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Thank you Jim...

Posted by Vinyl Valet (A) on February 7, 2015 at 08:00:43

In Reply to: RE: Test Results... posted by Jim McShane on February 6, 2015 at 18:08:50:

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.


Open up your mind, in pours the trash. - Meat Puppets, 1987

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