Could you tell us more about
the transformer?
I developed the LTHZ transformer because
when you are routing a guitar signal to
two amps, you will typically have two
problems: ground loops, which are especially annoying when using overdrive; and
phase inversion, possibly causing a thinner
sound. Both problems can be cured by
using a transformer. Standard transformers
are not built for guitar signals; even the
most expensive models will change your
tone noticeably. A guitar pickup isn’t like
a mic, with even bass, mids and highs. The
typical electric guitar sound is the product
of the resonant frequency in the mids of
the pups in combination with the guitar’s
electronics, your cable and the input stage
of the amp. When you use a standard
transformer together with a guitar signal,
you will shift this mid peak towards the
lower frequencies, resulting in a completely different sound, often perceived
as a loss in high frequencies. Strong signal
sources like active outputs from a key-
board don’t have any characteristic peaks
and a standard transformer will not change
the sound noticeably. A guitar signal is a
much weaker signal, comparatively, while
its input impedance is much higher than
any line-level input.
You can use this effect to build a low-cost,
A/B/Y box. You only have to boost the
signal with a small active preamp, then
you can use any standard transformer
afterwards. This will get rid of the phase
and ground problems we talked about, but
this way will also destroy the interaction
between the guitar and the amp. The best
thing to do is to use a transformer that
keeps this interaction untouched – that
does not change the resonant peaks of
the pickup in combination with the amp.
Because there was no manufacturer producing such a transformer, I developed
my own, starting from scratch. This transformer, used inside the Dual SGoS, Little
Dual and the P-Split II, has a very high
impedance and leaves the guitar signal
untouched. The typical input impedance
of a guitar amp is around 1 Megohm. The
native impedance of my transformer is
approximately 1kHz, which is ten times
higher. Because of this, the transformer
will not influence the mid frequencies in
any way. At the same time, the coil’s DC
resistance is very low while the coil inductance is very high. Because of this, the
signal will not lose any volume. Coupled
with a low-impedance source like a mixing
console or a preamp output, it is possible
to stay absolutely linear between 20Hz and
100kHz. I also sell my LTHZ transformer to
audio and hi-fi manufacturers.
