I have tested them using a Linux computer, its sound card and qloud software. I know the measurement is not very precise, but the real thing is not going to vary very much, I think. All controls were at noon during the measurement.
Original BOSS DS-1
Original DS-1 frequency response
As expected from a pure distortion effect pedal, frequency response is mid scooped, with a bump at 100Hz.
Modified BOSS DS-1
Modified DS-1 frequency response
As I expected after the modifications in the tone stack, frequency response has much more mids. The maximum is not at 800Hz, just because the circuit is not only the tone stack. By touching the tone control, the curve can be modified (I leave it for a next article).
As you can see also, at aproximately the same “level” value, the overall volume is higher (over -60dB for a wider range in the test), without changing any measurement parameter, even if the perceived distortion is higher in the original unit. The reason, I guess, is the red led in the clipping section instead of a common diode, see the article https://electric-safari.com/2019/03/17/turn-a-boss-ds-1-into-a-nice-overdrive/. Since the Vf of the led is higher than that of the diode, it clips at a higher voltage, giving the circuit more headroom. This is very common when doing this kind of modifications. I think the tone stack change alone does not explain that higher volume.
Recently I acquired a BOSS OD-3 Overdrive by chance, just because it was being sold by the same vendor than the BOSS OS-2, both to be fixed. Their problem was the same, just the potentiometers needed deep cleaning. I modified the OS-2, but after checking the OD-3 out, I didn’t feel like modifying it. Just started to love it: very natural sounding, following dynamics while playing, the most amp-like overdrive I have had in my hands.
I have played for a while with it and with my other favorite overdrive, the J.Rockett Tim Pierce Overdrive. This is an overdrive based on the typical operational feedback loop soft clipping (like TubeScreamer), very well designed and manufactured, with an additional, very useful and sweet boost. It cleans up very well when playing soft and have the distortion range I need. And because of it I have become a fan of a superguitar player, Tim Pierce.
Both overdrives are amazing, but sound differently, each one is good for each style and situation, and when stacked, you get a very mid rangey, cutting through tone, while not too dirty tone. I feel the OD-3 more dynamic, with more bass response, while the Tim Pierce is more focused on mids and covers a wider distortion range.
The circuits are very different. I don’t have schematics for Tim Pierce, but seems very similar to J. Rockett Animal Overdrive plus the boost circuit they call “Power Amp”, because it is designed to emulate one of Tim Pierce’s favorite amps, the Naylor SD60. Basically it is a Tubescreamer style overdrive with four diodes placed in pairs in the feedback loop of a JRC4558 opamp, and very well chosen values for the different resistors and capacitors to tailor the frequency response. BOSS OD-3, on the other hand, has a very original design I am still trying to understand, based on a two stage diodes clipping with JRC4558 JFET transistors. There is an operational amplifier, used only for tone shaping and signal level raising. You can see below the schematics:
BOSS OD-3
Trying to dig into the differences between the two styles of clipping, I did some measurements with my laptop. First I generated a couple of signals and captured the output with a Oscilloscope software, let’s see the results.
Pedal settings
These are the settings of both pedals for the measurements, they are basically my favorite settings:
BOSS OD-3 and Tim Pierce settings
Time domain
First, let’s see how they react in front of a triangle signal, probably the most simple signal with some harmonics. I have used my soundcard and a great tool called “Soundcard Oscilloscope“. Frequency is 440Hz and level is 100mV, green line is the original signal and red line is the distorted one, for all graphs:
BOSS OD-3 – 440 Hz triangle, 100mV
Tim Pierce – 440 Hz triangle, 100mV
Interestingly, the Tim Pierce seems to almost not distort the signal, while the OD-3 produces a nice gradual clipping of the signal. Working with smaller signals and different frequencies, both seem to be distorting signals as little as 5mV, keeping almost this same shapes. To explain why they seem cleaner to the ear for smaller signals, a more extensive study should be done, with many frequencies and levels and a real or simulated guitar signal.
