CONTEST Happy New Years Limited Parts Contest

CONTEST
Here's the first revision of my "Sho' Yo' Muff". I added a selectable clipping capacitor. It's an on/off/on switch and the middle 22n cap is tied to the middle lug. In one on position you'll have 44nf (close to the standard muff 47nf), middle position is 22nf, and the other on position you'll have 122nf. The switch selects how much CREAM you want in your muff (amount of signal to be clipped). I also fixed the zener in the schematic only. I played around with this during my practice session today. I wish it had juuuuust a bit more grit, but a chop shop cleared that right up :cool: . This will be my official submission for the contest.

1706199431703.png
1706199454478.png
 
BuddytheReow said:
Here's the first revision of my "Sho' Yo' Muff". I added a selectable clipping capacitor. It's an on/off/on switch and the middle 22n cap is tied to the middle lug. In one on position you'll have 44nf (close to the standard muff 47nf), middle position is 22nf, and the other on position you'll have 122nf. The switch selects how much CREAM you want in your muff (amount of signal to be clipped). I also fixed the zener in the schematic only. I played around with this during my practice session today. I wish it had juuuuust a bit more grit, but a chop shop cleared that right up :cool: . This will be my official submission for the contest.

View attachment 66805
View attachment 66806
Click to expand...
8996eed3-a026-4b6b-bc7f-afb0403b0448_text.gif
 
BuddytheReow said:
Here's the first revision of my "Sho' Yo' Muff". I added a selectable clipping capacitor. It's an on/off/on switch and the middle 22n cap is tied to the middle lug. In one on position you'll have 44nf (close to the standard muff 47nf), middle position is 22nf, and the other on position you'll have 122nf. The switch selects how much CREAM you want in your muff (amount of signal to be clipped). I also fixed the zener in the schematic only. I played around with this during my practice session today. I wish it had juuuuust a bit more grit, but a chop shop cleared that right up :cool: . This will be my official submission for the contest.
Click to expand...
That's really neat - I'm going to have to try that capacitor switch. Maybe more useful than just-another-diode-switch? More interesting, at least.
 
Now that you've showed us your Muff, what does R11 do?
BuddytheReow said:
Here's the first revision of my "Sho' Yo' Muff". I added a selectable clipping capacitor. It's an on/off/on switch and the middle 22n cap is tied to the middle lug. In one on position you'll have 44nf (close to the standard muff 47nf), middle position is 22nf, and the other on position you'll have 122nf. The switch selects how much CREAM you want in your muff (amount of signal to be clipped). I also fixed the zener in the schematic only. I played around with this during my practice session today. I wish it had juuuuust a bit more grit, but a chop shop cleared that right up :cool: . This will be my official submission for the contest.

View attachment 66805
Click to expand...
 
Your submission inspired me to try my hand at a modified HP. I can't show it while this contest is underway, but thanks for kickstarting my brain!

t1redhands said:
While I'm thinking of a non-fuzz pedal to submit, here's a rendition of a Harmonic Percolator that's been heavily tweaked and given the Bazz Fuzz treatment. The two clipping switches really give a wide range of tones - from usable high-gain distortion to squonks and squelches. Just a volume knob for this guy. Including the switches and stuff it's made of 27 parts, if I counted correctly. That's a very low-gain Russian GE transistor at Q. I haven't tried any others there, could probably be worthwhile to experiment.

View attachment 66539
Click to expand...
 
Alright, here's my entry. I've been on a germanium fuzz kick for the last year or so, and that's led to me developing some opinions on the subject. Although germanium fuzzes sound awesome, they can be a bit of a headache. Sourcing transistors can easily send you down a rabbit hole, and it can be hard to find components with the specs that certain classic circuits purportedly require. It's not too hard to find transistors that work in a rangemaster or a fuzz face—just grab a bag of P416B or GT308V or GT309E or GT309V or GT310B off of a reputable eBay seller and you'll have more than enough transistors to build multiple copies of both circuits. But finding suitable transistors for a leakage-biased circuit like a Tone Bender Mk. II or III can be much more of a challenge. I've found that leakage-biased circuits are very touchy about temperature and start sounding off if they're outside of a relatively narrow temperature sweet spot. I designed my entry to try and minimize those hindrances so that it's easier for someone without a large transistor collection to build a versatile Tone Bender-style fuzz that's less finicky about temperature than the classic circuits and is less picky about transistors. Here's the schematic:

Schematic_Hybrid Mk. II+_2024-01-30.png

As you can tell, the genesis of this circuit is the Tone Bender Mk. II, with changes inspired by the Tone Bender Mk. III family of circuits. The first stage is unchanged, and uses a 100k base-ground resistor for Q1. For Q1 (and Q3), you can use any germanium NPN with a gains between 40 and 70 (and probably higher, too, but I didn't check) and 80-350 µA of leakage. There are lots of relatively cheap, easily available devices that meet those criteria, e.g. MP11A, MP38A, 104NU71, or 2SD77. One of my favorite things about this circuit is that it isn't picky about transistors; all you need is at least some leakage and it works like a charm.

