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In the Forum: Analog Playback
In the Thread: 7788 tube mic pre design
Post Subject: The "art" of buying high transconductance tubes.Posted by Romy the Cat on: 1/19/2008
 hagtech wrote: |
| Romy, you were right. I just got in another pair of 7788 from eBay. This time, one tube has a little bit of microphony, not bad, really. The other was dead quiet! No ping at all. Very impressive, that sample. So now I guess I have to buy batches and select... |
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Well, it how it should be. The 7788, according to people who knows, at its max gain has the lowest noise among any other reasonable tubes. I have to admit that with exception the large party of the pulled Amperex tubes that I bought in the past (that were juts all severely burned out), and among all others 7788 that I have (perhaps 40-50 tubes of the few brands) I never come across any 7788 that was microphonic. I did not plug all of my tube in my phonocorrector but I did plug one or two of each brand (perhaps a dozen brands and vintages). Perhaps it was just luck or perhaps it was just the way how I buy them.
Talking about 7788…. I do not buy used tubes; I do not buy tubes that were measured; I do not buy tubes that have no original boxes. I do not buy single tube or a pair of tubes. I tend to buy the 7788 from a seller who has a party of NEW 10s or 100s of them. All of them should be sealed and then I buy my few tubes from that party. I tend do not buy the high transconductance tubes if a seller has a part of I would say 20 tubes and 2-3 of them without original box. To me it is bad sign saying that somebody who owned the tubes cared about them. Well, perhaps I am wrong, but not doing audio for living I know that if I sell anything then it is something that I really hate or do not need. Perhaps I am wrong… but I never seen the bad sounding or noise 7788. My experience with WE 417A/437A was very much different and at that times (~2001) I was buying variety of those tubes that did not comply with my “rules” above and as a result was horrible – 80% of my WE tubes were horrible. I am not saying the exceptions are not possible but… still I would be very anal if I was in market for high transconductance tubes, particularly since the price for 7788 went up last years and a dozen of a good 7788 might cost over couple hundred dollars.
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