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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 9 responses by dale_harder

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.
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.
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.
dale_harder OP
46 posts
 
Thanks aagian for the further input. Sorry I have not been able to give too much in further results... been sick with an abcessed tooth..Ouch!
Anyway, I have rebalanced my system with the B&K Mic and RTA and achieved some better results as of late last night. Tried to remove the EQ, but did not like the room effects. Bass was overwhelming with slight high absorbtion in the 16 to 20K range. Sill only about 2 db of loss here.
In addition, I may have some further info and perhaps I am now experiencing some poor quality tubes in another component shinging through. As I said, I use a modified Jolida JA100 CD player which is tube based. Part of the mods called for changing the original Chinese tube set for New Svetlanna 12AX7's. Talking with Dr. Tube, says he believes the Svetlanna tube to be very poor quality, so much so that he has discontinued selling them or supporting them. He says, only about a 30% yield was the norm and that 30% was mediocre at best. This is confusing to me as several High end places are doing the CD mod with the Svetlanna. Something I researched before i had it done..Oh well, Cest la vie.
This may be part of the problem, since the CJ is a very revealing preamp. Perhaps it is emphisizing what these tubes are doing. They are still very new with perhaps only 10 to 15 hours use on them. Still I have some problems with other input devices producing the same type of effect, i.e. tunner, or TV audio. Though these are not that important to me, as I use the CD or Phono most.
I guess I have much to do with trying different tubes and combinations. I will post with further results. Good listening. Dale.
dale_harder OP
46 posts
 
Sorry I haven't posted any further info gentlemen, I have been out of town on a family emergency.
Regarding the original problem... I have rebalanced the room acoustics using the spectrum analyzer and put a lot more hours on the tubes. Probably 75 hours + now. It does seem to be somewhat better, but the original problem still exists. I went to cheaper interconects and OFHC 10 ga. copper speaker cable as well. Seems the silver is a little too bright.
Still I would love to find a real solution. So, I intend to do some tube rolling with older tubes and experimentation here and there. Finally, I might just return the preamp to CJ and have it gone over throughly, so at least I can have peace of mind.
Interesting on the WXT tubes.
I also have two sets of mono block tube amps that I am rebuilding and I intend to use some of the new issue matched quads of Gold Lion KT88's and 6550's. Hope these live up to expectations.
Thanks,
Dale.
dale_harder OP
46 posts
 
Thanks for your comments guys. I tend to agree with you. Unfortunately, there is no one close by whom has a stereo with higher quality components to test the CJ in, so that is not an option. I also tend to agree regarding the checkout at CJ. They look for the obvious, such as complete malfunction or noise. As far as tube rolling, I would simply try other sets of tubes I already have here. I certainly wouldn't purchase any more. Finally, I just don't have the money to turn over the CJ and try something else. It took long enough just to save up and buy this one, let alone the WAF. I guess I will have to live with it for awhile, though I must admit it is a big disappointment.
dale_harder OP
46 posts
 
Thanks, Jim. I appreciate that.
A litttle update... the preamp is starting to sound much better since the tubes have burned in. The exagerated sibilance is softening and not nearly as extreme. I would say I have about 150 hours on the EH tube set now. Otherwise, little else has made much of a difference. Talked with CJ twice and they had little to offer except to return the preamp and check it out.
Dale.
dale_harder OP
46 posts
 
Hello to all,

Sorry I have not been on lately. I have been caught up in the whirl-wind we call life. I need to get back to the tunes.

Regarding some of the posts I missed. I have to say that my CJ PV-11 is now doing very well and apparently most of my original issue was simply tube break-in. It is now quite listenable and very, very quiet.

I also added a PS Audio Power Plant to my system, (I tried other products but none like the PS) and it made such an unbelievable difference it was beyond words. I like to call these my "Ah Ha!" light switch moments. Like someone flipped a switch and then there was magic. I really hate it when I have to strain and hem and haw...did that really make a difference? You all know what I mean.

Thank you JMO for the upgrade info too. I also found Bill Thallman of Music Technologies. 703-764-7005. They are an Apogee Ribbon dealer and specialize in upgrades for CJ and some other high end stuff.

Thanks again for all the interest and responses.
Dale
PS our new web site went on line last week. www.hhr-exoticspeakers.com
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