fOXX Tone Machine - Wow!

[strungout]

So, I breadboarded a fOXX Tone Machine, from the GGG schematic http://www.generalguitargadgets.com/pdf/ggg_ftm_sc.pdf. I used 2N3565 transistors and 1N34A diodes.

I like it a lot! The octave is very prominent. I was surprised. It's the best octave fuzz I've heard. It overwhelms the fundamental with the neck HB selected and the guitar tone knob turned all the way down (though I get the octave with whatever pickup combo/split coil I use, just to varying degrees. Really fun to play with. You just wanna keep going! It goes down to about the 8th or 7th fret, where the fundamental rises back in and is about equal to the octave. From what I read (referring to the GGG schematic), the trick to getting a good octave from this circuit is matching D1-D2 (1N34A) AND R7-R8 (4k7Ω). I also tried Mjolnir's suggestion of using schottky diodes to get an even stronger octave, but the trade off is the fuzz sounded less pleasing to me. I could've used a switch to take D2 out when the octave is not engaged, as suggested, but I was satisfied with the amount of octave I already had and the fuzz too, so... I will, however, socket those diodes, so I can change them if I feel like it. Long Live Sockets!

The fuzz itself is great. Fat and warm, but still agressive (and not agressing). It sounded like shit at first. With the tone knob on the treble side, it just went "BLAAT!". THAT was agressing to my ears. Very unpleasant. I thought, here is another fuzz I'll fail to get sounding 'right'... But, nope. I was trying different transistors combos (5088, 3904, 2222A, etc). I ended up with three 2222A for Q1-Q3 and a 5088 for Q4. It sounded decent, the "BLAAT!" was gone and it sounded more pleasing. But, it bothered me that I couldn't get the sound I'd heard from soundclips out of the 3565... So I put them back in, intending to figure it out and uhh... Well... it was there! And it sounds better than my previous combo. So, then, either I had something touching something else that shouldn't be (likely) or a certain hFE works better in a certain position. A higher hFE transistor will boost more than a lower gain one. Maybe I had too much gain in which ever section it was and that made it sound harsh. Am I on the right track here?

I experimented with the filter section between the Base of Q1 and Emitter of Q2 (feedback path?). Replacing the 100k resistors with a 100k pot, one at a time. On the 100k (R5) that goes to ground, the pot is essentially a 'gating' control. Gated fuzz has its uses! I might add that... The other 100k (R6), acts like a tone control. On one end, you get bassy, fat fuzz. On the other end, the highs take more space. It kind of acts like the Tone section further down the line. I might add that too... In between the two, you can remove some 'fatness' in favor of a little tighter low end. Very good for chugging. I'll have to add a resistor in series with this pot, as when fully on the treble side, it introduces white noise that I can't seem to get rid of. A 100Ω resistor in series with the 9V line helped some, but I put a cap to ground after it and some other noise comes in... Other than that, I like everything else the way it is. Resettled on the 100n input cap, returned to the stock Tone section values... This is a great effect! In the end, I want the stock circuit, as it was designed or so. That's why I'm building this pedal and not another, right? But, if I can make a few mods that won't change the tonal/gritty character of the circuit, I'm happy.

If you haven't tried out the FTM, and you like octavers, you need to! Anyway, I'm 'a go do my layout.

Anything to add about this great effect?

[duck_arse]

poke your fave transistor combo transistors into your DMM transistor test socket, and note the hFE's. are they all close/same? all over the shop? and how does the good set compare to the readings on yer blatt/bad set?

Q3 and Q4 particulars should have less effect on the sound due to their biasing setups.

[Mark Hammer]

Felicitations!
Congratulations! (don't want the régie to come after me  )

I've built easily 8 or more octave-up fuzzes, and the Tone Machine is the hands-down winner, for all the reasons you cite.  You don't have to go nuts about it, but "best" octaving occurs when the two complementary signals to be combined are equivalent/matched for level.  So, yes, using diodes with near identical forward voltages is optimal, but so is using 1% 100k resistors for R9/R10.

Personally, I've taken to using Schottky diodes for the D1/D2 positions, because they conduct at lower signal levels and subtract less from overall amplitude.

The key to the FTM's great octaving is, I feel, the network between Q2 emitter and Q1 base.  It would seem to provide more gain for the fundamental than for the harmonics, and is generally missing from a great many other octave-up units that are fuzzy enough but not octavey enough (e.g., Superfuzz).

