DESIGNER’S NOTES
The 5E3 is a very raw, elemental circuit where just about every stage is under-engineered.
The tone control only really works when the volume is turned down (but why would you
ever do that?!). When you crank it up everything just about gives up, the power supply
doesn’t keep up when you thwack chords resulting in the signature “sag”. The output
transformer and speaker saturates too… It is a system on verge of failure, but it sounds and
feels so good to play through!$"
We felt the best way to approach this sonic experience short of building an actual amp was
to employ hard-to-find JFETs to cascade gain stages in a way that more or less literally
reflects the actual 5E3 topology. JFETs have a soft, tube-like clipping quality that when
used correctly can be driven into compression while remaining touch sensitive to picking
dynamics and cleaning up with the instrument volume control. This is a quality that can’t be
achieved using the old “diode-clamp” trick, such circuits nearly always sound fizzy and
severely limit dynamic response. We also find that JFETs respond well to a wide range of
voltages. You can run it under 9 volts which “browns out” the circuit more making it more
compressed feeling. Running it up to 18 volts opens up the circuit resulting in a much wider
dynamic response.$"
We further honored the original 5E3 circuit by taking the tone control circuit directly from the
amp, this control is not so much an “EQ” as it is integral contributor to the behavior of the
real amp. It is more effective when your GAIN knob is down, cranking the TONE knob
passes less bass resulting in a less wooly feel. Rolling it back shaves off higher frequencies
before they get clipped in the subsequent gain stage. We recognize that there is a paradigm
amongst players about tone controls on pedals, thinking of them more as “EQ” controls
rather than circuit elements that change the behavior of amp. But we figured we’d invite
you to experience it for yourself."
POWER SUPPLY
You can power your Formula No. 5 with any quality power supply designed for use with
effects pedals. The output should be a negative tip DC from 9 to 18 volts. If you want more
volume, headroom, and percussive attack, try running an 18 volt power supply. A 9 volt
power supply will have a slightly softer sound that saturates more easily - it's sort of like the
difference between a 50 watt and 100 watt amp! Definitely try it on 18 volts though - there's
quite a difference! 18 volts is great for playing with the band. You'll get great attack and
clarity with power to cut through the mix. You can also try a battery that is drained down to
as little as 3-4 volts to get an even softer sound that is great for late night jam sessions
when you don't want to wake anyone up! Or use a power supply that is capable of
providing "starved" voltage. It's sort of like running a Variac and you get the same benefits -
a "browner" sound and less volume! We encourage to to try these different powering
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