exclus. Mesh flash is a handmade instrument based on a self-developed noise-generator circuit. The circuit design itself takes a circuit-bending approach to an IC manufactured for creating "echo" effects to Karaoke machine microphones (PT2399). Physically, the circuit is assembled Manhattan-style with salvaged copper clad pieces of FR-4. It is housed in an enclosure consisting of parts salvaged from factory scrap piles and electronic waste collection points. The materials include steel from a desktop computer tower and an unidentified device; transparent, translucent, and mirrored acrylic; and plywood. Conceptually, the instrument's design is guided by ideas such as partial visibility, unstable legibility, and latent attributes. Transparent, reflective, perforated, and exposed structures reveal internal relationships incompletely, shifting with use, lighting conditions, interaction, and viewing angle.
Bending the PT2399: Developing the circuit design for exclus. Mesh flash
This circuit started with a combination of influences: another instrument had just been finished for a friend who wanted something to make noise music with. exclus. Mesh flash was made with the goals of taking the circuit-bending-informed experimental approach to circuit design involved with the CD4093 and developing them further by applying it to another IC. Another goal was to generate noise in a less convoluted way than what was done with the CD4093 (essentially cross modulating square waves to such a degree that noise could be generated), and create a circuit that had more ability to shape noise. The PT2399 was appealing because there were pre-existing circuit designs developed for plain noise generation, and as an audio processing IC, the PT2399 is a very different IC than the CD4093.
Circuit One:
The first stage of design involved breadboarding up 3 different designs and evaluating which would be the best fit. The first design came from Carlos (a.k.a. [ominous noise] on Bandcamp and TikTok[INSERT SOURCE]) with whom a lot of shared designs and discussions were passed back and forth. Carlos published a tutorial video based on the first design[INSERT SOURCE], and shared the schematic (see below)
However, when this design was prototyped on a breadboard, it put out a very low amplitude signal (tested in a bass amp and through headphones), and a large amount of the signal produced was ground hum, particularly when rotating the second pot (seen on the right in the schematic). Carlos was using a different amplifier set up in his version and mentioned that it's possible the signal was low when testing and just might not have noticed. However, the ground hum sound was not present for Carlos, and the difference in results between our two versions was never fully identified.
Circuit Two:
The second schematic tested was posted by spectreman on diystompboxes.com[INSERT SOURCE LATER], with the schematic design attributed to Polish artist Ewa Justka [INSERT SOURCE].
This design didn't create continuous noise, but pulses of noise separated by silence. However, because the pot is associated with speed (pulse rate + pitch), on the faster end of its range, audibly continuous noise can be generated. The original design recommends 1M for the pot, and 2k seemed to achieve continuous noise. Another note was that the texture of the noise seemed to vary each time the circuit was powered on.
Circuit Three:
The third circuit was originally posted on r/synthdiy by user wraadefects, described as a "white" noise generator.
Comparisons with the other two circuits: This circuit produced much more smooth noise than the first or second circuit, and the high pass filter seemed to provide a lot of interesting performance possibilities. It also notably generates noise quite differently than the first and second circuit, mainly from the REF (pin 2), and therefore provides a very different sounding type of noise from the previous circuits. The HPF pot also provides a more steady performance interaction experience than the first circuit. While Carlos' build of the first circuit provided more varied textural possibilities overall, this third circuit seemed free of the (less unique) ground hum sounds that were present in my build of that first circuit. However, particularly because of the exciting sounds from Carlos' build, the first and third circuit had the best fit for the "noise generator" description of the designs. Whereas the second circuit seemed to be more obviously tied to the PT2399's delay functions.
Initial Circuit Three extensions and bends: After breadboarding this circuit design, some bends were explored which revealed that:
a.) shorting pin 6 to pin 15 adds a squelching sound.
b.) similarly, shorting pin 6 to either pins 16, 14, or 13 also produced different distortions and textures.
c.) From Carlos' original circuit, 0.1uF caps were added between pins 9 and 10, 11 and 12, and 7 and ground.
d.) Again, from Carlos' original circuit another 50k pot was added between pins 6 and 4 (in series with a 4.7k minimum resistor to pin 6).
Of the capacitors added, the one between 11 and 12 seemed to limit the performability of the 50k pot. The one between 9 and 10 seemed to limit this even more so. However, the one between 7 and GND seemed to exaggerate this perfomability.
Emerging design for exlus. Mesh flash:
Additional circuit-bending, and exploring further hybridization of Circuit One and Circuit Three significantly developed the design of the circuit into increasingly non-linear behavior. This included:
~A touch point on pin 16
~0.1uF capacitors between pins 1 and 3, and 7 and GND.
~The 0.1uF capacitor between pins 9 and 10 were also added back in, but with a 100k pot placed in series between the capacitor and pin 10. Pin 6 was also connected between the capacitor and the potentiometer via a momentary switch (normally open) at first, though this switch was later removed.
~More momentary switches were also added between pins 6 and 14, as well as pins 6 and 15.
~A 2k potentiometer was added between the audio out and pin 6.
Reflection
What I find most compelling about these non-linear zones is how quintessentially circuit-bent they feel. They are, in a sense, the "hidden voice" of the PSS-30 — operating far beyond the smooth, linear behavior of the unmodified keyboard. Through circuit-bending, these zones aren't artificially imposed; they are revealed. My approach to any circuit-bending project is shaped by a philosophy that values listening, responsiveness, and attention to emergent behaviors. Coming into this project with that perspective guided what to listen for and how to design toward building a relationship with this particular device.
