Big Muff Ram's Head clone (73 version)

Here is the Big muff Ram's Head clone I have made recently. The Ram's Head is one of the most iconic Big muff models. Produced in 1973, it was the second issued version of the Big Muff, just after the Triangle model. Multiple versions of the Ram's Head existed until 1977, including the "violet era" Ram's Head that sells around 1000 dollars on ebay! The Ram's Head v2 is well known as it was used by Pink Floyd's guitarist, David Gilmour. He used the Big Muff combined with a boost in order to have a nearly infinite sustain during some solos, like the famous Comfortably Numb's one.

I decided to make this version, with a PCB from musikding. I am currently prototyping a double sided PCB to use it in 1590B enclosures. Here, the PCB is single layer, so I had to use a 1590BB enclosure. I polished the enclosure with sandpaper 140, then 400 and 800 to have a thin polish, following the same direction to make it look like brushed aluminium. I washed it with acetone, and add 2 layers of satin varnish to avoid corrosion.

I followed the classic scheme of a 73' Ram's Head Big Muff (Gilmour!). I used Wima MKP2 capacitors and one electrolytic to stabilize the power supply. I added two switches to control the amount of mids (switch 1) and bass/trebles (switch 2). The first switch allows you to change the 4,7nF capacitor of the tone stack for a 10nF, thus increasing mids. The other switch plays on the resistor and capacitor at the entry of the circuit, giving us 2 options: a very bassy / smooth one which is the classical ram's head, perfect for doom or stoner rock, and another more trebly, gritty and scratchy!

With the PCB, it was quite easy to organize the wires inside the enclosure. With a BB sized enclosure, there is a lot of room!

How does it sound?

I did not have time to records samples of this pedal. You will have to believe me then! However, no surprise with this one, it sounds like... a Big Muff! Heavy, oversaturated, compressed, ideal to generate walls of saturation. Ideal for stoner, I played it during almost one hour, playing some Kyuss, Fu Manchu, Queen of the Stone Age whereas I just wanted to test it quickly! The tone potentiometer is really efficient and allows you to go from a bassy heavy sound to something more gritty and aggressive. The bass switch is also really efficient, on one side you have a classic ram's head with a lot of bottom end, quite smooth in the highs, and something more gritty on the trebles on the other side of the switch. The mid switch is also quite efficient, we can hear that sound is more "full" when switched on, and it really works well in a band situation. I am really happy with the result, it is exactly what I was expecting!

How does it work?

The Big muff is one the favourite circuit of guitar pedal builders (with the Tubescreamer). Indeed, its circuit is really well known, there is a lot of information available all around the internet, and it is really easy and fun to modify! Each component plays a particular role, and changing it for a different value will change the overall sound of the pedal without damaging the circuit most of the time. It is one of the most cloned guitar pedal, by DIYers or by boutique companies: Mojo Hand FX, Earthquaker Devices, Pete Cornish... Almost every brand has its version of the big muff!

Attack of the clones: all the pedals in this picture are Big Muffs 
or "heavily inspired" by the Big Muff pedal

Technically the Big Muff is not a fuzz but a distortion with most of the saturation coming from diodes. However, it has 2 distortion stages, causing the heavily compressed and saturated sound of the Big Muff. The sound is finally close to a fuzz. Lets have a look on the circuit schematic:

I know, it seems horrible and over complicated... Too many components! But lets divide it in 5 sections:

The first section (input section) is simply a buffer to adapt the impedance of the guitar to the first distortion stage, and which amplify also the signal. As OP amp did not exist at that time (1973, remember?), this is made with a transistor wired in common emitter. Today, a simple OP-amp would be enough! First, there is an input resistor which will diminish a bit the amplitude of the signal. Then, a coupling capacitor will remove any parasitic DC current that mights come from the guitar. Changing the values of the coupling capacitor and input resistor can changes the amount of bass and trebles of the big muff. That is how I made the switch on the pedal. A bigger value resistor and a higher capacitance for the coupling capacitor will increase the bass response of the unit. Then, a transistor wired in common emitter will amplify the signal. Depending on the amplification of this stage, the saturation will be more or less important. The amplification is set by the different resistors on this circuit. Changing resistor's values can increase or decrease the overall gain of the unit. Next, there is a coupling capacitor (again), and a potentiometer wired as a variable resistor that will allow the user to set the amplification on this stage = gain of the Big muff! 

