. Try calling them, I'm sure they'll be glad to help. Quote Link to comment Share on other sites More sharing options...
garymd Posted May 10, 2006 Share Posted May 10, 2006 Can you return it? Quote Link to comment Share on other sites More sharing options...
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