Group Actions
Engagement
  • Author Author: Andy Betts
  • Date Created: Date Created
  • Views 7689 views
  • Likes 10 likes
  • Comments 24 comments
Related
Recommended

Arbiter Fuzz Face Effects Pedal - Silicon Transistors

Andy Betts

Following on from my first haphazard foray into pedal building with the Colorsound Power boost fiasco, I can safely say that it was frustrating, educational and entertaining in equal measures. To this end I've decided to start blog posts detailing my various adventures, and misadventures in boutique pedal building.

 

Ahhh.. boutique pedal building. A licence to print money really, and all you get is a pedal that is a copy of an old 70's design, maybe with a few enhancements. Take for example the Power Boost that you're all familiar with by now. Total cost of that pedal to build was around £25 all in. that's the enclosure, the components and the PC board blank. To buy that exact same pedal in Macaris in London is a whopping £259!!!

 

I've probably not told you much about myself up to now, so here is a potted history. I've been playing the guitar since I was 13, semi pro since I was 18, turned pro at 22. Worked at various studios in and around London, did sessions, etc etc. Got out of the pro business when I met my wife, now i'm in Engineering as a Quality Assurance Manager for a motor sport company. my favourite guitarist is David Gilmour, and i'm currently working towards starting or joining a Pink Floyd tribute band.

 

My interest in electronics started last year when I decided that I couldn't afford to buy the pedals that I wanted.... So I decided to build them myself, however getting into electronics theory I've found to be a steep learning curve, but enjoyable. The Colorsound Power Boost was a labour of love for me as I wanted to create the pedal as accurately as possible to an original. Therefore the amount of research I did was probably over the top, collecting as many gut shot photo's of the pedal as possible, and copying the PCB as accurately as possible. I think i ended up with something that is for all intents and purposes a real functioning Power Boost the same as they had back in the day (Minus the Sky TV issue...... Obviously they didn't have Sky Q back in 1969)

 

So on with this blog post and without further ado my latest build. This is to be an exact copy of the Arbiter Fuzz Face pedal, this pedal is as simple as it gets with just four resistors three capacitors two potentiometers and two transistors. That's it! This was used by pretty much everyone in the late 60's and onward like Jimi Hendrix including David Gilmour (there's a pattern there isn't there) The first Fuzz Face came out in about 1966 and was powered by a single 9v battery with 2 matched germanium transistors, there were at least three types used NKT275 AC128 and SFT363E. All of which are fairly hard to come by nowadays. The original germanium Fuzz Face has a warm fuzzy distortion that is easy to tame. As time wore on Germanium transistors were slowly being phased out in favour of the more stable and consistent Silicon versions, as a result Dallas-Arbiter began equipping the Fuzz Face pedals with these new transistors from 1968 onward with differing results. They do sound different from the original Germanium versions usually with a more harsh and aggressive clipping as opposed to the "soft" clipping characteristics of Germanium. The silicon transistors that were used in these versions included  BC108CBC108C BC183L BC109  BC109CBC109C and BC209C.

 

Original germanium pedals are now highly sought after, and regularly change hands for anything upward of £1000!!! Just for four resistors, three capacitors, two potentiometers, and two transistors... Where's the logic in that? The silicon ones are obviously cheaper, at around £700!! Even the new reissues are over £120, which I think is criminal for what's in it... obviously you're paying for the name. Especially when they call one model the "Jimi Hendrix Fuzz Face" obviously that's going to cost more at around £170..... What's the old saying? Money for old rope...... repackage, and hike the price up, just don't change the innards. I won't be paying that.... This build is costing me around £20 all in, that's the enclosure, and the period correct parts which are slightly more expensive than modern equivalents. The rest is just my time, and enjoyment at creating something i can say "I did that".... And "guess what, it sounds just like that £700 original"

 

For this project i'm looking at recreating David Gilmours guitar tones from the early 70's to around 1975, during this time he used a silicon fuzz Face which can be heard on the guitar solos during this period, notably on the album Dark Side of The Moon where he used it extensively on the solos to the songs Money and Time. He also used it at Pink Floyds famous audience-less concert in the Roman Amphitheater in Pompeii in 1972..... Here's a brief clip of David Gilmour showing how this brilliantly simple circuit sounds when built into a pedal

 

 

here is the schematic and PCB layout that I'll be using for the build

 

image

 

image

 

Here is a photo of an original silicon Fuzz Face PCB

 

image

 

The PCB layout above which i'm using for this build is actually the issue 1 layout for the germanium Fuzz Face which was positive ground, therefore I'll have to remember to change a few components to ensure they work in a negative ground build. Notably the 2 polarised capacitors the 20uf and the 2.2uf will need to be turned around or it won't work. the transistors i'm going for are BC183L in Q1 and a BC183LC in Q2. This is a recommendation as they're exactly the same as what are in Eric Johnsons Fuzz Face, also the  hfe of each transistor has been matched to be the same as Erics fuzz Face.

 

 

so, here is my etched board ready populated.... you can see I had to twist the legs of the transistors slightly as the pin outs are different for this board. I've also used period correct parts, not that they sound any different from modern components but they just look "right", and as usual for my own builds I'll try and keep the components as authentic as possible. Hence the carbon comp resistors, and the flat polyester cap. The only brand new part is the 22uf polarised cap, that's a modern Vishay cap I had left from the Power Boost build. The 2.2uf cap is a NOS philips.