After Q1, things start changing. Rather than using a small pot on the emitter of Q3 to set the fuzz intensity, I added a C100k pot wired as a variable resistor after Q1 to attenuate the input to Q2. This gives a nice, even range of tones, from heavy overdrive to all out fuzz. I tried a few values here before settling on C100k. More than ~120kΩ of resistance resulted in dull, muddy, tones (unsurprisingly, as the input stage is fairly dark and relies on distortion in the later stages to generate higher harmonics), and the most drastic change was between 0 and ~30kΩ, making a C100k the logical choice, although a B100k works just fine, too.

For Q2, I replaced the germanium transistor with a mid-gain silicon device. To make this work, I added a 2.2M resistor from +9v to the base and a 220pF capacitor from base to collector. In my view, using a silicon device here offers several advantages. In an all-germanium Mk. II, Q2 is the hardest device to select, as its gain and leakage have a huge impact on the biasing of Q3. This also means that changes to Q2's leakage due to changes in ambient temperature can throw off Q3's biasing. Changing Q2 to silicon eliminates this issue; with a silicon Q2 in place, I raised the temperature of Q3 from 70ºF to 95ºF and its collector voltage did not change at all. There is a slight tonal change here between silicon and germanium, with silicon being a little more bright and aggressive, but I'm not sure how much of that is just the change in the device's hFE. For Q2, anything with an hFE of 250-350 works well, so a BC109 if you want mojo, or a 2N3904 or Tayda 2N5088 if you want cheap.

For Q3, I changed the voltage divider above the collector and replaced the 1k pot with a pair of resistors. The emitter resistor (R8) helps set the bias and has a noticeable effect of the harmonic content of the clipping. I tried a bunch of values between 470Ω and 2kΩ. Anything below 1.2kΩ led to abrasive and unpleasant high frequency content; values below 820Ω were even worse and created oscillation. Using a 1.5kΩ resistor tamed the harsh overtones and oscillation without killing the gain. I also played around with a bunch of values for R9, with similar results to R8. Lower values had harsh overtones and oscillation, and higher values had less gain than I wanted, so 220Ω was the sweet spot.

For tone shaping, I used a Tone Bender Mk. III-style tone control. I chose the values of C6, C7, and R10 carefully so that the tone control is useful from 0-10. One of my pet peeves is when pedals have a tone control that sound good from 3-7, but have unusably extreme settings at either end of the rotation. (Even worse are the pedals that sound best with the tone control at 10 and shouldn't have an external tone control in the first place). I think I managed to get this circuit to sound good at every setting on the tone control, but I'd be interested to hear what others think.

Enough of the circuit design talk—how does this thing sound? I think it sounds great. It definitely cops the classic Mk. II tones; as soon as I hit the first note I felt compelled to play the intro riff for Whole Lotta Love. It also does some of the more filtered Mk. III and Buzzaround sounds (unsurprisingly, given the origin of tone section). It cleans up more nicely than most Mk. II-style pedals that I have played, especially if the gain is at 9 or lower and the pedal's tone control is below 7.

Right now I've just got it put together on the breadboard; I'll update this post once I've laid out a PCB.

IMG_2108.jpeg

Update:

Here's the PCB. The pots are spaced to match Tayda's PedalPCB 3-Knob (Type 1) enclosures.

PCB.png

Edit 2/14: Here are some clips I put together over my lunch break. Usual caveats apply re: sloppy playing.
https://soundcloud.com/pedal-builder%2Fsets%2Fpedalpcb-limited-parts-contest-2024
 
Last edited:
Here's another one I cooked up. This is a bazz fuss into a Devi Ever Hyperion (PPCB Ionizer) into a baxandall tone stack. The tone stack on my breadboard is a stripboard build with an extra gain stage (a very versatile tool indeed). This circuit doesn't need it so I'm removing it from the schematic. In most Devi Ever circuits, there is a CONTROL pot at the beginning of the circuit, but in lieu of that (and to keep within contest rules) i simply use the guitar's volume knob and it makes a big difference. I run hot humbuckers, so I almost can't max out the guitar's knob. R3 on my breadboard is a 10k and 22k in parallel, but comparatively they are pretty much the same.

A nasty octave-y fuzz I'd like to call KONG. Why? With downtuning, this circuit sounds like Kooooonnnnggg, Kooooooonnnng.

