4 layers65 × 100 mm
Audcalc
sinitsinmike/Audcalc2
I'm happy with this, but its not 100% feature complete on the firmware side. Its really neat though, and I think you'll like it.
218 partsMIT
4 layers65 × 100 mm
Audcalc
jonbro/Audcalc62pocket sized groovebox
- Size
- 65 × 100 mm
- Copper layers
- 4
- Thickness
- 1.6 mm
- Parts
- 218
- Nets
- 222
- Pads
- 722
- Tracks, vias
- 2,116, 316
- Pours
- 1
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 29 Dec 2019
- Updated
- 4 Oct 2026
Overview
Audcalc is an open-source printed circuit board by jonbro, from the jonbro/Audcalc repository on GitHub, published under the MIT licence. It is a 4-layer board of 65 × 100 mm with 218 parts on 222 nets, routed with 2,116 tracks and 316 vias.
It is built around the RP2040, W25Q32JVSSIQ and HCPL-0631, with the MCP73831T-2ATI/OT-HXY, BAT54C and DMG2305UX-13 among its other parts. Its parts include 66 capacitors, 52 diodes, 35 resistors, 27 switches and 9 ICs. It belongs with the RP2040 boards of this library.
Main components
6
RP2040
LQFN-56(7x7)12bit 133MHz 30 LQFN-56(7x7) Microcontrollers (MCU/MPU/SOC) ROHSRaspberry PiMicrocontrollers (MCU/MPU/SOC)
W25Q32JVSSIQ
SOIC-8-208mil-40℃~+85℃ 100,000 cycles 133MHz 1uA 2.7V~3.6V 20 Years 32Mbit 3ms SPI SOIC-8-208mil NOR FLASH ROHSWinbondNOR FLASH
HCPL-0631
SOT-ALL-8-40℃~+85℃ 1.5V 15kV/us 2 3.75kV 4.5V~5.5V 5mA 75ns 75ns DC Output enable control、Open-collector output SOT-ALL-8 Logic Output OptoisolatorsBroadcom LimitedLogic Output Optoisolators
MCP73831T-2ATI/OT-HXY
SOT-23-5LBattery ManagementHXY MOSFET
BAT54C
SOT-231 Pair Common Cathode 200mA 2uA@25V 30V 600mA 800mV@100mA SOT-23 Schottky Diodes ROHSNexperiaSchottky DiodesDMG2305UX-13
SOT-23-55℃~+150℃ 1 P-Channel 1.4W 10.2nC@4.5V 20V 40mΩ@4.5V、52mΩ@2.5V 5A 77pF 808pF 85pF 900mV P-Channel SOT-23 MOSFETs ROHSDiodes IncorporatedMOSFETs
README
README.mdAudCalc
AudCalc is a portable synthesizer and sequencer.
It has 8 voices which can switch between synthesis (using Mutable Instruments Braids cores) and sampling. The sequencer supports parameter locks, conditional triggers, and various time signatures and loop lengths. There are also two built in effects sends for building a full track. It's fun to jam with by itself, and can link into your larger portable music setup via midi or cv clock.
