Tube Fuzz Face

[johnnybegoode]

Hi,

You know the standard Fuzz Face with 2 transistor (Q1 and Q2).
Can I replace them with pre-amp tubes?


I've been searching the Internet for a solution, cannot find one.
Some of these tubes have like 8 pins and transistor 3 (emitter, base and collector)

and I've seen pre-amp schematics using pins 1,2,3 then 6,7,8 ...etc

What am I trying to say is:
I want to know how the fuzz face schematic would be like using tubes in place of the transistors.

Thanks,
Jon

[johnnybegoode]

Has anyone build a tube fuzz face

[darron]

i think the answer would be don't bother. i've never built anything with tubes, but....one your only dealing with 9v power, which i think wouldn't come close to the requirement of a tube. you' need to step the voltage up by heaps. two, i believe some of those pins will be for the tube's heater. you need to keep those suckers hot to operate.

find a good tube project on the web and try not to electrocute yourself/gear i guess. there's be so much adaption to get the fuzz face to work with tubes that you would have designed a completely original circuit.

[Jeremy]

I think that a triode fuzz face would be a fun project.  It would have to operate way differently from the real thing, of course.  It would need high voltages, and would probably have a high input impedance (unless the circuit was designed to waste that high input impedance).  It wouldn't sound like a fuzz face, but it'd be fun as heck to try out, and some super bragging rights would go to the person who designed it.

[puretube]

DANGEROUS TERRITORY!

[R.G.]

Listen to what the guys have told you.

Just off hand I didn't think this was all that likely to work out. But I popped it into the simulator to see if there was any promise. Yes, I know that circuit simulators are not perfect. But they are good indicators.

1. The original power supply won't work, as was mentioned. 9V is really not enough for the commonly available tubes. I upped the power supply to 75V, then 150V (which you can get by rectifying the primary voltage of a back to back transformer setup. I could get that to bias up and amplify at least.
2. The original resistors won't work. They're in general too low.
3. The original biasing setup won't work, as tubes are depletion mode devices; they are naturally "on" and you have to do something to the input to turn them off. Bipolars are enhancement mode devices which are naturally off, and you have to do something to them to turn them on. So I diddled with the biasing setup.

By this time, there was none of the original circuit left, except that there was a first gain stage, directly coupled second stage, and feedback biasing to the first stage input. But it did amplify. The amplification made for a really sharp clip on the top side of the output and no clipping at all on the bottom side. There would be a prominent fuzzy octave effect, pretty harsh. Very little soft smooth tube distortion.

It's possible that more tinkering would produce something usable, but it would be an entirely new circuit.

Back when I was in school, they taught some stuff about generalized three terminal devices. This covered bipolars, triodes, pentodes, JFETs, and MOSFETs. All of these have an input pin (base, grid, grid, gate, and gate respectively) an output pin (collector, anode, anode,drain, drain) and an input/output pin (emitter, cathode, cathode, source, source) and can be used in generalized circuits of the same format except for the biasing and supply voltage provisions.

Sometimes you can make easy and simple substitutions, sometimes you can't.

Beyond that, you have some very good advice from the other guys. Tube power supplies can be as low as 12V, as they did in old car radio circuits, but the only tubes in current production are not like those specialized ones. The 12AX7 that we can actually get has a very hard time working that low, and sounds distinctly starved and astringent when you do it. It really needs over 50V and better yet over 100V. These voltages are downright dangerous.

So - good inspiration. But the actual execution of the idea will be long, difficult, and possibly dangerous if you don't have experience with high voltages.

[dano12]

I don't know about a tube Fuzz Face, but you could do a low voltage tube fuzz.

Check out the following patent, lots of detail in that one:

http://www.freepatentsonline.com/5022305.pdf

[bancika]

IMHO total waste of tubes. I mean, fuzz is meant to sound harsh and ugly. The reason everyone likes tubes is their warmer and smoother overdrive. Why would you want to do that when you can get the lowest quality transistor and get the same effect?

[The Tone God]

Simulators, bah. I actually built one quite awhile back. I ran it at a higher voltages and had to mess with the circuit quite a bit just to make it work most of which R.G. has covered. When it did work it was very much unlike the FF and was unimpressive in itself. To get anything interesting I has break the core FF design principals.

I would say unless you want to try it for a learning experience I wouldn't bother.

Andrew

[Dragonfly]

...i know daniel at dinosaural is building a "tube-bender"...what it has in common with the original tonebender, i have no idea....

...also...for low voltage applications there *are* tubes such as 6088 and ck512ax submini's....here a link to some info....
http://members.aol.com/sbench101/BatteryPoweredAmps/submin.html
http://members.aol.com/sbench101/


i doubt you'd have good results as a "fuzz face" style circuit, but heck....if youre gonna experiment, its much safer with these low voltage ones...and you may very well come up with something cool !

hope this helps,
   AC

[pinkjimiphoton]

ha! stay tuned......

[mozz]

Don't leave us hanging, give us a few hints. Space charge tubes? 12ae7?

