TT MIDI-Switcher - Version 2019
Introduction
The TT MIDI switcher is based on an ATMEGA 16 micro-controller and can be used as
switching central for channel switching and / or additional functions in guitar and bass
amplifiers.
The module does not necessarily have to be controlled via MIDI, but can also be operated
only with foot switches or switches mounted on the front of the amplifier. If a different
switching behavior than the standard configuration is needed, the use of external switches
is necessary.
General overview / inputs and outputs
If the TT-Midi-Switcher is operated with analog footswitches and panel mounted switches,
the following functions are available.
Footswitch inputs I1 - I4 are for channel switching. These are designed to work with the
usual cable lengths when footswitches are used. They correspond to the outputs A1 to A4
and output Z0, which is intended as a mute. Only one output can be active at a time in this
switching group, all other outputs are switched off automatically as soon as a new
switching state is initiated. Example: If input I2 is activated, then output A2 is set to ON
and outputs A1, A3 and A4 are immediately set to ZERO. In addition, output Z0 is set to ON
before the actual switching. This can be used to achieve a mute function (e.g., with an
optocoupler which switches the input signal to ground).
The inputs I5-I8 are for additional controls, e.g. panel mount switches on the front panel
and are assigned to the outputs A5-A8. These inputs have no added circuit to handle
longer cable lengths and are intended only for the use of control elements directly on the
amp, so the cable lengths should be kept as short as possible (maximum 0.5 m). The
purpose of these inputs is to control features like e.g. a "bright" or a "boost" feature. The
inputs or the assigned outputs work independently of each other. Thus, each of the
outputs A5 - A8 can be ON or OFF at the same time, or in any possible mixed combination.
The outputs A1-A8 are linked to a power driver ULN2803 (Darlington Transistor Arrays).
With the ULN2803, a maximum load of 500 mA per output can be controlled. Another
advantage is the internal wiring of the ULN2803, which makes it possible to control relays
directly without the need for an additional protection circuitry. Please note: it is always
switched to ground!
Tube-Town GmbH - www.tube-town.net -
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