Website | Manual | Shop | Contact
Specifications
Synthesizer
- Many different oscillators from MI Braids
- 2 assignable AD envelopes
- Lowpass filter
- Volume, pan, legato, finetune
- 2 effects sends (delay & reverb)
- Assignable LFO
- Simple sampler (sampling via line in or onboard mic)
- 16 patches, 8 simultaneous monophonic voices
Sequencer
- 16 patterns, with assignable lengths from 1-64 steps
- 4096 pattern lock locations for overriding synthesizer settings per step
- Each of the 16 patches can run at 2x-1/8 bpm rate, with some fun subdivisions
- Conditional triggers
- Pattern chaining
- Step ratcheting / retriggers
Hardware
- RP2040 core
- 1000mAh rechargeable and replaceable battery, USB-C charging
- TRS midi in/out, audio in/out (3.5mm TRS), USB midi
- 100x65x25mm - approximately the size of a cassette tape box + knob height
- Body made with FDM black PLA, buttons with FDM translucent TPU
- FR4 (circuitboard) faceplate
- OLED display
Building one
The BOM is contained within the Hardware KiCad project, ready for assembly via JLCPCB. There are several additional items that must be sourced and assembled:
| part | count | mfg part number | link | notes |
|---|---|---|---|---|
| oled screen (128x32) | 1 | ssd1306 | https://www.aliexpress.com/item/4000842671330.html | I'm using the white / solderable version. |
| battery (50x34x5mm, ~1000mAh) | 1 | 503450 | search for "503450" with a JST-PH connector | Widely available from many vendors. Confirm the correct polarity before using. |
| m2 4mm f-f standoff | 4 | https://www.aliexpress.com/item/1005002145042844.html | ||
| m2 6mm m-f standoff | 4 | https://www.aliexpress.com/item/1005002145042844.html | ||
| m2 3mm hex head bolt (black) | 8 | https://www.aliexpress.com/item/10000148429238.html |
Parts
218| Qty | Value | Footprint | References |
|---|---|---|---|
| 29 | 1u | MyLibrary:C_0402_1005Metric | C1, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19, C20, C21, C22, C23, C24 +13 |
| 25 | spst_4_pin_internal | MyLibrary:ts1187 | SW1, SW2, SW10, SW11, SW12, SW13, SW14, SW15, SW16, SW17, SW18, SW19, SW20, SW21, SW22, SW23 +9 |
| 24 | D | RandomJunk:D_SOD-323F_less_silk | D27, D28, D29, D30, D31, D32, D33, D34, D35, D36, D37, D38, D39, D40, D41, D42 +8 |
| 20 | WS2812C-v1 | RandomJunk:ws2812b-2020-lightpipe | D10, D11, D12, D13, D14, D15, D16, D17, D18, D19, D20, D21, D22, D23, D24, D25 +4 |
| 14 | 100n | MyLibrary:C_0402_1005Metric | C2, C3, C5, C26, C27, C28, C29, C30, C31, C32, C34, C40, C60, C62 |
| 11 | 10u | MyLibrary:C_0402_1005Metric | C4, C36, C38, C42, C43, C46, C50, C55, C56, C57, C61 |
| 7 | SolderJumper_2_Bridged | Jumper:SolderJumper-2_P1.3mm_Bridged_Pad1.0x1.5mm | JP3, JP4, JP5, JP6, JP7, JP8, JP14 |
| 5 | 10k | MyLibrary:R_0402_1005Metric_nosilk | R3, R9, R14, R24, R30 |
| 4 | .47u | RandomJunk:C_0603_nosilk | C39, C44, C45, C47 |
| 4 | 1k | MyLibrary:R_0402_1005Metric_nosilk | R6, R7, R17, R31 |
| 4 | D_Zener | Diode_SMD:D_SOD-323F | D3, D4, D5, D26 |
| 4 | MountingHole | Mounting_Holes:MountingHole_2.2mm_M2 | H1, H2, H3, H4 |
| 3 | 100k | MyLibrary:R_0402_1005Metric_nosilk | R8, R18, R25 |
| 3 | 220 | MyLibrary:R_0402_1005Metric_nosilk | R10, R11, R21 |
| 3 | 33 | MyLibrary:R_0402_1005Metric_nosilk | R12, R34, R35 |
| 3 | 5.1k | MyLibrary:R_0402_1005Metric_nosilk | R19, R20, R23 |
