This Week on the Breadboard: The Spirit in the Sky Fuzz

Chuck D. Bones said:
It lets us set the SUSTAIN lower if we want. Maybe nobody does. Max sustain is the same.
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To me, more choice is always better on a pot, so long as it's functional. The only thing I don't like is when a pot lets me paralyze an LFO or something like that... not an issue here, obviously.

I'm really eager to get these on a breadboard. I'm in the cult that is obsessed by the tone on the record.
 
Cybercow said:
Green is certainly the easiest. Blue entails cutting a trace cuz lugs #2 & #3 are joined on the PCB.

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Agreed GREEN is the way to go, as stated in my post, but if blue — NO NEED TO CUT A TRACE! 🙀

Should I have gone for blue I'd simply use a solder-lug pot (or simply not solder legs 2&3 to the board — tie lugs/legs 2&3 together on the pot and run the resistor to the Q2-side of C4. Lug 1 as it is, of course.


Nonetheless, I think we're green, Super, even...


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Feral Feline said:
Agreed GREEN is the way to go, as stated in my post, but if blue — NO NEED TO CUT A TRACE! 🙀

Should I have gone for blue I'd simply use a solder-lug pot (or simply not solder legs 2&3 to the board — tie lugs/legs 2&3 together on the pot and run the resistor to the Q2-side of C4. Lug 1 as it is, of course.


Nonetheless, I think we're green, Super, even...


c8d28507345d75f27314a35ef60b79ea.jpg
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Ghak! I missed that entirely. I guess my reading comprehension is now fully exposed. Green indeed.
 
Chuck D. Bones said:
One more mod. It lets us set the SUSTAIN lower if we want. Maybe nobody does. Max sustain is the same. I also reduced C1.

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Challenge accepted!
I'm currently building out to Overcast Fuzz boards, so I thought I'd try to adapt CB's 0.1.1 mods to one of them. Now I'm just trying to find some low Hfe NPN BJTs in my stock. All 98 of the 2N2222s I have measure higher than 160 on my Peak Atlas DCA75.

UPDATE: Found a coupla 2N3566 BJTs with Hfe's @ 96 & 105 for Q1 & Q2 respectively. With CB's changes this thing sounds great!

UPDATE AGAIN: I'm definitely modding the 2nd Overcast circuit to match CB's 0.1.1 changes. Awesome!

Overcast_Fuzz_CB_Mod_0.1.1_a.jpg Overcast_Fuzz_CB_Mod_0.1.1_b.jpg Overcast_Fuzz_CB_Mod_0.1.1_c.jpg
 
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Chuck D. Bones said:
One more mod. It lets us set the SUSTAIN lower if we want. Maybe nobody does. Max sustain is the same. I also reduced C1.

View attachment 120766
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I've got this on a breadboard now. It excels at letting you dial in as much or as little glitch as you want. I've got a matched pair of 126 hfe NPNs on there at the moment. I need to sort out some with a better spread.

For now, I bumped C1 down to 1 nF. I don't know how that will sound with 100/140 hfe, but I typically favor more top end than the average player and I like it so far.
 
genXslacker said:
I've got this on a breadboard now. It excels at letting you dial in as much or as little glitch as you want. I've got a matched pair of 126 hfe NPNs on there at the moment. I need to sort out some with a better spread.

For now, I bumped C1 down to 1 nF. I don't know how that will sound with 100/140 hfe, but I typically favor more top end than the average player and I like it so far.
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Thanks for the tip about those S9018's. I also have two at around hfe=125, I may try to find a 100,140 pair.

Chuck D. Bones said:
One more mod. It lets us set the SUSTAIN lower if we want. Maybe nobody does. Max sustain is the same. I also reduced C1.
Click to expand...

v0.1.1 is very nice, I have it bredboarded and think I might order a pcb for it
 
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Chuck D. Bones said:
Here's an alternate BIAS circuit:
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Just now getting back to this - your version looks very interesting, Chuck - it seems to have more changes to the original than I first noticed. Maybe I missed it earlier, but what was your motivation to set up an alternate Bias Circuit in both V0.1 and V0.1.1?
 
The original bias circuit was in Q2's feedback loop and affected both the bias and the gain. The bias circuit I implemented is outside the feedback loop and has much less influence over the gain.
 
I've tried the Big Cheese (mode 4), the EHX Ripped Speaker and the Danelectro Nichols 1966. They all make a proper vintage nasty-ass fuzz tone, but none of them nail the SitS tone.

I'll be posting TWotB articles for all of them.
 
I wanted a puzzle to solve so I made a stripboard layout for your last version, Chuck - V0.1.1. It's not all that pretty, but it's nice and small, keeps all of the controls together, and hey, it works! Yep, there are a couple standing resistors and even a "leaner". Jimmy crack corn. :) At least you can tell a human did it.

Maybe something is off because based on a quick test this seems LOUD! I changed the Vol control to an "A" taper, and that helped a bit. I used a couple 1N457A diodes instead of the 4003, but their Vf is only a bit higher. Still, that might be it..? Not really an issue, I just don't recall my breadboard having this much volume...

I haven't built the stock SITS yet, so I can't compare. It's fun, though! My guess is this is what it's supposed to sound like. I used a 2N3903 for Q1 and MPSA42 for Q2. I love Bosstones of all kinds, and this is a flavor I didn't quite have yet. Thanks @Chuck D. Bones! If something looks off let me know - again, keeping in mind that I mentioned the resistors. ;)

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Nice! Layout looks good. I can't tell from the photo if every component lead goes into the right hole. 1N457A are zeners and as you say, will have a slightly higher Vf. The volume difference between those and 1N4003 will be noticeable, but not huge. I ended up with A100K in my breadboard and set it around 10:00.
 
Thanks Chuck! Yep I believe everything’s where it should be on the board- it does indeed look like one diode is lower than the other for example, but they’re on the same tracks.

The Fairchild 1N457A is actually not a zener- it sounds like it would be, but it’s a small signal switching diode with a forward voltage of around .66.

Ah! You used A100K for Level too, good to know- and 10:00 is still pretty low, so yeah, this thing has some volume!
 
I was gonna plop my layout of V 0.1.1 in the Stripboard sub but wanted to double check if you've changed anything other than A100K for Level, Chuck. I just noticed the Bias reduced from 1M to 100K in your version - whoa! My guess is your new bias scheme eliminated the need for such a high value pot.
 
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