Tube went bad in my PV-12

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Tube went bad in my PV-12

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So it looks like one of the tubes in my Conrad Johnson PV-12 is going bad. I noticed a slight audible "shhh" sound and I called up Conrad Johnson and spoke with "Ed". He suggested I try swapping the tubes to see if the sound changes as it could be a tube nearing the end of its life. Sure enough, swapping the tube made the sound go away. It's great to have a company where you call up and talk with somebody who actually knows the product (even if it is over 10 years old)! Can you imagine calling up a company like "sony" and getting somebody on the phone that actually could trouble shoot a product that has been discontinued? Also, I only needed to buy one tube per Ed's suggestion. This was nice as I was expecting to have to buy a pair.

The tubes were sent out and after a quick swap I was able to identify the bad tube. The noise floor dropped to inaudible and all seems well again.
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Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
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Re: Tube went bad in my PV-12

Post by Animal »

Ed Deitemeier is one of the true gentlemen of the audio world. He is unfailingly well informed about his products and will do anything he possibly can to help a customer out. He is, in many respects, Conrad Johnson's "secret weapon". I have picked his brain regarding CJ products new and old and he never ever fumbles for an answer.
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Re: Tube went bad in my PV-12

Post by billyz »

The PV12 seems a bit hard on the line stage 12au7's. I have rolled many tubes in mine over the years and the best and most reliable is the RCA Cleartop 12au7. The sound is much more detailed and refined ,deeper sound stage, great tonal balance too. The best sounding is the Amperex Bugle boy, very 3D and full. The much touted mullard box plates I have tried were all bloated and microphonic. I preferred the CJ 12au7 to the box plate cv4003. I understand the grid resistor to the 12au7 could be the source of the sometimes trouble.
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Re: Tube went bad in my PV-12

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Well, after many more years of flawless use, I notice a very faint but noticeable noise in the left channel. I couldn't hear it when music was playing, but when silent and walking close to the speaker it was definitely there. I started doing my trouble shooting by crossing the channel wires, starting from the speaker and working down to the source equipment. Narrowed it down to the PV-12. Having gone through a similar situation some years ago (as noted above), the first thing I did was swap the tubes and it seemed to solve the problem.

Went online and decided to go with a JAN-GE 12AU7A / 6189 tube. https://www.thetubestore.com/jan-ge-12a ... ined=19.95 Seemed very reasonably priced and delivery was fast (5 days including the weekend) even though it shipped from Canada. Would not hesitate to recommend the thetubestore.com to anybody looking to buy tubes for their gear.

The system sounds great (zero noise) and I have put a few hours on it already. Interested to see how it further improves with more burnin.
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Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
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Re: Tube went bad in my PV-12

Post by roberto »

Hola,

Hissing is one of the symptoms of a bad tube. Usually the little tubes are the culprit of noise. Also, they are double triode, that means that one half could be working of the left channel, and the other half the right channel. The best way for testing a noise tube is its replacement. When you change it and the noise or hiss goes away, you just fund the bad tube...if not, then that tube is OK.

Having spare tubes is wise because you do not know when they are going to fail. Conrad Johnson is using usually a common easy to find tubes. My ET-7 after one year of use, I got the left channel with a hiss. Just replaced the 6922 for another fresh one, and that was it,

Happy listening!
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ML CLX BF-210 Stage X Motion 4. CJ 120SE amp ET7V2 pre, Holo May Kte Dac. Mac Pro. Power Cond. BPT Signature+ 3.5, Gaia II Feet. USB Lush^V3. Nordost SPM IC and Spk. Shun Mook, BCanto CD2 CD3. Linn LP-12/Unitrack tonearm/Denon DL103R MC.
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Re: Tube went bad in my PV-12

Post by AnotherJohnson »

One thing thing that many don’t realize is that the tube may be amplifying perfectly well when it becomes noisy. If you had a non-audio application for the noisy tube, you could probably continue to use it just fine.

With guitar amps, since in most applications, they’re played loud, some tube amp gurus turn the amp on, hear some hiss, and comment “the hiss shows that it’s on.”

