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The MaxiPreamp 2 seems to be very popular, until recently it was backordered. So, I'm wondering if anyone has compiled a set of "average new" transconductance (Gm) or gain (Mu) values? Or if we could do that here?I'll start out by suggesting that the average new for a 12AX7 is 1600. Anyone agree or have a different opinion?
Edits: 06/30/16Follow Ups:
1400 to 1600 sounds about right for new on the Heathkit TT-1..The Hickok 539c is also great for testing dual triodes,especially with the noise test and an AM radio..
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Hi Michael, The MaxiPreamp 2 is a currently produced, small signal tube tester. They provide the values for the voltage, current, etc that the tubes are tested at, but they don't provide values for "average new" test results for transconductance as other tube tester manufacturers do.I'm hoping that we can put together this information from personal experience. Say that somebody who owns a MaxiPreamp 2 tester has a tube that he bought from one of the good sellers that when tested by the seller was right on spec for "average new". That person can then test the same tube on the MaxiPreamp 2 tester and report the results here, and that eventually we can put together our own list of "average new" results for various tube types tested on the MaxiPreamp 2.
Has anyone here made this type of comparison yet? As I said, from my testing of 12AX7s on other tube testers and the MaxiPreamp 2, I think that the "average new" result for a 12AX7 would be around 1600 for transconductance (Gm).
What do others think?
Edits: 07/01/16 07/01/16
If they used the voltage and current specified on the data sheet, transconductance should match too - so 12AX7 at 250V, 1.2 mA should be 1600, at 100V, 0.5 mA should be 1250. Some tubes will have a graph of transconductance vs. current - for instance the GE data sheet shows 400 at 0.1 mA, 1900 at 2.0 mA (both at 100V). All these in micromhos, or uA/V (same thing. Move decimal left three places for millimhos or mA/V.
Edits: 07/01/16
According to the website:Filament voltage: 6.3 VDC regulated
Filament current: 1.5 A DC Maximum
Plate Voltage: 200 VDC regulatedSo what does that tell us? Is there a website that I could look up data for various tube types using these operational points?
Edits: 07/02/16 07/02/16 07/02/16
This simply tells you what the tester is capable of.In all my experience all these years told me you can't get a consistent relative reading on small high mu triodes because it varies from manufacturer to manufacturer.
I have some old Telefunken 12AX7s that test 15% of what many new 12AX7s test and they work fine when you put them in the circuit.
If you're buying this unit to sell tubes with,I get why you might want this tester for readings..If it's for personal use or even sales for that matter,you want a tester you use for noise and microphonics.How much do they want for this tester/matcher?
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 07/04/16
That is not enough information.
Just do a search for 12AX7 data sheet, and you should find several links.
The Maximatcher stuff is fine for testing tubes relative to one another, but is not flexible enough to correlate to "book" information as they seem to have operating points that do not compare to any typical values you would find in something like a tube manual.
If the Maximatcher people can't provide the information you are looking for, then no one can. If they are unwilling to provide it, I would look elsewhere.
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