The Fuzz Face series: 2-Alchemy Fuzz

The process that lead to my first (semi-)successful silicon Fuzz Face was a long, difficult and at times frustrating one, but working through several ideas about fuzzes and electronics in general and talking about this with my colleagues (Thei's blogspot) gave me a huge boost and a structural idea about why certain components work better than other. However, I came from almost nowhere and there's still a long way to go :)

The Alchemy Fuzz in glorious baby-blue finish :)

When I started building the Alchemy Fuzz I first decided on using Siemens MKT caps for input (.22uF) and output (.01uF) and a tantalum 22uF for on the fuzz pot. Also, I thought it was a good idea to make up the collector resistor for Q2 as a 4k7 resistor plus a 10k trimpot, because I figured I would never need less than half of the resistance that's in the original schematic. After testing, I found out that a 10k trimpot would've been plenty and that having a precision trimpot is not necessarily making things easy to work with. The 33k collector resistor for Q1 was made up of a 22k and a 11k metal oxide resistor in series.

When I got this up and running, it was time to try out different combinations of transistors, constantly trying to keep Vce for Q2 at around 4.5Volts. By now, a couple of months later, I find that this keeping to 4.5Volts very strictly doesn't necessarily give the best results, but I only found that out when I started listening instead of looking at the DMM. :-) Here, the precision trimpot doesn't help gain that knowledge, because the differences only start to be obvious after several turns of the set screw.

It's funny to see my notes from the original design transistor testing, because I was changing so many variables that they hardly make any sense now, but I did find out what kind of transistors I did and did not like. These are the notes I made for the original design:

• 2n2222a + 2n2222a: low gain, fizzy (by now, I know I just don't like the 2n2222a, their high frequency response is very fizzy and brittle)
• BC337-16 + BC107B: plasticky (I don't like the BC337-16 either, they sound flat and compressed)
• 2n2222a + BC337-16: "metal", very little low end
• BC107B + BC107B: "typical" silicon fuzz face sound.
• 2n2222a + BC107B: nice combo, nice "open" sounding low end, a little fizz on the top. A bit hissy though. This is the only one which has the Q2 collector resistor value jotted down: 10k4 (which seems a bit high)
• 2n2222a + BC107A: sounds a lot like the BC107B variety, a little bit less gain.

In the end I went with the 2n2222a + BC107B setup. But.. then I tried to compare it to my Arbiter/Crest Fuzz Face and I was in for a surprise..

At home, with a small amp and no real Fuzz Face to compare it to, it sounded cool, nice low end, cool grainy high end, but in the studio, on my MusicMan 115 Sixty-Five, compared to the Arbiter/Crest Fuzz Face, it sounded... completely different. The high end turned out to be much more muffled than I imagined, the low end sounded out of control, and the fuzz knob and volume control both influence the tone in a massive way. Dialling down the Volume acts as a high pass filter, but dialling down the Fuzz knob gives you less high end..

So I showed my board to my colleague and the first thing he said was: get rid of the tantalum cap, it probably adds the wrong kind of distortion. Also, he said the MKT caps are probably detrimental to the high end response. Reading up on this further I also came to the conclusion that I wouldn't want any MKT caps in any signal-bearing part of the schematic, except maybe in a tone stack where you are specifically looking for this low-pass sort of behaviour.

Last version: Ero capacitor, 2N1711 and BC107 transistors, styro 10.000pF

So, back to the drawing board: I got rid of the Siemens MKT input cap and changed it for a vintage Ero .22uF capacitor. I'm told it's a metallized capacitor, so it probably made little difference.. Better luck next time. To get rid of some of the fizziness I added a 47pF styroflex capacitor between de collector of Q1 and the collector of Q2, as described in the Axis Face schematic. Actually this schematic calls for a 100pF cap, but I found that to cut too much high end. In fact I tried a couple of different capacitors:

• 8.2pF ceramic: no noticeable difference, I guess the cut off freq is too high
• 47pF styro: a little bit of grit is still there, but the high end fizz is gone
• 100pF styro: the grit is gone too
• 220pF styro: noticeable less high end

I also got rid of the MKT output capacitor and put in a 0.01uF styroflex capacitor instead. The 22uF tantalum capacitor was disengaged as well and replaced with a 22uF audio grade electrolytic cap. At the same time I got rid of the 2N2222A in Q1 and obtained a low gain TFK 2N1711 transistor. It's got a Hfe of between 20-60. With such a low gain Q1 I probably could have done without the RF/HF blocker cap, but hey, it's there now. The Bias trimmer is all turned all the way down (0 Ohm), but the 4k7 resistor in series with it keeps Vce for Q2 at a supposedly okay 4.36V. 

