The Stupid Box was the first pedal introduced by Subdecay Studios in 20031. It is a simple op-amp based overdrive/distortion: one TL071 chip, silicon clipping diodes, and three controls, Drive, Tone and Volume1. The version this page covers is the V1, the original circuit, which reached the DIY community through a stripboard (vero) layout published by the Guitar FX Layouts blog in May 2014 with design notes from Brian at Subdecay1.
Brian's stated goal for the pedal was sustain and good harmonic response. He designed it against a specific reference amp: an ultra clean 100 watt 6L6 based tube combo that, in his words, "just did not seem to agree with anything I threw in front of it"1. He wanted "a big low end, without getting muddy, and an in your face sound, without the high end sizzle"1.
How the circuit works
The signal path is short and conventional for an op-amp drive pedal: the input feeds a 22n capacitor into the TL071, with a 100n cap after the op-amp stage, then the tone control, then the volume control, then the output1. A 500p capacitor in the circuit is assumed to be for noise filtering1. Clipping comes from silicon diodes in the feedback arrangement, and one builder reported using 1N4148s as substitutes with the pedal working and sounding good1.
The three controls do what their names suggest:
| Control | Function |
|---|---|
| Drive | Sets the gain into the clipping stage |
| Tone | Rolls the high end off or on |
| Volume | Sets the output level |
One wiring option worth knowing: the tone pot can be reversed so it brightens the sound counterclockwise, the same behavior as the Rat, rather than the usual clockwise-brightens arrangement1. It is a matter of which way round the pot lugs are wired, not a change to the tone circuit itself.
Fuzz or distortion?
The blog describes it plainly as "a simple, but good sounding overdrive/distortion"1. Builders who made it often heard something fuzzier. One Portuguese-speaking commenter called it "exelente pedal de fuzz"1, and another builder wrote:
"Built this one today and must say this is a brilliant pedal. Just has the most beautiful decay and a great Fuzz."
So while the circuit is an op-amp distortion rather than a fuzz face-style transistor circuit, at high Drive settings it leans toward fuzz territory, and players who like that edge recommend it as an easy build1. If you are comparing categories, it sits closer to distortion and overdrive pedals than to a vintage fuzz.
The vero layout error and its fix
The original vero layout published in May 2014 had a real fault. The input capacitor was routed directly to Vref, the virtual ground reference, which meant the guitar signal was effectively dumped to virtual ground before it could reach the op-amp1. A builder diagnosing the problem reported testing three different TL071 chips with the same dead result, which pointed to the layout rather than a bad part1.
The fix was to move the 500p capacitor and the 22n input cap so the signal path reached the op-amp's input properly1. The layout author updated the layout on 21 May 2014 after the error was reported1.
If you are building from an old saved copy of the vero layout, make sure it is the version updated on 21 May 2014. The original layout routed the input cap straight to Vref and will not pass signal.
What builders said
After the corrected layout, the pedal was verified working, with one builder confirming "This one is verified! It sounds nice!"1. The later builder quoted above called it a brilliant pedal with beautiful decay and a great fuzz, and recommended it as an easy build1. The build reports on this layout are notably more positive than some other vero projects of the era, where commenters reported noisy builds or disappointing sound1.
Questions
Who designed the Subdecay Stupid Box?
The Stupid Box was designed by Brian of Subdecay Studios. It was the first pedal the company introduced, in 2003. Design notes from Brian accompanied the vero layout published by the Guitar FX Layouts blog in May 2014.
Is the Stupid Box V1 a fuzz or a distortion?
It is described as a simple but good sounding overdrive/distortion. Some builders heard it differently: one called it an excellent fuzz pedal, and another praised its beautiful decay and great fuzz. So it sits on the fuzzy end of distortion, and players disagree on where to file it.
What op-amp does the Stupid Box V1 use?
The circuit uses a TL071 op-amp. One builder tested the pedal with three different TL071 chips and got the same results each time, which helped rule out a faulty chip when diagnosing a build problem.
Can the tone control be reversed to work like a Rat?
Yes. The tone pot can be wired in reverse so that it brightens the sound counterclockwise, the same direction the Pro Co Rat works in. It is a wiring choice rather than a circuit change.
What was the error in the original Vero layout?
In the original vero layout the input capacitor connected directly to Vref, the virtual ground reference, which dumped the guitar signal to virtual ground so almost nothing reached the op-amp. The fix was to move the 500p capacitor and the 22n input cap, and the layout was updated on 21 May 2014.
What diodes can be used for clipping in the Stupid Box V1?
The clipping uses silicon diodes, and 1N4148s were used as substitutes in a working build. They are a common, cheap silicon signal diode and were reported to work fine in this circuit.
Sources (1)
- Guitar FX Layouts: Subdecay Stupid Box V1, Guitar FX Layouts (tagboardeffects.blogspot.com), 2014-05-28
