Wattson EFY-6 Fuzz  [traced]

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Post by amp_surgeon »

We usually include schematics in the user manual. We weren't able to do that this time because the user manual had to be small enough to fit into a box only slightly bigger than the pedal, and the schematic would have been illegible at that scale. I'll eventually get around to uploading the schematic on our website. In the meantime, here it is.
Wattson EFY-6 Fuzz Schematic
Wattson EFY-6 Fuzz Schematic
Ok, so this is obviously the Shin-ei FY-6 circuit with a few relatively simple mods. I'll explain each of them.

First, you'll notice a 10KB pot has been added in the collector circuit of Q5, which is one of the two transistors in the differential amp that generates the octave step up. If you've ever fiddled with the balance trimmer in an FY-6 or Univox Super-Fuzz while looking at the signal on a scope then you probably noticed that moving the trimmer out of the center position causes half of the cycles to increase in amplitude while the other half decrease in amplitude. We just inserted enough resistance to cause half of the cycles to drop to near zero amplitude when the pot was at it's maximum resistance, and return to normal amplitude when the pot was at it's minimum resistance. This isn't really the same as bypassing the octave generator because the octave generator is still doing some waveshaping. For example, the width of the remaining cycles is still the same as it would be with both cycles present. Even so, the frequency is the original input frequency (with the additional waveshaping), and it has the desired effect, which was to eliminate much of the very high frequency harmonics the octave generator normally produces. This means notes played in the high register no longer sound "synthy", but it also means that chords of more than two notes are a lot less mushy, and low frequency notes sound a lot stronger.

Turning the pot fully CCW gives maximum resistance and minimum octave effect. Turning the pot fully CW gives minimum (zero) resistance, and maximum octave effect, and should sound just like an original FY-6. Also, the extra resistance in the collector circuit of Q5 changes the way the balance trimmer TR1 works. The circuit will begin to slowly oscillate (pop...pop...pop) if the trimmer is even slightly out of balance. Unlike the FY-6, where we adjust the trimmer for minimum hiss noise, we have to adjust the trimmer for the point where the oscillation stops.

Next, we hung a 100KB pot across the output of the voltage divider R24/R25 and the mid-scoop filter. In other words, right where the "Tone" switch used to be. Nothing mysterious here. We're just blending between the two tones.

Finally, we changed all of the resistors in the output amp Q6 stage to increase the gain to nearly 20 (about double the previous gain). This was in response to complaints that the original FY-6 sounded like it had a volume drop. It actually didn't have a volume drop, at least when looking at the signal on a scope, but it sounded that way because of the drop in mids. The changed gain of the Q6 stage leaves plenty of volume on tap, and the fact that the "Gain" pot is before this stage rather than after means that most of that volume can be used without adding any additional distortion. Unity gain is now with the "Gain" pot between 10 and 12 o'clock.

These changes should work on any reproduction of the Shin-ei FY-6, including the BYOC Leeds.

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Post by Bill_Mountain »

Looks awesome. Have you tried it with bass at all?

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Post by amp_surgeon »

Bill_Mountain wrote:Looks awesome. Have you tried it with bass at all?
Not personally. I downsized my collection a few years ago out of necessity - my new wife insisted on sleeping in a bedroom instead of a project studio - so I had to sell my bass. A friend of my test tech has promised to bring in his bass so we can test it. Hopefully that will happen soon.

Just based on what I've seen on the bench, I'm guessing it should sound pretty good. The original FY-6 always had pretty good bottom end response because Shin-ei went overboard on the coupling caps, but the octave step up sometimes resulted in notes sounding a little flubby. Turning down the octave should tame that considerably. On the flip side, losing the octave means losing some harmonics, which makes the fuzz sound a little less "SuperFuzz" and a little more pedestrian. Hopefully, the knob allows the user to find a good balance.

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Post by Bernardduur »

The FY6 -like pedal is good for bass although it must suit your taste...... the octave nasty sounds have enough bottom end to make sure it'll make your bass stand out, yet it sounds maybe too nasty for most players! Listen to the Beastie Boys..... they use it a lot on bass!!
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Post by beedotman »

Nice! :thumbsup
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Wattson EFY-6 Fuzz box
Wattson EFY-6 Fuzz box
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Wattson EFY-6 Fuzz guts 2
Wattson EFY-6 Fuzz guts 2
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Wattson EFY-6 Fuzz guts 01
Wattson EFY-6 Fuzz guts 01

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Post by flood »

