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