In my view, circuit-bending is not about coercion or forcing the device into unconventional states. It is about fostering conditions where the instrument can express itself and collaborate. The noises, textures, and unexpected rhythms that emerge are part of the PSS-30's language — non-verbal, inherently expressive, and alive.
References
1 Christian Oliver Windler. Yamaha PSS-30, PSS-130 (small squarewave keyboard with unusual percussion) Warranty Void, c. 2007 (archived).
http://weltenschule.de/TableHooters/Yamaha_PSS-30.html
Provides a detailed breakdown of the PSS-30, including analysis of its design and history. The site itself serves as a valuable archive of instruments commonly used in circuit-bending.
2 alex. Analog Relics. Yamaha PSS-120 / PSS-130 Circuit Bending. circuit-bent.net, January 9, 2020.
https://circuit-bent.net/yamaha-pss/analog-relics-yamaha-pss-120-pss-130.html
Write up including documenting the PSS-120, and provides descriptions of the PSS-120 and PSS-130.
3 hippyjon, Orangery, and boneless. yamaha pss 30. circuitbenders.co.uk forum, November 23, 2006 – May 17, 2011.
https://www.circuitbenders.co.uk/forum/index.php?topic=268.0
Community discussion of PSS-30 circuit-bending experiments. Documents shared observations about the instrument’s behavior and perceived limitations.
4 Forrest Galvin. UH YEAR. NOYSTOISE, January 16, 2012.
https://www.noystoise.com/2012/01/uh-year.html
A detailed project write-up documenting an extensive modification of a Yamaha PSS-30 keyboard. Includes significant added circuitry such as a sequencer, filters, CV integration, and a complete rebuild in a new chassis, demonstrating a highly expanded approach to circuit-bending.
5 darklife. Circuit Bent, or synth?.. Yamaha PSS-130. Electro-Music.com Forum, May 20, 2018.
https://electro-music.com/forum/topic-69989.html
A forum post detailing a PSS-130 circuit-bending project with a step sequencer modification. Includes build photos and schematic drawings, illustrating inventive approaches to expanding the functionality of the keyboard.
6 kagemichaels. My overkill circuit bent Yamaha PSS-130. Reddit (r/CircuitBending), c. 2016–2017
https://www.reddit.com/r/CircuitBending/comments/8jz5df/my_overkill_circuit_bent_yamaha_pss130/
Detailed PSS-130 circuit-bending project; overlaps content with Electro-Music forum post (5) by the same author (there using the username "darklife").
7 explodedsun, OneEyedPlankton, and DevanWolf. I'm having trouble finding a datasheet for IC YM2410. Reddit (r/AskElectronics), January 9, 2013.
https://www.reddit.com/r/AskElectronics/comments/1ccpm0/im_having_trouble_finding_a_datasheet_for_ic/
Community discussion about locating YM2410 datasheet information.
8 Yamaha Corporation. YM2413 Datasheet. n.d.
https://www.waveguide.se/?article=46&file=ym2413ds.pdf
Datasheet for YM2413, a possible YM2410 replacement.
9 Yamaha Corporation. Yamaha PSS-130 Service Manual. n.d.
https://static.wikitide.net/circuitbendingwiki/d/d4/Yamaha_PSS-130_Service_Manual.pdf
Official PSS-130 service manual; lacks YM2410 pinout info.
10 Sam Vs. Sound. LM386 Modifications – Yamaha PSS-30 May 10, 2017.
https://static.wikitide.net/circuitbendingwiki/d/d4/Yamaha_PSS-130_Service_Manual.pdf
Guide to LM386-based modifications including overdrive and bass boost.
11 Soundquist. Circuit Bent PSS-130. MATRIXSYNTH, July 23, 2014.
https://www.matrixsynth.com/2014/07/circuit-bent-pss-130-by-soundquist.html
Listing and images for a circuit-bent PSS-130.
12 Squidfanny. Circuit Bent YAMAHA PSS-30. MATRIXSYNTH, May 11, 2010.
https://www.matrixsynth.com/2010/05/squidfanny-circuit-bent-yamaha-pss-30.html
Listing and images for a circuit-bent PSS-30.
13 mad_marbled et al. The Yamaha PSS-30 my 1st successfully bent keyboard. Reddit (r/CircuitBending), October 2016.
https://www.reddit.com/r/CircuitBending/comments/7cm0vh/the_yamaha_pss30_my_1st_successfully_bent_keyboard/
Discussion of multiple PSS-30 bending projects.
14 Sam Vs. Sound. Tone Control and Line Out – Yamaha PSS-30.May 24, 2017.
https://samvssound.com/2017/05/04/tone-control-line-yamaha-pss-30/
Guide on tone control modifications for PSS-30.
15 darklifeimages. Yamaha PSS-130 Circuit Bend / Synth. Imgur, May 17, 2017.
https://imgur.com/a/yamaha-pss-130-circuit-bend-synth-by-kage-2018-UXI61hZ
Album of photos showing a PSS-130 circuit-bending project including schematics. Same author and project as (5),(6).
