Tube Fuzz Face

[Banjan73]

That sounds like even a better solution. But it runs good on a single 12V or even 9V supply also. Its, as I said, far out of spec, but it works😉

[Banjan73]

Cant find my schematics, but google matsumin valve caster. I think that was the base for it (I always modify those schematics after my own taste)...

[amptramp]

This sounds like you will have a Fuzz Face that is independent of ambient temperature.  All you need is a power supply regulator and you will be rid of the worst characteristics of a Fuzz Face - temperature dependence, supply voltage dependence and tone sucking from low input impedance.

BTW it may be difficult to find, but a 20EZ7 is a 12AX7 with a 20 volt 100 mA heater but the pinout is not the same and there is no centre tap for the heater.  I have an old tube AM/FM/FM stereo radio that uses them.  You could build a fuzz that runs off a 19 volt laptop battery, so it would be rechargeable.  The fuzz control could be the voltage adjust on an LM317.

[pinkjimiphoton]

12au7 draws way more current than a 12ax7.

for a fuzzface, it won't work better at a higher voltage. you guys are thinking like ee's, linearly. you cannot use that kind of thinking with a fuzz.  the higher the voltage, the CLEANER the tube will get. that's not what ya want in this kind of circuit.

the point of the example was it was claimed early on in this thread that to do this would be impossible. that's not true. this is running on 9 volts. it distorts. it sounds like what you'd expect soft clipping tubes to do in a fuzzface circuit.

you need to look at the current draw of the tubes as well. at 9 volts, a 12ax7 draws less than at 12v, and uses about 1/10th current of what it would draw at 6.3vac. a 12au7 draws close to 10x more current. the 12ax7 is the way to go.
with a fuzzface, you need gains of around 70 to 100 for the two transistors.  a 12ax7 has a gain of 100 for each side of the bottle. works perfect..... well... not perfect, but as expected.

we're not talking a tube overdrive here, we're talking fuzz.... lol the older guys will probably get the humor of this all.

the actual circuit i have i'm working with uses some tricks for a proper power supply. the fuzz will work on a damn 9 volt battery, for a while, anyways. that was also important. the actual units use a little simple wizardry to do a proper supply for the heaters. its regulated to and clamped at the proper voltage, tho still run in series, not parallel.

yes, the matsumin valvecaster answers most of the question of how to do it. it really comes down to adjusting the passives to adapt to the tube circuitry. the topography of the circuit/number of parts remains the same as the original circuit. that i can say

amptramp, that's all stuff i love about fuzzfaces, bro...lol... the key to this is i want the ultimate product to run on a standard 9 volt supply. i can easily do this with a 12ax7, and most of the specs work out right.

any of you watch the video? its only about 20 seconds long lol

mozz, higher voltages work fine for preamps and overdrives, but this is a fuzz. ya gotta think the other way for this one, or it .... sounds like a tube preamp. ya gotta starve that bottle to find the fuzz there's definite sweet spots, but the matsumin values for the valvecaster for the plate resistors are pretty much close enough for rock and roll.

i have hundreds of variants for the fuzz face circuit designed and built at this point. its insane.

banjan, thanks for the advice. i used to "pop" weak tubes with my tube tester by turning up the voltage to the heater supply. most tubes can take almost twice their rated voltage without damaging them. i had this thing running at 24 volts yesterday at one point for a few minutes. 9 volts worked much better. lower voltage is the way to go with this kind of circuit. you do NOT want headroom!

[pinkjimiphoton]

btw, for all my secrecy <hah> the entire freekin thing is laid out on the breadboard... you can see EXACTLY what i did in the pics lol


but i still didn't post the schematic 

[rankot]

btw, for all my secrecy <hah> the entire freekin thing is laid out on the breadboard... you can see EXACTLY what i did in the pics lol

but i still didn't post the schematic 

If anyone could build tube fuzz, that would be Mr PJP!

