yaf..... the double hit deux

[pinkjimiphoton]

nothing crazy special, but nice sounding fuzz/octave up
based on the ETI "Struzz"

somewhat tweaked in, and set up to run on a SINGLE 9volt source instead of having to mess with charge pumps or multiple batteries etc.

major changes are tweakability to q1, adding an output cap and master volume, redistributing some of the gain a little bit for better fuzztone, "focusing" the octave with a cap in octave mode, making it less noisy than the original 741 based circuit... blah blah blah... will probably get some video going one of these days.

this and the original circuit sound nite and day different.
a big part of it comes down to the opamps... the ca3140/lm301 combo is hard to beat out of all the others i tried... that 3140 has some real magic to it.

https://www.renesas.com/us/en/www/doc/datasheet/ca3140-a.pdf

anyways, here's a schematic if anybody wants to give it a try. no layout for it yet, i just modded up an old "graymark" kit board, but the schematic is verified and works great.




i mean, whats not to love? easy circuit, cleans up like a fuzzface, gotta decent octave built in... helllll yeah!

[amz-fx]

Nice project Jimi.

You should be able to replace the Q1 circuit with the input transistor stage of the Big Muff so as to eliminate the need for trimpots.

Best regards, Jack

[pinkjimiphoton]

hey jack,
thanks! and happy new year!

thats actually a great idea.... i will have to try it maybe next time i build one on vero.
this one was one of those "lets see how far we can take this crappy surplus fuzz kit" deals.

graymark international, or something like that. double sound fuzz. they sell the kits CHEAP! but they literally hogtie and sell ya into indentured servitude on the shipping if i recall. crazy.

juuuuuuust will fit in a 1590g i think it is. kind of a tall 1590 b.

tonite i looked at it funny for a while trying to figure out how best to do this. i think i can get the whole thing to fit in a too-small box with two footswitches and leds and 4 pots up top.

look forward to boxing it up. completely different animal.

i THINK the trimmers on q1 have quite an effect on the octave and how much noise artifacts get thru. i found when trying different combos of opamps... 741 5534. tl061 and lm301s all sounded very different, and had different characteristics with "spittyness" and noise. the 3140 was just a hmmmm.... single opamp, lets see kinda thing, but MAN! low noise, very clean octave, decent headroom and an actually useable fuzztone.. i'm diggin it.

well...


so far.....

you know how the fuzz addiction goes. tomorrow's fuzz is just 23 hours away....


peace, my friend

[diffeq]

a big part of it comes down to the opamps... the ca3140/lm301 combo is hard to beat out of all the others i tried... that 3140 has some real magic to it.

https://www.renesas.com/us/en/www/doc/datasheet/ca3140-a.pdf

anyways, here's a schematic if anybody wants to give it a try. no layout for it yet, i just modded up an old "graymark" kit board, but the schematic is verified and works great.




i mean, whats not to love? easy circuit, cleans up like a fuzzface, gotta decent octave built in... helllll yeah!

Thanks for mentioning CA3140, never heard of it before. Local supplier stocks it, I might try it somewhere, sometime. 

On the schematic, op-amp negative rail pins (#4) are connected to the 4.5V. Is that a feature? 

[pinkjimiphoton]

i dunno about "feature" but it appears to be working.

originally they were grounded, as in ground being the midpoint between + and - 9 volts (+9/-9).

shoot, now i gotta look at this thing lol

just checked, and yes, 4.5v. i'll try and take some pics of the original project book and pics of the actual pcb.

pin 4 of both oa's connect to the half supply voltage at the junction of the two 10k resistors in the power supply.

on the original project, they'd be connected to ground between the +/- 9 volt rails. connecting them like this i'd never done before, but it sure seems to work well.

originally, i thought it would be more complex than it was. pin 4 on both would have been connected to the negative terminal of the lower battery. that makes no sense of course so i gotta scan this thing.

but yeah, from what i gather, the half voltage or ground can be used pretty much interchangeably in a case like this.

or its a real happy accident? lol
beats me

all i know is it works and sounds really good compared to the original project!

the ca1340 is a really cool chip, i had no clue to how cool til i plugged one in.

be back soon with scans n stuff

[pinkjimiphoton]

ok, here ya go, the original stuff. if ya compare it to the schem posted above ya can see the changes and differences

all my value changes etc are scribbled on this




this is from the bottom of the board, and the power supply as i set it up sits to the left




how it all lays out originally, before i modded it...







and mine, again.

with all the weird shit on it.



