PedalBuilder
Well-known member
- Build Rating
Backstory
Two of my first builds were Jordan Boss Tone derivatives, the PTD Mini-Bone/Trumpeter and KMA Fuzzly Bear/Teddy Rupture. Although the insides of the enclosures are far from my best work, they are still some of my favorite builds. Both of them offer a wide range of tonal options, from edge of breakup to all-out fuzzy madness. (Note: If you haven't built one yet, this is the build that you have been waiting for—only a few parts, none of which are unobtanium, and both boards are in stock. Go forth and build!) Despite being very similar circuits, i.e. Boss Tones with a voltage starve and modifications to the input/output capacitor values, their respective tonal ranges have much less overlap than you would think. The Fuzzly Bear is less compressed and works better for hard rock tones, likely due to the extra diodes in the clipping stage, while the Mini-Bone is much better at generating brassy/synthy octave overtones. My love for both pedals lead me to contemplate building my own take on PTD's Rotobone, which seems to be a Mini-Bone with rotary switches to select the input and output capacitors, and has additional switches for changing transistors/gain structure. About a year ago, when I first decided to experiment with my own PCBs, the first PCB that I created was meant to be a Rotobone with offboard switches for the capacitors, similar to what @coltonius did here.
Unfortunately, I made a couple mistakes with the circuit design (the gain structure switch should add an emitter resistor to Q1, not Q2/3; the 100k voltage control that was only useful for the first 2/3 of its rotation), transistor selection (the output of the BC108C overpowered Q2/3), and overall layout (side jacks!). I also concluded that the 1P12T switches offered more capacitor selections than I really needed, and had unpleasantly stiff mechanical action. So while I ended up with a cool pedal, it wasn't quite what I had in mind. So back to the drawing board. But life and other projects intervened, and it was quite some time before I was able to get back to the drawing board.
Design
Fast forward to December, and I found myself with some time on my hands, so I decided to restart my Rotobone project. I began by creating a list of the features that I wanted. I knew from my past effort that I wanted to keep the same voltage starve controls as the Mini-Bone (B50k in series with switchable 1k and 39k resistors). I also kept the volume and gain controls. The gain structure switch, which switches in a 4.7k emitter resistor for a lower gain mode, was moved to Q1. I replaced the 1P12T rotary switches with board-mounted 1P8T switches for the input and output capacitors. I had used similar switches for my Rangefinder and a Tone Bender Mk. 1 derivative, and liked the action on them. I kept the Q2/3 silicon/germanium switch. I briefly considered adding a second silicon/germanium switch for Q1, but none of my NPN germanium transistors had enough gain and I couldn't figure out an elegant way to include a fourth switch in my design. Internally, I added dip switches to replicate the bright switch on the Mini-Bone. I don't find them particularly useful with my main guitar, which has humbuckers, but it's useful if you're playing single coils. I also added dip switches to switch in an additional series pair of clipping diodes, a la the Fuzzly Bear. Finally, I added a courtesy +9v pad for the relay bypass board and replaced the polarity protection diode with I/O breakout board with mosfet reverse polarity/over-voltage protection. Final schematic:
Build
I designed the PCB using EasyEDA and had the PCB fabricated at JLCPCB (bonus points for anyone who can find the goof on the PCB). Assembly went smoothly. For the transistors, I used a 2N5088 with an hFE of 330 for Q1, a GT310B with an hFE of 180 and no measurable leakage for Q2, and a 2N2907A with an hFE of 183 for Q3. I considered using an OC42 with similar hFE/leakage for Q2, but opted for the GT310B due to its compact size and because it's my favorite germanium transistor right now. Diodes are generic 1N4148s from Tayda. Here's how it turned out:
I've always loved the aesthetic of the Spaceman pedals, and I have been happy with the looks (and sound, but that's unrelated) of my Spaceman Sputnik clone. I'm also a fan of pedals like @Bricksnbeatles “Oops! Wrong 808” that visually evoke one device while containing the circuitry of another. So I opted for the Spaceman style for this build. For the enclosure, I used a 1590BBS from @StompBoxParts finished in Neutron Star, topped by a faceplate from @amplifyfun. I did the drilling myself with a cordless drill, which reminded me of how much I love Tayda's wonderful enclosure drilling service.
