Akashic Guitar effects circuit lookup
GAINVOLBASSTREBLE

125B · 4 knobs

TH Custom Effects

Tube Driver125B

Based on the Chandler Tube Driver· 2 other boards clone it

Category
Overdrive
Controls
Gain · Vol · Bass · Treble
Price
€10.70in stock
Buy the PCB at TH Custom Effects Build document1.2

From the vendor

An op-amp pre-distortion stage driving a 12AX7 (or 12AT7) dual-triode running on an internally-generated ~60V plate rail, with a Baxandall tone stack on the output. Inspired by the well-known classics used by David Gilmour, Eric Johnson and Joe Satriani — runs from a single 9V supply. The Tube Driver is a faithful take on the well-known circuit that runs a simple op-amp distortion stage straight into a vacuum tube. The result is the rich, dynamic harmonic content of a real triode pushed into compression — usable from polite overdrive to thick saturated lead tones depending on the gain setting and the tube fitted. The clever part is the high-voltage rail. A 40106 Schmitt-trigger oscillator dr

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 35 rows

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RefValueNormalizedTypeNotes
Resistors 13
R12k72.7k40106 oscillator timing resistor.
R41M1MInput pull-down (R4) and IC3A bias to VR (R17).
R171M1MInput pull-down (R4) and IC3A bias to VR (R17).
R547k47kV1A & V1B plate loads (R5, R6). R9 is the optional external-BIAS series resistor — populate only if you want an external BIAS pot mounted on the enclosure.
R647k47kV1A & V1B plate loads (R5, R6). R9 is the optional external-BIAS series resistor — populate only if you want an external BIAS pot mounted on the enclosure.
R947k47kV1A & V1B plate loads (R5, R6). R9 is the optional external-BIAS series resistor — populate only if you want an external BIAS pot mounted on the enclosure.
R722k22kR7 = shared cathode resistor + V1B grid leak. R24 = Baxandall network resistor.
R2422k22kR7 = shared cathode resistor + V1B grid leak. R24 = Baxandall network resistor.
R1510k10kR10 V1A plate-side coupling, R11 input series, R12/R13 VR divider, R15 V1A grid stopper, R16 V1A grid leak, R23 Baxandall.
R1610k10kR10 V1A plate-side coupling, R11 input series, R12/R13 VR divider, R15 V1A grid stopper, R16 V1A grid leak, R23 Baxandall.
R2310k10kR10 V1A plate-side coupling, R11 input series, R12/R13 VR divider, R15 V1A grid stopper, R16 V1A grid leak, R23 Baxandall.
R141k51.5kIC3B feedback divider lower leg — sets gain range.
R21100k100kBaxandall input series resistor.
Capacitors 11
C847n47nBox film, 80–100 V rating required — these caps see HV swings on the multiplier ladder.
C1047n47nBox film, 80–100 V rating required — these caps see HV swings on the multiplier ladder.
C1647n47nBox film, 80–100 V rating required — these caps see HV swings on the multiplier ladder.
C71n1nBox film. C7 sets the 40106 oscillator frequency; C28, C30 are Baxandall treble caps.
C281n1nBox film. C7 sets the 40106 oscillator frequency; C28, C30 are Baxandall treble caps.
C301n1nBox film. C7 sets the 40106 oscillator frequency; C28, C30 are Baxandall treble caps.
C1347p47pCeramic. C13 = input RFI shunt; C17 = IC3B feedback HF stability.
C1747p47pCeramic. C13 = input RFI shunt; C17 = IC3B feedback HF stability.
C1533n33nBox film — 7806 input HF bypass.
C296n86.8nBox film — Baxandall bass-mid network.
C3110n10nBox film — Baxandall bass shelf cap.
ICs 3
IC140106N40106NHex Schmitt-trigger inverter, DIP-14. CD40106 MC14584 74HC14
IC2µA7806UA7806+6 V linear regulator, TO-220. Mount the tab against the enclosure as a heatsink. L7806 LM7806
IC3TL072TL072Dual op-amp, DIP-8. Use a socket. JRC4580 OPA2134 TLC2272
Potentiometers 4
GAINA100kA100k9 mm Alpha (e.g. Tayda). All four pots are 100 kΩ log taper.
VOLA100kA100k9 mm Alpha (e.g. Tayda). All four pots are 100 kΩ log taper.
BASSA100kA100k9 mm Alpha (e.g. Tayda). All four pots are 100 kΩ log taper.
TREBLEA100kA100k9 mm Alpha (e.g. Tayda). All four pots are 100 kΩ log taper.
Trimmers 1
BIAS10k10k6 mm ACP6 or Piher trimmer. Sets the shared cathode bias of V1A / V1B.
LEDs 1
LED3 mm super-bright3 MM SUPER-BRIGHT"Tube glow" indicator under the socket — colour to taste (orange/red looks like a real heated filament).
Jacks & sockets 1
S1Noval print socketNOVAL PRINT SOCKETPCB-mount Noval (9-pin) socket. Musikding part . Plastic sockets can be drilled to fit the 3 mm "glow" LED behind.
Other 1
V1MyDrv 12AX7 Drv 12AT7MYDRV 12AX7 DRV 12AT7Dual triode, Noval (B9A) base. 12AX7 = high gain (default for MyDriver). 12AT7 = lower gain, more headroom (closer to the original Driver). Both are pin-compatible drop-ins. ECC83 (= 12AX7) ECC81 (= 12AT7)

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