The second and third part (first and second clipping second) are in fact exactly the same circuit. It is used to distort the signal, through the clipping induced by diodes. There is first a coupling capacitor (if you look carefully there is one at each section's start except the tonestack), followed by a resistor. Then, there is a transistor wired in common emitter like in the first part of the circuit with resistors to define its gain. A 470pf capacitor will allow more or less trebles to go through the section. Changing the three 470pF capacitors for a larger value (like 560pF) will diminish the trebles of the unit. This is the case in many clones, like in the Iron Bell from Mojo Hand FX for instance. The diodes will clip the signal and generate the saturation. In classical Big Muff, silicon diodes are used, but in some "boutique" clones, germanium diodes clip the signal (pharaoh fuzz for instance). With germanium diodes, there is less volume, and the sound is even more compressed and saturated! For more infos about diode clipping, read my article about the Jan Ray circuit.

The third part of the circuit is for me the most important part, the tonestack! This little circuit is what gives the characteristic sound of the Big Muff, and the medium loss, the enemy of guitarist playing in a band. Indeed, when you loose mediums, you litteraly disappear from the mix, as if the guitar was muted! A lot of mods do exist to avoid that: a switch which modify the values of the resistor linked to the ground or the 4,7nF capacitor (which I did on this Big Muff), or to use a potentiometer instead of a resistor, and modify the values of the components to have flat mids, to have a proper medium knob (AMZ tone stack). It is also possible to replace the tone stack by another one, like on the Pete Cornish G2. You will loose the Big Muff style distorsion for a much classical overdriven sound. You can even remove it! You will then have an "in your face" sound with a lot of mediums. You can find this system on the Dwarcraft Eau Claire Thunder for instance. Experiment by yourself, the tone stack is a simple circuit and changes a lot the sound of the Big Muff. A lot of fun! 

Finally, in the output / volume section, the signal is amplified again (to prevent volume loss due to the diodes clipping). It uses a transistor wired in common emitter biased to have a strong amplification. A coupling capacitor is present, followed by a potentiometer wired as a variable resistor to modulate the output signal amplitude. We can recognize (again !) the volume control of a fuzz face!

I really advise you to make a muff once. It is really fun to make and to mod. After reading the Big Muff page, you will know exactly what to change to make it sound like you always wanted!

To go further:
Big muff Page: THE website about big muffs! All the versions, schematics and more! A must read for muff lovers.
Big muff pi circuit analysis (electrosmash): precise analyse of the circuit
AMZ tone stack: study about the big muff tonestack, alternative tone stacks
Big muff mods and tweaks: Some easy mods for your big muff. They are easy but funny mods!

Dead Astronaut FX Chasm Reverb PCB

Today I received a PCB from Dead Astronaut FX, the Chasm Reverb!
Dead Astronaut (alias Robert Henry) is an effects builder based in the United Kingdom. He builds a lot of different effects (fuzz, distorsion, tremolo, delays...), with beautiful etched enclosures.

I recently had a crush on the reverb he makes, the Chasm Reverb. It is a beautiful, deep sounding reverb that can auto-oscillate to create great sounding "waves" of sounds, ideal for post rock or prog rock. It is based on a Belton Brick, an IC allowing builders to make digital reverbs. Moreover, it has interesting options compared to other reverbs: a mix potentiometer to choose the amount of dry and wet signal, and a bypass system that let the reverb ends when you turn the effect off. It is called "trails". There is also a "damp" setting and volume.

You can find demos on youtube (chasm reverb or prismatic reverb) that are really great sounding!

Dead Astronaut can make the Reverb for you, or you can order a PCB to make it yourself. As being a DIYer, I ordered the PCB for a reasonable price of 11 pounds. If you want to make one, you can buy the PCB here. Robert is very helpful and replies quickly to emails, he gave me a lot of useful informations. The PCB is of very good quality, double sided with a nice ground plane. The Chasm reverb layout is quite nice, and not too compressed:

We can see the big space necessary for the Belton Brick

(Digital Reverb IC)

 

The circuit is nice seen from the bottom too!

I started to populate the board. I could add every resistance, but I miss some diodes types and capacitors values. And of course the Belton Brick!

I am really looking forward to hear it!

