First build report - the Tweak-O - seeking input

[suprleed]

Just finished my first build, the Tweak-O from Small Bear.  It worked right off the bat and I didn't have to debug anything.  It was a great beginner project; I really learned a lot and I am now fully addicted to diy effects!!!

Tone wise, my impression of the Tweak-o is that its OK.  Mine seems a little bass heavy when playing chords, especially when I use my neck humbucker.  I was just wondering if anyone else had a similar experience with their Tweak.  I'm considering lowering the input capacitor from .1uf to .01uf to let a little more treble thru the circuit.  Problem is I don't want it to become too shrill as the Tweak-o sounds pretty good right now when doing lead riffs.  Any thoughts on this would be appreciated.

Another thing I've noticed, that I'm wondering if anyone else has experienced, is the unresponsive gain pot.  I don't get much variation in distortion until the final quarter turn of the pot.  Because of this I'm considering the following mod.  I'm thinking of pulling one of the 1n4001 diodes out of the clipping stage and replacing it with an LED.  Since LED's have higher forward voltages than 1n4001 diodes it should clip later.  This will not only increase the volume of my Tweak-o, but should also give me a wider range of clipping from when the circuit first starts to clip to when it reaches full clip, i.e. more variation in distortion.  At least that's what I infer from my study of Mark Hammer's excellent explanations of diodes and several threads on this forum.  Please feel free to correct me or give me any other ideas of how to get more varied response from my gain pot. 

If I could tame the bass a bit and get a little more variation in distortion on this baby, it could be pretty sweet.  Not too bad for a single tranny beginner project!

[8mileshigh]

The Tweak O was my first as well.  I also didn't like the way the Fuzz level control felt so I swapped it for a linear pot which gives a more natural/gradual increase in fuzz.  Dimed, it sounds pretty good but I don't like the way it sounds when you back off the fuzz.   The is the same issue I have with the Fuzz Face as well, the fuzz pot is pretty useless, even the reverse taper pot I installed doesn't do it for me.  Leaving the pot out and controling the level with the guitar volume pot is the way to go. 

Back to the Tweak-O, changing the input cap to .01uF would probably be a great mod for the circuit, it'll be brighter but not overly so.  I'll revisit mine one of these days because it just sits in a box on the shelf.  BTW, I also tried germanium diodes or maybe I mixed one in and got a decent overdrive sound.  Let us know how your tweaks go.

Chris

[suprleed]

Thanks for your input 8mile.  I don't have a lot of experience playing with caps to adjust the sound so I'm glad to hear you think the .01 cap will brighten things up without being too overbearing.  Just the kind of advice I was looking for.

Interesting note about the pots.  Maybe I'll consider changing to linear as well as playing around with the diodes in the clipping stage...

[Scott674]

Did you ever go ahead with those mods superleed?  I also have built the Tweak-O as my first build, and the thing I don't like is there doesn't seem to be much boost to it.  If I turn both fuzz and level up full, it's about the same volume as with the pedal bypassed... Maybe the battery is going on it...

[petemoore]

  You could try LED, I don't think the transistor feedback loop will cause enough voltage to clip it.
  gain knob thing sounds like a pot taper issue, I'd just live with the wierd taper as long as it covers the gain range [ie the pot is the correct ohmage value]..dahh you could make it operate over a smaller portion of the range etc., fixing it at abour or full and using the guitar volume's probly a good one.
  You can always increase the input cap value with a parallel cap [pick or calculate combined value], switched, or series two caps and short across one to have only the others value. can be done w/switch or just a stretch of wire right across the cap [solder one end, twist the other  end over the lead as a 'switch'], hear various values, 2 different values switchable is easier to sort out, then you can adjust other stuff...switch back...see what you like there.

[suprleed]

Did you ever go ahead with those mods superleed?  I also have built the Tweak-O as my first build, and the thing I don't like is there doesn't seem to be much boost to it.  If I turn both fuzz and level up full, it's about the same volume as with the pedal bypassed... Maybe the battery is going on it...

I finished my mods about a week ago and have been playing around with my Tweak trying to gauge how it has changed so I can report back.  The first thing I did was lower the input cap from 0.1uf to .047uf.  This helped remove some of the muddy/farty bass I was originally getting while playing E string powerchords.  I probably could have gone down to .01uf as I was initially intending but my Radio Shack didn't have any .01's in stock, and the .047 keeps the Tweak on the darker side which is fine for my tastes.   I wonder if playing thru single coils would also brighten up the sound a bit (I'm playing thru dual humbuckers at the moment)?

