"Good enough" synth pedal for bass

[Mark Hammer]

For bass, I find that when it comes to swept filters, faster decay makes for a much more synth-like sound.  A great many envelope-controlled filters have slower decay them.  That can be useful for rhythm guitar, but bass wants each note to be individually pronounced, and for that you need a faster decay.

I put together a clone of the EHX Bassballs, using the topopiccione layout, and modded it to have a faster attack (68R instead of 100R) and a variable decay time (47k to 547k, as opposed to 330k).  I also hardwired the "fuzz" setting (i.e., no clean option) and replaced the 100k/47k attenuation network for the "fuzz" portion with a 10k series resistor and pair of Ge clipping diodes to get something closer to equal bypass/effect levels (though one could easily use a pair of Si diodes and a volume pot on the final output, instead of the fixed 47k resistor).

With a faster attack, the upward sweep is less noticeable, leading to more of a "BOW", rather than "BWOW" sound, with a more punctate ending.

The other thing  did was panel mount the 10k pot for the upper filter, so I could vary the "stagger" between the filter sections, and also added a blend control to adjust the balance between, and dominance of, the two filter outputs.  I don't know how it compares to things like the EHX Enigma, but it sounds very nice on bass, for minimal outlay and difficulty.

[nexekho]

Quick demo of an idea I had, will explain tomorrow when it's not 3am


(click to view)

The circuit is missing the volume follower, square waver and the top left oscillator needs a push start but it seems to work for the most part...

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Ok, so it's no longer 3AM.  The square waved guitar signal is used to clock a 3 position counter in the bottom right corner.  There are three capacitors, each draining, taking voltage and then outputting in turn based on this clock.    A resistor is also in place so it forms a low pass filter and slowly fills up over the duration of the pulse.

The voltage now stored is passed over to a comparator the output of which clocks the flip flop inside an oscillator.  A similar RC network is used but with a smaller resistor - 20x smaller (as this oscillator works as a 2x frequency divider too) so the capacitor reaches the voltage from the earlier capacitor 20x faster and when it does the capacitor clocks the d-type controlling the oscillator.

From here, it's a 4017 attached to the d-type with a row of potentiometers to dial in your waveform.  I can't remember why I put MOSFETs in there.  I do want to be able to run two osciallator/4017 circuits off the same row of potentiometers for harmonizing using an intentionally mismatched resistor.  Maybe a rotary switch.  I take it that due to tolerances, I'm probably going to need to use trimmers too.

[liquids]

How did that actually work out?