Dead Astronaut's website:
http://deadastronaut.wix.com/index

Analogman sunface DIY clone #2

As I was curious, I decided to build another analogman sunface with the NKT275 red dot transistors I got. However, whereas my first Sunface used a veroboard, I decided to use a PCB. The layout I used for this was conceived by Scruffie, and uses a voltage inverter with a MAX1044. A very ingenious system allows you to switch the power off when you unplug the input jack, very useful with 9V battery. However, as the enclosure I used was quite small (1590B from Hammond), I did not have space left for a battery so I decided to go full power supply. Which is also more practical for a pedalboard stompbox that you are not going to move a lot. And with the voltage inverter, any 9V boss like power supply is perfect! I used a 3PDT PCB. It is very practical, and most of all, really really neat looking. I really paid attention to the wiring this time and try to make the cables as short as possible. I am really happy with the result, it is really nice looking inside.
I decided to make a simple yet classy look with an aluminium faceplate and a laser engraved logo. The logo were engraved by HPM laser, very helpful and affordable! On the faceplate, I drilled the holes for three potentiometers and I engraved letters (I painted the letters with black ink after engravement). F = fuzz, V = volume and B = bias of course. I am really happy with the result.

As I was planning to sell it, I also got some "boutique kit accessories" like a small cotton bag I got on amazon and stickers that I got from Moo. Used this link to have a 10% discount: http://uk.moo.com/fr/share/#8srxpd .

 

HOW DOES IT SOUND?

I made a small video to test my camera. It is not the best sounding demo ever (I do not have the gear necessary to record proper demos...) but it can give a quick idea of how the pedal is sounding. Do not mind the string noise please! I will remake a proper video when I will have a bit more time. For me, this guitar pedal sounds very good, plenty of low end, and very sensitive to the guitar volume knob.

HOW DOES IT WORK?
It is the same circuit as the Sunface, with the bias knob. I already wrote a post about the Sun Face circuit, you can find the Fuzz Face circuit analysis here. The PCB follows the same layout.
However, the power supply section is modified to accept a +9V classic power supply (finally!). For that, it uses a MAX1044 integrated circuit, which can invert the supplied voltage. Here is the schematic that we can find on the datasheet:

Just a few words about datasheets: they are like ID for components. You can find datasheets on the supplier's website (for instance Wima if you are looking for the Wima MKP2 capacitor's datasheet). All the characteristics of the component are written in the datasheet. Thus, it is really useful to look for the datasheet if you miss something about one component (exact size for PCB, max voltage...)

The voltage enters the chip through the V+ pin (number 8), and goes out inverted through the number 8 pin. The pin number 3 is connected to the ground, and a 10uF capacitor is connected between the cap+ (connected to the + lug of the cap) and cap- (Guess which side of the cap ^^). A 10uF is connected to the ground near the output voltage.

The power supply can be also a bit improved with a simple layout that you will find in many stompboxes. It is present in Scruffie's layout (without the 0.1uF capacitor)

 

The diode connected to the ground protects the circuit from polarity inversion. Indeed, the diode only let the current goes through in one direction (following the arrow of the scheme of the diode). So if we plug a classic center negative power supply, the ground will be 0V, and +9V will be +9V. No current will go through the diode. However, if we plug a center positive power supply (which can happen with fuzz faces that usually need center positive power supply), the ground will become +9V, and the voltage will be the ground! In a normal context, this would damage the components, and specially the transistors... However, here, the current will go through the diode straight to the +9V (ground), avoiding such trouble (quite annoying with NKT275 transistors, which worth almost 30 euros!)

The 100 ohm resistor, combined with the 47uF and 0.1uF capacitors eliminate all the residual oscillations that come from the power supply. Indeed, when the current is converted from alternating to direct, some ripples can still be there. As the capacitors only let the alternating current go through them, the alternate current will go to the ground instead of parasiting the circuit and generating "hum" noises! The different values of the capacitors are here to eliminate high and low frequencies of alternating current.

In the end, with this simple layout, we get an input voltage more stable (less noise), and a protection if someone plugs in the wrong power supply (center positive instead of negative). Which can happen with Fuzz Faces!

I hope that everything is clear! If not, post a comment!

To go further:
Geofex from +9V to -9V: an ingenious system to use the battery only when a jack is plugged in.

