The Yellowcake Pedals Psychotropia Sample/Hold Filter is a modulation pedal built around a sample/hold circuit, the kind of random voltage generator more often found in synthesizers than on a pedalboard. Pedal of the Day described it as "a bright, powerful modulation machine," combining "elements of tremolo, vibrato, looper, sampler, pitch shifter and more" in one box1. For a player, that means rhythmic, unpredictable filter movement that sits somewhere between a tremolo, a vibrato and a synth style effect, rather than the swept filter of a wah.
Controls and toggles
The pedal keeps its front panel compact: knobs for Rate, Glide and Level, plus three toggles, each shaping a different part of the sample/hold waveform. The Rate knob controls the sample/hold's speed, Glide sets the amount of Up & Down slide for the sample/hold waveform, and Level controls the overall output volume1.
| Control | What it does |
|---|---|
| Rate knob | Controls the sample/hold's speed1 |
| Glide knob | Sets the amount of up and down slide for the sample/hold waveform1 |
| Level knob | Controls the overall output volume1 |
| Left toggle (waveform) | Up gives a rising edge, Middle gives both a rising and a falling edge, Down gives a strictly falling edge1 |
| Middle toggle (shape) | Logarithmic rounds and softens the edges of the waveform; Linear gives the more traditional waveform1 |
| Final toggle (Hi/Lo) | Hi and Lo settings act as EQ treble and bass cuts, depending where they are set1 |
The Glide knob is the one that gives the Psychotropia its name on the demo circuit: it controls how the filtered tone slides between the random steps the sample/hold circuit generates, from abrupt jumps to long slides1.
CV in and out
Unusually for a guitar pedal, the Psychotropia works both ways as a control voltage device1:
- CV In accepts other control voltage modules, so external gear can drive the pedal's modulation1
- CV Out sends the Rate and Glide knob functions, along with the Up, Mid, Down and Lin/Log toggle settings, to other CV-equipped modules1
That makes the pedal usable as a modulation source in a larger CV setup, not just as a stand-alone effect1.
What reviewers said
Pedal of the Day's review was enthusiastic. The reviewer wrote that the pedal "produces sounds that seemingly come from the vast reaches of another galaxy, far far away," and that it "falls nothing short of amazing" overall1. The same review noted the pedal's neon pink enclosure, saying "there's a lot to explore in this neon pink gem"1.
Videos
Premier Guitar
Eirik Stordrange
Eric Merrow
Questions
What does the Glide knob do on the Psychotropia?
The Glide knob sets the amount of up and down slide for the sample/hold waveform. In other words, it controls how far the filtered pitch glides between the random voltage steps the sample/hold circuit generates, from sharp stepped jumps to smooth slides between them. Its function is also sent out of the pedal's CV Out jack, so the glide behavior can drive other control voltage modules.
What do the three waveform positions on the Psychotropia do?
The left toggle selects the waveform edge. In the Up position you get a rising edge, in the Middle position you get both a rising and a falling edge, and in the Down position you get a strictly falling edge. These choices shape how the sample/hold waveform moves, and the setting is also passed to the CV Out jack.
Does the Yellowcake Psychotropia have CV connections?
Yes. The CV In jack accepts other control voltage modules, so external gear can drive the pedal's modulation. The CV Out jack sends the Rate and Glide knob functions along with the Up, Mid, Down and Lin/Log toggle settings, letting the Psychotropia act as a control source for other CV-equipped modules.
What is the difference between Linear and Logarithmic on the Psychotropia?
The middle toggle chooses between two waveform shapes. Logarithmic rounds and softens the edges of the waveform, giving a gentler movement, while Linear gives the more traditional waveform shape with harder edges. The choice affects both the sound of the modulation and the signal sent from the CV Out jack.
What did the Lida Machine have to do with the Psychotropia?
The Lida Machine was Yellowcake Pedals' earlier resonant filter pedal, shown at Summer NAMM 2017 and demonstrated in videos by the Knobs channel. The Psychotropia followed it as the company's sample/hold filter, first noticed at Summer NAMM 2019 and launched in August 2019.
Sources (1)
- Yellowcake Pedals Psychotropia Sample/Hold Filter, Pedal of the Day, 2020-08-01