On Sep 7, 0:53, Tony Duell wrote:
> I'll bet that in, say, 5 years time you'll still be able to get 12AT7s
> (what's that? ECC82?)
Roughly. My Mullard 1977 Data Book lists as equivalents
12AT7 ECC81
12AU7 ECC82
12AX7 ECC83
12AZ7 ECC81
but I notice that my 1976 book lists ECC81 as obsolescent! You can still
get them, though. That's a long obsolescence period! There's not much
difference, actually; ECC81/82/83 are the same except for gm, mu, -Vg and
Ia:
gm mu -Vg Ia
ECC81 5.5mA/V 60 2V 10mA
ECC82 2.2mA/V 17 8.5V 10.5mA
ECC83 1.6mA/V 90 2V 1.25mA
And I found the 12AT7 data elsewhere:
12AT7 5.5mA/V 55 2V 10mA
The small difference in mu between 12AT7 and ECC81 might just be the result
of minor differences in measurement techniques or manufacturer quality; I
read something that suggests the ECC81/82/83 were designed as exact
replacements for the 12A?7 series.
All data refer to 250V anode voltage. Those dual triodes are/were often
underrun at 150-200V, and obviously the gain and currents etc change if you
do that.
--
Pete Peter Turnbull
Network Manager
University of York
Received on Sat Sep 07 2002 - 04:40:01 BST