For bypass indication, I used an UV LED under a violet amp jewel from @Amplified Parts. For anyone who's interested in doing a build in this style, the threading on the amp jewel is not long enough to go through the faceplate and the enclosure with enough threading for a nut on the other side. The guys at Spaceman solve this by tapping the enclosure to create threading for the amp jewel. I don't have a tap or a drill press, so I overdrill the hole slightly, make sure that the faceplate fits the jewel snugly, and use hot glue. It's worked for me so far, but I'm using these at home for personal use. I'd want something more secure if this was a commercial product that was going on the road.
Sound
It sounds just like the Rotobone demos that you can find on YouTube—everything from sparkly, lightly overdriven tones to buzzy trumpet sounds. It's also perfectly capable of being set up to be a stock Boss Tone, a Fuzzly Bear, or that one knob Boss Tone-style fuzz that seems to be popular but whose name escapes me at the moment. The germanium switch can be subtle or drastic depending on how the other knobs are set up. At higher settings of the Energy control (i.e. more starved), the germanium has a smoother decay and a softer treble than the silicon setting, which is choppier and can have a more abrasive treble character, depending on how the various capacitor controls are set. The gain structure control is very helpful for expanding the palate of overdrive and lighter fuzz tones. I particularly enjoy the more subtle horn tones that you get with the germanium transistor and low gain structure. You can get many of the same tones with a Mini-Bone/Trumpeter, but there are quite a few great sounds that are only possible with settings that aren't possible on the Mini. Still, if
Final Note
UV LEDs look really cool. It was tough to photograph, but the amp jewel glows in an absolutely surreal fashion, especially when viewed from the side. There's also a halo of purple light that flotas around the jewel that's visible from certain angles. Here's my best attempt at capturing it with a camera:
I'm thinking I might do a third revision of the circuit. The main changes would be moving the gain structure control to a footswitch, as it really does function nicely as a second channel. In the space freed up by the moved gain structure control, I would add a switch for a Germanium/Silicon selector for the Q1 spot. I'll need to find a high gain, low leakage for the germanium, maybe a 2N1308? I'd appreciate any tips that people have. In the meantime, I'm really happy with how this turned out.
Two of my first builds were Jordan Boss Tone derivatives, the PTD Mini-Bone/Trumpeter and KMA Fuzzly Bear/Teddy Rupture. Although the insides of the enclosures are far from my best work, they are still some of my favorite builds. Both of them offer a wide range of tonal options, from edge of breakup to all-out fuzzy madness. (Note: If you haven't built one yet, this is the build that you have been waiting for—only a few parts, none of which are unobtanium, and both boards are in stock. Go forth and build!) Despite being very similar circuits, i.e. Boss Tones with a voltage starve and modifications to the input/output capacitor values, their respective tonal ranges have much less overlap than you would think. The Fuzzly Bear is less compressed and works better for hard rock tones, likely due to the extra diodes in the clipping stage, while the Mini-Bone is much better at generating brassy/synthy octave overtones. My love for both pedals lead me to contemplate building my own take on PTD's Rotobone, which seems to be a Mini-Bone with rotary switches to select the input and output capacitors, and has additional switches for changing transistors/gain structure. About a year ago, when I first decided to experiment with my own PCBs, the first PCB that I created was meant to be a Rotobone with offboard switches for the capacitors, similar to what @coltonius did here.
Unfortunately, I made a couple mistakes with the circuit design (the gain structure switch should add an emitter resistor to Q1, not Q2/3; the 100k voltage control that was only useful for the first 2/3 of its rotation), transistor selection (the output of the BC108C overpowered Q2/3), and overall layout (side jacks!). I also concluded that the 1P12T switches offered more capacitor selections than I really needed, and had unpleasantly stiff mechanical action. So while I ended up with a cool pedal, it wasn't quite what I had in mind. So back to the drawing board. But life and other projects intervened, and it was quite some time before I was able to get back to the drawing board.
