dig dug / seek wah / vanishing point / etc etc, which one is the best to build?

[njkmonty]

just about to put an order in to do madbeans dig dug, then i stumpled upon vanishing point,and not sure if there are others out there? just wondering if someone can point me quickly in right direction and say    ..... build this one!

[Processaurus]

The Dig Dug looks similar to the Seek Wah, and the daughter board for all of the pots is slick.

If you do make the Dig Dug, I notice an issue in the schematic with the how the pots are varying the brightness to the step LED and vactrol LED: in the first quarter of the pots rotation, there will be no change in the effect, which the author is honest about.  This is because each step pot is set up as a voltage divider, and when it gets turned down past a certain point, there isn't enough forward voltage to turn on the aforementioned two LED's, which are in series.  They probably need about 2.4v (more or less, depending on the parts used) of forward voltage before they start making light.  

The easy fix is to simply break that ground connection on each step pot, turning the pot into a variable resistor in series with the two series LED's.  This is the approach used in the Vanishing Point.

A different approach using a couple new parts could lead possibly to a better feel to the taper of the step pots, it involves replacing the pot's ground connection with a 2.4v regulated supply, and replacing the 100K pots with 10K pots.  It uses an opamp to make a buffered 2.4v, which then feeds the bottom of the step pots.  Using the same type LED's in the 2.4v supply as are used in the rest of the pedal make it easy to get the right forward voltage, and it won't drift as the battery runs down.  The 10K pots I think will help the brightness be more linear across the pots travel.



Doesn't necessarily shed light on which DIY sequenced wah is better, but if you do decide on the Dig Dug, this should make it work better.

[njkmonty]

wow thankyou, so i gather you have made the dig dug?
apart fromt he short comings mentioned, you where happy with it?