Thanks for this! I'm working on my own superfuzz clone, and I'm pretty happy so far using a mix of BC108B and 2N3904, all in the hfe range of 190-200. I'm planning to try some BC107As or 2N2222As to see if the sound changes significantly. Does the sound get less harsh when the octave is turned down all the way, or is it still as clangy? I love this pedal, both on guitar and bass.
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Post by amp_surgeon »

flood wrote:Thanks for this! I'm working on my own superfuzz clone, and I'm pretty happy so far using a mix of BC108B and 2N3904, all in the hfe range of 190-200. I'm planning to try some BC107As or 2N2222As to see if the sound changes significantly. Does the sound get less harsh when the octave is turned down all the way, or is it still as clangy? I love this pedal, both on guitar and bass.
Yes, the octave adds a lot of sizzle, and that sizzle drops away as you turn the octave down. At the same time, the bottom end fills out.

Personally, I really like that sizzle with single notes and power chords, but full barr chords sound a lot better without it.

We've tried this circuit with a wide variety of small signal silicon NPN's with hfe's ranging from around 75 to over 300. It's worked more or less the same with everything we've used. Since the clipping is accomplished with the germanium diodes it's not really critical to have transistors with a specific hfe range. All of the transistors in this circuit are biased well below the beta of most common transistors. One place where it does matter is the differential amp. If these transistors aren't reasonably well matched, and you don't add the trimmer to balance the circuit, then one side of the amp will produce stronger cycles than the other. After clipping this comes out of the final stage as hiss noise. If you want it to be perfecty quiet when you're not playing then either match these two transistors or add the trimmer (much easier).

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Post by flood »

amp_surgeon wrote:
flood wrote:Thanks for this! I'm working on my own superfuzz clone, and I'm pretty happy so far using a mix of BC108B and 2N3904, all in the hfe range of 190-200. I'm planning to try some BC107As or 2N2222As to see if the sound changes significantly. Does the sound get less harsh when the octave is turned down all the way, or is it still as clangy? I love this pedal, both on guitar and bass.
Yes, the octave adds a lot of sizzle, and that sizzle drops away as you turn the octave down. At the same time, the bottom end fills out.

Personally, I really like that sizzle with single notes and power chords, but full barr chords sound a lot better without it.

We've tried this circuit with a wide variety of small signal silicon NPN's with hfe's ranging from around 75 to over 300. It's worked more or less the same with everything we've used. Since the clipping is accomplished with the germanium diodes it's not really critical to have transistors with a specific hfe range. All of the transistors in this circuit are biased well below the beta of most common transistors. One place where it does matter is the differential amp. If these transistors aren't reasonably well matched, and you don't add the trimmer to balance the circuit, then one side of the amp will produce stronger cycles than the other. After clipping this comes out of the final stage as hiss noise. If you want it to be perfecty quiet when you're not playing then either match these two transistors or add the trimmer (much easier).
:thumbsup

In the interest of full disclosure, I'd like to state here that my clone is a commercial project. That being said, I will be crediting the original FY-6 circuit, the Wattson EFY-6 as an additional inspiration (I learned about your version fairly late in the day) and sharing my schematic here as well as on my FB page/website as soon as I've finished building. Hoping that happens in Jan 2014, so that I can continue in my losing battle to get more Indian guitarists to play fuzz pedals. Over here, the metal/extreme metal scene pretty much dominates everything, so either you do extreme metal distortion or "transparent dynamic overdrives blessed with phantom harmonics and unicorn piss". I'm not sure how they'll receive this one, the local response has been pretty damn lukewarm - but I do have 80 PCBs and a ton of pots waiting to be soldered. :/

My first variation on the Superfuzz circuit happened around June, I think, I wasn't very happy with that, so I did a fair amount of experimenting around the octave section over the last few months, poking around hfe values, the 10k trimmer and an octave pot - to my ears, the PN2222 transistors with hfe ranges from 170-200 seem to work best in this circuit (or at least in my layout), especially with the octave turned off.

That being said, I can't get an octave pot of 10k to work correctly without causing thumping. I found the differences within the usable range of the pot so small that I've decided to use a switch to short a small (probably 2k2, but I need to verify that) resistor in the collector circuit of one of the transistors. in both my protos, this has lifted the octave without introducing thumps into the signal. any larger resistance than that seems to cause problems.

I'll be verifying this value over about 10 protos. a simpler way would be to use a trimpot, I guess, to compensate for component variations.

If this pedal actually becomes popular, I'd probably want to skip discrete transistors altogether and use matched arrays in the future.