Design
Fast forward to December, and I found myself with some time on my hands, so I decided to restart my Rotobone project. I began by creating a list of the features that I wanted. I knew from my past effort that I wanted to keep the same voltage starve controls as the Mini-Bone (B50k in series with switchable 1k and 39k resistors). I also kept the volume and gain controls. The gain structure switch, which switches in a 4.7k emitter resistor for a lower gain mode, was moved to Q1. I replaced the 1P12T rotary switches with board-mounted 1P8T switches for the input and output capacitors. I had used similar switches for my Rangefinder and a Tone Bender Mk. 1 derivative, and liked the action on them. I kept the Q2/3 silicon/germanium switch. I briefly considered adding a second silicon/germanium switch for Q1, but none of my NPN germanium transistors had enough gain and I couldn't figure out an elegant way to include a fourth switch in my design. Internally, I added dip switches to replicate the bright switch on the Mini-Bone. I don't find them particularly useful with my main guitar, which has humbuckers, but it's useful if you're playing single coils. I also added dip switches to switch in an additional series pair of clipping diodes, a la the Fuzzly Bear. Finally, I added a courtesy +9v pad for the relay bypass board and replaced the polarity protection diode with I/O breakout board with mosfet reverse polarity/over-voltage protection. Final schematic:
Build
I designed the PCB using EasyEDA and had the PCB fabricated at JLCPCB (bonus points for anyone who can find the goof on the PCB). Assembly went smoothly. For the transistors, I used a 2N5088 with an hFE of 330 for Q1, a GT310B with an hFE of 180 and no measurable leakage for Q2, and a 2N2907A with an hFE of 183 for Q3. I considered using an OC42 with similar hFE/leakage for Q2, but opted for the GT310B due to its compact size and because it's my favorite germanium transistor right now. Diodes are generic 1N4148s from Tayda. Here's how it turned out:
I've always loved the aesthetic of the Spaceman pedals, and I have been happy with the looks (and sound, but that's unrelated) of my Spaceman Sputnik clone. I'm also a fan of pedals like @Bricksnbeatles “Oops! Wrong 808” that visually evoke one device while containing the circuitry of another. So I opted for the Spaceman style for this build. For the enclosure, I used a 1590BBS from @StompBoxParts finished in Neutron Star, topped by a faceplate from @amplifyfun. I did the drilling myself with a cordless drill, which reminded me of how much I love Tayda's wonderful enclosure drilling service.
For bypass indication, I used an UV LED under a violet amp jewel from @Amplified Parts. For anyone who's interested in doing a build in this style, the threading on the amp jewel is not long enough to go through the faceplate and the enclosure with enough threading for a nut on the other side. The guys at Spaceman solve this by tapping the enclosure to create threading for the amp jewel. I don't have a tap or a drill press, so I overdrill the hole slightly, make sure that the faceplate fits the jewel snugly, and use hot glue. It's worked for me so far, but I'm using these at home for personal use. I'd want something more secure if this was a commercial product that was going on the road.
Sound
It sounds just like the Rotobone demos that you can find on YouTube—everything from sparkly, lightly overdriven tones to buzzy trumpet sounds. It's also perfectly capable of being set up to be a stock Boss Tone, a Fuzzly Bear, or that one knob Boss Tone-style fuzz that seems to be popular but whose name escapes me at the moment. The germanium switch can be subtle or drastic depending on how the other knobs are set up. At higher settings of the Energy control (i.e. more starved), the germanium has a smoother decay and a softer treble than the silicon setting, which is choppier and can have a more abrasive treble character, depending on how the various capacitor controls are set. The gain structure control is very helpful for expanding the palate of overdrive and lighter fuzz tones. I particularly enjoy the more subtle horn tones that you get with the germanium transistor and low gain structure. You can get many of the same tones with a Mini-Bone/Trumpeter, but there are quite a few great sounds that are only possible with settings that aren't possible on the Mini. Still, if
Final Note
UV LEDs look really cool. It was tough to photograph, but the amp jewel glows in an absolutely surreal fashion, especially when viewed from the side. There's also a halo of purple light that flotas around the jewel that's visible from certain angles. Here's my best attempt at capturing it with a camera:
I'm thinking I might do a third revision of the circuit. The main changes would be moving the gain structure control to a footswitch, as it really does function nicely as a second channel. In the space freed up by the moved gain structure control, I would add a switch for a Germanium/Silicon selector for the Q1 spot. I'll need to find a high gain, low leakage for the germanium, maybe a 2N1308? I'd appreciate any tips that people have. In the meantime, I'm really happy with how this turned out.