Vemuram Jan Ray clone

I recently made a Vemuram Jan Ray clone. For the record, the Jan Ray overdrive is one of the many scandals that shook the boutique pedal community recently. Indeed, the Jan Ray has been proven to be a Paul C. Timmy slightly modified as we will see by studying the circuit. However, Vemuram pretended that it was an original design he made up listening to old Fender amps during 3 years... And sold the pedal at an indecent price for an analog pedal: 370 euros (400 dollars) ! This is a typical marketing strategy: "the price represents the quality", which is totally absurd for a basic electronic guitar pedal... He sold a lot of them whereas Paul C. produced the same pedal for 120 dollars. This a pedal that deserves to be cloned, and if you want to buy this sort of overdrive, go for the Timmy!

 

I made it on a veroboard, using the scheme from the excellent website Guitar FX Layouts (best website when it comes across veroboard schematics). Not much to tell you about the making, this is quite a straightforward pedal to make, even if the board is quite compact in the end ! 1uF Panasonic SMF capacitors are very space consuming, so maybe it would be better with a slightly bigger board. I started with by drilling the holes and placing the linkers (and checking connections with a multimeter), then the IC socket, resistors, capacitors, pots and jack inputs. I used a PCB for the 3PDT to make it a bit cleaner looking, as there are already a lot of wires going everywhere (4 pots is quite a lot)... My advice in those cases is to wire everything directly in the enclosure. Solder the wires to the PCB with excess length, place the PCB or veroboard in the enclosure and then cut the wire to the appropriate size, and solder them. With high gauge (like 50), you can twist the cable to make a structure to maintain the veroboard in the enclosure. It also allows you to make the cables follow the same route, thus looking cleaner.

I used a prepainted enclosure from Banzai music (the European version of Mammoth electronics), in vintage orange sparkle. It is a little bit more expensive than raw aluminium boxes, but it is really cleaner. I used the same knobs as in the Jan Ray (vintage fender, yeah !), and used a laser engraved logo. Simple and classy look I find !

How does it sound?

The conception "work" done to create this pedal can be criticized a lot, but I have to recognize that it sounds very very good. Nice saturation that goes from something light like a klon, goes through blues / rock like AC/DC, to finish with a nice overdrive / distortion. Always very nice sounding, not compressed and mushy, with a possible huuuuuge volume intake. The volume equivalent to the bypass volume is at one quarter of the knob value ! Great for soloing or to play with a volume pedal placed after it. Equalization is reactive and allows you to add or withdraw bass and treble efficiently. It is a very transparent overdrive that respects the guitar and amplifier that you use. I recorded some samples (camera mic, sorry...) with my Les Paul 54 reissue (P90 goddess), my vox lil' night train and a malekko Spring Chicken to have a bit of reverb. In the end of the track, I used my boss DD2 for a 80s saturated type of sound (yeaaahh !)

How does it work?

Here is the schematic of the Jan Ray circuit as it is on the veroboard (a bit different from what you can find online, but functional !)

Vemuram Jan Ray schematic (Made with Eagle)

It is quite a classical layout, using the 2 OP-amps included in the LM4558 IC. The first OP-Amp is used to clip the signal to generate saturation, whereas the second one is used as a basic volume boost. Let's divide the circuit in different sections.

The first "input" section has different roles. First, there is a 47 uF coupling capacitor to eliminate any DC current that could go in the circuit. There is also a 1M pulldown resistor used to avoid popping noises when the effect is turned on. These noises are due to a small charge that accumulate at the entry of the circuit and cannot go through the first coupling capacitor. When the effect is turned on, this charge goes through the circuit and causes the awfully loud "pops"... To avoid this, a 1M resistor is linked to the mass to absorb the excess of current.

The signal then enters the gain/dirt section, which role is (obviously) to generate saturation. It enters in the first OP-amp of the LM4558 (it is a double OP amp), which has an inverted feedback loop to amplify the signal. The signal goes in the loop. High frequencies can go through quite easily with de 47 pF capacitor. The remaining signal will change depending on many parameters :

• the gain potentiometer acts as a variable resistor connected that will reduce more or less the current going through the loop. The amplitude of the voltage going through the diodes will varies, and thus will be more or less clipped.
• A trim potentiometer combined with the 9.1k and 600 ohms resistors allows you to tweak the maximum possible gain. This is useful to adapt the maximal gain setting depending on the output levels of your pickups.

