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.

3PDT and true bypass wiring

I found out that it was easier for beginners to make a proper true bypass wiring when they fully understand how does it work.

The 3PDT Footswitch

Before going any further, you have to understand how functions a 3PDT footswitch. The 3PDT stands for "3 poles, double throw". Here is a diagram showing the different possibilities :

Here, we can see that a simple pole, simple throw (SPST) is equivalent to a simple on-off switch; simple pole dual throw (SPDT): equivalent to a toggle switch. So basically, double throw just means that you have two positions for the switch.
A dual pole, simple throw (DPST) is equivalent to 2 SPST, DPDT: equivalent to 2 SPDT.  

From that we can easily conclude that a 3PDT is equivalent to 3 double throws at the same time. You have two position for 3 switches with 2 positions each:

 

That means to say that on one position, the middle pins are connected to the ones of the top (2 is connected to 1 for instance), and in another position to the ones on the bottom of the switch.

How to use it for true bypass?

When you want to do a true bypass, you want a simple thing:

• in one position (position 1), input and output jacks are directly connected, the signal does not goes through the circuit (bypass)
• Position 2: input jack goes to the input of the circuit, the output of the circuit is connected to the output jack, and a beautiful shiny LED is on.

For position 2, there are 3 conditions to be filled, that is why we need a 3PDT !

 

With this type of wiring, we have the two following positions: 

That is to say on and off for the guitar pedal!


If you do not want to bother to solder directly on the 3PDT (you have to be precise and it is not very practical if you want to modify it afterwards, and most of the times it does not look so good), you can directly use a small PCB to make your true bypass like a boss. You can either make it yourself (model here and here), or buy it (very cheap here).

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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

Analogman Sunface Build

Here is a first build I made not so long ago, an Analogman Sunface.

Very simple layout, a classic fuzz face with some light modifications, like a bias pot that I called "woof" here for fun. 

 
Since this first picture, I improved a bit the circuit with transistors sockets that are very nice in order not to overheat germanium transistors, and to test different combinations of hfe. 

You can see the really simple NOS components here: carbon comp resistors, Mullard "tropical fish" capacitors (love this name, very accurate description!) and of course two AC128 germanium transistors. 

I got most of these compounds in old radios that I disassembled a long time ago, except for the germanium transistors that I bought online. I used the guitar fx layouts scheme to do it and I enlarged a bit because my capacitors were axial. Since, I built another fuzz face using a PCB.

If you want to be super accurate, "vintage correct" or full mojo for your build, then you should get the original components (even if - apart from the transistors - I do not think that it will change the sound a lot): 

• NOS vintage NKT 275 Germanium Transistors
• NOS vintage Mullard Yellow Capacitor
• NOS vintage Philips Capacitors
• NOS vintage Allen Bradley Resistors

If you want to re-create a proper vintage fuzz face replica, I advise you to buy the pigeon fx kit with a Dallas arbiter board and most of the vintage components listed above. Personally, I preferred to stay with a Sunface design which more practical with the bias knob.

I reverse-etched the enclosure, which was quite of a job, but I love how it finally came out! If I do another one, I will maybe readjust a bit the position of the main logo.

How does it sound?

I made a few samples with my Gibson Les Paul 1954 reissue (gorgeous guitar, the best!), on a Vox Lil' Night Train, a small practicing tube amp that I use at home.
Germanium transistors gives the fuzz a nice smooth saturation, still a bit mushy/harsh, but not as gritty as other silicon fuzz like Big Muff for instance.

How does it work?

Fuzz face is really a simple circuit design, as you can already tell by the number of components of the circuit: 4 resistors, 3 capacitors and 2 transistors! And of course two controls: fuzz + volume! As simple as that! But when we look at the circuit:

Fig.1 Fuzz face circuit, classic 60s original schematics

(made with Fritzing)

Not so easy to understand, isn't it?

