Bass Balls is my favorite defect pedal because for me it is so versatile, responds to my touch, that nasty "fuzz" and up and down sweeping filters. IMHO the best version available is the
Mooer Sweeper as it has the most useful modification already done with controls for the up and down sweeps, for an unknown reason labelled "range & resonance" these set where the filters cross resulting in the unique pseudo flange like sound. Once you get a feel for how the sensitivity works with your plucking style you are golden, too low and the filters never close too high and they are not responsive. I get a lot of mileage by reducing the output on my bass, changing pickups or where and how hard I play there is a lot of nasty magic in the Bass Balls. I have a small collection of Bass Balls OG, NYC, NYC modified as well as a couple of the Rocktron variants [Heart Attack and Reaction Filter] My current one is a one built by John K10 dubbed the BassBalls+. I still remember seeing an ad for the Bass Balls in some magazine and going on a quest to find one to make my own, it took several months and it has been a mainstay for me ever since.
My other favorite filter pedal is the Spectrum from Source Audio that also does octaver, dirt and LFO sounds to boot. Spectrum has a wide range of filter types and parameters to control and modify with a vast array of creations on Neuro.
The current nano QTron looks interesting but I have not tried one, the full size
QTron is amazing a cross between early EHX filters like the DR Q and the MuTron III, co designed between EHX and Mike Biegel of MuTron fame. EHX has done a good selection of filters over the years, some quite unique. FWIW the Dr Q was my first filter pedal that I used on guitar and bass for decades.
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