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In Reply to: RE: Test Results... posted by Vinyl Valet on February 05, 2015 at 15:50:54
If I may just chime in one more time... As I've posted many times before, voltage - of and by itself - is not an indicator of how hard a tube is being used. For instance, at 80 plate volts if the tube is passing 10 ma. cathode current then it is dissipating .8 watts, well within the limits for the 6922. However, if the current was 20 ma., then the resulting 1.6 watts dissipation is above the 1.5 watt (2 watts total combined for both plates) limit listed in the RCA tube manual.
So saying that because the plate voltage is only 80 volts is only part of the story. The plate current must be factored in to determine how hard the tube is being run.
As well, it would be wise to check the heater voltages. Too high or too low can definitely shorten tube life in a number of different ways. and usually it takes some time for heater voltage issues to become audible or noticeable (short of a major over or under voltage issue!).
Also - the US distributor is also the people who own the Saratov, Russia plant that makes the tubes - New Sensor Corporation of Long Island City, New York. Their URL is listed below. If you get a response please post what you find out.
As I've told others who have asked me - the quietest 6922 I know of is the 6922 Electro-Harmonix. It also is very durable and tends to be long lived in most gear. It is the ONLY 6922 that will hold up reasonably well in a number of "tube eating" pieces of gear.
Having said that I can also say the 6922 Genalex has been excellent in many areas including typical lifespan and noise/microphonics performance. I do get lots of feedback from customers and many repeat purchases from customers who have experienced normal and typical life from the tube. However, in some cases the only tube to use IMHO is the EH.
In the meantime, if you decide to replace those tubes I'd be happy to have you send them to me for testing, I'll pay the shipping. I'd like to see what's going on, and be able to better comprehend what you are experiencing. I'll report my findings on this forum. Let me know if you'd like to do that.
Follow Ups:
I’m heading out shortly to go fishing with my sons for a few days and will ship the tubes when I return. I tested them for current, transconductance and amplification factor, both when new and after failure. I’ll send that data along with the test conditions so you can compare my measurements with yours to include in your final report. Please ship the tubes back to me when you’re done. Before that let’s talk since I obviously need some more tubes and I’d love to have a set of Gold Lions that are reliable. Would you be willing to provide an extended guarantee for noise issues beyond the normal period? I’d be happy to provide any other measurements to assure you that my phono and pre aren’t “tube eaters.”
Of course Vp isn’t the only relevant parameter. The question of proper equipment operation was initially raised in the context of faulty regulation. I tested and answered in kind. Yes, I also tested for filament voltage and plate current. The phono stage filament voltage is normal with plate current at 14mA/triode. I measured plate and filament voltage on the pre (no schematic), checked with the designer, he reported back that everything is normal so I did not see any reason to go further since I’ve run several brands of tubes (new and NOS) in it previously for thousands of hours with no significant tube failures for any parameter. As I reported earlier, I had great results with EH. Before that, the tubes that shipped in the pre (can’t remember the brand) also operated for thousands of hours without any major issue. I’ve also used NOS Tungsrams with no issues.
If these failures had occurred only on the phono stage or pre, I would have done a full analysis of the questionable piece by the second or third failure. But I was seeing failures in both, gear that I have owned for over a decade, that had used different brands or batches of tubes, both new and NOS, without any issue. It’s likely, if there was a major shift in operation that would cause this kind of catastrophic failure rate, I would have heard the shift in sound. I would not characterize either this phono or pre as a “tube eater.” I know “tube eaters” as I was once an Audible Illusions dealer.
Most of us are familiar with the reliability of the EH tubes. That’s why most new equipment manufactures (both home and pro) ship their gear with EH 6922s (including Herron Audio). There is no reason why the Gold Lions should be any less reliable. Would you not agree, especially at three times the cost? As you know, this type of failure is typically due to internal contamination during the manufacture of the tubes, something that can relatively quickly become a problem, whether you are running the tube hard or not (running it harder would certainly accelerate this noise defect but not cause it). Perhaps, because this is a fairly new product, there is some problem stabilizing the initial yields at the factory for any number of reasons. I spent the better part of my career dealing with semiconductor production yields and, in my case, those devices ended up in implantable pacemakers, a far more critical application. We would occasionally have yield busts on mature product, so anything is possible. It all comes down to how extensive your burn-in (accelerating defects) and final testing is; the ideal being that no yield bust, no matter how bad, makes it to the consumer (or in my case the hybrid level where failures would be substantially more expensive and difficult to detect). Another scientist and I pioneered techniques to accelerate defects at wafer probe through over stress and subsequent test, very challenging since we needed to keep test times at that level to just seconds on very large scale digital, analog and mixed signal ICs due to the crazy cost of these mixed signal IC test systems (LTX) and wafer probers. I doubt there is anything like this going on in the production and testing of most new tubes for economic reasons. I’m sure this noise problem could be accelerated by some type of burn-in (electrical and/or environmental) and then caught at final test. This isn’t a life threatening situation, so the costs can’t be justified. That’s where secondary screening by a competent tube vendor is so helpful, something I always recommend my customers take advantage of, the extra cost being well worth it. Even so, one can only do so much.
Thanks again for your kind offer.
I'll be happy to test and return the tubes, thank YOU for your help!!Of course I'm too late in the sequence to affect the build quality of the tubes as they are completed long before I see them. But I do my best to provide tubes that are top quality, which means I do quite a bit of testing myself - both to verify the tube is within a reasonable tolerance of meeting the nominal characteristics and to verify proper operation.
I also check each and every tube for noise and microphonics. Most 6922 Genalex measure about -80 to -82.5 db below 1 volt RMS from 20 Hz to 20KHz. As well I am able to listen to the actual noise generated by the tube in 3 different test setups. And I can see heater-cathode leakage in microamps. So I can find noisy tubes with pretty good consistency and accuracy.
I would just like to point out that 14 ma and 80 plate volts means each triode is dissipating .014 x 80, or 1.12 watts. That's about 75% of the max per triode, but the sum of the two - 2.24 watts - exceeds the RCA and Philips spec for total dissipation of both triodes operated simultaneously - 2 watts. That exceeds the spec by about 12%, although it should be noted that RCA and Philips both used the "Design-Center" rating system which is the most conservative of the tube spec ratings (as opposed to Design-Maximum or Absolute-Maximum ratings).
I'll leave it for others to decide whether that makes the preamp "hard" on tubes or not. I will say the tubes definitely aren't "loafing".
I'll post my test findings as soon as I have them for all to review. It may take a couple weeks as I'm going to be out of the office February 16-20.
Edits: 02/08/15
I also had similar results with 2 tubes but on different halves, both developed a lower gain output on one side of the tube, and that side became noisy. They were early production tubes marked 1012, since then I have had no premature failures with later production runs up to 1202, after that I can't say. But for the other tubes that didn't fail they have been running since early 2011, mostly in BAT phono stages and preamps. Jim I can send you these tubes if you are interested, just give me your mailing address, and you don't have to send them back to me.
Do me a big favor - go to my website and email me, I'll send the address back to you...
Thank you VERY much!
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