MP EffecTor 16in1 Guitar, Bass, Vocal and Instruments High Definition Stereo Effect

The idea for this project arose as a desire to connect several open source groups around the world in order to achieve the best results without any commercialization in the background. In this way, I want to share my many years of experience in designing electronic circuits and printed circuit boards and connect with open source communities working in these areas. This is specifically about a community of non-profit enthusiasts gathered around the programmable audio DSP (Digital Signal Processing) chip FV-1 from Spin Semiconductor and this one, OSHWLab/EasyEDA community.

MP Effector is High definition audio project made around FV1 Spin semi chip. Effector is both stereo in and stereo out effect. It contains 8 built in effects and additional 8 in EEPROM you may download freely from chip producer or related forum sites. RP 2040 has been used as support to the FV1 to shift effects, work with EEPROM, live monitor on OLED and run true bypass gears. There are lot of programing and uploading, both in audio effects way and in RP2040 Zero support.

SCHEMATICS

The MP effector schematic consists of 3 main parts, one analogue for signal mixing and shaping for digital processing and two digital, FV-1 DSP (Digital Signal Processor) and RP 2040 Zero as support for smart use of DSP. The analog part of the audio signal flow consists of two double low noise operational amplifiers LM833, and NE5532 or low distortion OPA1678 that can be used. The mentioned operational amplifiers work well at 5V via the USB port on the RP 2040 Zero and there is no need for a standard 9V power supply for the pedals. Dual operational amplifiers that are not listed may not allow smooth operation at 5V due to problems with signal distortion and headroom, but will work well on the standard 9V (TL072, TL062, JRC4558…).

The audio signal at the input and output is stereo, in order to make the most of the capabilities of the FV-1 chip, and it can be short-circuited, at the input or output, for use in mono mode. For that, I recommend the use of already prepared Stereo to Mono, Mono to Stereo (it is same just rotate it J or Y 1/4 inch audio cables. Mono cable will grounded one of channels on input or output and mitigate capabilities of FV-1 which will work just with one channel (grounding one input and/or output does not affect the functionality of the chip and if that suits you, feel free to keep that setting).

Pay attention that all pots, rotary encoder, OLED display and LEDs have to be soldered from the back side of PCB to apear properly on the front panel :)

You may replace rotary encoder with ON-OFF-ON toggle momentary switch and you may roll up and down effects from internal and external memory, or even ad two separate momentary footswitches as for true bypass (code support both of changes), just what you have to do is to edit drill holes on enclosures and front panel or drill it manually.

MP EffecTor acting as development board and allows you to develop custom programs or/and upload open source effects freely on the following address (MP EffecTor 16in1 allows to be updated with new 1 to 8 externall effects in soldered EEPROM via pins I have left for this purpose on the far bottom of the PCB (SCK, SDA, GND and 3V3) when conect all 4 pins with belonged programmer you do not need additional power supply).

https://mstratman.github.io/fv1-programs/

This repository contains a collection of programs (or patches) for the Spin Semiconductor FV-1 IC. The goal is to be an open, community-driven resource containing the most comprehensive list programs for DIY guitar pedal builders.

https://github.com/mstratman/fv1-programs

PROGRAMING AND SOURCE CODE

The only code you need to operate with internal FV-1 effects is MP EffecTor INO file included in download section. By uploading it on RP2040 Zero you will be able to shift all 16 effects (first 8 are internal), live monitor pots position, effects names and order numbers, memorize desired effect for quick shift by short press or rotary encoder (long press is for memorize desired one, turn on with last memorized effect). For uploading I use latest version of Arduino IDE (to mention again, all software, codes, and lot of effect banks are free to use) installed on PC, USB A to USB C cable. To install it properly, with needed drivers and libraries, find tutorials on official Arduino, Spin Semi FV-1 and GitHub pages.

For uploading another 8 effects in 24LC32 EEPROM chip you need USB EEPROM programmer such as a CH341A (cheap/common), or an Arduino used as a programmer. 24LC32 EEPROM chip may be uploaded with effects soldered on PCB by using 4 pins on the bottom of the PCB (SDA, SCL, 3V3 and GND) to prepare all for uploading operations find detailed tutorials on official Arduino, Spin Semi FV-1 and GitHub pages.

As for enclosure box production I have projected two types for this project. Stainless steel and Aluminum one from existing K343 box, both have been produced by JLCMC and JLCCNC departments after sending proper STEP files (both are includedin attachment section) Production are have been finished after few coordinations, with kind support guys in few days literally. Both are in similar price range of about 10$ per piece on amount of 3 or 4 pieces, but take care about weight of steel enclosure which is twice as heavier than aluminum one and has direct impact on shipping costs :)

I have projected both STEP files by using Autodesk Fusion 360 for non comercial use (free edition). Guys from both JLC departmen have been produced enclosures fully according to STEP files.

You may find all needed production files in download/attacment section of this project, STEP files for enclosures, Gerber files for PCB and front panel, Source code for RP2040 Zero, and HEX effect files. All are free to personal use. For comertial use, contact MP Custom FX.

Whole project has been hand soldered and SMT format is 0805 mostly. If it is as complex to you, may order stencil and bake it :)

My methodology based on experience in projecting guitar effect pedals is not to put everything on the PCB, especially Footswitches and audio and power supply jacks for two reasons. 

1. Thermal stress and
2. Mechanical vibration stress

Those two stresses are very intense during daily operation outdoor and indoor (for example Christmas gigs :) and cause miss function by cold soldering or break. If you obey this rule it will ensure longevity of the gear.

Also, if you force yourself to practice skilled hand soldering in your projects, there will be significantly less thermal stress on components, up to 50 times if you solder one SMD pin in 1 second, comparing to hundred times more overheating in ovens :) 

MP EffecTor videos:

https://vt.tiktok.com/ZSC83oBEA/

https://youtube.com/shorts/S263u3wkobM?si=udxyDV7WqIGEL5YU

https://youtube.com/shorts/2Sz2SWD1xD0?si=mPylBxpzIHjfcLOd

https://youtu.be/FviNRZzD93M

https://youtube.com/shorts/m3V88SqH_QY

https://youtube.com/shorts/g1sgVUFFze0

https://youtube.com/shorts/72_bzrXsQd8