All 12AX7 Tubes are NOT Equal - Some are crap!

[James Wolf]

Tubes?

Must be a true audiophile.

Jim, KR9U

-----Original Message-----
From: tacos-bounces+jbwolf=comcast.net at amrad.org
[mailto:tacos-bounces+jbwolf=comcast.net at amrad.org] On Behalf Of Joseph
Bento
Sent: Thursday, April 25, 2013 12:30 AM
To: Tacos AMRAD
Subject: All 12AX7 Tubes are NOT Equal - Some are crap!

I've been ripping my hair out trying to get a circuit to perform properly.
Seems the culprit was brand new Chinese manufacture (J&J
brand) tubes - 12AX7 and 12AU7.  My circuit uses both. Noise, feedback,
microphonic... any undesirable characteristic was there!  Tried some old
1950's RCA 12AX7 and 12AU7 and everything worked perfectly.  Tried a
different manufacture Chinese 12AX7 that I've had for a few years, and all
is well - a bit hotter than the old RCA.  I actually sub'd a 12AX7 (another
older Chinese manufacture) for the 12AU7 and am happy with the result.

Now why am I playing with tubes?  The answer will be revealed when we gather
for Hamvention.

Joe, N6DGY

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