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Help reading Amplitrex Tube Testing Data

J

JollyGreen_

New Member
Hello all,

I've found some of my dream tubes, very hard to find but I have no idea how to read the tube testing data. Can someone help me with this to see if they are matched and good tubes?

I know one will "burn out" before the other, but Im not worried about that, I just want to make sure that if I use them both in my gain stage of my Schiit Freya+ preamp that there will not be a noticeable difference in sound/sound quality between them and between channels
 

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just a clarification question are "results 1" for triode #1 in each tube, or are the two "results 1" pictures both for the same physical tube, but I'm looking at the two different triodes?

Just trying to make sure I think I understand what I'm looking at before running my mouth too much :)

The other question is what are you looking for in terms of matching? Tube to tube, section to section, or both? Sort of depends on the specific unit and how it uses the tubes which matters.
 
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gadget73 said:
just a clarification question are "results 1" for triode #1 in each tube, or are the two "results 1" pictures both for the same physical tube, but I'm looking at the two different triodes?

Just trying to make sure I think I understand what I'm looking at before running my mouth too much :)

The other question is what are you looking for in terms of matching? Tube to tube, section to section, or both? Sort of depends on the specific unit and how it uses the tubes which matters.
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82/84 emission are the same tube, and the other two are the other tube. The only metric that matters to me is that they don't sound too "different" because I'm going to be using them in the L/R channels of my preamp and I want to make sure they justify the cost. I paid a crazy amount for these because they're rare. They initially weren't sold as a pair, he found a second one later. He says they won't sound "different" but I don't know how that is measured. It looks like the triods in each tube are matched "enough" but I don't know how much difference between those numbers is "ok"
 
There is probably enough feedback in the circuit that I doubt you'd hear any difference, but they aren't what I'd call matched to one another. Section to section within tube #1 is pretty decent, not as good in the other.
 
gadget73 said:
There is probably enough feedback in the circuit that I doubt you'd hear any difference, but they aren't what I'd call matched to one another. Section to section within tube #1 is pretty decent, not as good in the other.
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If I'm not mistaken the "GM" number is how well it tests vs the "expected" numbers for that tube type NOS, correct?
 
GM is transconductance, the % is how it compares to datasheet values. 2600 micromhos is spec at 250 volts on a 6SN7. What that actually tells you is how much current flow changes through the tube when the grid voltage changes by 1 volt. In this case its 2.6 milliamps per volt, or 2600 microamps if you like that unit better.
 
gadget73 said:
GM is transconductance, the % is how it compares to datasheet values. 2600 micromhos is spec at 250 volts on a 6SN7. What that actually tells you is how much current flow changes through the tube when the grid voltage changes by 1 volt. In this case its 2.6 milliamps per volt, or 2600 microamps if you like that unit better.
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And would you consider that to be in "normal acceptable range"?
 
96% at the minimum and 110% at the max is pretty good

First tube's emissions numbers are a little lower but still north of 80%. Nothing I'd be overly concerned with honestly. If these were sold as NOS for big money I might not be happy though.
 
gadget73 said:
96% at the minimum and 110% at the max is pretty good

First tube's emissions numbers are a little lower but still north of 80%. Nothing I'd be overly concerned with honestly. If these were sold as NOS for big money I might not be happy though.
Click to expand...

These are impossible to find and I only paid $85 a tube so they weren't crazy expensive or anything. That's right around what they cost anywhere you can find them online. And currently NOBODY has any of them. Best sounding 6SN7 I've ever heard so I snapped them up quickly.

Thanks for the info
 
For me more than about 10 bucks a 6sn7 is nuts, but I have a box full of the things that I've ended up with for free over the years and nothing that uses them.
 
gadget73 said:
For me more than about 10 bucks a 6sn7 is nuts, but I have a box full of the things that I've ended up with for free over the years and nothing that uses them.
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Well different folks like different flavors and some of those flavors stopped being made decades ago and are found less and less each year. So it goes...
 
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