JJ 12AX7 : Standard, V1, Balanced …

I bought 3 versions of the JJ 12AX7 : “standard”, marked V1, marked B (balanced) selected by Tube Town, german online shop I appreciate. I tested them on my tube tester (Hickok 600A) to compare transconductance of triode #1 and triode #2.

The Hickok 600A user manual indicates a value of 1250 (Hickok value !) for a 12AX7 transconductance. Not really the transconductance value 1.6mA/V as indicated in the datasheet, it is simply how Hickok determines if a 12AX7 is good or not.

JJ 12AX7 standard V1 and Balanced

JJ 12AX7 standard (left), V1 (middle) and Balanced (right)

Hickok 600A used for measureThe Hickok 600A used to measure the transconductance

JJ 12AX7 Std, triode #1 : 1050
JJ 12AX7 standard triode 1

JJ 12AX7 Std, triode #2 : 1250
JJ 12AX7 standard triode 2

JJ 12AX7 “V1″, triode #1 : 1200
JJ 12AX7 V1 triode 1

JJ 12AX7 “V1″, triode #2 : 1200
JJ 12AX7 V1 triode 2

JJ 12AX7 Balanced, triode #1 : 1250
JJ 12AX7 Balanced triode 1

JJ 12AX7 Balanced, triode #2 : 1100
JJ 12AX7 Balanced triode 2

I don’t know exactly how Hickok does its calculation. Ua = 207V, Vg = -1V … It would be interesting to compare with the results from a Metrix 310, for instance, and test many more tubes std, V1 and Balanced to establish statistics …

Moreover, the transconductance is only one parameter among others and it would be a mistake to rely only on this one …

To be continued (or not ;-)

Website Pin Facebook Twitter Myspace Friendfeed Technorati del.icio.us Digg Google StumbleUpon Premium Responsive

This entry was posted in Amps and tagged , , . Bookmark the permalink.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>