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Tubes from the Tone Selection are multiply matched and
selected tubes which are intended for the following uses
and amplifiers:
1. Amps without adjustable bias (non-adjustable bias) such
as Mesa amps. Because the bias is fixed at a specific voltage,
and no adjustment of the sound is possible, tone tuning
can only be achieved by use of tube sets defined by required
current. As such, a „softer“ set consumes less
current, whereas a „harder“ set consumes more
current.
2. Amps whose bias is set for a particular selection grade,
and in which no bias adjustment is desired when swapping
tubes. (Nevertheless, we always recommend – as far
as possible – that the bias be checked and set when
replacing tubes).
3. Amps in which the bias range is limited; for example,
Marshall and similar amps. It could happen, depending on
the tubes, that the range of the bias pot is insufficiently
wide so as to permit correctly setting the bias. In such
amps we recommend the use of a „standard“ set,
which normally can be used without a problem.
4. Users who wish to extract the maximum performance from
the tubes. In this case, ‘hard’ or ‘extreme’
sets are recommended. These tubes measure 30% - 50% over
the ‘standard’ sets.
Classification
The classification is performed under conditions of constant
bias, anode, and screen voltage. A change in the bias voltage
would shift the definition accordingly.
Soft: a tube set with soft tone and gentle
attack, without a particularly high output. Useful for low-gain
amps or to attain a slight output reduction. Also good to
warm up a harsh, cold output stage.
Standard: A set with this classification can be used in any
amp designed for the tube type without problems. A balanced tonal spectrum will
be produced, which provides a clean fundament for diverse uses. Recommended
for all guitar and bass amps.
Hard: these tube sets will consume more
current, sound harder and more sharply defined, but also
slightly ‘analytic.’ Depending on the amp, they
can sound cool. Interesting for audio/hi-end applications
where clear reproduction is required; as well as in modern
hi-gain amps.
Heavy: Tubes in this classification are rare, and have a very
high current consumption and transconductance, far beyond that of the standard
tubes. These tubes are used in applications where the absolute maximum performance
is required. The tone is very clear, defined, and highly dynamic.
Application examples:
A Peavey 5150 is shipped with a cold bias voltage. A set
of ‘hard’ or ‘extreme’ tubes results
in a higher current flow; which in turn will produce a harder,
sharply defined tone, with excellent dynamics.
Tonal differences:
It is difficult to describe and measure the tonal differences in any real-world
application, as these differences are dependent upon many factors. Basically,
any amp which is designed for a relatively neutral tone, and which uses high-quality
components – especially the output transformer – and which is also powering
a neutral and well matched speaker cabinet, will show a greater change than
amps built from inferior parts and circuitry, or with a poorly dimensioned output
transformer or a poorly matched speaker cabinet.
Mesa Cross-Reference:
Soft : Mesa red
Standard: Mesa red / yellow
Hard: Mesa green
Heavy Mesa gray |
