Akashic Guitar effects PCB lookup
INPUTLOWOUTPUT

125B · 3 knobs

Aion FX

424 Preamp

Based on the Tascam 424

Category
Distortion· Boost / Distortion
Controls
Input · Low · Output
Difficulty
Beginner
Price
$12.50in stock

From the vendor

A pedal conversion of the input preamp of the Tascam 424 four-track tape recorder, most notably used by Mk.gee for his main drive tone.

The 424 Tape Preamp replicates the dry audio path of one channel of the Tascam 424 Portastudio Mk. I, a 4-track tape recorder from the late 1980s to the early 1990s. While 4-track recorders have a long history of being misused to create interesting drive and distortion effects, the 424 in particular is one of the foundational pieces of Mk.gee’s unique guitar tone.

The 424 Preamp has four knobs, each corresponding to a control on the original Tascam unit. The Input control is the equivalent of “Trim” on the Tascam, a potentiometer that cuts the input signal. It’s intended to prevent clipping, but can be used to intentionally overload the op-amp stages as a drive control.

This is followed by a standard 2-band Baxandall EQ which boosts or cuts frequencies by +/-10dB, centered at 100 Hz and 10 kHz. The volume control is equivalent to the channel’s “Master” slider. These are the only four controls that affect the audio signal; the slide switches only control the routing of the signal to the tape recorder or outboard effects.

The Demo Tape Fuzz by Mid-Fi Electronics (available as our Torus project) is a similar circuit that was also designed to sound like an overdriven tape recorder, and no doubt the Tascam was one of the inspirations for that circuit. But, the DTF is not based directly on any specific model as far as we know—so while it does capture the spirit and functionality, the 424 Preamp is actually an exact copy of what Mk.gee uses.

Schematic

The schematic is in the vendor's build document, page 6. Open the build document. No KiCad fragment has been drawn for this circuit yet.

Parts list 49 rows

Report a wrong parse
RefValueNormalizedTypeNotes
Resistors 17
R1100k100kMetal film resistor, 1/4W
R2470k470kMetal film resistor, 1/4W
R3100R100Metal film resistor, 1/4W
R410k10kMetal film resistor, 1/4W
R510k10kMetal film resistor, 1/4W
R622k22kMetal film resistor, 1/4W
R718k18kMetal film resistor, 1/4W
R85k65.6kMetal film resistor, 1/4W
R9470k470kMetal film resistor, 1/4W
R1047k47kMetal film resistor, 1/4W
R11110k110kMetal film resistor, 1/4W
R12100k100kMetal film resistor, 1/4W
R1310k10kMetal film resistor, 1/4W
R1410k10kMetal film resistor, 1/4W
R1547R47Metal film resistor, 1/4WPower supply filter resistor.
RPD2M22.2MMetal film resistor, 1/4WInput pull-down resistor. Can be as low as 1M.
LEDR10k10kMetal film resistor, 1/4WLED current-limiting resistor. Adjust value to change LED brightness.
Capacitors 16
C110uF10uElectrolytic capacitor, 5mm
C2100pF100pMLCC capacitor, NP0/C0G
C310uF10uElectrolytic capacitor, 5mm
C410uF10uElectrolytic capacitor, 5mm
C51n81.8nFilm capacitor, 7.2 x 2.5mm
C615n15nFilm capacitor, 7.2 x 2.5mm
C715n15nFilm capacitor, 7.2 x 2.5mm
C810uF10uElectrolytic capacitor, 5mm
C910uF10uElectrolytic capacitor, 5mm
C1047pF47pMLCC capacitor, NP0/C0G
C1110uF10uElectrolytic capacitor, 5mm
C1210pF10pMLCC capacitor, NP0/C0G
C1310uF10uElectrolytic capacitor, 5mm
C1447uF47uElectrolytic capacitor, 5mmReference voltage filter capacitor.
C15100uF100uElectrolytic capacitor, 6.3mmPower supply filter capacitor.
C16100n100nMLCC capacitor, X7RPower supply filter capacitor.
Diodes 1
D11N58171N5817Schottky diode, DO-41
ICs 2
IC1LM833LM833Operational amplifier, dual, DIP8
IC2NJM4565DNJM4565DOperational amplifier, dual, DIP8
Potentiometers 4
INPUT10kCC10k16mm right-angle PCB mount potReverse audio (antilog) taper.
OUTPUT10kAA10k16mm right-angle PCB mount potAudio (log) taper.
HIGH100kBB100k16mm right-angle PCB mount potLinear taper.
LOW100kBB100k16mm right-angle PCB mount potLinear taper.
Switches 1
FSW3PDT3PDTStomp switch, 3PDTAvailable from Aion FX.
LEDs 1
LED5mm5MMLED, 5mm, red diffused
Jacks & sockets 5
IC1-SDIP-8 socketDIP-8 SOCKETIC socket, DIP-8
IC2-SDIP-8 socketDIP-8 SOCKETIC socket, DIP-8
IN1/4" stereo1/4" STEREO1/4" phone jack, closed frameSwitchcraft 112BX 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 2
BATTBattery snapBATTERY SNAP9V battery snapOptional. Use the soft plastic type—the hard-shell type will not fit.
ENC125B125BEnclosure, die-cast aluminumCan also use a Hammond 1590N1.