1706619360975.png

1706619486932.png
 
Last edited:
PedalBuilder said:
Alright, here's my entry. I've been on a germanium fuzz kick for the last year or so, and that's led to me developing some opinions on the subject. Although germanium fuzzes sound awesome, they can be a bit of a headache. Sourcing transistors can easily send you down a rabbit hole, and it can be hard to find components with the specs that certain classic circuits purportedly require. It's not too hard to find transistors that work in a rangemaster or a fuzz face—just grab a bag of P416B or GT308V or GT309E or GT309V or GT310B off of a reputable eBay seller and you'll have more than enough transistors to build multiple copies of both circuits. But finding suitable transistors for a leakage-biased circuit like a Tone Bender Mk. II or III can be much more of a challenge. I've found that leakage-biased circuits are very touchy about temperature and start sounding off if they're outside of a relatively narrow temperature sweet spot. I designed my entry to try and minimize those hindrances so that it's easier for someone without a large transistor collection to build a versatile Tone Bender-style fuzz that's less finicky about temperature than the classic circuits and is less picky about transistors. Here's the schematic:

View attachment 67171

As you can tell, the genesis of this circuit is the Tone Bender Mk. II, with changes inspired by the Tone Bender Mk. III family of circuits. The first stage is unchanged, and uses a 100k base-ground resistor for Q1. For Q1 (and Q3), you can use any germanium NPN with a gains between 40 and 70 (and probably higher, too, but I didn't check) and 80-350 µA of leakage. There are lots of relatively cheap, easily available devices that meet those criteria, e.g. MP11A, MP38A, 104NU71, or 2SD77. One of my favorite things about this circuit is that it isn't picky about transistors; all you need is at least some leakage and it works like a charm.

After Q1, things start changing. Rather than using a small pot on the emitter of Q3 to set the fuzz intensity, I added a C100k pot wired as a variable resistor after Q1 to attenuate the input to Q2. This gives a nice, even range of tones, from heavy overdrive to all out fuzz. I tried a few values here before settling on C100k. More than ~120kΩ of resistance resulted in dull, muddy, tones (unsurprisingly, as the input stage is fairly dark and relies on distortion in the later stages to generate higher harmonics), and the most drastic change was between 0 and ~30kΩ, making a C100k the logical choice, although a B100k works just fine, too.

For Q2, I replaced the germanium transistor with a mid-gain silicon device. To make this work, I added a 2.2M resistor from +9v to the base and a 220pF capacitor from base to collector. In my view, using a silicon device here offers several advantages. In an all-germanium Mk. II, Q2 is the hardest device to select, as its gain and leakage have a huge impact on the biasing of Q3. This also means that changes to Q2's leakage due to changes in ambient temperature can throw off Q3's biasing. Changing Q2 to silicon eliminates this issue; with a silicon Q2 in place, I raised the temperature of Q3 from 70ºF to 95ºF and its collector voltage did not change at all. There is a slight tonal change here between silicon and germanium, with silicon being a little more bright and aggressive, but I'm not sure how much of that is just the change in the device's hFE. For Q2, anything with an hFE of 250-350 works well, so a BC109 if you want mojo, or a 2N3904 or Tayda 2N5088 if you want cheap.

For Q3, I changed the voltage divider above the collector and replaced the 1k pot with a pair of resistors. The emitter resistor (R8) helps set the bias and has a noticeable effect of the harmonic content of the clipping. I tried a bunch of values between 470Ω and 2kΩ. Anything below 1.2kΩ led to abrasive and unpleasant high frequency content; values below 820Ω were even worse and created oscillation. Using a 1.5kΩ resistor tamed the harsh overtones and oscillation without killing the gain. I also played around with a bunch of values for R9, with similar results to R8. Lower values had harsh overtones and oscillation, and higher values had less gain than I wanted, so 220Ω was the sweet spot.

For tone shaping, I used a Tone Bender Mk. III-style tone control. I chose the values of C6, C7, and R10 carefully so that the tone control is useful from 0-10. One of my pet peeves is when pedals have a tone control that sound good from 3-7, but have unusably extreme settings at either end of the rotation. (Even worse are the pedals that sound best with the tone control at 10 and shouldn't have an external tone control in the first place). I think I managed to get this circuit to sound good at every setting on the tone control, but I'd be interested to hear what others think.

Enough of the circuit design talk—how does this thing sound? I think it sounds great. It definitely cops the classic Mk. II tones; as soon as I hit the first note I felt compelled to play the intro riff for Whole Lotta Love. It also does some of the more filtered Mk. III and Buzzaround sounds (unsurprisingly, given the origin of tone section). It cleans up more nicely than most Mk. II-style pedals that I have played, especially if the gain is at 9 or lower and the pedal's tone control is below 7.

Right now I've just got it put together on the breadboard; I'll update this post once I've laid out a PCB.
Click to expand...
NICE!
Great write-up.
What collector voltages do you get on Q1-Q3?
 
You must log in or register to reply here.
Back
Top