For this article, I have used a formula that yields a signal with some harmonics, trying to mimic what a guitar output signal could seem like: a*sin(w*t) + a/2sin(w*2*t) + a/3*cos(w*4*t). It is not by any means a guitar signal emulation, just something a little more complex than a triangle-shaped signal.
OD-3 – 440 Hz formula, 100mV
Tim Pierce – 440 Hz formula, 100mV
Not very different, just seems that the OD-3 distorts more the signal. It is very clear in the X/Y graphs, obtained in this case for a 250mV signal. The reference signal is of 160mV to keep the signal at similar levels, the difference only affects the angle of the shape. This graph represents the output signal (Y) as a function of the input signal (X), for the whole cycle, that’s why it gives different values for each X. The Y value is the value for that X at a certain instant, and X can have several times the same value in the complete cycle.
In summary, with no distortion at all you obtain a diagonal line, with two sine waves out of phase you get an ellipse and with a distorted signal you get a beautiful shape that can remind you of a signature, a baby, a seahorse… The more distorted the signal, the less similar to a diagonal line it is.
OD-3 XY
Tim Pierce XY
The shape is almost the same for smaller signals at 440Hz and for other frequencies. Tim Pierce Overdrive signal seems to be less distorted, more close to a diagonal line.
Frequency domain
Let’s see now the frequency response, for each one of them and for the stacked set. It has been measured with a soundcard and REW software, with this parameters:
Stepped sine measurement at -20,0 dBFS
1/3 octave, 2 averages, FFT length 65536
0 ms silence
31 measurement points.
Please click on it to zoom:
Yellow graph represents BOSS OD-3 response. A more flat response curve (from 100Hz up to 10KHz) compared to the blue line, which represents the Tim Pierce response, more focused on mid range frequencies. The yellow OD-3 line reminds me of the typical Kilimanjaro shape of many amplifiers, with two bumps in low (200Hz) and high frequencies (1KHz), and a slight scoop in between. The high frequencies bump varies a lot when rotating the tone control.
Tim Pierce response is the typical Tubescreamer shape, with a maximum around 500Hz. When stacked (green line), the result is an even more mid rangey tone, with a slight bump at 300Hz.
Summary
After this brief study, I have no idea why I like these two overdrives. Even more, BOSS OD-3 seems more “transparent” or natural to my ear than Tim Pierce Overdrive, but OD-3 is distorting more the signal. I suppose it has to do with the frequency response of the OD-3 compared to the Tim Pierce, which is more open and roughly similar to the response of the amplifier. Or maybe it has to be with the harmonics they are generating, it can also be measured with REW.
When stacked, you notice that the guitar tone cuts through the mix, and it is confirmed by the combined frequency response. That combination will give you that “more” needed for a solo or a particular riff.
Out of curiosity, I bought a second hand SD-1, just to try it as is, and try some of the mods people have been doing to this pedal for the last decades. Some mods try to transform it into a TS9 or even a TS808, so you can turn this relatively cheap pedal into a more expensive one. But this box has its own personality, the design is very similar to TS9 but with some remarkable differences:
Clipping is asymmetrical, two diodes forward and one backwards (in the direction of the operational). Asymmetrical clipping sounds different than symmetrical one, some people describe it as harsh or hairy of fuzzy compared to the latter.
There is no capacitor in the feedback loop of the clipping amplifier. This capacitor smooths the clipping a little, giving the TubeScreamer part of its particular tone.
Tone control is very similar but with different component values and with a capacitor (C6) in the feedback loop of the tone control operational amplifier. This capacitor is the first thing I have seen every mod removes because it sucks a significant amount of bass frequencies to the signal.