how it all lays out on the graymark board. yep, battery + goes to the upper right, battery - goes to lower right.





so yeah, i put pin 4's to the middle of the power supply instead of ground. this way, one battery, done deal. i dunno if its RIGHT, but it sure sounds good!

this is what i did for a power supply. the 4.5v goes to pin 4 on both chips

[pinkjimiphoton]

so, i boxed this thing tonite. ended up ditching the e resistor on q1, and went with a mpsa13 for a transistor after sampling a bunch of npn ge and si's. that gave the best fuzz on its own, almost overdrivey more than fuzz, and helped even out the volume with the octave side.
basically, the fuzz volume about half way up = the octave volume pegged.
its not super loud, but it cleans up really well with guitar knob twiddling, even on the octave side.
the octave side is weird. but cool. can still kinda hear the fundamental in there with the octave, like on "the sky is burning" by bad company.
enough output now to be over the unity gain it was, just slightly.. hard to tell cuz its late and i already got the warning text from the woman lol...

this thing is @#$%ing HIP with a ge fuzzface in front of it, pegged. unreal weird stuff,....  like playing an electric saxolin or something... it spits and swells into notes, and if ya play legatto its like it charges up and goes into hyperdrive. weird weird weird!!!!

but i like it.
video tomorrow....
errrr.. today

but here's the thing... how the hell can this thing possibly even work? the ground is, i think, just to the chassis for the pots n jacks like a normal box...
but the 9v power hooks up so the + goes to the top of the 10k x 2 voltage divider,
the - of the battery/ground goes to the middle of the voltage divider, and the bottom of it goes to ground.

something seems very wrong here to me. i would expect the - of the battery to go to ground, not the center point, right?

i suspect the chip has a lot to do with it... cuz it can run on pretty low voltage

but i guess what i'm not getting is i thought the mid point of the voltage divider would be ground in between two 4.5v sources for all intents, as all i'm giving it is a 9v battery...

maybe its just cuz its real late and i'm tired, but there's something mighty weird going on here that i don't think i've ever encountered before with the way i hooked up the juice to it.

i would be jazzed and grateful if some kind soul could enlighten my darkness, cuz man, i can't even find a speck of light as to how this could work.

how the hell does ground get made without returning to the circuit somehow?
is it happening thru the pots?
duh. i just looked. ground gets made thru the bottom resistor. but i still don't get
why the bottom of the battery/ ground of the power supply only works hooked up to the center point of the voltage divider.

i'm confusing myself more i think lol



i really don't get it

[anotherjim]

Yes, that power arrangement is totally whacked. The chip pin4's should go to battery negative and the ground symbols and chassis to the 4.5v mid point. So with dmm neg on the chassis, pin4's will read -4.5v  and the +9v connections would read +4.5v.
If you had it as it should be with the mid point grounded, it would have to run on its own power supply and not in a common daisy chain power with other pedals.
Of course, the modern way of doing it is to replace the -9v battery with a 7660 or whatever converter chip so it runs as originally designed but from a single +9v power.

Why would it work wired as shown? Yes, CMOS can run low voltage, but I think more important is they can work even if the inputs swing negative of the pin4 voltage, so it can get away with pin4 voltage being higher than ground.

[pinkjimiphoton]

weird weird weird, jim!!

i DID try hooking it up the other way, not a sound from it.
i think i drew it wrong on the hand drawn schematic the way i drew the power supply, on the layout of the pcb i drew the parts on is actually right.

i will take some voltage readings of it when i go back to my dungeon, i tried it up here with the volume cranked <little woman is out> and i got an oscillation problem i gotta suss out.
the 2.2n cap from pin2 to ground of u1 is gonna get ditched i think, it does make the octave sound better but it detracts a lot from the fuzz.
live n learn.

i will try hooking up the power the other way and see if i can get it to fire.
thanks for the help bro!

in the mean time

DON'T TRY THIS YET other than on a breadboard!

