Akashic Guitar effects circuit lookup
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TH Custom Effects

Headphone Amplifier & Stereo Simulation

Category
Utility
Price
€8.35in stock
Buy the PCB at TH Custom Effects Build document1.2

From the vendor

A clean, low-noise headphone amplifier built around the TDA2822M with a four-stage allpass network that synthesises a stereo image from a mono input. Drop a cab simulator (we recommend the ROG Condor) in front and you have a complete silent-practice or direct-recording rig in one small box. V2021 reworks the layout — all resistors lie flat, the trimmer is repositioned, and the build is more forgiving. This is a HiFi-grade headphone amplifier with built-in faux-stereo generation, designed for silent practice, direct recording, and any situation where you want to plug headphones in and hear something that doesn't sound like it's playing in the middle of your skull. The faux-stereo effect is ge

Schematic

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

Parts list 52 rows

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RefValueNormalizedTypeNotes
Resistors 28
R110k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R210k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R310k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R410k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R510k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R610k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R1110k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R1210k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R1310k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R1410k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R1610k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R1710k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R1810k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R1910k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R2210k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R2310k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R2610k10kR1/R2 = VR divider; R3-R6 = allpass feedback; R11-R14 = allpass series; R16/R18 = stereo path attenuator; R17/R19 = mono path attenuator; R22/R23 = power-amp input bias; R26 = IC3A feedback fixed
R720k20kAllpass +IN bias resistors. For more selective stereo use 220k, 68k, 20k, 11k respectively (see filter analysis)
R820k20kAllpass +IN bias resistors. For more selective stereo use 220k, 68k, 20k, 11k respectively (see filter analysis)
R920k20kAllpass +IN bias resistors. For more selective stereo use 220k, 68k, 20k, 11k respectively (see filter analysis)
R1020k20kAllpass +IN bias resistors. For more selective stereo use 220k, 68k, 20k, 11k respectively (see filter analysis)
R151M1MInput bias resistor — sets 1MΩ input impedance to source
R202k22.2kTDA2822M gain-set resistors. Range 1k2 – 2k2: raise to reduce overall gain if amp gets warm. See troubleshooting
R212k22.2kTDA2822M gain-set resistors. Range 1k2 – 2k2: raise to reduce overall gain if amp gets warm. See troubleshooting
R244R74.7Zobel snubber resistors at IC2 outputs 5R1 OK
R254R74.7Zobel snubber resistors at IC2 outputs 5R1 OK
R27100k100kIC3A input-side gain-set resistor
R28100k100k6 mm trim pot — sets stereo width / depth
Capacitors 18
C1100µF100uC1 = supply bulk decouple; C8/C9 = TDA2822M gain-network caps. 16 V or 25 V rated, observe polarity
C8100µF100uC1 = supply bulk decouple; C8/C9 = TDA2822M gain-network caps. 16 V or 25 V rated, observe polarity
C9100µF100uC1 = supply bulk decouple; C8/C9 = TDA2822M gain-network caps. 16 V or 25 V rated, observe polarity
C247µF47uVR (virtual ground) decoupling cap, 16 V or 25 V rated, observe polarity
C71µF1uC7 = input AC-couple from VOL pot; C10/C11 = channel coupling into IC2. 16 V or 25 V rated, observe polarity
C101µF1uC7 = input AC-couple from VOL pot; C10/C11 = channel coupling into IC2. 16 V or 25 V rated, observe polarity
C111µF1uC7 = input AC-couple from VOL pot; C10/C11 = channel coupling into IC2. 16 V or 25 V rated, observe polarity
C14220µF220uOutput AC-couple to headphone jack 100µF OK for ≥32Ω loads . 16 V or 25 V rated, observe polarity
C15220µF220uOutput AC-couple to headphone jack 100µF OK for ≥32Ω loads . 16 V or 25 V rated, observe polarity
C1810µF10uLocal decouple at IC3A −IN, observe polarity
C310n10nAllpass +IN coupling caps — box film, low ESR
C410n10nAllpass +IN coupling caps — box film, low ESR
C510n10nAllpass +IN coupling caps — box film, low ESR
C610n10nAllpass +IN coupling caps — box film, low ESR
C12100n100nZobel network shunt caps at IC2 outputs — box film
C13100n100nZobel network shunt caps at IC2 outputs — box film
C161u1uMKTHF bypass in parallel with C14/C15 — MKT polyester film
C171u1uMKTHF bypass in parallel with C14/C15 — MKT polyester film
Diodes 1
D11N40011N4001Reverse polarity protection — observe cathode band
ICs 3
IC1TL074TL074Quad JFET-input op-amp DIP-14, all four gates form the allpass cascade TL074CN TL074IN
IC2TDA2822MTDA2822MDual stereo power amp DIP-8 — drives the headphone load
IC3TL072TL072Dual JFET-input op-amp DIP-8 — IC3B = mono buffer, IC3A = stereo-prep amp TL072IP preferred
Potentiometers 1
POT1 (VOLUME)100k AA100k16 mm right-angle PCB-mount, A-taper (logarithmic)
Switches 1
SW1SPDTSPDTSTEREO / MONO toggle — wires to X / X_ST / X_MO pads on PCB