[Updated 4th July 2014 - correction to treble control resistors]
This is an easier build and is perfect for someone who wants the Klon tones without having to mess around buying charge pumps and curing squeals. This came from a thread on FSB where earthtonesaudio wrote the following:
The charge pump in the Klon seems a bit unnecessary to me. The only
logical reason it should be used is to keep op-amp U2 from clipping.
But
here's the thing. When the gain pot is at maximum, the only signal
hitting U2A has already been clipped by the diodes, so a typical Ge
diode will limit the signal going to U2A to under 1V p-p. For this
signal U2A has a gain of about 8.3. Granted, this would clip a TL072
with a 9V single supply. BUT, if you used a rail-rail op-amp, then
you'd get no clipping.
That would ensure no signal coming from the
distortion stage could cause clipping in U2A, even if you used +9V and
0V as the rails.
From U2A the signal goes into the tone section,
where the maximum treble boost gives a gain of about 8.2 to the highest
frequencies. Again referring to the situation where the gain pot is at
max, that means the signal coming from U2A into U2B is about 5V (.6V p-p
signal times U2A's gain of 8.3), so U2B will try to make the highest
frequencies into a 40V p-p signal. The power supply can't reproduce
anything (even with a rail-rail op-amp) greater than 27V, so the op-amp
clips.
Another useful scenario to analyze is when the gain is
set to minimum. For high frequencies, the maximum gain from lug 1 of
the lower half of the dual gang Gain pot to the output of U2B is 266.
An average guitar signal (especially if boosted) can easily make a .1V
p-p signal, which would cause op-amp U2B to clip if the gain was set to
minimum, and the treble at maximum. Of course, before the signal gets
to the that lug of the gain pot, it is attenuated by the input voltage
divider as well as the network at the output of U1A.
Anyway,
my point is that there is some op-amp clipping possible in the Klon at
normal settings, even when using the charge pump. To me, the whole
point of using a charge pump is to avoid op-amp clipping. But the Klon
uses a charge pump and still clips the op-amps. So why not just ditch
the charge pump and use op-amps that sound better when distorted (or
will operate at their rails to minimize the amount of time they spend in
clipping)?
For those people that would like to fit a Klon into a
smaller package (though that is of course limited by the dual gang pot
and other hardware), or those who just want to use fewer of the Earth's
resources in their pedal building, I think it would be nice to have a
Klon alternative which operates from a single supply, with no charge
pump.
And mictester very kindly produced a schematic based on the discussion. Thankfully there's some very clever people on FSB to keep us busy!
Youtube demo: