Triplicator
Stereo Triple Tracker with Effects Loops
Overview
In every band I've played in, I was the only guitarist. It can sometimes be challenging to get a nice, full soundscape when you've only got one guitar, which has led to the proliferation of double trackers. Some of the more advanced ones have multiple voices, as well. However, I decided I wanted to do a triple tracker that allowed panning of the signals in stereo as well as having effects loops for the voices. This naturally led me to want an effects loop and panning controls for the “dry” signal as well. Letting all these ideas stew in my brain led me to come up with the Triplicator.
How It Works
The Triplicator consists of a single effects loop with level and pan controls in parallel with what are essentially two of my Stalker circuits with added effects loops and panning. The circuit is large, but not overly complex.
The first stage of the Triplicator is an input buffer/splitter. This is a non-inverting opamp stage. The signal “Dry” goes to the input to each of the delay stages while the D_S solder pad is the effects loop send pad for the dry/direct signal.
Triplicator Input Stage
The return from the effects loop goes through the volume control first, followed by the panning control. This control topology comes from R.G. Keen's “Panning for Fun” article. I changed resistor values so that I could use a W20k potentiometer, as I found a linear potentiometer bunched the panning effect at the two extremes quite a lot. A W taper pot is designed specifically to deal with that and it makes the control much more responsive. You can use a B taper in a pinch, but I highly recommend the W taper. They are available at Tayda, StompBoxParts.com, and other places. The output from the pan control goes to the inputs of the left and right summing amplifiers (more on those later).
Triplicator Direct Signal Volume and Pan Controls
Each delay stage is identical and is based around the ES56033. The circuit could be designed around the more commonly available PT2399, but the ES56033 was chosen because it has a minimum delay time of 14 ms as opposed to the 28 ms of the PT2399. The setup of this stage is essentially a copy/paste of the Stalker. I may have tweaked the values of a couple resistors or capacitors to slightly change the corner frequencies of the multi-feedback low pass filters on both input and output of the chip, but the architecture is the same.
Triplicator Delay Stage
The output of the delay stage is then sent to it's effects loop out. Because there is no feedback control, the output opamp stage of the ES56033 serves to buffer the signal to the loop. The return of the loop then goes to pads for the footswitch that controls whether the delayed signal is summed into the output signal or not. I actually have solder pads that will ground each stage's effects loop return to disable that voice, if desired. The volume and pan controls are identical to that of the dry/direct signal and they sum into the output signal in the same way.
Triplicator Delay Loop, Volume, and Pan Controls
Each delay stage also has modulation. The topology is that of a relaxation-mode LFO feeding a current sink to modulate the ES56033's delay time. Because of the internal VCO compensation of the ES56033, a current sink must be used instead of directly varying the voltage on the F_adj pins. Note that we don't have to change the current being sinked by the VCO very much, as evident by looking at the resistor values in the Pitch control section. These values won't give wild oscillation; they are intended just to give some slight modulation to the pitch to further help with the double tracking effect by slightly detuning each voice. The speed is set by a trim potentiometer, as I didn't have space for more pots, and because it's meant to be very subtle, I set one to be very slow and one to be less slow, but not fast. This results in a more gradual detuning effect with longer time before the LFO voltage changes slope.
Triplicator LFO
The outputs from each of the loop/volume/pan circuits are then summed into the stereo outs using a bog-standard inverting summing amplifier. These have some added gain to make up for the signal loss in the pan controls so that the panning doesn't cause weird volume increases or drops throughout its sweep.
Triplicator Output Summing Amplifiers
The power section is the last part of the circuit. It's pretty basic with a 5V regulator for the ES56033 chips and a buffered Vref to utilize the last opamp stage and to provide a stable reference voltage. The plethora of ground pads are for the normal connections as well as the plethora of jacks for the effects loops. Note that, due to the current draw of the ES56033 chips, a TO-220 package LM7805 regulator should be used rather than the TO-92 sized 78L05 for heat dissipation purposes.
Triplicator Power Section
I'm not going to lie, the Triplicator is a bit of a beast to build, with the jack wiring alone taking quite a while. However, it's a really fun effect and totally worth it if you want some double tracking with each voice having its own effects. Give it a shot! You can find everything you need for it here.