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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
elevick
2,636 posts
 
When I've played with CJ, they always used US made tubes (GE). With 5751's for the final gain tubes instead of 12ax7's. What it in yours? A 5751 is capable of much more current. This may make a difference when you are pushing it hard???
Personally, I like NOS european tubes even though CJ always pushes much drier, hardier tubes. 1 Telefunken or Mullard for the CD tube and a pair of GE 5751's for the gain tubes will make a difference (yes, in my opinion). Keep in mind that I've never had a PV-11, only a 5, 10 & 12.
soundwatts
221 posts
 
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.
audphile1's avatar
audphile1
5,131 posts
 
the bass suckout/lack of bass, may make higher frequencies appear more prominent, forward and brittle.

I also wanted to ask, do you experience sibilance with only a few particular recordings or basically on everything you listen to?
dale_harder OP
46 posts
 
Hello Gentlemen,
Thanks again for your responses. In answer to some more questions, I have replaced the silver IC's with generic IC's and no difference was noted. Pertaining to phase, I have phase inverted the speakers as recomended by CJ and stated in the manual. The bass is definately not suffering so I think the phase is correct. I did speak with CJ today and they informed me that they do indeed use EH tubes that have been hand selected and tested to their standards. One tube is infact a 5751. They felt that the tubes may need to burn in for awhile, but that what I am experincing is not the usual for this product. They also recomended removing the EQ for a test period. I will do so tonight, as well as try flipping the electrical plugs.
As for my system I am using several types of amps (tube based) and some solid state. The present configuration consists of a professional series BSR 4000 EQ and a Carver M1.5t magnetic field amp. I have not tried my Audio Symphony tube amps as of yet.
More later.
Dale.
dale_harder OP
46 posts
 
Oopps, just noticed another response...Unfortunately, the sibilance and harshness are present in all cases and all recordings.
Thanks,
Dale.
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