Lots of current amps say "all
tube" unfortunately this is just not totally true.
The companies exclude
effects like the reverb, effects loop, channel switching, even
some have a solid state preamp driving the input of the
overdrive stage to avoid an extra tube - and they say "all tube"
7025, 12AY7,5751 ETC) tubes have two stages each I will count
EACH stage as 1/2 tube, both stages as "1 tube.
it takes 2 of the 1/2 tubes to make "one tube"
If the amp has
power tubes it has to have a phase inverter = 1 tube ALWAYS.
BE SURE TO ADD THIS ONE TUBE TO ALL AMPS
A Marshal preamp (tone
control section) with ONE channel has three stages for just a clean
channel = 1 & 1/2 tube
vintage Marshall has an extra volume (no distortion channel, just more
bass on that volume) = 2 tubes.
a fender tone
control section = 1 tube. Optional
that is 3
preamp tubes for a vintage Marshall NO EFFECTS, OR OVERDRIVE
like "overdrive" is at the least = 1/2 tube optional
More commonly 1 tube
double this if you
amp has two complete channels (both with their own set of tone controls)
a reverb at
the cheapest = 1 tube
a good quality (fender like) reverb = 2 tube Optional
a vibrato as used by
marshall = 1 tube optional
an effects loop at the
least = 1/2 tube
a good effects loop with level controls = 1 tube optional
companies like to end up with an even count of tube halves. they do not
like 1/2 tube hanging around, just not economical.
Add them up,
kind of hard to do, all the one tube and 1/2 tubes and see how many
preamp tubes are NECESSARY to have an "all tube" amp with the effects
your amp has. If it doesn't add up, some stuff is solid
state. For Example, a Marshall 900 with 3 preamp tubes CAN'T
have a tube reverb, overdrive, effects loop etc.
See, kind of
tricky and LOTS AND LOTS of amps are NOT all tube
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