Evil Harmonic Overdriver Fuzz (18JUL2016 Schem added)

[Lubdar]

Hey team,
  it's been a while since I've been able to sit down to fully assemble a pedal, but over the course of the past two months I've managed to find bits of time to piece this guy together. You've probably figured my appreciation for DBA stuff, and this is the result of my examination of multiple DBA schematics and ideas.

It's a combination of ideas from the newer Evil Fuzz/Harmonic Transformer/Interstellar Overdriver.
It is comprised of 2 reverse beta gain stages, with level controls for each, that way you can turn level1 all the way down and get fairly clean overdrive tones, or max it out for fuzz, and anywhere inbetween.  The density knob controls the input capacitance for thin treble all the way to bass bass bass.  The toggles are for switching out a transistor stage in the 1st gain stage, and the second is an output pulldown resistor to give a slight volume boost.

I'm pretty happy with the way this turned out, My main goal was reducing my issues with offboard wiring, which I think i can now say I will try to do that with my pcb designs from now on as often as possible. 

In addition to this, for the enclosure I tried a couple new aesthetics. I screenprinted the sides of the pedal with a lion logo, and used some brass parts from the hardware store to make portions of the pedal pop a little bit. Kind of like character design, I wanted to have a primary dominant color(black sparkle), secondary less dominant color (White), and tertiary highlighting colors (gold/brass/silver from the hardware).

I dig the sound, although it may not be for everyone, but for me its a really cool feeling to have taken this from looking over schems, slowly understanding how to create a circuit, and taking the design from concept to completion. Heh, I goofily gave myself a pat on the back, it still makes me smile thinking about the process.





Best,
   Lubdar

[selfdestroyer]

Very cool Lubdar. I am really digging the enclosure aesthetics. The screen printing looks so pro. Also very interested in the circuit, any plans on doing a group buy on the PCBs?

Cody

[midwayfair]

Beautiful build.

[Martan]

Excellent job! I like the brass parts, too.

[stringsthings]

Excellent job! I like the brass parts, too.

+1

[beneharris]

Very cool Lubdar. I am really digging the enclosure aesthetics. The screen printing looks so pro. Also very interested in the circuit, any plans on doing a group buy on the PCBs?

Cody

I'd be interested, too. The circuit concept is intriguing. Really cool build, the enclosure is great!

[Lubdar]

Heh thanks you guys for the compliments! It means a lot


I'll work on getting a demo up of the different sounds coming out of this guy.
If there is still interest I'll figure out how to make the pcb better and more accessible, either via OSHPark sharing or trying to have some boards printed.

The Gold ink didn't stick too well, even the higher quality ink doesn't last over a certain period of time.  Heh I've had that ink for about 3 years now and I finally had to replace it. Not bad considering the very slow rate of printing that I do.


I like the brass look too.  at one point I'd seen powdercoated hex nuts and the like, and thought that was pretty cool, but I can't do any powdercoating right now.

[m-Kresol]

great looking pedal. while the pcb might be bigger than necessary it is very functional! cool design

[flanagan0718]

Great build man! Are these going to be available on oshpark? Love those bypass boards too.

[lincolnic]

Very cool, and congrats on your design! Looking forward to hearing it.

[Tremster]

This is great!
Do the three pots make a Master Volume unnecessary?

[Lubdar]

Thanks you guys!!
I'll try and get something recorded ASAP and post it this week.

This is great!
Do the three pots make a Master Volume unnecessary?

The "Gain 2" pot is more or less a volume control, there isn't a volume control at the end of the circuit, the "Gain 2" pot is limiting the signal that goes into the last 2 transistors.  I was trying to make "controlling gain stages" more accessible.  ALternative label choices were "pre", and "post", or "input" and "output". Just something to describe the position of the signal limiters in the circuit.  I'll post the schem after hours when I get off work.

[mrclean77]

Hello from Cullman, AL!

I dig the idea and sounds like you nailed what you were after - also eager to hear this guy and possibly do a build. Nice work!!!

[Lubdar]

I'm not sure if I should have started this in a different section of the forum, but if a moderator wants me to redirect it I will.

Below is the schematic for the pedal for any of you breadboarders out there curious to give it a whirl.
You can see the common "DBA" biasing method on the transistors in reverse active orientation.If you max everything out, you get a fuzz sound close to the 7 tranny fuzz war.  Look close and you can easily see why. MPSA05s handle the 910k to base biasing approach better than 2n5088 and 2n5089s...

I'm not so sure about the toggle switch at the end, really it just lifts the signal shunt to ground, which in effect gives a little boost in volume.

If anybody has a chance to look over this schematic and has any suggestions on improvements, let me know what you think. I would greatly appreciate any/all feedback.
  Like I said I'll try and record a clip probably Wednesday night and post it up here for those interested.


I use Diptrace to create the schem and then layout the board, I have yet to try eagle, but so far Diptrace works out great for me

best,
  Lubdar

Hello from Cullman, AL!

I dig the idea and sounds like you nailed what you were after - also eager to hear this guy and possibly do a build. Nice work!!!

Another Alabamian!!

[storyboardist]

Nice and clean guts. I'm with you, I hate offboard wiring. Thanks for sharing the schematic. Seems like you've figured out the weird biasing of DBA designs. Wonder if MPSA05s will make building the 7 transistor version of the Fuzz War easier...