XENOTRON MODULATION MACHINE 4
CIRCUIT DESIGN NOTES
When designing the Xenotron, we started with an ambitious idea: what if we could fit the full circuit
with all of its features in a 1590XX enclosure, all using the same components as the original unit? Some
past DIY implementations used larger enclosures, while others eliminated features so it would fit.
But with a whole lot of planning, some creative space-saving solutions, and several revisions, we made it
work. It ended up being by far the most challenging and time-consuming layout we’ve ever done, but also
the one we’re most proud of.
We don’t have a lot of design notes on this one because we didn’t really change anything from the
original design or add anything new like we’ve done with the other Lovetone projects. However, here are
some high-level things to be aware of that are different than most other pedals.
Bypass
The original Flange With No Name does not have a master bypass. The “Space” footswitch cancels the
LED modulation, which essentially reduces the tremolo depth to zero. The “Time” footswitch makes it
so the “Time” jack output is taken from the tremolo path rather than the delay path, which is then mixed
down to mono if only the Space output is used. In both cases, the signal passes through the full tremolo
path. (The effects loop is contained within the “Time” sub-circuit, so when Time is disabled, Loop also has
no effect.) This means the Input Gain control also impacts the signal level in bypass mode.
Original Lovetones only used DPDT footswitches, so none of them are true bypass. However, even
with a 3PDT, true bypass is not really possible for this particular circuit due to the stereo operation.
Therefore, unlike our other Lovetone adaptations, for the Xenotron we opted to leave the bypass
switching exactly as in the original. (We still specify 3PDTs due to standard availability, but only two
poles are used in each.) When both modes are active, you have to hit two footswitches to fully bypass
the effect. They’re close enough that they can be pressed at the same time, but it’s a little more
complicated than most effects.
Rotary switch
The original unit has a rotary switch for the LFO shape. This is a 4-position switch that selects between
pairings of LFO modes for Space and Time. Rotary switches are a sort of signature aesthetic for
Lovetone, with each of their pedals having at least one. However, in this circuit, it’s really performing
two separate functions in a logic-table setup (i.e. AA, AB, BA and BB). It’s much more straightforward,
not to mention space-efficient, to control these features with two 2-position toggle switches.
Power handling
As mentioned in the user manual of the original pedal, this circuit is designed for 9V supply with a
maximum voltage of 12V. There is no overvoltage protection, so be very careful to ensure that the
correct power supply is used.
If you accidentally plug in an 18V supply and it stops working, the most likely culprit is the BBD (IC3) and
possibly the clock (IC4). All the other components should be able to handle 18V with no trouble, but the
BBD has a strict maximum of 10V. The BBD supply voltage is dropped by a 330R resistor (R77), which is
enough to keep a 12V supply safely below 10V, but not an 18V supply.