After trying the pedal for a while, I quickly noticed what most people complain about, this makes the guitar sound thinner. This has not to be bad in every ocasion, especially in live gigs situations where you want to sound in a different spectrum space than the rest of the instruments. But ok, I want more bass too. In this clip I recorded the original sound of the pedal, playing with a RS420 (humbuckers) and a Fender Blues Deluxe amp (please don’t pay attention to the music, just the sound 😉 ):
To correct this defect or feature, there are multiple mods out there, usually people remove capacitor C6 and change values of R6 and C3, which connect the feedback loop and the negative operational input to a voltage divider, in a similar way to he TS9 connects those to ground. lowering R6 and raising C3 values results in more bass response from the clipping circuit. See below the schematic:
BOSS SD1
I chose to make this changes in order to get a nice tone from the pedal:
C6: instead of removing, changed it with a 100pF capacitor from its original value of 10nF.
C3: raised from 47nF to 100nF.
R6: lowered to 3K3
The other section where people make changes is the clipping circuit. Many mods aim in the direction of getting symmetrical clipping, but I didn’t want another TubeScreamer. Instead of that, I wanted to enhance the personality of the effect by exaggerating the asymmetry of the clipping section. Asymmetry comes from using a different quantity of diodes in each direction, or from using diodes with different specifications, especially with different forward voltages (Vf). Vf is different for the following types of diodes:
Ge diodes: low Vf, around 0,3V
Si diodes: usually around 0,6V
LED diodes: depends on the color, 2V for green ones, 1,6 for red ones.
So using a Ge diode in one sense and a LED in the other, we get asymmetrical clipping, right? Right, but Ge diodes are expensive, hard to find and unstable. I read about simulating Ge diodes with schottky diodes in this article:
Ge diodes are used in some mods also because of the smooth I-V curve the exhibit. Schottky diodes have a low Vf too, but the I-V curve is more abrupt than the Ge one. By adding a resistor in series, you can get a similar response, at a lower cost and with more stability.
In my mod, I have replaced D5 and D6 (in series in the original circuit) with a resistor (10 Ohms) and a schottky diode (BAT46) with a Vf of 365mV. And D4 has been replaced with a green LED with VF=2V. You can see the measures below:
The components used:
And the changes to make:
For the clipping section, that I suppose will be subject of further modifications, I have replaced the original components with sockets. In the picture below you can see the other components replaced too:
Here you can see a detail of the changes in the clipping section:
And the result in the following record. I was not trying to play a song, just to get all the possible tones from the pedal. Please forgive me if I get sloppy:
I can perceive these differences after playing for a while:
More volume at the same “level”.
Much more bass frequencies, without being too much for a band situation, I think (has to be tested in a band situation).
More of the asymmetrical character: “harsher” when playing harder, keeping dynamics (I think more than the original, maybe I am somewhat subjective).
I think the sound changes more than the original when moving the drive control: from a smooth, almost TS9-esque overdrive at low gain levels to almost fuzzy and even octave-like at maximum gain.
If you are interested in this mod, please try it, test it and give me your opinion in the comments section. If you improve it, tell me how. If you like it, give me a “like”, and if it’s possible for you, mention my blog to yout friends 🙂 Mods have no copyright, but we like some recognition, don’t we?
Edited on March 16 2019:
Some days ago I put a red led instead of the green one. Now the overdrive is more usable and versatile, although the octave effect is less pronunciated.
PD (May 2 2022):
A more simple modification that makes the pedal even more usable is just changing D4 for a red led and leaving the other diodes as they are. I did this for a friend that wanted a less edgy sound, and the result is better than my original mod.
PD: si hacéis ese mod, ponedlo en los comentarios abajo. Me gustaría saber si la gente disfruta (o no) de mis mods.
This new project is based on that archi-known japanese green overdrive. It is different in the component values (as many clones over there) and in the absence of tone control.
It all began as a simple overdrive circuit to be hidden inside a stratocaster, and it lived like that for a couple of days. For that purpose I didn’t need a tone control, because the guitar has its own one, and the amount of distortion was controlled by one of the strat pots (the middle one), while the other tone pot was controlling the tone of all pickups and also of the overdrive circuit.
