Akashic Guitar effects PCB lookup
DELAYFEEDBACKLEVEL

125B · 3 knobs

Aion FX

AmethystAnalog Delay

Based on the BOSS DM-2 Delay

Category
Delay
Controls
Delay · Feedback · Level
Difficulty
Advanced
Price
$12.50in stock

From the vendor

One of the earliest analog delay effects to use a bucket brigade chip, and still widely considered among the best ever.

The Amethyst Analog Delay is based on the BOSS DM-2, which was originally released in 1981 and is still widely considered to be one of the best delay pedals ever made.

The DM-2 circuit uses the MN3005 bucket-brigade delay (BBD) chip, which has 4,096 stages and makes the unit capable of around 300ms of delay time when properly calibrated. It also uses a compander to significantly improve noise performance for the delay line.

In 1982, Boss updated the circuit to use the MN3205, which has better audio specifications at the expense of lower maximum voltage and headroom. This is called the “Second Edition” or DM-2 V2. There are no actual changes to the audio portion of the circuit, but the BBD and clock run on inverted power so the PCB had to be modified slightly to accommodate either version.

For many years, the DM-2 V1 was out of reach for most DIYers due to the scarcity of the MN3005 and MN3101. However, with the Xvive reissue of the MN3005 released in 2015 and Cabintech’s CT3101 clock released in 2023, the classic circuit is once again convenient (if not cheap) to build.

The Amethyst PCB has jumper pads so you can choose either the MN3005/MN3101 or the MN3205/MN3102 chipset depending on availability. Otherwise, it is a direct adaptation of the original DM-2 with no modifications or substitutions.

The PCB also includes space for a few extra components so that you can build the Way Huge Aqua Puss, which is a slightly modified clone of the DM-2 from the mid-1990s. See the build notes section in the documentation for more information.

Note: The PCB-only version of this project uses a type of capacitor that has been temporarily discontinued by WIMA. Please see our news article about the issue and the substitution spreadsheet for project-specific recommendations. We are stocking a limited supply in the mean time. The build document has not yet been updated to reflect this. This does not impact the kits.

Schematic

The schematic is in the vendor's build document, page 10. Open the build document. No KiCad fragment has been drawn for this circuit yet.

Parts list 101 rows

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RefValueNormalizedTypeNotes
Resistors 38
R110k10kMetal film resistor, 1/4W
R2470k470kMetal film resistor, 1/4W475k for Aqua Puss.
R310k10kMetal film resistor, 1/4W
R410k10kMetal film resistor, 1/4W
R547k47kMetal film resistor, 1/4W47.5k for Aqua Puss.
R647k47kMetal film resistor, 1/4W47.5k for Aqua Puss.
R710k10kMetal film resistor, 1/4W
R810k10kMetal film resistor, 1/4W
R910k10kMetal film resistor, 1/4W
R1010k10kMetal film resistor, 1/4W
R1110k10kMetal film resistor, 1/4W
R1210k10kMetal film resistor, 1/4W
R1310k10kMetal film resistor, 1/4W
R14100k100kMetal film resistor, 1/4W
R1510k10kMetal film resistor, 1/4W100k for Aqua Puss.
R1618k18kMetal film resistor, 1/4W
R1722k22kMetal film resistor, 1/4W
R18100k100kMetal film resistor, 1/4W
R19100k100kMetal film resistor, 1/4W
R2010k10kMetal film resistor, 1/4W
R2110k10kMetal film resistor, 1/4W
R2210k10kMetal film resistor, 1/4W
R2310k10kMetal film resistor, 1/4W
R2410k10kMetal film resistor, 1/4W
R2510k10kMetal film resistor, 1/4W
R2610k10kMetal film resistor, 1/4W
R2722k22kMetal film resistor, 1/4W
R2847k47kMetal film resistor, 1/4W47.5k for Aqua Puss.
R2947k47kMetal film resistor, 1/4W47.5k for Aqua Puss.
R3010k10kMetal film resistor, 1/4W
R3147k47kMetal film resistor, 1/4W47.5k for Aqua Puss.
R32470R470Metal film resistor, 1/4W150R for Aqua Puss.
R33100k100kMetal film resistor, 1/4W
R3410k10kMetal film resistor, 1/4W
R3510k10kMetal film resistor, 1/4W
R3622R22Metal film resistor, 1/4WBBD power supply filter resistor.
RPD1M1MMetal film resistor, 1/4WInput pull-down resistor.
LEDR10k10kMetal film resistor, 1/4WLED current-limiting resistor. Adjust value to change LED brightness.
Capacitors 35
C247n47nFilm capacitor, 7.2 x 2.5mm
C31uF1uFilm capacitor, 7.2 x 3.5mm10uF electrolytic for Aqua Puss.
C46n86.8nFilm capacitor, 7.2 x 2.5mm
C5100pF100pMLCC capacitor, NP0/C0G
C610uF10uElectrolytic capacitor, 5mm
C710uF10uElectrolytic capacitor, 5mm
C8100n100nMLCC capacitor, X7R
C9220n220nFilm capacitor, 7.2 x 3mm
C10100pF100pMLCC capacitor, NP0/C0G
C1110uF10uElectrolytic capacitor, 5mm
C126n86.8nFilm capacitor, 7.2 x 2.5mm
C1382n82nFilm capacitor, 7.2 x 2.5mm100n for Aqua Puss.
C14330pF330pMLCC capacitor, NP0/C0G
C151uF1uElectrolytic capacitor, 4mm
C1610uF10uElectrolytic capacitor, 5mm
C17100pF100pMLCC capacitor, NP0/C0G
C181uF1uElectrolytic capacitor, 4mm
C192n22.2nFilm capacitor, 7.2 x 2.5mm
C2033n33nFilm capacitor, 7.2 x 2.5mm
C211n1nFilm capacitor, 7.2 x 2.5mm
C2239n39nFilm capacitor, 7.2 x 2.5mm
C23330pF330pMLCC capacitor, NP0/C0G
C2410uF10uElectrolytic capacitor, 5mm
C25220n220nFilm capacitor, 7.2 x 3mm
C26100pF100pMLCC capacitor, NP0/C0G
C271uF1uElectrolytic capacitor, 4mm10uF electrolytic for Aqua Puss.
C28100n100nFilm capacitor, 7.2 x 2.5mm220n for Aqua Puss.
C291uF1uFilm capacitor, 7.2 x 3.5mm10uF electrolytic for Aqua Puss.
C30100pF100pMLCC capacitor, NP0/C0G
C316n86.8nFilm capacitor, 7.2 x 2.5mm
C321uF1uFilm capacitor, 7.2 x 3.5mm10uF electrolytic for Aqua Puss.
C3447uF47uElectrolytic capacitor, 5mmPower supply filter capacitor.
C35220uF220uElectrolytic capacitor, 6.3mmPower supply filter capacitor.
C36220uF220uElectrolytic capacitor, 6.3mmPower supply filter capacitor.
C37100n100nMLCC capacitor, X7RPower supply filter capacitor.
Diodes 4
Z1(omit)(OMIT)Zener diode, 500mW, 8.2VUse 1N5237B (8.2V zener) for MN3205 version.
D11N58171N5817Schottky diode, DO-41
D21N9141N914Fast-switching diode, DO-35Jumper for MN3205 version.
D3(jumper)(JUMPER)Fast-switching diode, DO-351N914 for MN3205 version.
Transistors 4
Q12N50882N5088BJT transistor, NPN, TO-92MPSA18 for Aqua Puss.
Q22N50882N5088BJT transistor, NPN, TO-92MPSA18 for Aqua Puss.
Q32N50882N5088BJT transistor, NPN, TO-92MPSA18 for Aqua Puss.
Q42N50882N5088BJT transistor, NPN, TO-92MPSA18 for Aqua Puss.
ICs 4
IC1JRC4558DJRC4558DOperational amplifier, dual, DIP8LF353N for Aqua Puss.
IC2NE571NE571IC socket, DIP-8Coolaudio v571 is a current substitute.
IC3MN3005MN3005Bucket-brigade delay, 4096 stagesCan also use MN3205 or v3205. See build notes.
IC4MN3101MN3101Clock driver for bucket-brigade delaySee build notes for sourcing.
Potentiometers 3
DELAY1MBB1M16mm right-angle PCB mount potCalled "Repeat Rate" on the original DM-2.
FEEDBACK50kAA50k16mm right-angle PCB mount potCalled "Intensity" on the original DM-2.
VOLUME50kBB50k16mm right-angle PCB mount potCalled "Echo" on the original DM-2.
Trimmers 3
BIAS22k22kTrimmer, 10%, 1/4", Bourns 3326PCan substitute 20k or 25k.
CANCEL10k10kTrimmer, 10%, 1/4”, Bourns 3326P
CLOCK1M1MTrimmer, 10%, 1/4”, Bourns 3326P
Switches 1
FSW3PDT3PDTStomp switch, 3PDTAvailable from Aion FX.
LEDs 1
LED5mm5MMLED, 5mm, red diffused
Jacks & sockets 7
IC1-SOCKETDIP-8 socketDIP-8 SOCKETIC socket, DIP-8
IC2-SOCKETDIP-16 socketDIP-16 SOCKETIC socket, DIP-16
IC3-SOCKETDIP-14 socketDIP-14 SOCKETIC socket, DIP-8
IC4-SOCKETDIP-8 socketDIP-8 SOCKETIC socket, DIP-8
IN1/4" mono1/4" MONO1/4" phone jack, closed frameSwitchcraft 111X or equivalent.
OUT1/4" mono1/4" MONO1/4" phone jack, closed frameSwitchcraft 111X or equivalent.
DC2.1mm2.1MMDC jack, 2.1mm panel mountLumberg NEB/J 21 C or equivalent.
Hardware 1
ENC125B125BEnclosure, die-cast aluminumCan also use a Hammond 1590N1.