CJ PV-12 - ringing probelm solved

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riffwraith
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CJ PV-12 - ringing probelm solved

Post by riffwraith » Mon Mar 05, 2018 1:47 pm

Hey all

I am the original owner of a Conrad Johnson PV-12, which I purchased new from a dealer about 20 yrs ago. Up until around June of last year, it was all original, incl. the tubes. One day I discovered a high-pitched clanging noise when I tapped on the faceplate, and at the recommendation of Jeff Fischel from CJ, and several members from another forum, I got new tubes, direct from CJ.

That noise still exists, but I understand now, that it's due to the monophonics of the tubes. Which probably means I didn't really need to replace the tubes, but hey - they were 20 years old, so I am not going to complain.

The reason I seek help is not for that - it's for something else. I high-pitched noise that appears from time to time (without touching the unit), which I first noticed after the tube swap. This noise might have been present before the new tubes, and maybe I just didn't notice it. Regardless, I need help now. A little history:

After replacing the tubes, and then finding this noise soon after, I had brought the PV-12 to a local electronics dealer. He cleaned the switches, and contacts, and I was hoping that would be the end of it. I get the unit home, and it doesn't sound quite right. I call Jeff @ CJ, (who by the way was helpful and nice), and he says to me, "send me the unit and I will make it like new for you".

I send the unit to CJ, and get it back not too long a period of time later. Plug it in, and now it sounds as it should. Great. But the high-pitched noise is still there. It is highly possible that due to the complete randomness, Jeff (or whoever actually worked on the unit) did not come across the noise, and therefore a clean bill of health was in order at the time.

I then purchase another pair of op tubes - Mullard 12AU7s from another dealer - just to see if the unit acts the same way with diff tubes. Which it does, meaning the issue is something other than the tubes.

I then get back w/Jeff, who tells me I might have better luck with some EAST GERMAN 12AU7’s or PHILIPS 6189’s. I got a pair of the latter, but the ringing is still there.

The other thing that Jeff told me is that it is the tubes that is the issue (the tube grid oscillating), and not the unit itself.

I was wondering if anyone here has experience in this matter, and whether or not any of you have found a resolution.

Thanks in advance.
Last edited by riffwraith on Sun Apr 01, 2018 5:26 pm, edited 1 time in total.

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jahatl513
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Re: CJ PV-12 advice needed

Post by jahatl513 » Sat Mar 10, 2018 10:31 pm

I have had a PV12, but never this issue. I would get back with jeff F and relay to him what you have done as a troubleshooting method. I'd refer to send it back to them to have them replace the tubes and to test it. Question; were they ever able to recreate it in their labs when they had it? You did not say so. I love my old PV12 and no one has ever said a bad thing about them when working properly, so it is worth dealing with. If you are done and want to get away from it, let me know, otherwise I'd go back to Jeff F as I have said, and let them recreate the issue in the lab and let them replace the tubes after recreating the problem to ensure they are enjoined in the issue and the fix.

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jahatl513
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Re: CJ PV-12 advice needed

Post by jahatl513 » Mon Mar 19, 2018 9:09 am

Please update your situation when you can. We all learn from one another

riffwraith
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Re: CJ PV-12 advice needed

Post by riffwraith » Mon Mar 19, 2018 11:58 pm

Hi. I did see your post, and thank you for replying, but I wasn't sure how to respond. The concerns you brought up were already addressed in my op.

Jeff did say that this issue is a known one, and in his words, almost everyone that has purchased a PV-12, has complained about the same thing happening.

I wound up getting a pair of EAST GERMAN 12AU7’s from the tube store, which arrived three days ago. My initial tests tell me there is no audible diff between these, the originals, the PHILIPS 6189’s and the Mullards, and the two times I have left the unit on for a while, I have not heard any noise. Hopefully these new tubes have taken care of the issue. Will report back in a few weeks with further findings, either way.

Cheers.

riffwraith
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Re: CJ PV-12 - ringing probelm solved

Post by riffwraith » Sun Apr 01, 2018 5:29 pm

Hi again.

So, after almost two weeks of extensive testing, which included simply having the unit on and monitoring the op for hours per day every day, and running plenty audio through the unit, I am happy to report that there is absolutely no high-pitched ringing noise whatsoever with the aforementioned 12AU7’s.

Cheers.

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Re: CJ PV-12 - ringing probelm solved

Post by roberto » Sun Apr 01, 2018 9:07 pm

Hola. I am going to chime something here. The tube dampers that are made for basically signal tubes, like the 12AUT7s, and make to stop some noise. This small tubes are microphonic. These rubber rings or high temperature silicone made rings, prevent to build up this microphonic possibility into the tube. I highly recommend the use of them. They are not too expensive.

https://www.amazon.com/Eurotubes-EuroDa ... B019P7KA1C

Trying them will not harm the quality of the sound...sometimes might be improved the quality using them.

Riffwraith, that is a very good news! It is good to know that now you are enjoying again your beloved CJ hi quality sound!
Happy listening!
Roberto.
ML CLX speakers, BF-210 sub, Classic One Twenty SE amp. ET-7 C-J pre. Exasound E-32DAC, Mac Mini i7, Anthem MCA-3 power amp, Anthem AVM-60, Oppo BDP-103. ML Stage X Center, Motion 4, BPTSignature 3.5 Plus condiciones.

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