After trying the concept, I didn’t like the idea and removed the artifact from the guitar. But I liked the tone and tested it as an independent effect, even without the tone stage. Also, it would fit inside a 1590A enclosure, hence being a very practical device as a backup for my regular overdrive pedal or to be carried to jams or occasional gigs.
Here is the pcb (veroboard) after leaving its guitar life and before starting to be an effect pedal:
I can live without tone control, because almost all electric guitars has at least one tone control, I have an equalizer pedal and all amplifiers have a tone stack. I have adjusted the tone in the circuit to my preferences, but some components can be changed to shape the tone. On the other hand, the tone stack can be missed if you have other effects after this one that can be affected by its tone (stacking overdrives, phasers, etc).
Of course, feel free to use the concept and the schematics if you like it. If someone needs the veroboard layout I can prepare it and publish it also. Just buy me a beer and we’re even 🙂 I’m planning to record a demo for this pedal in the following days.
And why the name? The Flying Cloud was a fast clipper that sailed the seas in the XIX century. I like ships and this pedal is also a fast clipper (a soft clipper, to be more exact).
PD: the 220nF capacitor at the output of the operational amplifier can be removed for a less muddy sound. It is included in the original green overdrive and I had to included it at first in order to avoid oscillation with an LM348 as operational amplifier. After switching to 4558 kind of IC, the oscillation is not present even in abcense of that capacitor.
LM358 has a slew rate of 0.3V/uS, while JCR4558 has a slew rate of 1V/uS, which I think is the cause of that difference.
I have a BOSS FW-3 pedal bought in the 90’s when I started to play guitar, looking for a Jimi Hendrix or SRV sound. Why this pedal instead of a Cry Baby or VOX? Because back then you bought what they had in the shop.
Some months ago I decided to sell it because I didn’t like its sound and behavior any more. Too subtle when placed before dirt and too uneven in volume when placed after. But nobody seemed to be attracted to this squared tank in spite of the low price I asked for it, so I kept it.
It is not a bad product compared to other wah pedals, it is just you get sick of the same tone and problems, and want to get a different tone (and problems). In fact I like its size and robustness, it is solid like a tank and fits very well under my feet.
So I decided to tweak it a bit in order to find a different sound, and started to look for possible mods in the web: nothing at all.
After studying its circuit, I found that the BOSS FW-3 wah pedal is essentially a modded Cry Baby. A very clear and in depth analysis of the Dunlop Cry Baby can be found here: https://www.electrosmash.com/crybaby-gcb-95
There is plenty of information about mods for Cry Baby. In many sites they talk about these particular mods, in Cry Baby terminology, for a GCB-95 PCB:
True bypass (more details in the referenced sites)
Mid range response: R1 resistor change from 1.5K to 2K-2.7K
Q: R5, from 33K to a bigger value, up to 100K. This mod is already done in a BOSS FW3, there is a pot in the pedal panel for adjusting this value.
Sweep Range, change C5 from 0.01uF to a bigger value for lower frequencies and a lower value for higher frequencies range. Typically 0.068uF for a bass wah.
Gain and bass response: changing R9 from 390 to a lower value will raise gain and add bass content, while a higher value will reduce the gain
In order to apply this valuable information to modify a FW-3 and find our personal tone, we need to map these components to those found in the BOSS PCB. I didn’t fight with the true bypass mod because I like the BOSS buffer, and it is useful for me in most situations.
From the schematics:
Mod
Cry Baby (GCB-95)
FW-3
Gain
R9
R6
Sweep range
C5
C12
Mids response
R1
R4
See below the pictures for FW-3 pedal PCB. In the top picture I have marked these components in the board.
Which values to choose depends a lot on your personal preferences. I have experimented with some values and ended choosing these ones:
R4 (Mids): 2.2K, gives some more mids content.