[pinkjimiphoton]

ok, so i found some problems, fixed some others and re-drew the whole thing as it sits now.

i still don't really get how the power supply thing works. i had drawn it WRONG, of course. for the life of me, i don't understand why this thing just wouldn't run off a plain old 9volt battery. is the voltage divider thing really necessary? doesn't seem to do anything or be hooked up to anything.
that said, without it? circuit won't fire.


and apparently this has a ground AND a - 9v connection, even tho the -9v of the battery  and ground connection are to the same place on the power supply jack.

standard tip/ring/sleeve on/off input jack.

but dig this.... if ya connect the - side of the 9v supply DIRECTLY to ground, it will NOT fire. even tho its connected at the ring of the input jack!!!

weird weird weird.

but it sounds pretty good. i will try n get more video tomorrow, my family is probably ready to kill me.

still can't get the octave part as loud as the fuzz. may add a simple boost stage hacked in there somehow.

changed the diodes in the rectifier. one side is pink led, the other 1n34 and pink led in series. if ya want it to swell, use two 1n34's in series on both sides, and run a fuzz face into this thing. holy cow.
if ya want this to clean up with volume pot on guitar, ge is the way to go. i opted for the ge/led combo in search of more balls on the fuzz, which stock is fairly anemic. two leds makes the octave two spitty, and no possibility of turning your guitar down.

changed the 10k bias trimmer on q1 to 50k. it makes a huge diff on the volume of the octave. i was reading 23k with one side disconnected, so 22k should be ideal.

i ditched the cap bypassing pin 2 to ground on u1. it sounded cool, but not worth keeping in the end. it really made the octave pop out more... but... the big problem with this and switching from fuzz 1 to fuzz 2 is that each wants opposite settings on the gain pot.

the fuzz wants the gain/sustain pegged. when ya go to the octave, it wants it off. what to do?

well, i used the same footswitch connections i had used for the cap, and simply ran wires to the pot.. the wiper, and the unused side, so when the footswitch is in octave mode, it automatically shorts the pot off. huge improvement. trying to find a happy medium meant a splatty jawari-esque octave and a gated buzzy fuzz. now ya can just crank the thing up full and get a decent sound out of each. some folks may like the gain down a bit for more velcro-y sounds.

as it turned out, i totally dropped the ball on the power supply, and i apologize for that. i'm still confused on it.

i checked today, i had thought the - of the battery/power supply was jumpered to the junction of the two 10k resistors and the 33u cap, but that node is connected to nothing. the cathode of the cap is to ground along with the low side of the voltage divider. the 33u cap comes off the junction of the two resistors, but it doesn't seem to be connected to anything else. without it? won't run right, tho it makes some really amusing envelopey sweepy weird noises, particularly with the tone knob on the guitar down.

weird weird weird.
ok, that it for changes. for sure, for real, THIS is what i got running. all hacked onto that cheezy graymark kit board





so the billion dollar question.... why the hell is -9v different from ground on this? or is ground floating somewhere between ?

like... i am confused more by the minute. or is it really somehow
its running at +/- 4.5volts with ground in the middle somehow?

i don't get it at all.

this thing sounds great with a fuzzface driving it, too. holy crap. it compresses like crazy, then releases when ya play legato and automatically swells in. its sick!

OR i messed something else up.   

[pinkjimiphoton]

grafted in a big muff input stage to replace what was there. still not digging it.
messed with it some more tonite... trying to get a useable volume for the octave part is problematic in that if ya do get a good octave sound, the fuzz sound suffers. oy. if ya get a good fuzz that doesn't gate too much... i hate crackly fade outs... then the octave is weak and sucky.
gotta play with it more tomorrow.
determined to make this sucker run on 9 volts and sound good somehow.

stay tuned

[diffeq]

The -9V is used only for the op amps. For more headroom, I guess? I'd try the following mod, simply biasing the non-inverting pin of the first op amp and connecting both -V's to GND:

I'm too dumb to figure out the second stage input biasing with all those diodes in place , they seem to be connected... so it may work. 

[anotherjim]

If the ground was floating instead of halfway, and if it has connections to the + & - around the circuit - real via resistors/pots or thru leaky caps, then it might well "float" to somewhere in between the supply voltage.
I see in your readings U1 pin 3 as 2.23v. That voltage will be coming in via the 10k resistor, not from the amp pin - so a voltage reading at the ground end of that resistor might prove if it really does have that ground connected to supply -9v.

I got a warning - the fact that the CMOS amp may have an input "misbiased" could be an important part of the effect you hear. There a well known single amp full wave rectifier in the RCA CA4140 datasheet figure34 that has both pin 4 and pin3 to ground and deliberately referenced to 0v instead of 1/2V. The way that rectifier works absolutely relies on the 0v bias and the CMOS chips ability to handle an input that's more negative than the negative supply pin.