L-R: Bias trimmer, BC107, 47pF styroflex anti RF, 2N1711, Ero .22uF

The result, as you might imagine, was completely different from the first version.. However, it doesn't sound like the original Crest Fuzz Face. By now I'm starting to think the BC107B in Q2 might not be the best option after all. And with the Bias trimmer all the way down, there's no way to try anything else. Yet, as a proof of concept it was a complete success and it helped me so much in understanding fuzz electronics. And it does look nice in its baby blue box. Next up I'll be looking at some varieties that, even though they still don't sound like an original, are very useable and they even got a place on my pedalboard :)

Alchemy Fuzz schematic

BF-2 Bazz Fuss Deluxe, commercial succes! :)

Just a short post showcasing my commercial succes :) This is the first box I actually sold! It's a Deluxe version of the Bazz Fuss with a toggle to switch between a 1n4148 diode and a low power yellow LED in the clipping part of the circuit. Turned out a low power yellow LEDs gives the best grit-to-rumble ratio. Compared to red, green, tiny red, tiny green, the mystery see-through one and several high power LEDs. The transistor is a BC550C, which I think is the best choice for this circuit, giving a nice edgy sound with just the right amount of compression and smear.

The BF-2 in all its butterfly glory with its manual and special box :)

Initially I built this box with the version 2 schematic (which is apparently optimized for MPSA darlingtons) and when I compared it to the original it turned out to be completely different (a lot less distortion and no synthy sounds), even though the components were the same. Ah, except for that one resistor that's 100k in version 1 and 10k in version 2.

I thought the amp-style jacks would be a good idea at the time, since it would be a lot easier to get all the grounding right, but it turns out the open style jacks work just fine and don't take up as much space inside the box.

The guts of the BF-2. Notice the toggle on the top right.

Looking at the guts shot now shows me how far I have come in the last couple of months. The boards look a lot cleaner now :) To facilitate more adventures, the toggle has sockets to change out the diodes for different types. Also, the transistor is socketed, but that's just to make it easier for me to test for the right transistor.

The Fuzz Face series: 1-The Original (?)

A couple of years ago I got a blue Fuzz Face with the original Dallas-Arbiter England logo and I was under the impression that it was one of the 1970's silicon varieties.

For a long time, it's been a bit of a mixed bag sound-wise. I mean, the sound is really impressive, but I guess I just wasn't a good enough guitar player to get all the nuances of it. Also, it seemed to have a hard time cutting through the mix, either because of lack of boost or the muffled tone I got with my sloppy playing style. So it spent some time on my FX board, but in the end I had to come to terms with the fact that I just wasn't good enough to get it to work for me..

But, since I was building Bazz Fusses and had some good results with those, I decided to give the old Fuzz Face design another try, and I thought it would be easy to come up with a better sounding device than my supposed old original unit. (spoiler: that turned out to be harder than I thought)
I'll be looking at that attempt in the next blog post, but when I got a working unit and compared it to the sound of the original Fuzz Face I found that I was not even close to getting a box that sounded better to that one..

In the process of trying to build a nice Fuzz Face I read a lot about the unit and saw some pictures of the original Dallas Arbiter units (Technology of the Fuzz Face, Fuzz Central and the story of Dave Fox on Analog Man and the pictures of his Fuzz Face prototypes on the FoxRox website)

So when I consistently got results that weren't as good as the blue Fuzz Face, I opened up that one to look at that board once more to see if it would give up its secrets and I realized my unit wasn't an original one, but very probably a Dave Fox/Crest Audio early '80s reissue. From what I can tell, Dave Fox spent a lot of time tweaking the original schematic so I wasn't competing with a "run of the mill" Fuzz Face, but with a thought-out tuned box.. That certainly set the bar a bit higher..

Transistors are BC109C, input capacitor is a 1uF Philips, output cap is a 47nF film cap. The Q2 collector bias resistor is 6k2, setting Vce for Q2 at 4.3V, which looks good!

I'm not entirely sure where the 68nF film cap goes (it's no doubt there to tame some of the high frequency oscillations), it might also be between the +9V rails and Q1's base. What's surprising is that even though the BC109C's are high gain transistors, the unit sounds surprisingly open and without any low end choking. After having built a couple of Fuzz Faces myself, I know this is one of the more challenging parts of the Fuzz Face design.

Bazz Fuss optimizations: the fish variety

After the successful building of my first Bazz Fuss, I was ready to try more. There are some pointers on the Bazz Fuss page at home-wrecker, so I decided to check them out:

1. put the transistor and diode in a socket, so you can actually try some different ones without having to build a new board every time :)
2. add a pot between the emittor and ground, so you can dial back the fuzz a bit
3. use a 10k collector resistor instead of a 100k resistor, for... reasons.. :)
4. make switchable (on the website it's done with a balance pot) input caps to get rid of the ultra low end. (Hint: this did nothing for me..)

So, this is how it came out:

BF-2 Fish Fuzz, artwork by Petra Randewijk

When I finished putting it in the box, I found out that I wired the volume pot the wrong way around, so this is my first pedal with an Attenuation knob. The unmarked mini toggle adds a .47uF Wima MKS cap to the input, which should give a total of around .33uF input.