| 2 | 100 | Resistor_SMD:R_0402_1005Metric | R32, R33 |
| 2 | 1m | MyLibrary:R_0402_1005Metric_nosilk | R27, R28 |
| 2 | 27.4 | MyLibrary:R_0402_1005Metric_nosilk | R1, R2 |
| 2 | 3.3k | MyLibrary:R_0402_1005Metric_nosilk | R4, R5 |
| 2 | 30p | MyLibrary:C_0402_1005Metric | C35, C37 |
| 2 | 330 | MyLibrary:R_0402_1005Metric_nosilk | R22, R26 |
| 2 | 47uf | Capacitors_SMD:C_1206 | C48, C49 |
| 2 | ME6211C | TO_SOT_Packages_SMD:SOT-23-5 | U9, U11 |
| 2 | Q_NMOS_GSD | TO_SOT_Packages_SMD:SOT-23 | Q3, Q4 |
| 2 | R_POT_US | Potentiometers:Potentiometer_Alps_RK09K_Horizontal | RV1, RV2 |
| 2 | SolderJumper_2_Open | Jumper:SolderJumper-2_P1.3mm_Open_RoundedPad1.0x1.5mm | JP1, JP2 |
| 2 | spst_4_pin_internal_side | MyLibrary:SKSCLDE010 | SW26, SW27 |
| 1 | 10 | MyLibrary:R_0402_1005Metric_nosilk | R13 |
| 1 | 100u | Capacitor_Tantalum_SMD:CP_EIA-3528-21_Kemet-B | C65 |
| 1 | 10n | MyLibrary:C_0402_1005Metric | C59 |
| 1 | 10u(tant) | Capacitors_Tantalum_SMD:CP_Tantalum_Case-A_EIA-3216-18_Reflow | C58 |
| 1 | 128x32OLED | MyLibrary:oled_ssd1306_14pin_91 | LCD1 |
| 1 | 2u2 | MyLibrary:C_0402_1005Metric | C66 |
| 1 | 330k | MyLibrary:R_0402_1005Metric_nosilk | R15 |
| 1 | 4.7k | MyLibrary:R_0402_1005Metric_nosilk | R16 |
| 1 | 750k | RandomJunk:C_0603_nosilk | R29 |
| 1 | BAT54C | TO_SOT_Packages_SMD:SOT-23 | D1 |
| 1 | Conn_01x02_Female | Connector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_Vertical | J8 |
| 1 | Crystal_GND24 | Crystals:Crystal_SMD_3225-4pin_3.2x2.5mm | Y1 |
| 1 | DMG2305UX-13 | digikey-footprints:SOT-23-3 | Q1 |
| 1 | D_Schottky | Diodes_SMD:D_SMA | D53 |
| 1 | HCPL-0631 | Package_SO:SOIC-8_3.9x4.9mm_P1.27mm | U5 |
| 1 | LED | LEDs:LED_0603 | D54 |
| 1 | LEDYellow | LEDs:LED_0603 | D2 |
| 1 | LM4040DBZ-2.5 | Package_TO_SOT_SMD:SOT-23 | U7 |
| 1 | MCP73831T-2ATI_OT | TO_SOT_Packages_SMD:SOT-23-5 | U6 |
| 1 | Q_PMOS_GSD | TO_SOT_Packages_SMD:SOT-23 | Q2 |
| 1 | RP2040 | MCU_RaspberryPi_and_Boards:RP2040-QFN-56 | U2 |
| 1 | TLV320AIC3204 | Housings_DFN_QFN:QFN-32-1EP_5x5mm_Pitch0.5mm | U3 |
| 1 | USB_C_Receptacle_USB2.0 | RandomJunk:USB-C_SMD-TYPE-C-31-M-12 | J2 |
| 1 | W25Q32JVSS | Housings_SOIC:SOIJ-8_5.3x5.3mm_Pitch1.27mm | U1 |
| 1 | WMM7037AT2_mic | MyLibrary:LGA-4 (3x3.8) | U4 |
| 1 | battery | Connectors_JST:JST_PH_S2B-PH-SM4-TB_02x2.00mm_Angled | J7 |
| 1 | headphone_out | RandomJunk:HRO-PJ-327C-A | J4 |
| 1 | line_in | RandomJunk:HRO-PJ-327C-A | J3 |
| 1 | midi_in | RandomJunk:HRO-PJ-327C-A | J5 |
| 1 | midi_out | RandomJunk:HRO-PJ-327C-A | J6 |
| 1 | picoprobe_debug | RandomJunk:pico debug header | J1 |
Questions
How big is the Audcalc PCB?
It measures 65 × 100 mm and has 4 copper layers, 1.6 mm thick.
What parts does the Audcalc use?
218 parts, built around the RP2040, W25Q32JVSSIQ, HCPL-0631 and MCP73831T-2ATI/OT-HXY. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Audcalc KiCad files?
From the jonbro/Audcalc repository on GitHub, at the commit this page was made from: the board is Hardware/audcalc/audcalc.kicad_pcb and its schematic Hardware/audcalc/ButtonsLEDS.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Audcalc design in my own project?
Its repository publishes it under the MIT licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).
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