Diodes are the main actors in creating saturation. They will more or less crop the signal in the feedback loop. This is a classical "soft clipping" system that you will find in many many guitar pedals, like the famous Tubescreamer from Ibanez. Depending on the nature of the diodes, the signal will be more or less clipped. Silicon diodes usually clip at 0.7V whereas germanium diodes clip at 0.35V approximately. This is why saturation with germanium diodes can be more compressed, and why there is volume loss with germanium diodes : the signal amplitude is smaller.

Fig. Diode clipping system in an amplification feedback loop

Using two diodes following each other like in the Jan ray makes the clipping less important, and thus "uncompresses" the sound. Your playing and pick sensitivity is still audible because the signal is not as clipped as in other saturations like a big muff. A very simple mod to ear that is to use a switch to choose between 2 or 4 diodes in the loop. The Timmy by Paul C has this option for instance. 


Then, the signal goes through the output/volume section. A potentiometer is wired as a variable resistor to act as a low pass filter to adjust trebles. The signal then goes through the second OP amp that is just used to amplify the signal. The 3.3k resistor determines the gain of the amplifier, which is set quite high.
Finally, a coupling capacitor filtrates DC current that could have gone through the loop and thus only allows the signal to go through. Then, a potentiometer wired as a variable resistor to the mass allows you to diminish the amplitude of the final signal, constituting a classical volume knob. This almost the same volume control than in the fuzz face !

Last section of the pedal: stabilization of the power supply and "creation" of the VREF ("power supply section"). The diode at the entry protects the circuit from polarity inversion. Two grounded capacitors are there to get rid of the ripples that might be present in the power supply. Low frequencies are eliminated with the large 47uF capacitor, whereas the 100 nF capacitor is used for high frequencies. In the end, we have a proper +9V voltage that can be used with the OP amp. Another part of the current is used to create the reference voltage (VREF) by going through a 9,1k resistor. 


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To go further:
Pulldown resistors: http://www.muzique.com/news/pulldown-resistors/
Tube Screamer circuit analysis (circuit is closed to the timmy / Jan Ray) : http://www.electrosmash.com/tube-screamer-analysis#power

Big Muff Variant (in process)

I am building a Big Muff variant. As a base, I am using a classic ram's head PCB (made by etronics, cheap and quick, really good manufacturing!), which was quickly populated with BC109 and MPSA18 transistors (cool combination!), metal film resistors and a lot of Wima film capacitor MKP2:

Fig. 1 Empty board, and populated PCB ! Very quick and funny to do !

I have already done few modifications on the circuit: possibility to bypass the tone stack circuit, feedback loop between the transistors for a maximal gain with a momentary footswitch. I changed a lot of values to make it smooth and not too scooped in the mids. It is already a very funny and good sounding device ! Last thing missing would be a 3-bands equalizer alternative (it would be possible to choose between classic big muff tonestack or a 3 band EQ with a switch).
It is already a "smooth" big muff, not too gritty, and has a lot of bass. The tone control is really efficient, but I still need more mids!

I am also trying to make a smaller proper PCB for this variant, in order to fit it into a BB enclosure. I am working on this with Eagle, a software to conceive PCB. Hopefully I will manage to finish it soon!

Strymon Favorite Switch DIY

I love my El Capistan from Strymon. It is a great tape delay, with a lot a features to adjust the sound exactly how you want it. Great ambient sounds, rhythmic delay or something subtler for solos... What was missing was just a way to save settings and have presets like on many delays (TC electronics Flashback, Line6 DL4, Timeline...)

I looked into Strymon Favorite Switch, but it was a bit expensive for me, and unfortunately impossible to find used... As I read that it was super easy to build, I searched a bit on the Internet, and it REALLY is extremely simple!

 

Fig. 1. Most simple and useful scheme in the world

 

You just need a simple footswitch (Single PDT is enough!), a LED, a 1k resistor (you can use different values depending on how bright you want the LED to be), a stereo jack input and a small enclosure like Hammond 1590 LB. You do not need any battery or DC power jack because the DC current is directly provided by the Strymon pedal with the tip of the stereo jack.

Fig. 2. Step 1: drill a hole in the box. Step 2: put your junk in that box.
Step 3: make her open the box (sorry, had to be done)

The most annoying part of this build is drilling the box, you have to be a bit precise in order that all the components will properly fit in. Apart from that it is really simple and totally worth it.

How does it sound?

The setting is properly memorized, which is useful when you want to use two types of delay during the same song for instance. You just need a small stereo jack cable (not so easy to find).

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Any questions? Suggestions? Post a comment!