C12 (Sweep range): .022uF, lowers the sweep range in the frequency spectrum, giving a very pronounced WOOOO effect in the lower frequencies end.
R6 (Gain): 390. It lowers the gain a bit, making it more even with the effect not engaged
These values give a very personal tone to the FW-3 wah. Even placed before dirt, the effect is very pronounced and significantly different from the original, specially in the lower end of the sweep range.
In a next post I will try to record the sound of the modified pedal.
I’m planning to add some pots in the future to regulate the mids and gain, and even a selector to change among different values for C12. The unit has space in the panel to place the pots and enough space inside to place another two PCBs, so I think it is a perfect platform to play around a bit.
After cabling audio internally with shielded wires, and solving a grounding problem in the input jack, noise has been reduced drastically when working from battery. There is still an annoying computing noise when connected to an external 9V power supply. I am going to put a removable ferrite bead, still waiting for the parcel to arrive.
First recordings of POP through a Fender Blues Deluxe 40W AB tube amplifier. Camera is a GO Pro HERO. The amplifier is looking towards the wall in order to save our ears. Guitar is a Yamaha Revstar 420, I love it.
Impressions
Sound quality looks promising, though still I can hear some computing noise, specially when configuring a compressor or a distortion/overdrive. When using delay type effects, or reverb, noise is quite bearable.
I am using a 512 bytes buffer, and getting around 20ms of latency, still too much.
Some more research is needed to get the best from this unit, keeping in mind the limitations: CHIP board works at 1GHz, and sound card is integrated in the SoC, as long as I know.
This is my most recent project. Based upon the C.H.I.P. board form Next Thing Co, I have built a stompbox guitar digital pedal. These are its main features:
stereo output
true bypass
standard 9v input
three modes of operation
reset/shutdown button (the red one)
additional programmable button (the black one)
wifi, enabled inly in one of the modes
microusb input, for serial connection
USB input, where you can connect a MIDI controller, so effect parameters can be modified on the run
backup battery, so if you unplug the unit, you have the chance to shutdown gracefully
C.H.I.P board offers a good opportunity to build this kind of units because it has audio capture capabilities natively, without the need to plug an external (usually slow) USB sound card.
At this moment I am still doing tests, trying to improve sound quality. Some software stacks I have tested up to now:
Rakarrack on jack: unstable in this platform
Guitarix on jack: quite stable and very good sound quality, but a lot of CPU consumption. The good point is that you can configure and control the unit graphically, doing a SSH -X from a computer.
Supercollider on jack. Super-flexible, Supercollider is a programming language, so you can create any effect your imagination dictates. The problem is that I haven’t reached the sound quality I am looking for, maybe a SC expert can do.
LV2 plugins on jack, running with mod-host. With this combination I have got the best results, in a next post I will upload some sound clips. You can control parameters with a MIDI controller, and preset parameters. You can choose from a huge list of already programmed effects, and combine them in any order.
My current software configuration is based on LV2 on jack. I have programmed three modes of operation using the switch you can see at the right in the above picture:
switch up: double delay, controlling feedback and delay time of the two delays with a Korg Nanokontrol2 MIDI controller
switch middle: compressor, controlling attack, release and gain
switch down: reverb, controlling room dimensions and warmth. In this position, I activate wi-fi interface and sshd, so I can connect my computer and make changes, update the software, fix issues, etc.
Some advices for anyone looking for something similar:
WIFI
Wireless interface can be a problem if you enclose a computer inside an aluminium box, as is the case in this project. If you use a plastic box, you will have too much electromagnetic noise. For a compromise, I decided to drill a hole in the case, right above the wireless antenna. With an eight millimiters hole, and putting the unit not far from an access point, I am getting a quite good network access.
FAN
Another problem derived from the case is temperature. Without a fan, temperature was reaching 70 Celsius degrees. With a small 12V 25 mm fan, powered at 9V, temperature keeps stable at 51 degrees, even lower with wireless deactivated. I put the fun below the hole I had already done for wifi waves to escape the enclosure, as you can see in the pictures just below the switch.
