My Hell Dice Pedal Board Design

I have been performing way more than I use to! I play club gigs twice a week or more these days…and as a result, my relationship with my rig has really changed. Which is to say, my perspective on what I actually use and what features matter most, has evolved. My conclusions are these: I want small, light weight rugged equipment…I don’t want too many knobs or complexity. I like to use a few basic settings and sounds and that is it.  So I have designed a compact amplifier and set of small 1590a form factor pedals to create a complete amplifier/pedal board rig that weighs a couple of pounds and is about 12 inches long and 4 inches wide. It includes: My 100 watt stomp amp with an auxiliary 9 volt output, a high performance PT2399 type delay, a simple but really nice sounding LDR based envelope filter,  A very pleasing two stage LDR phase shift Vibrato and a hex inverter based overdrive with slightly different approach than the typical design.

My New Compact Pedal Board

pedal board2

As an aside all of these pedals are made with machined(not die cast) Hammond sized aluminum enclosures from Ebay (alpinetech), which I etched and anodized. You cannot properly anodize die cast enclosures because of other ingredients that are mixed with the aluminum…so you have to get CNC milled enclosures if you want to anodize the enclosures.  I discussed my home anodizing process here: Anodizing discussion

More Pictures:funkyfilt

vibrato board

delay board

Links to Schematics and Design Notes:

A few notes: Many of the part choices are  not transistors, op amps and voltage regulators I use.. The LDR based effects will need tweaking based on the output efficiency of the LED/photo-resistor combo or if you use a commercial opto-coupler instead. The vibrato uses my pic based LFO…but it can easily be replaced with other LFO circuits. The delay uses a 8 pole switch cap filter IC but if desired, this can be replaced by using the unused op amp on the PT2399 IC as a low pass filter.

Compact Stomp Amp:

Hell Dice Delay:

Hell Dice Vibrato:

Hell Dice Overdrive:

Hell Dice Funky Filter:

Pedal Board Demos From Live Show:

Demo of Delay and Vibrato:

Demo of amp clean no effects:

Demo of Envelope Filter(two minutes in):


PWM Vibrato that sounds Awesome!

Vibrato is the slight changing of frequency of a musical note. This can be accomplished by means of a varying time delay in a delay line or by phase shifting and analog signal over time.

The delay approach works fine but creates inherent latency and can sound clownish. So I wanted to create an analog design.

A modulated allpass filter can be used to change phase over time (which is frequency). This analog approach can sound lovely but to sound really good has to linear in its sweep and be modulated  in a sinusoidal manner. Both the design objectives are not trivial.

It occurred to me that my PWM phaser design does all this but simply mixes the original signal back in to create the phasing notches. So I modified the circuit and optimized it to simply modulate the filter and it works great. The PWM driven analog switches are very linear and the PIC DDS works great to create the sine wave modulation. I added some pre- emphasis/de-emphasis, adjusted some values and made an improved layout…so the pedal is super quiet. I left in the peaking filter adjustment to allow for some cool modulated filter effects along with the Vibrato. The range of PWM controls the extent(depth) of the effect at a given modulation rate and so the vibrato pitch bend level is easily adjustable.  Keep in mind the faster the modulation rate; the pitch shift is also greater because a faster the rate of change of phase over a given time, produces more pitch shift.  An alternate analog modulation circuit can be used if desired but the output swing needs to be limited from 0 – 2 volts.

Link to Schematic:


Brainwash Phaser converted into Vibrato pedal:

Coming Shortly Demo: