Warm Audio WA-2A Mode D'emploi page 8

A LOOK INSIDE
A quick look inside and you will find the WA-2A sports an all discrete, class-A, all tube circuit, using
only through-hole components on a hand-populated board. The WA-2A has a robust power supply
to deliver current to its four vacuum tubes, a socketed Kenetek T4B module (optical attenuator), and large
custom transformers by CineMag.
A FEW WORDS ON TUBES
The WA-2A operates on four tubes: two 12AX7's, one 12BH7, and one 6P1 miniature power tube.
The classic units of the past used a 6aQ5 valve in place of our 6P1; unfortunately the 6aQ5 has
not been manufactured new since the 1980's. Though still available in smaller quantities as NOS
tubes; we determined there were not enough reliable 6aQ5's left in the world to go into production
with. One of our early challenges was to find an available tube that had the exact same specifications
and characteristics as the vintage 6aQ5; because we did not want to deviate from the classic design
at all. We finally came upon the 6P1, a tube once used in hi-fi, which is essentially the same tube in
a slightly larger housing with a different pin configuration (in fact, the 6P1 valve has slightly better
specs than the original 6aQ5). To stay true to the classic in every sense, we have placed an original
6aQ5 socket wired directly in parallel next to the 6P1's socket; so you may in fact replace the 6P1
with an original 6aQ5 if you can obtain an original one in good working order. This will not by
any means improve the performance of the WA-2A and should not be considered an upgrade; but
we have left this option available for the sake of nostalgia and as a testament to the fact that the
original circuit has not been changed.
KNOWN TUBE SUBSTITUTION LIST
The two 12AX7 sockets may be populated with any 12AX7 (ECC83), ECC803S (hi-fidelity 12AX7), or
12AX7A/7025 (low-noise 12AX7). The 12BH7 socket may be populated with any current or NOS brand of
12BH7. The 6P1 socket may be populated with any 6P1 (Asian) valve or 6N1N (Russian equivalent). The 6aQ5
socket may be populated with any working NOS 6aQ5 valve or 6005 (high performance military grade 6aQ5).
DO NOT POPULATE BOTH THE 6P1 AND 6aQ5 SOCKETS AT THE SAME TIME! The 6aQ5 and 6P1 sockets
are wired in parallel, and only one socket must be populated at a time to avoid serious damage to the equipment!
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