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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 2 responses by bondmanp

bondmanp
1,785 posts
 
I figured this would be a good thread to hijack for a moment ;-) I have had a used PV-11 for a little over 2 years, and recently ordered new tubes from C-J. Although I do like the overall sound of the PV-11, I do find it a little on the bright side with all but the best source material. I guess this is just what you get with a very revealing, unforgiving preamp. However, two issues remain troubling:

1. Channel imbalance. As the PV-11 warms up, the center images seem to drift right. The balance control usually helps, but I really wish I didn't have to use it. I have tried new tubes, new ICs (from both CDP to PV11 and PV11 to amplifier), swapping L/R interconnects between CDP and PV11, a different CDP, all made no difference. I have yet to switch amplifier channels or speakers, which I will do when I have the time, but I am very frustrated. I fear it might be acoustical, yet when first powered up, the channel balance seems spot on.

2. Hiss (tube rush?). Until I added a PS Audio Quintet to my rig, I never thought of the PV11 as excessively noisy. Dead-quiet it never was, but because of a hum/buzz issue with my amplifier, the added noise I could hear when the PV11 came on was minimal. With Quintet, the amplifer noise has been vastly reduced (I now must place my ear within 2" of the speaker to hear it). When the PV11 comes on, the jump in background noise, even at lower volume settings, is quite large, and easily audible from the listening chair. Is this a normal amount of noise from a properly functioning PV11?

Any ideas on these issues would be greatly appreciated.
bondmanp
1,785 posts
 
Glad to hear things are looking better. I retubed my PV11 (tubes from C-J). Still having channel balance issues, and I am beginning to suspect room acoustics or even my power amp.

However, even though I installed the new tubes with C-J's supplied dampers, I have been hearing a lot of microphonics (I think). Sounds like a very high frequency ringing or feedback-type noise. It comes and goes, and can be pretty annoying. Plus, the pre is pretty noisy. It got a tad quieter when I plugged it into my PS Audio Quintet, but I wonder if that's just a price to pay for a tubed pre, or perhaps my PV11 needs servicing?

Any thoughts on this would be very much appreciated.
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