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SPAX7-A

Sensibly equivalent to:
12AX7 12DT7 6057 6L13 B339 CV492 E2162 ECC83
See also:
Mesa SPAX7-A Box
    
Extras ▼

 

The SPAX7- is a 21st century special quality ECC83.
The it is a high impedance amplifier triode was designed specifically for audio use and has a high amplification factor of 100.
The plastic sleeve over the glass obscures the inner structure.
This example has had the plastic sleeve raised to show the construction. Note the depression in the anode.
The anode depression means that like the ECC86 the working face of the anode is very close to the grid whilst the bulk of the anode and hence the heat radiating surfaces are further away.
The box shape of the outer anode can be seen on the left. The screen is in the centre. The grid supports are copper. No grid heat sinks are required for this low power audio valve.
Looking directly at one anode: the screen can be seen to extend beyond the electrodes. Typical of modern construction the three part base pins have copper wire for the internal section.
The thin glass tube envelope is 22 mm in diameter, and excluding the B9A base pins is 49 mm tall.
Reference: Datasheet.

 

Pin Connections
B9A
1
2
3
4
5
6
7
8
9
a(2)
g1(2)
k(2)
h
h
a(1)
g1(1)
k(1)
hct

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
Vg
mAa
ra
gm
6.3
0.3
250
-2
1.2
62.5K
1.6
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated May 10, 2016.
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