🤣🤣🤣
Last edited by AnotherJohnson on Sat May 22, 2021 9:17 am, edited 1 time in total.
It’s just stuff. I like mine. I hope you like yours. I probably like yours too.
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Re: Tube went bad in my PV-12

Post by admin »

Good points. Not to mention that it is sometimes hard to tell when the tube is failing. Mine was a barely audible hiss when I was near the speaker without music playing. I could not appreciate anything with music playing.

I am lucky to have remembered Ed's words of wisdom from all those years ago. Really did make diagnosing the problem really easy.
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Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
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Re: Tube went bad in my PV-12

Post by roberto »

Yup, signal to noise ratio is the first thing to know when a bad tube is somewhere the path. I hate noise, the micro dynamics are at that level. My system at late night, you can not tell that it is on...no hissing and no hum. I have a ceiling fan in our bedroom. When our weather is hot, of course we use our fan. The problem is that next to our bedroom, is my bat cave...so I can hear the motor of the fan working...I did try to isolate it, with no luck. The fan is supposed to be low noise, but it is not.

Oh well, the noise is only when the wife is in the dorm...just a couple of hours usually only...and then she goes to sleep. The then hum is gone...the truth is: clean sound is require to listen nuances and boundaries that belong to the room where the recording took in place. There are so hidden details that I really enjoy when I do a critical listening. As an example, the natural plucking of the bass strings. Listen to Hank Jones, Rockin' in Rhythm, track no1, Your Feet' Too Big, the Ray Brown solo is amazing real! Only having a quiet ambiance is the way to listen this amazing bass player. Also the cymbals are projected in the air with outstanding reality too. And the Fender Rods, what a Master is Mr. Jones...

Happy listening!
ML CLX BF-210 Stage X Motion 4. CJ 120SE amp ET7V2 pre, Holo May Kte Dac. Mac Pro. Power Cond. BPT Signature+ 3.5, Gaia II Feet. USB Lush^V3. Nordost SPM IC and Spk. Shun Mook, BCanto CD2 CD3. Linn LP-12/Unitrack tonearm/Denon DL103R MC.
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Re: Tube went bad in my PV-12

Post by admin »

So after putting some time on the new tube, I developed another problem. I have noticed that after 10-15 minutes of on time, the left channel will produce a faint but noticeable high pitched but coarse sound. Did the standard trouble shooting and it was in the preamp and when I switched tubes V5 and V6, it went away. Contacted thetubestore.com and they were very helpful. Jon immediately replied and he thought it was a bad tube. He offered to send a replacement or use the credit to upgrade to a Gold Lion/Genalex ECC82/B749 which he specifically recommended (I had asked if they had a different recommendation). I went with the upgrade and it's in the mail now so I hopefully will receive it this upcoming week. It's always disappointing to get something that doesn't work as planned but the customer service at thetubestore.com was outstanding so I have no question about ordering from them again.

I'll keep you guys posted.
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Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
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Re: Tube went bad in my PV-12

Post by roberto »

Yes Admin,

Also you don't know when a tube is going to have a failure. Just happens. Odd noise at one channel is the most common problem. Also lower signal at one channel too. The only way to find out which is the problem is swap them. If the tube is shared with both channels, then changing it for a new one will tell if that tube is the culprit. It is wise to have spare tubes on hand.

Happy listening!
ML CLX BF-210 Stage X Motion 4. CJ 120SE amp ET7V2 pre, Holo May Kte Dac. Mac Pro. Power Cond. BPT Signature+ 3.5, Gaia II Feet. USB Lush^V3. Nordost SPM IC and Spk. Shun Mook, BCanto CD2 CD3. Linn LP-12/Unitrack tonearm/Denon DL103R MC.
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Re: Tube went bad in my PV-12

Post by admin »

Quick update. Looks like the Gold Lion tube fixed the issue. Very happy with the results. Haven't been able to put "serious hours" of listening on the tube but so far it looks like everything is working better than ever without any hum/noise/volume issues.

Have to give credit to thetubestore.com. Excellent communication and service. I had emailed them late Thursday night (after business hours), they responded Friday morning, we agreed on the tube replacement and they sent it out the same day, was at my home by Monday. Pretty good considering it was an international order (Canada to US).
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Home Theater in Member Gallery
Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
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