An easy mod to a Bass Balls clone

[Mark Hammer]

I picked up a Behringer Vintage Bass over the weekend for thirty bucks.  It is a clone of the EHX Bass Balls and comes in an "old school" style folded metal chassis...except that the top part is aluminum, rather than the folded steel EHX used to use.

The board inside is VERY small, with all components, except for some electrolytic caps, and a pair of trimpots, being SMD.

I made two simple, but useful mods.

1) As you recall, the Bass Balls uses twin staggered bandpass filters, that are swept simultaneously.  The spacing between the two filters is adjusted via a trimpot for each filter.  Behringer has glued the trimpot for the lower filter in place, but left the trimpot for the upper filter tweakable.   I desoldered it and replaced it with a 10k linear pot.  It is not usable throughout its entire range, but about 75% of it yields useful differences in sonic character.

2) The decay time on the BB is set, more or less, by a 330k resistor to ground, that bleeds off the charge stored in a 4u7 averaging cap.  I replaced it with a 1M 1/8w resistor, and ran leads from each end of that resistor to a SPDT on-off-on toggle, that added a 470k or 91k in parallel with the 1M, or no parallel resistor (middle position).  This gives roughly stock (1M+470k), slow (1M), and fast (1M+91k) decay times.  the 330k resistor itself is clearly marked, and very accessible on the corner of the board, without having to risk dislodging other components.

The result is not exactly the tricked-out behemoth that was Marjan Urekar's famous "Fuzzy Balls" ( http://urekarm.tripod.com/synth/fuzzyballs.html ), but for $30 and less time than it took me to drive to the store and back, I got a much more usable pedal.  I see someone had posted a video of their own modded VB-1.  Where I panel-mounted one filter-tuning pot, they mounted both.  I installed the decay-time switch where they installed one of the tuning pots, just below the distortion switch, and mounted the remaining tuning pot on the corresponding other side of the chassis, where the video shows a tuning pot.  It was necessary to remove the plastic back covering the pot in order to fit it comfortably, and also necessary to orient the toggle so that it switches fro side to side, rather than up/down.  But within those constraints it worked out great.

There ARE, of course, other mods that could be done, but these were dead simple and fast.  Sometimes, if one wants to get into DIY pedals, modding cheap commercial products is a great pain-free way to start.