done electronically with a pair of vacuum tubes, but
perhaps in an effort to cut costs, DeArmond didn’t
use any electronic components.
His steampunkish Trem Trol contained a motor
fitted with a tapered shaft, with a rubber wheel
pressing against it. The speed of the wheel varied
when you turned a knob to reposition the wheel
up and down the shaft. The wheel, in turn, cranked
a little capsule of “hydro-fluid,” in which two wires
were immersed, carrying the audio signal. As the
capsule rocked to and fro, the fluid sloshed from
side to side, and the resistance between the electrodes fluctuated. This modulated the audio output.
Today, Trem Trols are antique collectibles. When
industrial designer Dan Formosa acquired one,
he found that the hydro-fluid had long since dried
out, and was advised to replenish it with mercury.
Somehow he didn’t believe it. “I asked internet
questions, and I actually went to a patent office
in New York and looked up patents,” he recalls.
“Eventually I got word secondhand that the fluid
could be replaced with Windex.”
Sure enough, Windex inside works just fine,
and Formosa’s website at danformosa.com/
dearmond.html shows how to top it off. You can
even hear MP3s of the Windex-powered Trem Trol
at Formosa’s site and also that of Johann Burkard
in Germany: makezine.com/go/burkard.
The Trem Trol started me thinking about other
possibilities for a steampunk tremolo. Imagine a
rotating, transparent disc. It’s masked with black
paint, except for a circular stripe that tapers at
each end. While the disc rotates, if you shine a
bright LED through the transparent stripe toward
a light-dependent resistor, you’ll have the basis for
a tremolo device, modeled in Figure A, on the next
page. You could even create never-before-heard
tremolo effects by swapping discs with different
stripe patterns (Figure B). For a real fabrication
challenge, how about an automatic disc changer?
But, back in the real world.
In 1955, Bo Diddley became a tremolo legend using
a DeArmond Model 60, and Buddy Holly followed.
At this point Clarence Leonidas Fender, known as
Leo, jumped on the sound-bending trend by building tremolo into his Fender amps. He named it
vibrato, even though this term really means modulating the frequency of a note, not its amplitude.
Perhaps Fender simply wanted to protect his
market share from one of his rivals, Magnatone,
which sold an amp that did have genuine vibrato.
But he compounded the confusion by also introducing a “tremolo arm” for his guitars, which actually
produced vibrato. Many rock musicians have been
confused by the two terms ever since.
Today, transistors can create tremolo with more
options and cleaner sound than the old tube amps.
One of the most widely praised circuits originated
in the November 1968 issue of Electronics Australia
magazine, after which it was tickled and tweaked
by a loose-knit worldwide fraternity of semi-profes-sional circuit designers. Stomp-box authority J.D.
Sleep of Raleigh, N.C., offers a modded version in
kit form at his highly informative site, generalguitar
gadgets.com. With his permission we reprint the
schematic in Figure C. (The kit version differs in
some very minor details.)
Sleep has been fascinated by DIY guitar effects
for most of his life. “I started to get seriously into
it about 12 years ago,” he says. “The web brought
some ‘community’ to effects builders; it was a
lonely hobby before then.”
Describing himself as a “hands-on learner,” he has
no formal education in electronics and doesn’t even
own an oscilloscope. He recommends Electronic
Projects for Musicians by Craig Anderton as a good
starting place for people who want to experiment,
and he downplays the complexity of electronics,
pointing out that almost all audio schematics can
be broken into blocks that have discrete functions.
In the tremolo circuit, the first block starts at the
input jack and ends in the Q4 transistor stage. “This
is a buffering circuit,” Sleep explains, “to allow for
better use with multiple effects [boxes], or a guitar
with hot pickups.” The second block contains Q1,
which amplifies the signal, with Q2 going out to the
volume control. Sleep believes the pleasing sound
of the circuit is largely a function of this very clean
The actual tremolo is generated by Q3, which is
wired to oscillate, diverting a varying proportion of
the positive audio signal to negative ground. Simple
enough, but the devil is in the details, especially the
“This kind of circuitry requires a lot of tweaking,”
Sleep notes. “Guitar audio doesn’t always follow
the same rules as hi-fi audio. Formulas don’t always
give the best guitar tone.” His recommendation
for beginners: “Look at schematics of effects and
compare them. There is a plethora of guitar effect
schematics on the web now, so this is easy and fun
to do, and you can learn a lot from it.”