The board: L-R: the .1uF output cap, 10k collector resistor, unmarked LED, BC107, 4.7uF input cap

I tried a lot of different diodes and transistors, some of which were more successful than others. On the transistor side:

• MPSA14: overpowering amount of gain, heavy compression
• BC517: another Darlington, a little bit more controlled than the MPSA, but not my cup of tea
• BC109C/BC108C: a lot of gain, but pretty okay
• BC550C: the one I used in the BF-1: nice but a bit compressed
• 2n2222A: I don't like the high end on these, and the note trails are very fizzy, severe gating
• AC127: ouch, my vintage AC127s are unhappy, loads of hiss, very little signal, farty distortion.
• BC107: just the right one for me, I love the open low-mid range on these and even though the high end is not as controlled as for example on the BC550C, it's very musical, I think.

on the diode side:

• 1n4148: classic Bazz Fuss fuzz. Lots of compression, a lot of high end fuzziness
• Germanium diodes (probably 1n34a): A lot less compression, but the mid range gets a bit honky and some of the low end sounds like it's killing the diode
• OAZ205: A vintage (early 1960s) Germanium Zener Diode. Very nice open distortion, but very little high end
• Red LED (5mm): dark distortion, but the low end is too much for this one, some of the notes sound like they don't get clipped at all.
• unmarked clear LED: the right one! just a hint of compression, the open LED distortion characteristic, but with a better high end. All in all a very nice mix between the classic diode fuzz and the dark LED distortions. It's sad that I only have two, and I'm not even sure what color it is..

I've already taken this plastic box on the road with The Legendary Pink Dots and it performed very well. I think I like the magic toggle in the "up" position a bit better, but I'm not even sure if that's with the extra capacitor engaged or not..

BF-2 Fish Fuzz schematic

Back to building: the Bazz Fuss

In the years after building that first successful Fuzz Face I just built a couple of passive boxes, among which a looper/switcher that I use a lot.

Also, after watching how older Meyer Sound processors use LEDs to clip/compress excessive input levels, I decided to modify my DOD OD-250 Overdrive/Pre-Amp to have LEDs instead of the normal silicon diodes that are used to clip the signal. The result was a lot more output and a more "open" distortion characteristic. Eventually the footswitch started failing so I got an MXR Distortion+ and did the same mod on that one. 

Earlier this year I was looking around the internet in search of a nice little project I could do and found the Bazz Fuss on home-wrecker, from a design by Christian H, (neither of these pages have been updated in a while, by the way) and thought that I should be able to build a small project like that (5 components, plus bits) so I went ahead to make a proof of concept:

BF-1 Butterfly (artwork by Petra Randewijk)

This is what the board looks like: transistor is a BC550C, diode a 1n4148. The sound is very dark and fuzzy, played with a bass guitar you get very nice bass synth sounds. Also, because the diode "steals" a lot of current/voltage from the transistor, there's a lot of gating going on and note decay is very fizzy. In a good way, though :)

BF-1: 0.1uF output cap, BC550C, 4.7uF input cap

BF-1: 100k resistor, 1n4148 diode, that's it :)

This is what the schematic looks like:

All in all a very easy build an highly recommended if you want to try your luck at soldering :) Also, using sockets for the transistor and diode add a lot of fun, because you can try different combinations, as you'll see in my next post..

If anybody's curious about listening to these pedals I made, I will soon start putting up soundbites here and there.

Building fuzzes, early attempts

Back in 2000-2002 I built my first fuzz. It was a Fuzz Face clone with BC109C transistors. As I had no previous experience in electronics, I was pleasantly surprised it worked at the second try (after I switched around the transistors a couple of times to get the legs lined up...)

The old 2.2uF Sanyo electrolytic cap probably wasn't the greatest idea for an input cap and with no clue about biasing transistors, the high Hfe BC109Cs are probably not running very efficiently (iCircuit tells me Q2 Vce=7.31V)... The schematic looks like this:

All in all this box makes a lot of noise, chokes on the low end, oscillates like crazy and picks up all kinds of radio stations, but it worked! Even the LED lit up, albeit not very brightly behind that 470k resistor..

About that LED, I only figured that I needed about 1.5Volts to get it to work, so I set to finding a resistor that would give me around 1.5Volts, no clue about Amperes... (iCircuit tells me the Voltage over the LED is in fact 1.383Volts) :-)

After this succes I decided to build another one, but it sounded whimpy, I figured I must've done something wrong, so I set to building yet another one, which didn't work at all, so I scrapped the whole DIY project and put everything in a closet for 12 years.

I did use this Fuzz Face a couple of times, but it kept breaking, because of crappy wiring, so eventually it got an early retirement..

Welcome

Hi folks,

welcome to the BC107 Love blog. I will be writing about my adventures in electronics, particularly about building Fuzz boxes..