[pinkjimiphoton]

brother ranko, how ya been, mate?

hahah... thanks for the vote of confidence. i am still working on it. its not too hard to figure out, ya just gotta decade thru some resistors til ya find what works best... of course, every change re-biases the dang tube, so ya gotta wait for it to settle in, etc...

but now i've gotten it to where i think the volume is adequate, and it's fuzzing about where a good ge will sound with the guitar volume just barely rolled back.

into a clean amp, its almost in the vein of say, a kay fuzz... lotta upper harmonic, as RG and others cautioned it would have.  but into a barely overdriven amp, it freeking SCREAMS. will try n get more video in a bit.

obviously, ya gotta go with pots to dial in the plate voltages... ya gotta bias it to a point where it fuzzes, but doesn't velcro. but the two resistors remaining, well.... the little one gotta go wayyyyyyyyyyyyyyyyyyyyy down, and the big one has to go wayyyyyyyyyyyyyyyyy up.

bigger caps for in/out/fuzz are definitely in order. think huge. go up and down in decades til ya find what ya like.

there's a bit of a compromise between output volume and fuzz at this low voltage. exploit it. find the sweet spot where ya get a fair amount of distortion, and still enough to be well above unity gain.

a lot of the "flavor" of the fuzz face comes thru, cuz the circuit remains largely the same with the connections... identical, in fact... other than the  +/- connections to the heater of the tube. its NOT gonna clip as hard, tubes clip much softer... but it will still fuzz when ya find the sweet spots, which are seriously starved down with the biasing pots most of the way up. before you hit cutoff, is where you'll find the fuzz. in the middle regions, it will sound more like a tube preamp that's fairly clean. exploit the un-linearity and ya can make it fuzz.

so far, for the first attempt, i'm fairly satisfied. since the video last nite, i've changed the values of the two remaining resistors and gotten good result.

think of it as an npn fuzzface. think of the two halves of the 12ax7 as two transistors. think of plate as collector, think of grid as base, and think of cathode as emitter.  other than running the heaters in series,  and changing the values to account for the tubes and the way they work,  the circuit is still the circuit.

with transistors, gain goes up with bigger resistances. with tubes, think the opposite, as reported 14 years ago.... its weird

but it works. not necessarily RIGHT.... yet.... but its passing signal, loud, and relatively fuzzy.

[mozz]

Are you talking a 12au7 draws more fil current or plate? Filament current is the same 150 ma. Plate current is really small and shouldn't make much of a difference in the very short life you would possibly get out of a 9v battery. I can measure the 12au7 plate current and compare to a 12ax7 just for my own curiosity. Preamp and fuzz is the same thing, just direct coupled.

[Banjan73]

Mr PJP.
Love you language😉 😅

[Ben N]

This looks to be SO COOOOL, Jimi. Getting FF like cleanup/sparkle in a not-so-fuzzy circuit would, I think, be incredibly useful.

[pinkjimiphoton]

i was just chatting with petey twofinger about this thing.. lol

the biggest bitch is that the tubes don't saturate and STAY saturated like transistors do, so its not as phat sounding as you'd think. a 12 volt supply to the heaters will likely help, but this things at 9 volts.
tubes, as the decay begins, lose distortion quickly. they're completely misbiased in this application, so you can get a fair amount of distortion... if ya tag in the valvecaster tone control it helps to warm it up some, its fairly bright ... i mean a fuzzface is a treble booster in some ways. dialing back the treble makes it a bit warmer.

i tried adding various clippers, and found one i liked at a highly improbable place in the circuit.

think of each triode half of the 12ax7 as an npn transistor.

for the 470r resistor, think REALLY tiny. gigantically smaller. its really only there to decouple the two stages anyways, right?
for the 100k resistor, do the opposite. there's a definite sweet spot you'll have to find. think big.

for the first stage, use a 500k pot to find your bias. second, use a 1 meg. there's compromises to be had that you'll have to find.... ya gotta find spots with each stage where its distorting without going all fizzy, and where ya have a decent amount of gain. like most such things, its all compromise.

you'll get it eventually where it sounds and acts like a fuzzface pretty much. it responds to the guitar knobs almost the same, and at max distortion, will give a nice decent if slightly gated overdrivey sound into a clean amp, and will scream into an overdrive pedal or overdriven tube amp... in which case, it acts much like a normal fuzzface, but without the mud.... like having a bass cut.

