| New tungsols from SRS tubes and hickock results [message #9222] |
Sun, 02 October 2005 11:23  |
Russellc
Messages: 397
Registered: May 2009
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Illuminati (1st Degree) |
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I recently just could not resist the new very cool looking remake on the tungsol 6650. i have used SED 6550 or SED KT88 previously, but the tungsols are so cool looking I had to have a set. I purchased a quad from a well respected dealer of this brand (SRS), not just someone selling them. their testing is fairly rigorous, and I have had nothing but straight forward business with them in the past. When the Quad came, they were very well packed with no damage and arrived super quick.
When I put them in my properly working hickock 532. (yes I understand the limitations of vintage testers, even one that tests for dynamic mutual trans conductance or what ever) According to hickock info the settings should result in readings of 7000 gm. I have never had even known good tubes test this strong, usually I get just over 6000 for good ones. My current set of SED 6550 with 15 months on them are still at 6000-5025 on this tester. The tungsols tested like this: Three of them were very close, around 5500. but one was rather droopy, sagging to around 4250, then seeming to hold there, but subsequent test seems to indicate maybe 1/2 a needle width lower, but that may just be a little inherent deviation in testing. Upon contacting SRS they responded very quickly with a long letter which basically outlined their testing procedures and how it is done under more real world "dynamic" conditions that my vintage tester cannot reveal, and to "just plug them in and enjoy" Now I will be the first to admit that vintage tube testers are not the burning bush word on results, but if one (likemyself) uses the same one for years (particularly one that tests for dynamic mutual transconductance) on a limited number of tube types ( that I use myself in my equipment, not for resale) you can get a good sense for those particular tubes. The aforesaid testing I performed and the results I get indicate a "problem" to me with the one tube. the lower read of 5500 likely is a characteristic of the tester, (yes, even thought he SED 6550 tested as strong or stronger 15 months later) but the descrepancy in the testing of the one tube isnt. I have never had a well balanced matched set (properly done) that would show a variation of this sort in one tube only. To be fair, I thought I would inquire as to any that HAVE seen a properly matched se that would measure like this on a dynamic mutual transconductance tester, but still be properly balanced under "dynamic" conditions. While I hope I am wrong and it is possible, I cant help but think this would be an explanation that would always answer any descrepancy actual testing would show. I have had other business with this supplier and with no problems, I just cant bring myself to plug them in and enjo with out more.Russellc
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