TRIP

The TRIP project is the second part of the RadioShack Musical Elephant Keyboard(see PAL). 

The TRIP is an experimental drum machine made from a dual-voice drum chip. The drum chip has 8 pre-programmed rhythms. Only the sound chip was used for this mod. The rest of the circuit and enclosure are built from scratch.

FEATURES

-Global Pitch modulation

-8 preprogrammed rhythms with start/stop, and tempo-up/down

-Two drum voices; "TONE" and "NOISE"

-Two independent Envelope generators(one per voice)

-Two independent resonant Filters(one per voice)

-Two independent VCA's(one per voice)

-PT2399 Echo circuit with two independent mix knobs(one per voice)

-Dual 8-step analog Sequencer with reversing clock inputs

-VARI SYNC variable Sequencer Clock

-ARG Attack/Release Generator

-8 Roll/Flam EG trigger inputs

-8 input multi-use capacitive-touch keys

PITCH

The PITCH knob changes the global pitch of the TRIP. It will change the pitch of both voices, as well as the Tempo of the Rhythm being played. The Pitch can be modulated by SEQ1, SEQ2 or the ARG with the modulation slide switch above the PITCH knob.

RHYTHMS

There are eight push switches to select the current Rhythm to play, as well as two switches for tempo Up and Down, and a Start/Stop switch.

VOICES

The TONE voice is a basic square-wave. The NOISE voice is a pseudo-noise square-wave with harmonic undertones. The Global Pitch sets the approximate note fore both voices.

ENVELOPES

Each Voice has its own Envelope Generator with DECAY and DEPTH controls. The envelopes are triggered independently, or by the ROLL input. Each envelope's Decay can be modulated by SEQ1, SEQ2, or the ARG with the modulation input switch above the DECAY knob. The Decay of the envelopes can also be modulated by external 0-5 volt CV inputs with the 3.5mm DEC1/2 CV INPUT jacks on the back side.

FILTERS

Each voice has a Resonant 12db Lowpass Filter with Cutoff and Resonance knobs. The filters' Cutoff can be modulated with their respective Envelope Generator, Sequencer, or the ARG with their respective modulation slide switch located above the respective RES knob.

VCA'S

The Voltage Controlled Amplifiers control how much of each voice is passed to the mixed signal going to the ECHO circuit. The VCA's can be modulated with their respective Envelope Generator, Sequencer, or the ARG with their respective modulation slide switch located above the respective VCA knob.

ECHO

The two voices are combined to one Dry signal that bypasses the PT2399 Echo circuit, while two independent Mix knobs, NOISE ECHO and TONE ECHO mix each voice's Wet signal into the Dry signal before being sent to the Master Volume. The Wet signals can be set to maximum momentarily with the use of the FULL switches(one per voice). The ECHO RATE knob controls how fast the Echo repeats, and the REGEN knob controls how many times the Echo repeats.

TOUCH-KEYS

The eight Capacitive Touch Switches at the front are used to control three different parameters of the TRIP. Each of the Touch Switches selects a different ROLL trigger multiplier that can be used to trigger either EG1 and EG2(see Roll). The switches can be used to manually select each Sequencers' step(see Sequencer). The switches also gate the ARG when any one is pressed(see ARG).

ROLL

Both EG1 and EG2 have their own ROLL switch that allows the envelope to be retriggered continuously by a set multiplied frequency of the Clock Sync input(see VARI SYNC). The frequency multiplier is determined by the capacitive touch key last pressed. The Depth of the Roll sent to the envelopes is determined by the ARG, giving the Roll a swelling effect at longer Attack and Release times. Depending on the Clock Sync input, the multiplied frequencies can be anything from slow sub-rhythms to hyper-flams to stuttering poly-rhythms.

SEQUENCER

The Dual Sequencer has a single bank of eight analog voltages. There is one knob for each of the eight steps. Any one of the eight steps can be selected independently by the respective voice's Sequencer control input. There are eight LEDs for each Sequencer to indicate what step each of the two Sequencers is on. The two Sequencers can be advanced by the respective SEQ CLOCK input switch. Both Sequencers can be clocked by VARI SYNC, NOISE+TONE envelope triggers, NOISE envelope triggers, or TONE envelope triggers. Each Sequencer has an UP/DOWN switch to change the direction the Sequencer advances through the 8-step CV bank. Each Sequencer also has their own REVERSE clock source that can be turned on or off. The Reverse Clock toggles the UP/DOWN direction of the Sequencer at the set rate of the respective Reverse Clock. An LED indicates the set direction. The two Sequencers' RUN switches activate the clock input when they are pressed down. In the up position, the respective Sequencer's step will be set by the last pressed touch key-switch, making it possible program each CV step one at a time, or play the Sequencer like a keypad. Each of the Sequencer's 0-5 volt analog outputs can be sent to external devices with the SEQ1/2 CV OUT 3.5mm jacks on the back side.