make the fuzz control freeking huge, too. gigantic.

every time ya make a component swap, give the circuit a couple seconds to stabilize.

it sounds REAL nice into my 80's solid state marshalls. warm, phat, really makes 'em sing.

and STILL the same basic circuit layout as the actual fuzz face.  same four resistors, same three caps, just different values...

i used a huge 2200uf cap for the power supply rails, hoping to keep it quiet and reasonably stable, this isn't the actual product i'm working on, but it will get ya in the ballpark of it if ya take the time to read this crud crap stuff i spew... and look at the pix. beware, there's components there from me tinkering that aren't actually in the circuit.

for the rest of the caps, multiply by decades to find what you like. again, think big.

not gonna tip my whole hand yet

tried a simple gain stage driving it... not super exciting. it definitely will make it more fuzz face (tonebender?) like, but it gates in a fairly ungraceful way as the transistor and tubes decay at different rates and in different ways. a slight boost into the front, however, WILL help the tubes saturate and sustain better... but then it's no longer, well, a fuzzface.

the other way to go is to seriously starve the tubes much more, and then add a recovery stage...

BUT...

tube preamp distortion at this voltage level... and face it, the design needs to run on 9 volts to keep guitar players happy... is fairly fizzy. if ya crank it up to where it truly fuzzes, it gets REAL fizzy as predicted 14 years ago. its not as pleasant as germanium or low gain silicon in this circuit. but ya can get it to where it sounds and reacts fairly well, and sounds with the guitar dimed about where a dimed fuzz face with your guitar rolled back to about 8 sounds for distortion level, which is still fairly useful.

add in the valvecaster tone control, and when ya roll off some of the treble, it sounds much better.

output pot 500k at least.

damn. giving away all mah secrets agin. sumbeech.

for the clipper... look in the circuit for the only couple places you can add one... will add a tiny bit of compression and a bit more wood to the tone, and help the tubes stay saturated a little longer. again, transistors when saturated, stay saturated til they're off... tubes the distortion fades in and out depending on attack, decay and to a certain degree, envelope.... it doesn't stay saturated as easily as the transistors do.

but... you can exploit that, and the way it acts like a fuzz face, into a marshall pretty effectively.. when ya turn down, you can get a phat brassy crystaline clean that is really cool, even into a dimed marshall with this thing dimed as well. it just kinda adds overtones and sustain.... and ya get back the rest of the missing gain from the voltage  being so low

consider researching how to get yourself a 12v supply for the heaters off a 9 v power rail

ok... done. stick a fork in me. i'll try n get a little more video as i get this thing done. i'm about done molesting this circuit's poor electrons for now...

think of it as a building block. maybe build a fuzzface around it, with the first stage of the transistor fuzz face part driving the tube part and the second stage of the transistor part amplifying the tube part output.

the world's your oyster,  lol... get your breadboard, crack a beverage, load your favorite smoking utensil, if you partake of such with your trusty pair of xircon encrusted tweezers, and mess around with it. just remember, its tubes... so every time ya change something, it gotta recover.
at 9 volts, its safe enough even for my re-intarnated arse to mess with, ya can't really hurt tubes like ya can transistors ... well, ya CAN, but... the point is, i think if ya tackle this as a circuit snippet, there may be something cool you'll find to call your own.

peas

here's a schematic for how it goes together. since its gonna be a commercial product ultimately, i'm not posting the values, but with a breadboard, you'll figure it out. notice the similarities in hooking up the triodes to how transistors would hook up. this does not include the entire circuit, this is just the fuzzface part of it. it DOES work. and doesn't sound as bad as you'd think it would




ok... enough secret handshake stuff for one day. if ya follow me down this rabbit hole, have fun... if not... well, another day... another fuzzface.

[pinkjimiphoton]

moz, the filament current changes depending on whether you run it on ac or dc. on ac at 6.3v, a 12ax7 draws about 150ma, but at 12vdc, i believe its more like 10 or 15ma instead. i suck at math, so that part, yer on your own at 9v, its different still, but the au draws more than the ax in this application... there's another ancient thread comparing them somewhere here on the forum.