While cancelling one of the complementary signals from Q2 cancels the octaving effect, it also  cancels a half-wave of the signal.  So what I like to do is use a SPDT switch - toggle or stomp -  to select between having normal octaving, and simultaneously lifting the D1 connection and bridging/shunting D2, such that the entire signal passes, rather than chopping off half of it.  The result is a somewhat "smoother" non-octave fuzz sound.  I have to say that the impact of doing things this way is more obvious when using higher Vf diodes like germanium or silicon than when using Schottky types.

And, as I've droned on about before, a small-value resistor between ground and the ground side of D3/D4 can also provide a smoother sound.    If you omit/lift those diodes, you'll find there is no shortage of fuzz at all.  What they do in the FTM and many other octave-up units is to provide a crude limiter that maintains the illusion of constant signal level, and permits the octave to "bloom" as you hold the note.  Doubling everything the string provides also doubles any incoming harmonic content, which provides a kind of "haze" that obscures the octave until the fundamental becomes more obvious and the haze disappears.  Holding the volume level constant allows that emerging octave to be heard more clearly, rather than only emerging as the note dies out.  The price you pay for such a simplistic approach is that the diodes do add a little more harmonic-haze of their own.  Sticking a small (<1k) resistance in there keeps the limiting, but with less harmonic haze.

[strungout]

DA: Good thinking. My hFEs are ( from a combo I like):

Q1 - 157
Q2 - 201
Q3 - 131
Q4 - 365

I have one other, but I only used the same four. Would those numbers be called close? Except that 365 one. That's a big jump from the other hFEs.

While I was trying to reproduce the 'Blaat' issue, I found it! Then lost it... Then I noticed a mistake: I put in Q2 backwards and it's pretty much that same 'Blaat'. I'm pretty sure that was it It's interesting permuting transistor positions. It changes how fat/slim and loose/tight the fuzz is. I'll go check those clips again and see how close I can get to the original.


Mark: First, thanks, I'm glad I finally built a good sounding fuzz. Second, lol! I have a figurine that 'wears' a Kiss T-shirt, originally. But on mine, made for the Québec market, it was replaced with the word 'Bisou'. Everytime I look at it, I roll my eyes and wonder... Did they not have the rights for the Kiss brand name or did the Régie just get over-zealous... Wouldn't surprise me, haha.

About that network, I forgot to check what happens to the octave while I set my two extra pots that replace the 100k's. Could have interesting effects too.

I did use a small (470Ω up to 1k I think) to ground from D3-D4 while I had the 'Blaat' problem. It did make it less harsh. I also have a 1n cap to ground, parallel to the diodes + resistor. I think it was another suggested attempt at smoothing out the harshness.

I'll try the Schottky diodes again, there's some stuff you mentioned that I hadn't done along with the diode change. Maybe the fuzz will be more pleasing to me then.


I'll probably make a soundclip when it's boxed up.

[Mark Hammer]

Sounds like you have it under control.

For those unfamiliar with the quirk of Quebec law, in an effort to promote the use and dominance (some would say "survival") of French amidst the surrounding onslaught of English, language laws require that any bilingual signs have the French words/titles in larger letters than English.  There are inspectors that go around measuring sign lettering to make sure it conforms to the law, and who issue fines if it doesn't.

[bluebunny]

For those unfamiliar with the quirk of Quebec law, in an effort to promote the use and dominance (some would say "survival") of French amidst the surrounding onslaught of English, language laws require that any bilingual signs have the French words/titles in larger letters than English.  There are inspectors that go around measuring sign lettering to make sure it conforms to the law, and who issue fines if it doesn't.

Incroyable!
Unbelievable!

(No, actually it's quite believable...  )

[highwater]

For those unfamiliar with the quirk of Quebec law, in an effort to promote the use and dominance (some would say "survival") of French amidst the surrounding onslaught of English, language laws require that any bilingual signs have the French words/titles in larger letters than English.  There are inspectors that go around measuring sign lettering to make sure it conforms to the law, and who issue fines if it doesn't.

Like Dan Ackroyd?

[tubegeek]

Like Dan Ackroyd?

Brilliant!
Doué!

[strungout]

Man, I chuckle everytime I watch that scene! Love that movie. I wish John Candy was still around...

