Tube test data-can someone decipher this for me?

[ben.]

Tested on METRIX LX109 Tube Analyzer @ Ua=Ug2=250V DC Uh = 6.3 VAC.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Plates values indicated are in Milliamperes. (mA)

TUBE # S (µmhos) Ip @ Ug1= -18V Ip @ Ug1= -14V

14 7.750 62.50 93.50

15 7.900 69.90 101.50

16 7.725 52.00 82.90

23 7.950 50.80 82.60

26 7.625 64.00 94.50

These are examples from a batch of tubes I bought. Can someone tell me what I'm looking at? Thanks in advance for the education.

Ben

[ben.]

[NOSValves]

Me Too !!

All I understand is the testers I have ! Never even heard of the one your mentioning. But the results sure look impressive. Where did you get the use of that tester ? Sounds like way more information then you or I would need LOL !!

[ben.]

Ok, thanks for the translation.

Short term question. In order to match tubes with this data, what figures do I need to get as close as possible? I am guessing mutual conductance.

Long term question. Any recommended reading where I can gain some actual understanding of how tubes behave, and an overview of different topologies?

[3dzapper]

Ben, Transconductance is the most used measurement for tube matching, but you have much more valuable information there.

Using transconductance you'd match 14 & 16 and 15 & 23. But, if you look at the plate current those are not the best matches. 14 & 26 and 16 & 23 have closer measuring plate current at both -18 and -14V at the grid and IMHO would be a better complementary pair. In other words those pairs "track" better.

Rick

[ben.]

Thanks, guys. I should have been more specific, I guess. Yes, they are power tubes. 350B intended for Heath W5M and/or MC30.

[leok]

For the Heath W5M you can match the S value. There is a very effective bias balance circuit, which you are expected to use to remove differences in tube to tube bias points. This will give you the most matched signal into the output transformer during class-A operation. If the bias adjust can't bring two tubes into balance, then choose a pair with closer values on the -18V bias reading (the Heath biases at about 50mA but at a significant 430V Plate to Cathode), and as close as you can get in "S" value.

They are all really pretty close in gain.

Leo

[Allan Songer]

And for the MC30 you don't have to worry about matching at all . . .

[ben.]

Thanks, guys. Straight sh!t from those who know. What more do I need?

[ben.]

[Benesesso]

I am presently running two 2A3 tubes (one per channel) that have very different Gm values, but I hear no difference in volume (preamp knobs set ~ the same) or "clarity" in my Wright SETs. Shouldn't the much lower value have less output for the same input, or is it simply a case where the lower tube can't make the same "full-power" wattage of ~3.5 watts? I think I'm only running a watt or less on most music.

Benesesso