I have a Conrad Johnson Premiere 17LS. This will be the third time in recent years that my tubes have become microphonic. I read somewhere that the reason is because Conrad Johnson preamps are known to be hard on tubes, and that is the result of high gain (usually 26 to 29 db of gain). Is there any truth to this? I just ordered another quad of tightly matched, balanced, & low microphonic Jan Sylvania 6922 tubes from a reputable online dealer. Once installed, I don't tube roll and hardly ever move the preamp. I do play the volume pretty loud at times. I don't use the silicon dampers that came with the preamp, but I am thinking of using them this time around. Your thoughts and experiences?
The gain is high because they don't use negative feedback, which may also tend to show up microphonics more. The tubes come with the silicone damper rings, and that's what I've always used on mine, never had a problem on either my Premier 15 phono stage or 17LS2 preamp. I have experimented with different tubes, but never due to microphonics or other issues, just for sound quality. I have heard the newer preamp range with the GAT topology is harder on tubes, the ET3 for instance just uses the one 6922 since it has a MOSFET output buffer, and some complain that it goes through tubes faster, but that would be related to bias and operating curve. The 17LS is the previous ART topology, so uses four 6922 tubes in parallel to form one monolithic gain stage, no output buffer needed. Anyway, just my experience with those two pieces.
If so, that’s something I’d want to know for sure. And a test socket like this: Vintage Vector 9 pin Vacuum Tube Socket, Tester? | eBay . . . plus a voltmeter and the 6922 data sheet would enable you to start confirming for yourself.
For Chinese & Russian tubes 2 to 3 years is about max for CJ's. That's when tubes wear down to 70% and sound becomes compromised. Telefunken smooth plate goes an easy 7 years. (Best sounding by far). Telefunken waffel plates 5 years. Mullards about 4 to 5 years. USA types 3 to 4 years. Needless to say I've been hoarding all the Smooth plate Tele's for myself. Buck
I had a CJ Classic 2SE. It was a great preamp but it was hard on tubes. Gold Lion 6922 lasted but if you don't pay a little for triode matching and noise screening you risk getting a bad one. They have had some duds , although I have mostly had good luck with them in that and as amp driver tubes
I do seem to have to change the (6 !!!) tubes in my CJ Premier 16 LS2 more often than I would have guessed.
What causes you to change them, are you hearing a loss of quality, or do you get actual failures? My 17LS2 is similar, just 4 tubes in parallel instead of 6, haven't had any need to change them in a few years, but I have maybe three or four different sets that I've tried, mostly very old types. Still, the latest set has been in for quite some time and it's on 12-16 hours most days so piles up the hours quickly. Interesting to hear some of the responses.
In days gone by I've owned various iterations PV7,PV8 and PV 10 with no tube issues.Perhaps this is model specific?
I don't know about the newer gear, but their older preamps always used to run a 330V power supply, and never pushed the tubes especially hard. CJ amps on the other hand did tend to push the output tubes fairly hard and biased them on the high side.
I had an ET3 SE and it was almost like clockwork, changed the 6922 every 9 months. I ended up selling the CJ and purchased a Luxman CL38U se. It's been four and a half years and I still have the original tubes.
If you really like the sound, it's a small price to pay. I had a mid 70s Rocket logo Reflektor 6n23eb in there that seemed to last forever. I sold it with that tube and two modern issues. I bet the new owner still has that tube in it . The Classic was very picky with tubes. Tubes that were quiet in other gear had a faint noise. Hit or miss with new production but that Reflektor was dead silent
Not too small of a price. My ART mono's had 10 tubes each and required changing about once a year. If it wasn't for that I would have never sold them.
I think this might be true. I have the original Classic SE ( two NOS Mullard 8080; no phono stage, line only). No problems whatsoever; I must have 3500+ hours on the current pair, and they still sound Mullard/CJ sweet. Love the things. I believe the Classic 2 and the ET3 moved to a single 6922. Maybe that puts more strain on the tube? I also have a PV7. I'd say I normally got 1500hrs out of the tubes on that one. I'd consider that acceptable. Obviously, what I say only applies to my own models. CJ has made a lot of great preamps over its career.
Part of the problem is that many new 6922 suck. And I don’t necessarily mean every type sounds bad They don’t but you may go through a few before you find one that has matched triodes or really has the emissions of what is considered a new tube. NOS are way overpriced , many aren’t really NOS but strong testing pulls. They were very popular in everything from test equipment like oscilloscopes , medical equipment, defense electronics…. A lot of stuff. I am steering away from stuff that uses 6922 because good ones are scarce and expensive
Totally agree. I'm not impressed with the new manufacture 6922 I've listened to. Very dead-sounding. I would be tube rolling if I bought an amp/preamp using them. I'm a big NOS Mullard fan, but I don't recall seeing a Mullard 6922. Maybe they made one under a different number, but I haven't seen that either.
I have an ET 3 . It was delivered wit a Russian tube but after 500 h it became nosy so I replaced it with a Telefunken tube. Much less noise and it sounds much better. But I still do not know which side of the ground is Hot and which side is cold on the electric input dwell.. Eurupewan and japanse products it the ground is on top. left side is hot ( brown) and right side is blue neutral cold. But I heard Conrad - Johnson is opposite. Is that true. Left side is cild and right side is hot.