 

PCB Board

 

Component side

 

You'll notice that comparing the photos of my board and the original some of the components are in a different place. When I populated my board I followed the schematic and not the photo, transistor Q2 (The bottom one in the photos) is in a different position on this board to the original. I can only assume that in 1968 when they first brought out the silicon versions of this pedal they changed the board layout to compensate for the changes etc. however, nowadays it's standard practice in the pedal building fraternity to use the same board for both and just make the adjustments with components placement and orientation during soldering. Also I'm using a 22uf capacitor instead of a 20uf... This is purely down to availability, I also don't think it'll make much difference to the end result as I've seen Fuzz Faces with 22uf caps in as well as 20uf. I also had 22uf caps left over from the Power Boost builds.

 

The wiring diagram for the various parts of the PCB are as shown in this diagram here.... Obviously I'll be using the NPN Silicon diagram on the right. Here you can also see that my component placement is as shown in this diagram. (This diagram was supplied to me by the guy that created the PCB layout... PigeonFX)

 

image

 

Now I just need to wire it and test it.... I'll do that during the course of today, and post the results later.

 

UPDATE - 08/28/17

 

I have wired the pedal, and will post a short demo of it soon. I've decided to show a proper demo so you can see how this thing interacts with the guitar, the only way I can do that is to film the demo hand free, in other words so i can play the guitar properly as opposed to holding my phone in one hand, and just making noises on the guitar with the other. not very good and sounds awful. i've therefore ordered a cheap tripod adaptor for my phone so I can mount the phone on my camera tripod and film properly.

 

This pedal is awesome, and sounds just like the video above, (although the video above of David Gilmour does have a small amount of echo on it)

 

I did have one issue with the build however and that was after wiring it, i had no sound..... not a peep, so triple checked the wiring to ensure it was correct, and also rechecked the placement of the components. I then got my multimeter, and started checking continuity across the board. that's when I saw this............ A small break in the track for the positive battery lead. i simply re-soldered a bridge across from the pad to the track and it burst into life. i'll post the video in a few days once the tripod adaptor has arrived.

 

image

Attachments:
imagepcb.pdf
  • in reply to jc2048

    Ahh, yes you are of course correct regarding the transistors... 2 boards then

  • in reply to Andy Betts

    You can't do it with one board and a socket. One pair are NPN (the Sony germanium parts) and the other PNP (the Mullard OC204).

     

    The transistor symbol for an NPN transistor has the emitter arrow pointing outwards away from the base, the symbol for the PNP transistor has it pointing inwards towards the base.

     

    Which of the circuits you use depends on whether the part is NPN or PNP, not the semiconductor material it is made from.

     

    The reason someone has added Ge to the PNP one is that in the very early days transistors were essentially hand made and the processes they used favoured PNP types, so you can usually assume that a part from that era is PNP. But by the time Sony were making these in the sixties, there was no longer that restriction and they could be either.

     

    With silicon parts, NPN transistors have always had a edge over PNP when it came to speed, so they were developed first and even now there are a lot more NPN devices available than PNP, but you can't assume that a silicon part is NPN. The Mullard parts are definitely PNP.

     

    Take care soldering them. They are a lot more fragile than modern parts. Back then, the usual advice was to use a heatsink on the leg to conduct heat away whilst it was being soldered.

  • Hi Jon, This is all really interesting and I'm learning so much.... I must get myself an Oscilloscope, that is definitely on my "must buy" list. I've been scouring EBay for a reasonably priced one, as new they're quite expensive and for a hobbyist probably not worth spending loads of money on yet.

     

    The transistors have arrived, many thanks Jon it's much appreciated. I'll etch another board and this time i'll solder in a transistor socket so that I can swap out the transistors easier. then I can do a proper A/B test of the transistors and maybe do a short video to show how they perform in the circuit with a guitar..... I'n very much curious as to how they'll affect the fuzz effect... Really looking forward to this.

     

    I've been hoping to post 2 videos actually, the power boost demo, and this fuzz face demo... I've been really Ill the last week so haven't really been in the right place to do that, but hopefully i'll get both done this weekend as i'm starting another project now that will be taking a bit of my time, I've also started writing the blog post for this new project (You've probably seen some of the videos that I've linked in the new blog in my content) Well, this new project is going to be a goodun, so I'm investing time into it. However, i want to get these demos posted so that I can concentrate on this new project.

  • in reply to jc2048

    I made a wrong assumption with the above posts. I assumed that the output coupling capacitor would pass the signals unchanged driving the 500k pot, but it doesn't. The time constant is so short that it's acting as a differentiator. So the traces above, which show the signal at the junction of the 330R and the 8.2k resistors, don't represent the output of the pedal.

     

    I've added the 10nF cap and a 330k resistor to ground (to simulate the pot and an assumed 1M input resistance to whatever it feeds) to my breadboard and here's what the output looks like with modern transistors. I've superimposed the waveforms for both extremes of the 1k pot so you can see what the adjustment does.

     

    image

     

    Now here it is with the OC204 parts (old silicon devices). This is much softer and gives a range of control from something like the old germanium parts through to a softish version of what a modern part would do. The major advantage they'll have over the germanium parts is the much lower leakage (leakage varies dramatically with temperature, so the germanium pedals probably wander all over the place as they warm up, whereas these should be fairly stable).

     

    image

     

    The main disadvantage I see with this circuit is the way that it's so dependent on what is feeding it and what it is driving. The base feedback clobbers the input waveform to some extent, so the sound will partly depend on the guitar that's driving it, how many coils it has and how they're wired and so on, and the small coupling cap at the output means that the waveform shape also depends on the input resistance of whatever is being driven.

  • Just for completion, I've been given a copy of the Arbitor issue 2 PCB layout. This was the layout for the silicon Fuzz Faces from around 1968 onwards.

     

    image