Conrad Johnson PV11...Extreme sibilance, harsh sou


Hello everyone,
I have an issue and was wondering if I might prevail upon the community to help me out. I am a seasoned audiophile, I would like to think, but I am sure this old dog can still learn a few tricks.
I have recently acquired a CJ PV11 preamp that is basically in mint condition and came with a brand new tube set from CJ. The tubes were installed around 7/10 and I received this amp on 7/28/07. (strange though, they used Electro-Harmonics tubes)
Anyway, After I installed the preamp, I now have very serious issues with harsh mid range and extreme Sibilance issues that I never had before.
My system is very revealing. I use NEW Walsh drivers based on the Ohm Acoustics design of the model "F" and "A". In fact I have both. These units I make and build myself.
I have not even attempted to use the phono section of this preamp yet. Just the line stage.
While I have never encountered this problem before, I have it now, so much so that I can barely stand to listen to my system. Nothing in my system has changed except the preamp. I intend to rebalance the room and speakers using my calibrated mic and high quality RTA. And even though I am a purist at heart, I do use a high quality graphic equalizer just to cope with some room acoustic issues, but it is set to a very low and flat curve and mainly compensates for low end reflections from my omnidirectional speakers.
I have read about the usual tube rolling, try different interconnects and ac conditioning, but most of that seems very subjective, even to those that suggested it.
I do use dedicated 30 amp lines and separate grounds for my system and even have an ac conditioner, but found the conditioner caused hum issues, strange as that might seem. So I took it out and run direct to the line.
My speaker cables unfortunately are long runs of 25 feet by necessity, but are high quality OFHC braided cables with a 10 ga. size. I also use silver interconnects that I have designed.
Does anyone have any ideas? I have put into CJ for help, but no response yet. (Holiday) and have also been in contact with Dr. Tube.
I would appreciate any help.
Thanks in advance.
Dale
dale_harder

Showing 3 responses by soundwatts

I own this preamp for years and have 2 friends that own this peamp as well. None of is ever experienced what you are describing. Either the preamp is defective or your problem lies elswhere. When you retubed the preamp did you poace the tubes correctly? Also what is the preamp yoy replaced aqnd what is the rest of your system?
The PV11 uses 12au7's for the line stage and 1 5751 1 12au7 and 2 12ax7 for the phono stage.

What components are in the rest of your setup and why an equalizer?

audphile1 is correct this preamp inverts phase and you need to swap your speaker connections pos to negative. I dont think you would get a harsh mid but a suckout in the bass.

Let me know what the rest of your components are.