[pinkjimiphoton]

hahah...
well, connecting them to ground doesn't work. tried it. connecting them to the half voltage doesn't work. tried it.

i had my rhythm guitar guy here yesterday, full on EE. he couldn't figure out how or why the thing worked.
his suggestion? run it on TWO 9 volts and see what happens lol

The -9V is used only for the op amps. For more headroom, I guess? I'd try the following mod, simply biasing the non-inverting pin of the first op amp and connecting both -V's to GND:

I'm too dumb to figure out the second stage input biasing with all those diodes in place , they seem to be connected... so it may work. 

[pinkjimiphoton]

If the ground was floating instead of halfway, and if it has connections to the + & - around the circuit - real via resistors/pots or thru leaky caps, then it might well "float" to somewhere in between the supply voltage.

here's the thing. if i connect the -9v (the neg on the battery or power supply) directly anywhere but the star ground on the input jack, it just won't fire!! if ya hit it super hard, ya may get a cracke or phart.

the way its wired is weird. from the power in jack, +9v goes to the board and then the voltage divider for the two led's. normal, right? the - from the power in jack goes to the input jack sleeve. also normal. but if ya hook the negative up to ground, it will not work. taking a lead from the star ground, which only connects to earth when plugged in via the sleeve of your guitar cable plug, if ya go to the actual ground plane, it won't work. if ya go to "-9v" it will work.
if you try to take a wire from the ground plane directly and connect it to the star ground, same thing. will not work.
curiously, all the POTS grounds are connected (well, pin 3, leftermost from the back with the pins facing up) and that does connect to the ground plane. connecting them to the star ground? same freeking issue!!

the only place i can see ground connected as i'd expect is at the bottom of the two 10k resistors i made the voltage divider with, and of course all the places various parts of the circuit ground to.

obviously, once plugged in, the -9v and "ground" all connect to the star ground on the input jack.

but if ground is ground, why can't it be connected directly, and only work when its shorted to the -9 of the battery?

I see in your readings U1 pin 3 as 2.23v. That voltage will be coming in via the 10k resistor, not from the amp pin - so a voltage reading at the ground end of that resistor might prove if it really does have that ground connected to supply -9v.

i will check when i get a chance! thanks jim!!

I got a warning - the fact that the CMOS amp may have an input "misbiased" could be an important part of the effect you hear. There a well known single amp full wave rectifier in the RCA CA4140 datasheet figure34 that has both pin 4 and pin3 to ground and deliberately referenced to 0v instead of 1/2V. The way that rectifier works absolutely relies on the 0v bias and the CMOS chips ability to handle an input that's more negative than the negative supply pin.

would that account for the cool/weird swelling in effect? i thought i was just overloading the hell out of it with no headroom lol

[pinkjimiphoton]

 mucho tweakage later, and with thanks to Jack Orman for his suggestions, its a little further along...

modified the front end to a big muff pi style stage, messed with the feedback loop of the second opamp some, and, well, this is where i'm at so far.

i'm digging it a lot more than the stock circuit... but still got a ways to go.
the octave side is crazy and sick and outta control in a good way.

i gotta try and make sure i get it right and draw it up,  changed the bias trimmer to a fixed 10k resistor.
but basically for the b to c feedback resistor, ended up with a 50k trimmer in series with a 130k resistor.  there's a definite sweet spot ya gotta hit that varies with the q's.  this wanted 187.5 k according to my shitty meter.

q was a 2n4401, didn't check hFE

ditch the snubber on q1.

make the b to ground resistor in the voltage divider 33k.
input cap 100n, e to ground resistor 100r.

that perks up the fuzz some.

on the second opamp, changed the 10k feedback loop resistor to a 100k trimmer.
its noisy but fun in a good way.

all a balancing act.

this thing is MADE to be driven by a fuzzface. wait til it gets to the feedback parts.

its very synthy at some settings, envelope responsive at others. a bass cut in the guitar makes it almost auto wah-ish.

still gotta long way to go, but... as a work in progress... check it out, yo

https://www.youtube.com/watch?v=qgsZMgUhNC8&feature=youtu.be

[amz-fx]

With the conversion to a single 9v battery, you have to watch where the grounds are going. I believe this should work:



regards, Jack

ps: Thanks for the shout-out in the vid!

[pinkjimiphoton]

its an honor to be able to do so, jack!

at this point, i need a break
but i will try it again with your ideas and see what happens.

i am really digging the weirdness of this thing at this point.
sometimes it sounds like it has a delay on, or a phaser or something!

[pinkjimiphoton]

i tried it, couldn't get it happening.
this thing is weird.

more revisions.. stay tuned

[amz-fx]

Slightly revised for clarity:



regards, Jack