MIDI-Tap Tempo Tremolo

Abe's Custom Effects:

MIDI-Tap Tempo Tremolo

I wanted to share this project ever since it was completed but life got in the way :)  This was a very cool project because an artist finished the pedal with incredible artwork and looks awesome!

This was a custom tremolo build request that required MIDI clock input, Time Division selection (from whole notes to eighth notes), different wave selection (sine, triangle, etc), and able to run off from 12V 400mA power supply.  Also the requester wanted all the jacks on the north side of the pedal.  As we started communicating, it made sense to add the Tap Tempo switch for ease of setting the tempo. 

Here is a picture of the enclosure (top left) and freshly etched circuit board (bottom left) before it was worked on.  The blue enclosure and the circuit on the right side is a custom Blues Breaker build with couple modifications that I've added.

I designed the pedal to work with LED/LDR combo driven by digital LFO to accommodate MIDI clock and Tap Tempo inputs.  The audio signal is still completely analog, providing nice warm tremolo effect.  This pedal also benefits from being run at 12V for slight advantage in headroom.

Due to the nature of digital controllers, I had to be careful isolating digital and analog grounds to keep the digital noise out of the audio signal.  I also used couple heavy duty Voltage Regulators to prevent any failures down the road due to heat.  Here is a picture of the circuit board after all the components have been populated:

The pedal end up drawing a little less than 200mA but it's well below the power supply limitations.  There are two LEDs; one for ON/OFF indicator and the other "blinks" in time according to how SPEED is set.  Here is a picture when I finished it up (left pedal is an external tap switch that could connect up to 3 different pedals at once):

Painting in progress:

MOD: Digitech JamMan Stereo Looper

"Soft-Click" Footswitch Modification for Digitech JamMan Stereo Looper

This was a modification project that I've worked on recently.  The looper was working fine but the owner was not satisfied that the footswitches had a "click" as it was being stomped.  This action is very common in many stomp-boxes where you feel and hear the switching occur as you press it.  Typically, the "click" is associated with latching type of switches.  However, some momentary switches also has this "click" action and this looper came with them.  Here is a close up of the original footswitch.

The owner's problem was that the "click" made the preciseness of looping difficult.  The "click" would present itself as an obstacle creating physical latency when activating the switch.  The result was slightly inaccurate, out of sync loops.  The request was to get "soft-click" foot-switches installed which would eliminate the click and achieve more precise results for live use.

When I opened up the unit and saw the solder joints of the footswitch, I saw 6 joints and assumed it was a DPDT (Double Pole Double Throw) switch.  I thought this project could get slightly more challenging because soft-click switches are SPST (Single Pole Single Throw).  If all 6 terminals were fully utilized to communicate with the main board, my immediate thought was to implement a digital interface sending multiple pulsed signals to eradicate the lack of terminals that SPST had.  Then upon closer inspection, I noticed that the switches were actually SPDT (Single Pole Double Throw) as you can see on the photo.

Knowing that it was SPDT made everything simpler.  After checking all the relevant connection on the PCB, I came to discover that the third terminal was not being utilized at all.  The first two terminals were connected until the switch was pressed; breaking a connection whenever the switch was being pressed.  That meant the SPDT switch was used just like a SPST switch with Normally-Closed operation.  This was true for all 4 of the footswitches on this device. So after installing some high quality SPST Normally-Closed momentary switches, this unit responded just like the owner wanted.  Modification Complete!

So why would Digitech use SPDT switches, when they could use SPST?  My guess is that it's probably cheaper to get or that they already had a big stock of SPDT and needed to use them.  Because there were enough holes on the PCB for DPDT switches, if they would ever run out of SPDTs, I'm sure they would substitute with DPDTs.  Whatever the reasons are, I'm glad I was able to help this artist create music without the "clicks"!