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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
5,119 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.
dale_harder OP
46 posts
 
Additional information:
In my present set up...
CJ preamp input impedance 50K line and 47K Phono. Output impedance 500 Ohms.
Equalizer (Yuk!) input impedance 47K. Output 600 Ohms
Amp input impedance 30K Ohms.
Thanks,
Dale.
audphile1's avatar
audphile1
5,119 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
5,119 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.
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.
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