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In Reply to: RE: LMAO.... posted by PakProtector on June 27, 2016 at 08:17:56
You are right in that the tube manufacturer doesn't make a different structured tube for an audio manufacturer however,it was very common for high end audio manufacturers like Fisher and Mcintosh to get better testing tubes to their specs for overall data,especially when the tube company puts the Mcintosh or Fisher logo on the tubes..Mcintosh doesn't personally go to the JJ or SED factory and hand select tubes,they do however get the best testing tubes and they pay extra for this especially when their name is going on it. JJ no doubt hand picks the tubes to meet the specs McIntosh requested before they print the logo on them. All in all they are still selected from same batches of production tubes,they just test better.
I was surprised to learn a few years back there were were A and B stock tubes..It sort of reminds you of when the auto industry rejects millions of tires each year from the tire companies because they don't meet the car manufacturer's standards,even tho they are perfectly good tires.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 06/27/16Follow Ups:
"it was very common for high end audio manufacturers like Fisher and Mcintosh to get better testing tubes"
That's absolutely correct. I've always been disappointed by the section-to-section and tube-to-tube variation in RCA 'SN7s. However, a few years ago I bought some of these that no one else seemed to want because they were labeled "Zenith." The matching on those tubes was unlike any I've ever seen, so good I wouldn't hesitate to just pull them out of the box and install them in an amp as-is. After seeing that, I went back to the seller and bought all he had. :)
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Buy Chinese. Bury freedom.
Back in 2005 on Ebay,a gentleman was selling these NOS/NIB Fisher branded EL37s.Of course these are Mullards but anyway these tubes came from a Fisher warranty service center back in 1968 and he worked there and had them all that time..He was selling for them for 90 dollars each and I bought the last two he had.He didn't sell these as matched tubes but when I got them I had noticed the number 946 at the bottom and being they both had this number,I thought I would throw them in my Heath TT-1 and they both tested identically on mutual conductance and emission and I mean to the number.I then put them in my maxi-matcher I made up out of a 475vdc power supply and biased thru 10 ohm resistors.I tested the tubes at 425vdc and minus 46 on G1 and the current draw was around 48ma as I recall but it was identical for both tubes. I then put them in my Fisher 80AZs which I have several and I measured plate temperature and even that was identical on both tubes when put them in the same socket and i measured at several different points.
Ten months later to the day almost I found another vendor selling some of these same tubes but he was in Parsipinni NJ where the other guy was in Chatsworth CA.I got two more of the same type NOS/NIB branded Fisher EL37s for 190 for the pair this time..I got these tubes a couple days later only to find out these tubes also have that same 946 code..That made me put all four of them in a friend's real Maxi-matcher and all four drew identical amounts of current at the 400vdc voltage..These four tubes were perfectly matched in everyway from mutual conductance,emission,plate temperature,and in even the maxi-matcher.
That's when I realized why this had to be.Being these were factory replacement tubes,the Fisher amps that use EL37s have no bias adjustment, so these tubes had to be matched and ready to go when you dropped them in.
Since I don't have a curve tracer,I match my tubes in a more primitive manner but it at least tells you they possess very similar characteristics.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 06/28/16
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