For the rest of the software (LV2, mod-host) I will write a dedicated article.
SOUND INPUT AND OUTPUT
I have got the best results using the minijack input for audio capture, and board connectors for output. I have grounded the audio capture and output with the board connectors and at this moment there is almost no computer noise.
So I am very excited now with this project. My main concern now is sound quality and usability. I’ll write some additional posts with audio clips and new notes and advices. I would like to upload some schematics with the internals of the unit.
If someone is interested in more details about the project, or have some questions, please write some comments, or send me an email to manolonte@gmail.com.
Why does a melody sound good to us, to some of us but not to others? Why does a song sound sad while another one sounds glad or awfully dissonant? I don’t know, of course, but it seems to have to do with evocation of known melodies, cultural conventions and something in our brain that is still to be discovered.
Some time ago I was curious about what kind of sound resulted from the addition of two notes in a chord or a melody.
Let’s consider a root note, let’s say A440, known to have a frequency of 440Hz. The sound will be a sinusoidal wave, something that would seem like a flute.
Now let’s add a perfect fifth. We’ll consider a perfect fifth to have a frequency = 3/2 of its tonic.
In black we have the tonic, in red perfect fifth and in blue the sum of both signals. What happened? The resulting sound is a signal with a frequency of 1/2 * 440Hz = 220 Hz.
Now let’s consider our A flute and an added major third. There are several standards for major and minor third frequencies related to tonic (see https://en.wikipedia.org/wiki/Major_third) but for this exercise I will take the just intonation, in which the major third has a frequency of 5/4 multiplied by its tonic frequency.
In black the tonic, in red the major third and in green the sum. Now we have a resulting signal of 1/4 * 440Hz = 110 Hz.
Now let’s add a minor third to the tonic. In just intonation, minor third has a relationship of 6/5 with its tonic frequency.
In black the tonic, in red the minor third and in green the addition of both. Now the resulting frequency is 1/5 * 440Hz = 88Hz
The last plot will consider a very dissonant note, a minor second, with a relationship with the tonic of 16:15.
The frequency of the resulting signal is 1/14 * 440Hz = 31.42Hz
Obviously, as the second note’s frequency approaches the tonic’s frequency, the resulting signal has a lower frequency.
Now let’s take a chord. A major chord will be something like this:
In black the tonic and in red the addition of tonic, major third and perfect fifth. The resulting signal has a frequency of 1/4 * 440Hz=110Hz.
Now with A minor:
Now the resulting signal has a frequency of 1/10 * 440Hz.
Let’s summarize the results:
interval/chord
frequency
note
tonic
440Hz
A4
perfect 5th
220Hz
A3
major 3rd
110Hz
A2
minor 3rd
88Hz
~F2-F#2
minor 2nd
31.42Hz
~B0-C1
A major
110Hz
A2
A minor
44Hz
~F1-F#1
Perfect fifth and major 3rd have a curious property: when you add them to the tonic note, you produce a signal whose frequency has the same frequency of the same note in a different octave. However, when you add a minor 3rd or a minor second to the tonic, the resulting signal frequency has no relationship with any note.
I hope you have enjoyed this mathematical experiment and that it will make you think about intervals in a different way. But above all, please enjoy your favorite music, either thinking about intervals or not thinking at all.
A new modification to applaunch.sh, so you calibrate and map the joystick and force mixer before launching the emulator.
Don’t take the arguments as is, they are just an example. Well, the amixer arguments force audio output to HDMI.
#!/bin/bash
# Check for arguments
if [ -z "$*" ]; then
echo "No arguments provided."
echo "Usage:"
echo "launcher.sh [/path/to/]executable [arguments]"
exit
fi
he design is very similar to TS9 but with some remarkable differences:
electric-safari 