MODIFICATION
If you’ve been in a music store anytime since 1978, you’ve no
doubt seen the ubiquitous orange Boss DS- 1 Distortion pedal.
Universally recognized as a good, inexpensive distortion pedal,
you’ve probably even owned one or two in the past. Although it
houses a simple circuit design, it produces a very good sound,
particularly for a mass produced pedal. Let’s look a little more
closely at the circuit and check out some changes that are available to make this great pedal even better.
this won’t do too much, although you may be able to coax a little
more brightness by changing it to a 100 pF capacitor.
The circuit is a buffered bypass circuit with electronic switching, as
are all Boss pedals. The circuit comes in through R1, a 1K resistor,
and then travels through C1, a .047 microfarad, or µF, capacitor
into the first buffer. This buffer goes out through C2 and then into
a JFET (junction gate field-effect transistor), which is part of the
switching. If the pedal is off, the signal goes out to the switching circuit and through the output through Q7, which is the other
JFET. These JFETs act as a switch, allowing the signal to either go
through the distortion circuit or out through the buffers, producing a clean signal.
When the pedal is on, signal travels to Q6, through C3 and into a
transistor gain stage. R7 controls the gain of this circuit by chang-
ing the voltage bias, consisting of a 470k resistor which you can
increase or decrease in value to adjust gain before the next stage.
Increasing the value increases gain, while decreasing it will give
you a little less gain overall but will tighten up the DS- 1’s low-end
response, ridding it of the flubbiness many people dislike. We can
also decrease C3 to get this same effect by not allowing as much
bass to come through. I like to change its value to either .022µF
or .033µF if I’m looking for a less flubby tone. To clarify, to me
“flubby” means a deeply compressed tonality. C4, which has a
value of 250 picofarads (pF) also filters out some highs. Changing
The signal then goes out through C5 into the opamp. This opamp
is used in a unique way to clip the signal. R11 controls the gain
in combination with the distortion knob, R13 and C8. The gain
control is set up this way to enable the clipping of higher frequen-
cies as you turn the distortion up. When it’s turned down, it allows
lower frequencies in – giving it a muddy sound since the signal
is clipped beforehand through the transistor gain circuits, then
clipped again when the distortion control is turned down. The first
stage clipping is still occurring and as a result, the pedal doesn’t
sound as clear and articulate as many would like. R13 and C8 are
part of this “non-inverting” opamp circuit which provides nega-
tive feedback to ground. This is important for several reasons.
The resistor value of R13 and the capacitor value of C8 basically
provide a frequency range where the signal is made to clip. In this
case all frequencies above 33hz is being clipped. To contrast, a
Tubescreamer only lets frequencies above 728hz clip. This means
that none of the lower bass frequencies are being boosted and/or
clipped in the Tubescreamer.
The signal goes out through R14, which is a 2.2k resistor, through
C9, which is a .47µF capacitor running across two diodes – D4
and D5 – and then to ground. All the usual diode tricks can be
done here to allow more asymmetric clipping or different clipping
flavors. Here C10 is also in parallel with D4 and D5 and is used to
filter out highs in conjunction with R14. R14 and C10 form a low
pass filter, cutting out high frequencies.
Go to indyguitarist.com/filter.htm and scroll to the bottom. Plug
these values into the corresponding fields to determine which fre-
Boss DS- 1 Schematic
www.premierguitar.com
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