I also replaced one of the clipping diodes with a 5mm green LED from Radio Shack.  Per the packaging the LED has an average forward voltage of 2.1 volts.  I could not confirm this as I don't have a DMM yet.  Adding the LED did seem to boost the volume a bit and I am now getting a decent boost.  Before the mods I would have the volume maxed as Scott stated above, now I keep it at about 2:00 for a comfortable home playing level and have a little room to go higher in case I want to annoy the neighbors.

  You could try LED, I don't think the transistor feedback loop will cause enough voltage to clip it.

I was little worried about this when I was planning my mods.  I originally wanted a blue LED but found that they have a forward voltage close to 3 volts and clip much later than si diodes.  That's why I went the green LED with the lower voltage.  It's still a little too high.  I mounted the LED so I can "see" the clipping a la Keely SEM style.  I only notice the clipping when I have my guitar volume nob dimed.  So the LED only clips when I max the signal from my guitar.  One day I might switch out the green for a red which I think has a lower forward voltage around 1.7 volts which will clip sooner and give me a brighter LED (it's still pretty weak now with the green).

 

gain knob thing sounds like a pot taper issue, I'd just live with the wierd taper as long as it covers the gain range [ie the pot is the correct ohmage value]..dahh you could make it operate over a smaller portion of the range etc., fixing it at abour or full and using the guitar volume's probly a good one.

I decided against playing around with a different gain pot.  I've invested enough money into this beginner project already.

Overall, I feel that the mods I made improved the sound of the pedal.  This is not a subtle sounding pedal, but a pretty gnarly fuzz.  With the gain dimed and the volume on my guitar cranked, this reminds me a little of my DS-1.  I wish I could get a little "smoother" distortion out of it, but I may have to go to more of an overdrive project to get that sound.  I just noticed in the mod FAQ that a small cap bridging lugs 3 and 1 of the output volume pot can help smooth the tone of the pedal.  Maybe I'll try this at a later date as well.

One interesting thing I noticed the other night when I was playing around with the Tweak-o, was that as I backed off on the gain pot, it would add more bass into the signal.  I think the pot is interacting the the capacitor in series with the diodes (C3 on the small bear schem) and acting like a low pass filter.  So the pedal is a little brighter with the gain at max as opposed to min.  Adds a "minimal" amount of tone shaping.   I may post some pics later, mostly for sentimental purposes (first build), but it's nothing special to look at.  I'm still trying to decide if I want to actually paint the enclosure.

Thanks to all for your input.  Now I have to somehow decide what project to tackle next, there are just too many to choose from...

[Scott674]

One interesting thing I noticed the other night when I was playing around with the Tweak-o, was that as I backed off on the gain pot, it would add more bass into the signal.  I think the pot is interacting the the capacitor in series with the diodes (C3 on the small bear schem) and acting like a low pass filter.  So the pedal is a little brighter with the gain at max as opposed to min.  Adds a "minimal" amount of tone shaping.  

I notice that too!  I wonder if it would be possible to separate out the gain and the tone into 2 separate controls.  Nice work though, I'll have to try some of that with mine, espically the LED swap.  Have you added a power jack into yours?  That's the other thing I'd like to do . 

[suprleed]

I notice that too!  I wonder if it would be possible to separate out the gain and the tone into 2 separate controls.  Nice work though, I'll have to try some of that with mine, espically the LED swap.  Have you added a power jack into yours?  That's the other thing I'd like to do. 

The separate tone control is an interesting thought.  I've read about other circuits in my research that change character as the gain is adjusted.  Hammer's Chaos comes to mind.  This is where things start getting a little too advanced for a novice like me.  But simple circuits like this are ripe for modding.  Tone controls often weaken your signal, so you'd want to use a recovery stage since the boost from the Tweak isn't overwhelming to begin with and you wouldn't want to suck the life out of it.  But we're talking about the gain pot in the feedback loop so that may not apply here???  See, too advanced for me already.  Guess I better read up on tone controls and filters...

I'd definitely try swapping one of the diodes for an LED if you want a volume boost.

I'm just going to keep mine on battery power for now.  I think I'll incorporate the DC jack into my next build (still pretty noob, one thing at a time for me  ).  That doesn't seem like too hard of a change though.  There are good wiring diagrams on all the normal sites (GGG, Tonepad, etc.).