I have old sparkle drive. Great design. It was modded by Analogman (or Keeley) I cannot remember, sounded much better than original. Now, I play mostly bass, for
http://www.bigdaddysunshine.com. The sparkleDrive concept is a very generalizable product platform. Functionally, its really "Loop Blender".
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My product design recommendatations are as follows
Factor out the blend knob, with a single loop (in/out jack pair).
Keep an internal drive module and EQ module. (selectable center freq)
Allow the loop to be engaged and blended back to original signal
with or without the Distortion and EQ.
This is especially valuable for BASS Overdrive, where often you want a clean portion of the signal (10Hz - 200hz) and (2K-20K), and dirt or grit portion of the signal in the middle. With this design you have internal drive in one portion and External drive and EQ with a loop in another portion of the signal.
With a product platform design, and social media marketing, you can have a hole product line appear from this design idea.....
Note, another way to position this design as "Drive Stacker", where the loop provides the external drive to blend or switch to, in addition to internal one.
Cheers, Chris Rigatuso
http://www.Skyfollow.com