I promise to share my schematic on FSB once I'm ready to release it - I'd just like to complete building first since I'm dumping my savings into this venture. This board has taught me a ton of stuff, I'm ready to start giving back. :horsey:
In the interest of full disclosure, I am Animal Factory Amplification.

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Post by Gila_Crisis »

I've implemented in one of my superfuzz clones the octave pot mod by wattson, and while trying I used a 50k log pot.
Since the pot is a log one, up to 3/4 of the pot open you reach about 10k resistance, but if you go up more, in the last 1/4 of the pot, the pedal starts to self-oscillate! Which for me is a genius thing!
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Post by flood »

Gila_Crisis wrote:I've implemented in one of my superfuzz clones the octave pot mod by wattson, and while trying I used a 50k log pot.
Since the pot is a log one, up to 3/4 of the pot open you reach about 10k resistance, but if you go up more, in the last 1/4 of the pot, the pedal starts to self-oscillate! Which for me is a genius thing!
strange. hasn't worked for me to date, i'm guessing it has to do with the individual transistor characteristics - 2N5088s have a lot more hFe than PN2222, mine are around 200 +/- 50. i match the octave pair within 5-7 hFE of each other. base junction transistors are 100k/22k in my version... the oscillation (more like thumping) starts around 30% of the way of a 10k pot for me. i do have to conduct measurements though, and also finally put my brand new tektronix scope to use 8) should be a fun hunt.

i'm not using a pot, finally, just an on-off-on switch. very minute collector resistance changes seem to have dramatic effects in my version.
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Post by Gila_Crisis »

if you build the superfuzz with the "octave/balance trim" on the 22k or 15k resistors going to ground from the bases of the transistors, the trick to get the best oscillation, is to unbias the transistors with the trim!
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Post by flood »

Gila_Crisis wrote:if you build the superfuzz with the "octave/balance trim" on the 22k or 15k resistors going to ground from the bases of the transistors, the trick to get the best oscillation, is to unbias the transistors with the trim!
you know, i have done unbiasing on my pedals while setting the octave, and i've NEVER had the oscillation happen :scratch:

i'm going to fool around with this a bit again, but most likely i'll be shipping it out with the trim biased for the best octave - i've found that resistances of as little as 1k in the transistor's collector circuit do a pretty good job of lifting the octave without inducing the thump/oscillation. a fixed resistance of 2k2 is enough to cause it to creep in.

i'm really happy with my version on the whole, except for the thump - i'm going to have to sit down this weekend and scope 5-10 completed boards to see what the hell is going on.

EDIT: I am even stupider than I think I am, the first post has a very graphic description of the same problem that I have, I guess I would have solved it on my scope on Sunday, but it's comforting to know that the same circuit in only slightly different configurations creates the same issues. I can safely rule out my layout as the root cause, I guess, which is a relief to know. I don't like the idea of tossing all those boards that have put up with neglect over the last couple of months... FWIW, I didn't get too much hiss from the circuit even unbiased, just a deterioration of the octave effect. I will stick with the octave switch instead of the pot though, as I had originally planned. For one, it keeps things a bit simpler as I already have 4 pots, and besides, I don't want to step on Wattson's turf :) more dedicated modders can put a pot in if they're so inclined.
Turning the pot fully CCW gives maximum resistance and minimum octave effect. Turning the pot fully CW gives minimum (zero) resistance, and maximum octave effect, and should sound just like an original FY-6. Also, the extra resistance in the collector circuit of Q5 changes the way the balance trimmer TR1 works. The circuit will begin to slowly oscillate (pop...pop...pop) if the trimmer is even slightly out of balance. Unlike the FY-6, where we adjust the trimmer for minimum hiss noise, we have to adjust the trimmer for the point where the oscillation stops.
Gila_Crisis, it's strange that i can't/don't get the self-oscillation that you talk about, even with the second transistor completely disconnected - is it more like the "pop-pop-pop" :popcorn: variety or the high-pitched feedback/velcro from self-oscillating fuzzes?
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Post by flood »

minor updates... interesting, interesting. turns out that the superfuzz circuit scopes beautifully with a sine wave input. i get clear octaving waveforms (that i think i will capture and post here for all to behold in the future). saw something brilliant between two clones, identical except for the transistors - all Qs on one were PN2222A and the other were all metal cans, the metal can versions had lower hfe IIRC. the plastic version sounds better to me, the metal can version is great too but less robust and a bit more velcroey as a fuzz. the plastic version was just a lot more versatile, especially with the octave defeated.

