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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
audphile1's avatar
audphile1
1,368 posts
 
Harsh mids and extreme sibilance you are experiencing is most likely a distortion somewhere. You have to find the component in the chain that creates it.
1) make sure the tubes in the CJ are fresh.
2) make sure the CJ pre matches well with your power amp as far as impedance is concerned. Phone CJ and give all the specs to a tech support person to evaluate may be the pre and amp are not an optimal match.

Does it sound too loud when the volume on CJ is relatively low?

Also, try taking the Silver ICs out of the equation, as Thorman suggested.

I don't think rolling tubes or changing cables will do anything major unless the tubes and cables you use now are broken.
muzcal
66 posts
 
If everything was ok until you put in this preamp then, duh, it' the preamp. Check the tubes. In my opinion, EH's arn't the best in CJ's. Try to get hold of some box plate Mullard's. Also, make sure the polarity of the AC cord is correct. Try reversing it. The warmest sound is the correct polarity. If all else fails, send it in to CJ.
viridian's avatar
viridian
4,184 posts
 
What is the input impedance of your power amp and how long are your home-brew interconnects?
dale_harder OP
46 posts
 
Hi Guys,
Thanks for some of the comments and suggestions thus far. I agree Soundwatts, This preamp should rock.
Regarding the tubes, this set is brand new and provided by Conrad Johnson. The set, RT11 was $175.00 plush $17 shipping. That's why I was suprised by them using EH tubes. They placed the tubes, but come to think of it, I will check their placemnt. All the tubes have dual tube damping rings in place as well. I have removed the silver IC's and tried other cables, but so far no change. My IC's are from 18" to 3 feet depending on their purpose. Rebalancing the system has helped some, but the mids are still harsh. I will try the plug thing tomorrow and talk with CJ regarding my amps impedance match.
Regarding your comment Audiophile 1, you are correct I do not have to turn the CJ up very loud to get a good volume, but it is not much different than my previous amp. typically 10 to 10:30 position on the dial now and was about 10:30 to 11 max on the prior.
I will have to dig to find my amps input impedance. The manufacture did not specify it.
Thanks,
Dale.
audphile1's avatar
audphile1
1,368 posts
 
oh, and by the way, there is nothing stange about CJ using EH tubes. That's a normal tube of choice for supplied tubes. Either EH or Sovtek in most cases. Some manufactures pack Chinese tubes with their equipment.
Don't be expecting CJ to give you a nice set of NOS vintage Mullards.
:)

Please keep us posted on how it goes with the sibilance issue.
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