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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

Showing 7 responses by audphile1

audphile1's avatar
audphile1
4,189 posts
 
Also, if I am not mistaking, some CJ preamps invert phase. Double-check if the PV11 does and take appropriate action to invert phase.
Do the phase correction at the amplifier end by switching speaker cables "-" and "+" and see if this helps....only if the PV11 inverts and your amp does not.
audphile1's avatar
audphile1
4,189 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.
audphile1's avatar
audphile1
4,189 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.
audphile1's avatar
audphile1
4,189 posts
 
I would try taking the EQ out and running the CJ direct into the amp. See what it does then.

Did you replace the Silver ICs with a cheap-s generic copper ICs as recommended above to eliminate the ICs as being the cause?
audphile1's avatar
audphile1
4,189 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?
audphile1's avatar
audphile1
4,189 posts
 
Dale, yes, remove the EQ for now.

I don't think running tubes some more would cure anything in a major way.
audphile1's avatar
audphile1
4,189 posts
 
Dale, I suggest you either borrow a different preamp same in class as the CJ or take the CJ to check in another system to see if the sibilance problem is there as well.

I agree with Maril555 about tube rolling. Applies to cable changes as well. The sonic foundation of the unit will always prevail does not matter the tubes or cables. Especially with a sibilance problem. I doubt you will get rid of it completely by rolling tubes or changing cables.
Also, I think sending the pre back to CJ may be a waste. If it is working, not making any strange noises but just does not sound right to you, sending it back to the factory won't do a thing. Most likely it is fine.

just I said before, I believe the only way to check the pre is to either insert it into another system or borrow another hi-rez preamp to try in your system.

Also, is the sibilance problem you get on particular recordings or is it on every recording?
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