BOSS SD-1 SUPER Overdrive MOD

 

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, tsd-1he 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 de music, just the sound ūüėČ ):

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-super-overdrive
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 unestable. I read about simulating Ge diodes with schottky diodes in this article:

http://rezzonics.blogspot.com/2014/01/germanium-diodes-vs-schottky-diodes-for.html

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:

BAT46green_diode

 

 

 

 

 

 

 

 

 

The components used:

componentes

And the changes to make:

PCB-antes

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:

sockets

Here you can see a detail of the changes in the clipping section:

detalle_clipping

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 ūüôā Mods have no copyright, but we like some recognition, don’t we?

 

 

Advertisements

BOSS FW-3 sweep range switch (mod)

In a previous post (BOSS FW-3 Mods) I told how I did some basic mods to a BOSS FW-3 Wah pedal, which is basically a Cry Baby design with a potentiometer for varying the Q.

For the capacitor that controls the sweep range (C12), I chose a value of 0,022uF, to give the effect a very personal lower sweep range. I found it problematic in some situations, because the effectiveness of the variable band pass filter as a musical device is very dependent on the color of the signal that it encounters at its input. For instance, if I am using the brigde pickup in an already bright sounding guitar (tele or strat), playing high pitch notes, a low frequency sweep will let the sound almost without volume at the low end of the range. The same happens in the opposite situation – high sweep range with dark sounding pickups, or lower notes.

So, in order to have an all terrain wah effect, I have put a switch for alternating between three different values:

  • 5nF – higher frequencies sweep range
  • 10nF – the original one
  • 20nF – lower frequencies sweep range

Given the behavior of a DPDT on-on-on switch, you can get those three values and their corresponding sweep range values (see https://www.electrosmash.com/crybaby-gcb-95) using three 10nF capacitors, this way:

sweep_switch

Other values can be chosen, of course, to obtain more radical or subtle changes. For instance, with 10nF in the center, 56nF at right and 4.7nF on top you get:

  • 3.2nF – very high range, good for a very bright guitar and higher notes
  • 10nF – original sweep range
  • 66nF – very low sweep, suitable for a bass guitar

The real life device, as built for this project:

IMG_20180604_102036_HHT

As I mentioned in the previous post (BOSS FW-3 Mods), this pedal, apart from being a tank, has space enough inside for storing all the money I have. In this picture you can see how the DPDT switch fits inside the case:

IMG_20180604_131340_HHT

In the main PCB, the cables from the switch are soldered instead of the original capacitor:

IMG_20180604_132724_HHT

And the final result from the outside (the scratches and dents were already there, they are natural relic as this pedal has more than 20 years):

IMG_20180604_133345_HHT

If you have any advice about the execution of the project, or simply have tried it, or in case you had any problem, please let me know in the comments below.

 

Flying Cloud – overdrive with its own tone in a 1590A enclosure

IMG_20180516_191822_HHT

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:

IMG_20180515_192943

And the schematics:

fc_esquema

As you can see, it is basically a thatjapanesepedalthateverybodyhascloned but there is no tone stage. Compare with: https://www.electrosmash.com/tube-screamer-analysis

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 ūüôā 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.

EQD Tentacle clon in 1590A enclosure

Mission acomplished! I managed to fit an octave pedal in a 1590A enclosure. It is not hard because you don’t have any potentiometers at all. That’s why I chose this effect to be my first 1590A project. It sounds great, by the way, thanks to the guys in tagboardeffects for the layout:

http://tagboardeffects.blogspot.com.es/2016/11/earthquaker-devices-tentacle.html

In order to save space, two rows have been omitted from the layout, so it is 19×9 instead of 19×11. There are two rows with no components, they can be saved by using small resistors and ceramic capacitors.

I have put the octave after wah and compressor and before overdrive, not¬†sure if that is the right place, let’s give it a chance.

img_20180512_152905_hht.jpg

 

BOSS FW-3 Mods

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.

20170727_155340

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:

FW3

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.

IMG_20180201_143735_HHTIMG_20180201_143846_HHT

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.

References

http://stinkfoot.se/archives/549

http://www.wah-wah.co.uk/diy.html

https://www.electrosmash.com/crybaby-gcb-95

POP: Autoovation feature

Now POP has a new feature, that I call “autoovation”. You start playing with your favorite effect, and when you stop playing, sometimes, if the pedal likes your performance, you hear an ovation from a digital audience.

Autoovation is made basically by detecting audio activity in input, then waiting for silence and playing a file randomly from a list of mp3 recorded ovations. For audio detection, silentjack (https://www.aelius.com/njh/silentjack/) was used (thanks Nicholas J Humfrey for your work and for letting me add a feature to your code).

This feature is just a joke, of course, but gives an idea of the kind of things that can be done with a device like this one. Think about things like backing tracks, automated rythm boxes, etc.

POP: noise reduced and schematics uploaded

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.

I have also finished schematics for the project, that have been uploaded to https://www.hackster.io/manolonte/pop-programmable-open-pedal-9acddf

popv1-0_esquematico

 

Next steps:

  • Trying with ferrite bead
  • Adjusting output volume, too high right now
  • Giving a function to second switch, maybe fast reset for changing mode quickly
  • Reducing latency
  • Creating new effects: some ideas:
    • dubbler
    • auto-ovation: just for fun, when you stop playing, simulate an audience ovation, just like in ¬†“Blues Deluxe”, from Jeff Beck Group
    • tremolo,¬†phaser, etc.

POP: Programmable Open Pedal, first test

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.

Stay alert for new tests.

I have also still to publish some documentation about the project. More details can be found here: https://www.hackster.io/manolonte/pop-programmable-open-pedal-9acddf

https://www.hackster.io/manolonte/pop-programmable-open-pedal-9acddf/embed?use_route=project

Please leave any feedback you consider relevant or funny.

POP: Programmable Open Pedal

What is POP?

dsc_0022

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.

JACK

I mean jack software. You have to compile it for no GUI, as they describe here: https://capocasa.net/jackd-headless

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.

POWER SUPPLY

My advice is to power the board using pin U13-2 CHG-IN, instead of powering it using the microUSB connector: it is discussed here: https://bbs.nextthing.co/t/chip-power-pins-maximum-current/7164/9.

I built a¬†5v/9v converter using a tipical 7805 IC, and fixed to the case with a screw. Don’t put the thing too close to the board.

FLASHING CHIP

With kernel 4.4, I got errors when capturing audio, so I sticked with kernel 4.3, until I can do some new tests or someone tells me it is fixed:

https://bbs.nextthing.co/t/dsp-with-c-h-i-p-and-audio-capture/6993/5

dsc_0006

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.

The ugly, the good and the minor third

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.

root

Now let’s add a perfect fifth. We’ll consider a perfect fifth to have a frequency = 3/2 of its tonic.

5th

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.

M3rd

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.

m3rd

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.

m2nd

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:

majorchord

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:

minorchord

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.