[antonis]

ha! stay tuned......

Should we also stay tremendously scared, Jimi..??   

[pinkjimiphoton]

if it works, and it should, well..... lets just say its gonna run on 9 volts. i figured out a couple weird little tricks i'm currently playing with. i mean...

a fuzz face ya want around hfe's of 70-100.  that's easy to do with a 12ax7 with a gain of 100... make the first stage less gain . easy breezy.

the trick is getting enough current to run the tubes, and also to run the heaters for the tube cathodes.

matsumin did most of the heavy lifting, really. compare a fuzz face and a valve caster.  if ya think of the plate grid and cathode as collector, base and emitter, well... you can most certainly wire up a fuzzface using much of the standard ff circuit, and matsumin's power supply ideas for running it on dc.

dc runs about 130ma of current with a 12ax7 heater circuit if ya run it at 12 volts instead of 12.6. it will still light up the heaters. if ya can light the heaters, you can make the tube work.

the one i'm working on uses charge pump circuitry and voltage regulation to get enough juice and current to take care of the heater supply, then uses a simple diode bridge to run the plates off a 9vac 2000ma supply. i'm not supposed to really mention this shit cuz its gonna be coming out commercially, so i can't give all the details, but i think most of you brethren are savvy enough to figure out what i did.
remember, you don't need to worry about linearity in this, its a @#$%in' fuzzface you don't need much headroom, and low plate voltages with a decent supply of current will help you fuzz. the big thing is setting the gain for each triode right, and then biasing correctly.

think of the support circuitry for the tubes as being completely separate, yet simple. think valvecaster and the couple clues i gave... think of plate grid and cathode as collector base emitter and wango...

you too can make a tube fuzzface. it's semi working on my bench already. i just gotta dial it in a bit more. standard fuzzface values for most parts, too, cuz a lot of the tone of the ff circuit comes from the passives, imho.

i'm gonna get murderlyzed for posting this shit lmao

but down the road a mite, if i can do it ethically/legally, i'll post the project here. technically its gonna belong to mla.

[patrick398]

Have you been winding the transformer for the last 14 years?

[pinkjimiphoton]

hahaha well, ya know.....
<pink draws hard on his herbal jazz cigarette....>

no transformer necessary if all goes according to plan, shit , ya could probably run it on a 9v battery, at least for a few minutes

[pinkjimiphoton]

i've got a semi working tube fuzzface on my breadboard right now, passing signal. i used the stock topography of the fuzzface so far, have indeed had to mess with values some. it sounds like a fuzzface with a very dead battery at this point... but its working, and fuzzing. sounds decent driving an overdriven amp.
the fuzz control at the moment is back down to 1k, with a 220u bypass cap. big input cap helped some, too.
obviously its gonna likely need some work to develop into something useful, but it DOES pass signal and does it at 9v. sounds a bit better at 18v, so... gotta play with it a bit.

who knows what will happen.

[pinkjimiphoton]

.......ahem

https://www.youtube.com/watch?v=1QTMZFAJC2o&feature=youtu.be

values of resistors and caps a bit different. 470r resistor still the same value you'll have to play with values a bit and make some things much bigger. but the topography of the circuit is the same other than using the valvecaster bit to run on 9volts.

its not as fuzzy <yet> as a transistor fuzzface. but it still reacts and sounds quite a bit like what you'd expect a tube one to sound like.

this is running on a 9 volt adapter. i can't post the schematic and values at this time, but they were easy enough for me to figure out, and i hope someone tries it. its kinda cool. into a dirty amp it screams.










i can say this...its still the same number of parts other than the heater supply.

when i can, i'll post the whole thing up. may be a while. hopefully i've posted enough clues for peeps to figure out what i did.

think big on the caps

i think it sounds fairly good. the quick video is just into a pos ibanez 5 watt el84 toob skreemer amp with the volume and tone about 3 o'clock.

peas

[Banjan73]

A year or so ago, I built an overdrive pedal with one preamp tube. This one works well at 9V, but it is even better at 12V. There are schematics for this at the net. The 12AX7 wont work very well, due to the low voltage. I think I used 12AU7 tube for this one (might have been 12AT7, I dont remember as we speak). Remember that all the tubes mentioned are dual stage tubes. That means you only need one to replace two transistors.
When that is said, the tube in my overdrive got voltage far out of it specs. But it did work!
Be careful, thought that you don't use higher voltage than 12V, since this is the maximum for the heater of the tube. If you have higher voltage, then you need to lower it to max 12,6V for the heater.
If I was you, I would try to replace the transistors, and off course set the bias and gain accordingly to what a tube needs. Maybe the tube will not make this pedal act as a "fuzz", but it will at least clip in some way.
I will try to dig up my schematics for this pedal (I think I stole it from somewhere on the net. Perhaps on this forum?)

[mozz]

Also found 12au7 works much better than a 12ax7. I was running a transformer with dual 12.6 vac secondaries. 12v to heaters and 20 vdc to the plate.