Sunday, March 1, 2015

LeSpork Bass Prototype - Winter Time

In the winter time
When all the leaves are brown
And the wind blows so chill

Not very pleased with the Electra Distortion circuit I built to audition for the LeSpork Bass in the early winter, I decided to move on to another circuit.  The small part count and simplicity of the Bazz Fuss intrigued me and so it seemed it might be a good fit.  Substituting a more powerful 2N5089 transistor for the 2N5088 shown in the schematic, I put this together and gave it a try.

Although it was quick and easy, the Bazz Fuss had too rough of a tone for my tastes.  At the suggestion of a friend, I moved on to a home-brew incarnation of the Electro-Harmonix Big Muff Pi.  Considered by many as an essential distortion stompbox, variations of the basic BMP circuit have attracted a lot of attention and endorsements over the years.  I started with a typical schematic courtesy of beavisaudio, sourced a variety of parts from some eBay vendors near and far, and made a few substitutions to match my at-hand assortment of semiconductors.

As the folks at beavis and numerous others have documented, there are many ways to modify this basic circuit to suit a variety of tastes, including some better suited for bass guitars.  Due to the numbers of opportunities to make mistakes while bread boarding this circuit, and realizing it would take me a few days to fit all this in to my calendar, I decided to test each of the five stages beavis identified as I built them.

First came a clean preamp.  To be sure I'd have enough room on the bread board, I started at the far left side, using as little space as possible.  I also used a 100k trim pot in place of the "sustain" pot just to get things moving.

A quick sound check verified that things were where they belonged and that I could move on to the first of two identical fuzz stages.

Again, a quick sound check verified that things were working fine.  As expected, there was a loss of volume with this addition, and the germanium diodes introduced a slight, mellow fuzz.  That fuzz was more pronounced yet pleasantly mellow with the addition of the second fuzz stage.

Moving on to the tone stack, I replaced the 100k trim pot sustain control with an audio-taper potentiometer and added a linear-taper potentiometer for the tone control.

After a good night's rest, I added the final stage, including the volume-out control.

With my son's help, I made two quick recordings of this circuit with my iPhone held about two feet from our Crate bass practice amp.  The first one was with the LeSpork Bass straight from the pickup into the BMP.

The second was with my son's Epi LP, with the volume and tone controls both on 10.

My son was very pleased with the sound of his Epi through this basic build, compared to the built-in effects on his amplifier.  So, it looks like a pedal-version build of this is in the near future at These Old Guitars.  I'm not so impressed with the range of the tone control.  I also have some gain and overall volume issues to be addressed.  My goal is to get the same volume and tone levels between the clean and distorted signals with only three knobs on the bass.  Next time, I'll do some tweaking of some of the values.

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