True Bypass and True Sound
Today more and more effect pedals fea‑
ture true bypass switching to completely
bypass the pedal in the signal routing
when the pedal is switched off. The target
of this design is to ensure that the pedal
does not affect the electrical signal when
it is switched off. This way the sound is
left unaltered ‑ in theory.
In practice, however, connecting several
pedals featuring a true‑bypass design in
series does not improve the sound or keep
it unaltered at all. Long runs of cable and
multiple connections lead to a weak and
lifeless sound. On large pedal boards the
overall length of the cable is enough for
the capacitance of the cable have a nega‑
tive effect on the sound. The capacitance
of the cable acts as a low‑pass filter (=
the low frequencies pass through the fil‑
ter while the high frequencies are filtered
out). The price and quality of the cable you
are using will not change this physical
phenomenon.
A solution would be to use only devices
with buffered bypass design instead of
true bypass. This, however, is only a good
solution if the buffer is of very high qual‑
ity. If several units with buffered bypass
are connected in series it only needs one
buffer to be noisy, cut the dynamics of
the sound signal or negatively affect the
sound in any other way for the sound of
the whole effect chain to be spoilt. As the
saying goes “a chain is only as strong as
its weakest link”. In addition, the noise of
the individual buffers adds up to produce
audible noise; it is a fact that every buffer
produces some noise, even if it cannot be
heard when only a single buffer is used.
The ideal solution is to have a very
high‑quality buffer at the beginning of
the chain that brings the signal down to
a very low impedance. This makes the sig‑
nal insensitive to the length of the cable.
It is important, however, that this buffer
is of the highest quality with the dynamic
range and headroom necessary to ensure
that all the details of the bass signal stay
are retained unaltered.
The effect pedals in the downstream loops
should then ideally have true bypass so
that they will not have a negatively effect
on the now buffered signal, as the true
bypass design does not reduce dynamics
and headroom or produce any noise.
Conclusion: having a True Sound Lehle
buffer at the beginning of your effect chain
combined with good true‑bypass‑equipped
effects in the loop guarantees the best
sound.
What is Lehle True Sound Technology?
Lehle True Sound Technology is a combina‑
tion of several electrical design measures
with only one aim in view: to transmit the
sound and the character of the instrument
without altering it.
The voltage supplied to the RMI Acouswitch
IQ DI is internally rectified, filtered and
stabilised and then brought to 18V. Sup‑
plying the buffer with 18V gives enough
headroom to guarantee an open and dy‑
namic sound in all situations without los‑
ing any detail, even when confronted with
pickup power peaks of up to around 7V.
The buffers are designed to effortlessly
handle signals reaching the megahertz
range. At the output, the frequency band‑
width is limited to the audible frequency
range to prevent HF interference from,
disturbing the electronic circuitry. This
Tech Talk
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