I'm not gonna get into anglo/franco politics.  But, language is a huge part of a people's identity and the Québécois needed to establish and affirm theirs. They did a lot of it through the 'strengthening' of the french language. If you're curious, check out the Quiet Revolution (la Révolution Tranquille).

Learning english has taught me that to truly understand a people, their culture, you have to know their language. And I mean to the point where you think and even dream in that language! A real and deep integration. That way you understand how a particular people views itself, the world and their place in it: through watching their shows and films, reading their books and poetry, conversing with them. And that's as true of lingo and slang as well. If I say 'res' or 'cap' here, everybody knows what I'm talking about. If I use those same words to a gamer, 'res' will mean 'resurection' (when the big bad boss killeded you) and 'cap' will mean 'capture' of an enemy position, flag, etc.

We all, here, in this forum, can vouch for the value of being able to communicate with a common language. We profit a lot from the knowledge we share amongst ourselves! It's really cool knowing another language.

Anyway... the thread got side tracked a bit, but here's to languages!

[Mark Hammer]

Absolutely! 

[willienillie]

While cancelling one of the complementary signals from Q2 cancels the octaving effect, it also  cancels a half-wave of the signal.  So what I like to do is use a SPDT switch - toggle or stomp -  to select between having normal octaving, and simultaneously lifting the D1 connection and bridging/shunting D2, such that the entire signal passes, rather than chopping off half of it.

I just did this on my Octavia, I've been meaning to try it since I saw this post two months ago.  I used a DPDT on-on, I can't imagine how to do it with a SPDT.  But anyway, it works.  I wasn't expecting the volume boost, but I suppose it makes sense, the signal no longer having to punch through Vf.  I'm not very impressed with the fuzz-only sound of my Octavia, I must say, but I've only tried it at low-low 3am volume so far.  It does sound quite good with a Rangemaster in front though, but really a distortion rather than a fuzz in that case.  Tomorrow I'll try it with just the diode lift, I guess that will even out the volume, maybe I'll like the half-wave sound better, we'll see.

[Elijah-Baley]

I built in these days the circuit of the Foxx Tone Machine using the tagboard layout. Actually, I modified it a bit and I used the Fulltone Ultimate Octave schematic changing some caps.
I got just one problem. A whine using my PSU, an old Boss (red label). Further 100uF and 100nF are useless. As well a 1N5817 in line ot the 9v. I tried some resistors, but I got some tame of the whine with "big" resistor like 180R, though I can hear it a bit at high gain setting.

This thing is happening to me with my last build, especially with transistors, I guess.
(With a Pharaoh Fuzz I solved it with a 47R, as well a LPB-1. My Woolly Mammoth is still in pause because this.)

[willienillie]

So yeah, I know this thread is about the FTM, which probably has better standalone fuzz than the Octavia, but the Octavia sounds KILLER with the half-wave/simple diode lift.  With the full signal it was just lacking in fuzz and sustain.  Now I'm kicking myself for not experimenting with this before, instantly one of my favorite fuzzes.

[Mark Hammer]

Hey, more "wow" is a good thing.

Which Octavia is it, the transformer-based Tycobrahe, or the non-transformer Roger Mayer?

[willienillie]

Tycobrahe.

BTW, does anybody know how to pronounce that name?  -bray?  -brah-hee?

[Mark Hammer]

I believe it was bra-hee, and it was two words, the words being the gentleman's first and last names.  https://en.wikipedia.org/wiki/Tycho_Brahe

[willienillie]

Ah, thanks!  I had no idea where the name came from.  I'm really not up to speed on 16th century Danish astronomers.

[Mark Hammer]

Brother, I'm ALL ABOUT 16th century Danish astronomers.  It occupies my every waking moment.  That's why I'm taking so damn long to finish the Hyperflange. 

[duck_arse]

Brother, I'm ALL ABOUT 16th century Danish astronomers.  It occupies my every waking moment.  That's why I'm taking so damn long to finish the Hyperflange. 

tell him about Tycho's nose, Mark .....

[bluebunny]

tell him about Tycho's nose, Mark .....

That's one for the "jokes" thread...

    My 16th century Danish astronomer's xxx xx xxxx!

    How does he xxxxx, then?

    Xxxxing awful!

(Fill in the blanks please, Mr H.)