ARG

ARG simply stands for Attack Release Generator. It is gated by pressing any of the Capacitive Touch switches. There are knobs to control the Attack and Release times, and an LED that follows the shape. The ARG is hardwired to the Depth control of the ROLL function, but can also be used as a modulation source for other parameters. The 0-5 volt analog ARG signal can be sent to external devices with the "ARG CV OUT" 3.5mm jack on the back side. 

VARI-SYNC

The VARI SYNC clock, and the ROLL clock are derived from the CLOCK SYNC input switch. The switch can be set to "NOISE+TONE envelope triggers, NOISE envelope triggers,  TONE envelope triggers, or an External clock source from the 3.5mm CLOCK INPUT jack on the back side. The VARI SYNC clock has 12 settings that are controlled by the VARI SYNC slide-pot. The 12 settings are different divisions and multipliers of the input clock source. They are; 1/4, 1/2, 3/4, x1, x1.25, x1.5, x1.75, x2, x2.25, x2.5, x3, and x4. The VARI SYNC signal tracks and synchronizes to the CLOCK SYNC input whether the clock is consistent or not, and is capable of creating "broken" beat clocks to be used as clock sources for the Sequencers, or sent to external devices from the 3.5mm VARI OUT jack on the back side. The ROLL clock is separate from the VARI SYNC clock. 

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BUILD PROCESS

The enclosure dimensions of the TRIP are the same as the PAL. The goal for the TRIP was to create an experimental Drum Machine to accompany the PAL. The toy chip already had 8 rhythms with tempo controls and two basic square-wave voices that could be modulated separately. The TRIP could never be a fully functional Drum Machine due to its lack of programmability, synchronization, and voice count, so I decided to go in the direction of Drone-Machine. To make up for the lack of voice variety, I added the dual Sequencer with the intention of using them to modulate the two drum voices' Decay time, and/or global Pitch to not only simulate more drum sounds, but also chop up the toy-rhythm patterns to make them more interesting, albeit chaotic. The addition of the resonant filters give the voices a lot more punch, and give the sound a more "professional" quality. To further broaden the toy-rhythms' dynamics, I added the ROLL function to be able to swell in different low frequency clock signals to the Envelope triggers from multiples of the master Clock Sync input. Depending on the toy-rhythm, and the channel that the Clock Sync is set to, the ROLLs can be consistent multiples, or broken patterns of the different multipliers, but still in sync with the toy-rhythm. The swell time can be adjusted with a simple Attack/Release generator that is also gated by the capacitive touch switches that set the ROLL multiplier. The result is a rhythmic Drone-Machine, perfect for nostalgic IDM. 

The Dual Sequencer is borrowed from the PT100 design, but includes the UP/DOWN toggle clock inputs to make the sequences feel longer than they are. I still think using one bank of potentiometers for two separate sequencers is pretty brilliant, and I haven't seen it used anywhere else. Not that I have looked all that hard.. 

I also threw in a PT2399 ECHO circuit because why not? Putting Echo on percussive sounds is not nearly as satisfying as a smooth synth voice, but it adds dimension, and is fun to tweak in real-time. 

In the original Musical Elephant Keyboard, the Piano voice section and the Drum voice section never really sounded right together. Not that they should. It was just a cheap holiday toy after all. My goal was to create two instruments from the Piano voice chip and the Drum voice chip that could work together and compliment each other. In the end, the PAL and the TRIP still do not sound all that great together.. They have their moments, but it takes a bit of compromise. On its own, the TRIP is a fantastic Drone-Machine that is easy to get lost in for hours. That is why I called it the TRIP. That, and for the stumbling rhythms it creates when the Pitch is set to the Sequencers. 

The faceplate had a little extra space that I had no use for, so I decided to add a graphic above the speaker grill. I wanted the graphic to be something psychedelic to reflect the character of the instrument, but not so brazen as a pot leaf or a magic mushroom. I thought about drug molecule structures that look kind of cool and science-y, but thought it would be kind of dumb. In the end I went with the Datura flower from a Carlos Castaneda book I read last year, "The Teachings Of Don Juan"(thanks Dad). I don't use drugs anymore(I'm old..), but I thought it was kind of cool how these guys in this book were using these SUPER DEADLY-dangerous herbs to trip on. So I guess that it is kind of ambiguously symbolic is some way. And it is a flower!