Let divide this schematic in 3 sections:

Fig.2 Fuzz face circuit, classic 60s original schematics

with different sections of the circuit

(made with Fritzing)

The first capacitor (C2, 2.2uF) filters the DC current at the entry of the circuit to avoid troubles with the next part of the circuit. This kind of capacitor (that you will find in a lot of circuits) is called a coupling capacitor. It also acts as a high pass filter, removing some bass frequencies. Enlarging its value will let more bass go through the circuit.

The gain amplifier section (blue part of the circuit) is a simple common emitter layout to amplify the signal. It has the maximal gain possible in this configuration: the emitter is directly connected to the mass, and the collector is directly linked to the base of the second transistor. It is a very classical layout that you will find in many many transistor based circuits, even if usually a resistor is present between the emitter of the transistor and the mass. This stabilizes the circuit, and allows a fine tuning of the transistor gain by creating a negative feedback. The second transistor is in the same layout, except for its emitter.

The main interest of the circuit is the feedback loop (in green). The emitter of the second transistor is linked directly to the base of the first one through a 100k resistor. A part of the current goes back to the first transistor, creating an amplification loop: current from Q2 comes back to Q1!

The counter reaction (therefore the gain) of the second transistor is modified by a variable resistor placed between the emitter of the transistor and the mass: the fuzz potentiometer! By diminishing its value, the quantity of current going to the mass increases whereas the amount of current going through the feedback loop is diminishing. If the value of the variable resistor increase, more current goes through the feedback loop: the base of Q1 receives more current, saturation increases.

The volume / output section (in red) is the simplest volume control that you can imagine: a 0.1uF coupling capacitor to eliminate DC current, and a volume potentiometer wired as a variable resistor. The output signal will be more or less important depending on the value assigned to the potentiometer.

Fig.3 Analog.man Sunface circuit

(made with Fritzing)

The Analog.man version of this circuit introduces some little improvements to this circuit. First of all, a trimpot (wired as a variable resistor) is present at the input of the circuit before the 2.2uF capacitor. Thus, the entry impedance can be adjusted a bit. It plays the same role as a guitar volume pot, so you can adjust the fuzz gain, which is really useful for high output pickups for instance.

Another modification to the circuit is the 8.2k resistor that is replaced with a 2.2k resistor plus a 5k linear potentiometer. I prefer to use a 10k potentiometer so the original 8.2k value is reachable. This modification allows you to set the bias of the second resistor. It is useful in order to have the maximal gain, especially as the circuit is really temperature-sensitive.

Finally, some values are changed compared to the original circuit: the coupling capacitor is 1uF and the one before the volume pot is 0,01uF. The volume potentiometer is 250k. All together, this will remove a bit of low end, making it a brighter fuzz. This is probably done in order to compensate the deeper tone of the NKT275.

Nothing difficult, but still good improvements to the circuit !

How to make it?

Even if the circuit is really simple, there are some recommendations to follow in order not to mess with it:

• Beware of the orientation of the 10 and 22 uF capacitors: electrolytic capacitors are polarized. Messing with the orientation can result (in the best case) in a non-working circuit, or in the explosion of the capacitor, which really not a nice thing to happen !
• The transistors are the main part of the circuit, and there are some precautions to take with it. Verify that the orientation (Collector, Base, Emitter) is correct before plugging the DC power. 

 Fig. 3 Collector, Base and Emitter of germanium transistors

(C, B and E, respectively)

• Do not overheat germanium transistors! These pieces are very fragile, sometimes a bit of solder can kill them... Additionally, germanium transistors are most of the time quite expensive devices, so I would really recommend to use a solderless method like transistors sockets, and to wait that everything is really cool before putting them in. So, of course, the couple of transistor is the last component to be added to the circuit.
• Last but not least: the circuit needs a negative tension to work properly (-9V). Do not try to use your good old boss charger! 

References / to go further:
http://www.geofex.com/article_folders/fuzzface/fffram.htm 
http://fuzzcentral.ssguitar.com/fuzzface.php
http://www.electrosmash.com/fuzz-face
http://www.analogman.com/fuzzface.htm