when i scoped it out, the plastic version had doubling going on, and the metal can version was all tripling :D

tried to null the popping purely with the scope, but that didn't work - i'm going to do it audiovisually and see what i can come up with. will remember to keep a camera (or cellphone) handy to take photos and share here, in case it helps anyone in the future :)
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Post by tabbycat »

flood wrote:In the interest of full disclosure, I'd like to state here that my clone is a commercial project. That being said, I will be crediting the original FY-6 circuit, the Wattson EFY-6 as an additional inspiration (I learned about your version fairly late in the day) and sharing my schematic here as well as on my FB page/website as soon as I've finished building. Hoping that happens in Jan 2014, so that I can continue in my losing battle to get more Indian guitarists to play fuzz pedals. Over here, the metal/extreme metal scene pretty much dominates everything, so either you do extreme metal distortion or "transparent dynamic overdrives blessed with phantom harmonics and unicorn piss". I'm not sure how they'll receive this one, the local response has been pretty damn lukewarm - but I do have 80 PCBs and a ton of pots waiting to be soldered. :/

My first variation on the Superfuzz circuit happened around June, I think, I wasn't very happy with that, so I did a fair amount of experimenting around the octave section over the last few months, poking around hfe values, the 10k trimmer and an octave pot - to my ears, the PN2222 transistors with hfe ranges from 170-200 seem to work best in this circuit (or at least in my layout), especially with the octave turned off.

That being said, I can't get an octave pot of 10k to work correctly without causing thumping. I found the differences within the usable range of the pot so small that I've decided to use a switch to short a small (probably 2k2, but I need to verify that) resistor in the collector circuit of one of the transistors. in both my protos, this has lifted the octave without introducing thumps into the signal. any larger resistance than that seems to cause problems.

I'll be verifying this value over about 10 protos. a simpler way would be to use a trimpot, I guess, to compensate for component variations.

If this pedal actually becomes popular, I'd probably want to skip discrete transistors altogether and use matched arrays in the future.

I promise to share my schematic on FSB once I'm ready to release it - I'd just like to complete building first since I'm dumping my savings into this venture. This board has taught me a ton of stuff, I'm ready to start giving back. :horsey:
hey flood, i hope all is bon in bombay.

am in the middle of a superfuzz modding phase. reworking aspects of my 2011 clone as a result of new learning to max its potential. reviewing every possibility.
i'd be very interested to check out the schematic for the chemical burn (you mentioned it might be posted jan 2014?) to compare it with other modded superfuzzes and variants i'm looking at (derringer mods, efy-6, etc).
i visited your shop site and shop facebook page but couldn't find it on the CB pages.

thanks,
tabbycat.

ps. congrats on getting to namm this year. that's a big one. i bet us customs loved your suitcase full of electrical gadgets inscribed 'chemical burn'. their eyes must have lit up.

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Post by flood »

tabbycat wrote: hey flood, i hope all is bon in bombay.

am in the middle of a superfuzz modding phase. reworking aspects of my 2011 clone as a result of new learning to max its potential. reviewing every possibility.
i'd be very interested to check out the schematic for the chemical burn (you mentioned it might be posted jan 2014?) to compare it with other modded superfuzzes and variants i'm looking at (derringer mods, efy-6, etc).
i visited your shop site and shop facebook page but couldn't find it on the CB pages.

thanks,
tabbycat.

ps. congrats on getting to namm this year. that's a big one. i bet us customs loved your suitcase full of electrical gadgets inscribed 'chemical burn'. their eyes must have lit up.
hey there tabbycat,

thanks for the congratulations :) yep, it was massive. i'll be back next year, that's for sure. why TSA didn't rip me a new one still baffles me :) i did take all my pedals back to india in a carry on, though, so i guess they've figured out that effect pedals are harmless...

profuse apologies for not having shared a schematic yet, as promised. this has been for a couple of different reasons; one of them is very slow sales, much slower than anticipated, at the moment; the bigger one is that it isn't complete and i haven't had a chance to include some of the offboard wiring. so i need to clean it up a bit and i've been way too overloaded to wrap my head around anything thus far.

however: this thread pretty much covers everything that is in the chemical burn. i think the key to my sound is using higher gain transistors for q1+q2 and very painfully matching the hfe of Q5 and Q6 by hand to within +/- 5 of each other.

chemical burn also likes being slammed at the input by an overdrive. the gnarl is just filthy then.

EDIT: I'll upload the complete schematic in about 4-6 weeks; some stuff should be sorted out by then. sorry for that delay again.
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