Some questions about modifying my first distortion pedal

[chupucabras]

Hi there,

I've just built my first guitar pedal that actually works! I used the 'Muff Boost' schematic from this site:

http://www.muzique.com/schem/projects.htm

I'm very pleased just that the thing's worked but the sound could be better... I guess this is the fun part; tweaking components and values to get the sound just right. I'm still very much a beginner when it comes to electronics in general, let alone guitar FX, so I could use some advice on a few things.

I used a 2N3904 transistor, and germanium diodes.

1. Next to the two diodes in the original schematic is a 10uF capacitor. The text on the website mentions that this affects the 'brightness' of the sound, and suggests a smaller-value capacitor to add some brightness.

When I first tried with the 10uF capacitor, the effected sound was indeed lacking in the higher frequencies, so I swapped the 10uF capacitor for a 4.7uF capacitor, and then a 1uF capacitor.

The 4.7uF capacitor sounded the best out of the three, although there was still a noticeable difference in the high end.

Strangely, the 1uF capacitor seemed to be as bad if not worse than the 10uF capacitor in filtering the high frequency content of the signal.

I also noticed that with successively lower values of capacitor in this position, the amount of distortion (which was not very prominent with the 10uF capacitor) seemed to decrease; with the 1uF capacitor the box didn't seem to be distorting the signal at all, just filtering off the high end a bit...

Is this behaviour normal, or could it be a fault elsewhere in the circuit causing this?

2. As I mentioned, the distortion was pretty subtle to start with, and seemed to get less and less noticeable as I reduced the value of that capacitor...

On the AMZ page where I got the schematic, it mentions that you can use germanium diodes (as I did) but that four instead of two might be necessary to keep the output volume at a decent level.

I'm guessing this is part of the reason that I'm not getting a huge amount of actual distortion from the pedal... but I'm not sure exactly how I should wire up the extra two diodes. I vaguely remember something from an electronics course at uni several years ago that involved four diodes in a sort of diamond formation on the schematic, which I think was a full-wave rectifier. Is that the kind of thing I want to be doing here? Another option that came to mind would be adding the extra two diodes just before the output to get hard clipping...

What do you guys think?

3. Would it be easy/worthwhile to adapt the circuit to include a second transistor? Would I be right in thinking this would provide more gain going into my diodes?

4. I've got two spare pots in the case I put this circuit into, and I'd quite like to use them, maybe as a gain and tone control or something (I THINK the single pot I'm currently using, as seen on the schematic, controls the volume rather than the gain/drive - it's hard to tell as the distortion isn't very pronounced, and I'm not 100% sure how to work it out using the circuit diagram)... Are there any other interesting things I could do (relatively easily!) with these two extra pots?

I think that's all my questions for now... Any advice you can give me would be very much appreciated.

Thanks,

Dan

[tcobretti]

As I just mentioned in another thread, I am not real smart at this stuff, but I'll throw out what I think.  The first thing I would do is use a 2n5088/2n5089 tranny.  They have more gain and will likely sound better.  I would also try a darlington just to see what happens.  Watch the pinouts!  This is why you always socket the tranny so you can figure out which one best suits the circuit.

1.  These caps affect the sound by subtracting lows, not boosting highs.  So, as you subtract more signal, the distortion decreases.  Finally the gain has decresed so much that the sound changes very substantially and you lose the highs that were being created by the distortion itself, so the pedal sounds darker.

2.  The four diodes will go in a series, split in sets of two.  So, where the schematic now has one arrow with a line pointing left and one pointing right, it will now have two pointing in each direction.

3.  I think that if you want to rewire and add a transistor you would be better off building a well known two tranny fuzz - fuzz face leaps to mind as does the axis fuzz.  I personally would tune the muff boost to sound as good as I could get it to sound, then build a bazz fuzz version 2.  It kicks giant butt.  It will blow you away, especially considering how simple it is.
http://www.home-wrecker.com/bazz.html

4.  Your current pot controls output volume.  You could add a pot before C1 to control gain (which you could just as easily do by rolling off your guitar vol knob).  I believe that if you add a pot in place of R4 or even R1 that you would also get a gain control.  Essentially, any resistor can be replaced with a pot, so experiment.  This classic article might offer some ideas.
http://www.geocities.com/tpe123/folkurban/fuzz/fuzzyfaces.html

Finally, invest in a breadboard.  It will allow you to try all of these ideas before you ever commit to any of them.  I have breadboarded more than one pedal that I decided not to build, and I have spent hours tinkering with a breadboarded pedal before I finally built it.

[petemoore]

  A one transistor with Ge's will be about the most distorty setup for the MB, Si Diodes will be higher output, less distortion.
  Stick another transistor up front or another Muff Boost behind and tweek the more distortion/output available, check out Big Muff Pi, and compare..adding transistors starts to look more like a Little muff or part of the B.M.P., different Qtype [say Jfet or other] as Q1 in....whatever it's looking like will have a different flavor, Maybe that and/ or a minibooster?
  we're about talking breadboard, but I never got one, opting to just have the board for whatever I'm trying handy in the future [once taken off the breadboard..it's off the breadboard] and /modifying/adding/tweeking on the perfboard or perfboards.
  I buy large perf, and cut it down to smaller sizes.
  As you can tell, I'm leading you toward redefining things to your needs, want's and preferred flavor...because I think that's what it takes to get a circuit to 'do' for you what it could...hopefully something you want it to.
  Messing with myriad configurations...you get intuitive like you have, then more intuitive...along the way you're bound to hit on something your'e liking more than the last way.
  Disregard if all this is more than you're wanting to have answered...not really answers, just suggestions..anyway that's how it goes...lookin' at schematics...putting something together by any means doesn't have to be 'verbatim'.

[G.Neyrey]

   Try reducing the input cap, C1 for brightening sound or reducing muddiness as it prohibits some lows from passin' through. Try .47uf down to .01uf for starters and see whatcha think. .01uf and .02uf work for just about all my DIY pedals. 
Although some claim it heresy, I did this to a fuzz face.......and never regretted it!

George