[mozz]

Filament current doesn't change. 6.3v draws 300ma, wired in series at 12v draws 150 ma. Watts is watts. AC or DC does not matter. If you're running at 9v on the series arrangement it's just going to be dim.

[pinkjimiphoton]

300 and 150 are the same ?

works for me. i don't really care one way or the other, the point was to see if it would work. that's all i really gave a shit about.
there's definitely a thread around here about it. i just read it a day or two ago when i first started messing with it.

got it almost to the point of boxworthyness last nite. gonna need some support circuitry to get it "right" i imagine, ain't worried about it. may take this monkey 10,000 years and 10,000 trashed components, but eventually i'll get something i figure is worth keeping.

ya'll rock on and have fun. lates.

[pinkjimiphoton]

This looks to be SO COOOOL, Jimi. Getting FF like cleanup/sparkle in a not-so-fuzzy circuit would, I think, be incredibly useful.

hi ben!! how's the weather over there? hopefully this pesky covid crap isn't as bad as it is here in new england.

its an interesting circuit bro... obviously! worth a play with, you may find it useful! rock on, bro

[digi2t]

gigantically smaller.

And there's my new sig line. Better than a tube fuzz.

[pinkjimiphoton]

<3

its now fairly dialed in and almost ready to box. sounds great after a


ready?


an actual fuzz face.

[mozz]

Any pot with voltage on it is going to be scratchy. Best off to use resistance on the second triode grid to ground.
Not continuing to nitpick but i said "6.3v draws 300ma, wired in series at 12v draws 150 ma." Filament current does not change if it is AC or DC. I said filament current doesn't change due to you saying it is different from AC/DC. It's the same. Same as a light bulb. It doesn't care if it's AC or DC, if you run lower filament voltage, the gain of the tube will be less. I'm sure all the other tube parameters are also thrown out the window.

Filament current is going to be much larger than any draw from the plate, whether it is 1ma from a 12ax7 or 10ma from a 12au7. You would be best to run a 9v voltage doubler or tripler for the plate if using a large enough external power supply.
I can only see a 9v battery lasting 1 hour, maybe 2 hours. I spent many a day and hour tweaking a valvecaster running 12v fil and 20v plate. No such thing as a separate fuzz circuit, as i said, it's a direct coupled amplifier.

[pinkjimiphoton]

hahaha.... dude, you're trying to explain theory to an ape.

and missing the point. it works, even tho it shouldn't. raising the voltage will make it fuzz less. do you think i didn't already go there? the higher the voltage, the less fuzz. 9 volts actually FUZZES. above that, its a ...as you said... direct coupled preamp.

no worries, rock on, man! all good.

adding series resistance to v2 isn't necessary, as it already has a bypassed resistance to ground. the cathode isn't very much voltage even on a high voltage circuit, pretty negligible here.  'sides, its for the fuzz pot... which generally is left dimed, anyways.

6.3vac is parallel wiring at 300ma. 12.6vdc is 150ma. i understand what you are saying, but 300 and 150 are NOT the same, 300 is double 150. the tube will run either way,  but at 12vdc it draws less current than it would with an ac 6.3v supply. how can 150 and 300 be the same? they are, but they aren't. the tube's the same, the circuit's the same.... mostly. but the differences in current draw make a big difference when designing the supply for it.

but its all good. remember, you're talking to an ape with opposable thumbs

i don't know nothing about electronics engineering. all i know is that which fuzzes is fuzzy.  they don't teach fuzz in electronics class i don't think. i don't know the rules, so i don't know not to break them.

and again, its a guitar pedal. gotta be able to run it on 9 volts. i'm not looking for any ideals. just experimenting with YAFF.  when i saw it said it couldn't be done, i decided to see if that was accurate.

peace

[Ben N]

Hey, Jimi. Weather's nice. It's a good thing we have a nice little garden, otherwise I might not get to appreciate it, hiding in the house. Spring temps are running a littler later this year than usual, which is great for the electric bill, too. We're starting, ever so gingerly, to de-isolate. We'll see how that goes.

I may give this a breadboard go with some of my Russian submini stash and trying higher voltages. It just seems like it could be such a "character" pedal.