Aion Electronics THULCANDRA User manual

THULCANDRA BOOST/OVERDRIVE 1
PROJECT NAME
THULCANDRA
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Xotic Soul Driven
A mid-gain overdrive with three different tone controls to fine-tune the character. Developed in
collaboration with Allen Hinds as a signature effect.
Boost / Overdrive 1.0.0 (2019-10-18)
BUILD DIFFICULTY
Easy
Actual size is 2.3” x 1.86” (main board) and 1.78” x 0.86” (bypass board).

THULCANDRA BOOST/OVERDRIVE 2
TABLE OF CONTENTS
1Project Overview 7Enclosure Layout
2Introduction & Usage 8Wiring Diagram
3-4 Parts List 9Licensing
5Schematic 9Document Revisions
6Drill Template
INTRODUCTION
The Thulcandra Boost/Overdrive is an adaptation of the Xotic Soul Driven, a cousin of the classic AC
Booster with roots in the Tube Screamer family, originally released in collaboration with Allen Hinds.
This is an original trace by Aion FX.
The Soul Driven replaces the tone section of the AC/RC Booster circuit with a gyrator-based bass boost
stage that emphasizes the 120Hz frequency. Using internal DIP switches, four bass boost settings are
available: flat, +2.4dB, +3.6dB and +6dB.
The “Mid Boost” control is similar to the Zendrive’s Voice control or the Timmy’s Bass knob, varying
the resistor in the R-C filter to ground from the op-amp clipping stage. This has the effect of raising or
lowering the bass cutoff frequency as well as changing the overall gain ratio.
The Thulcandra project is faithful to the original, with the exception that the DIP switch has been
replaced by a potentiometer to allow fine control over the amount of bass. (The DIP switch just selects
between four pre-set resistor values, and it’s likely due to space considerations that they made it an
internal control rather than an external potentiometer.)
USAGE
The Thulcandra has the following controls:
• Gain controls the amount of gain in the op-amp clipping stage.
• Treble is a passive treble-cut filter similar to the one found in the RAT, Zendrive and Timmy.
• Bass is an active bass-boost at 120 Hz, from flat at minimum position to +6dB at maximum.
• Mid Boost raises or lowers the cutoff frequency of the clipping stage.
• Volume controls the overall output of the effect.

THULCANDRA BOOST/OVERDRIVE 3
PARTS LIST
This parts list is also available in a spreadsheet format which can be imported directly into Mouser for
easy parts ordering. Mouser doesn’t carry all the parts (most notably potentiometers) so the second tab
lists all the non-Mouser parts as well as sources for each.
View parts list spreadsheet →
PART VALUE TYPE NOTES
R1 10k Metal film resistor, 1/4W
R2 1M Metal film resistor, 1/4W
R3 18k Metal film resistor, 1/4W
R4 1k8 Metal film resistor, 1/4W
R5 470k Metal film resistor, 1/4W
R6 18k Metal film resistor, 1/4W
R7 1k2 Metal film resistor, 1/4W
R8 10k Metal film resistor, 1/4W
R9 470k Metal film resistor, 1/4W
R10 100k Metal film resistor, 1/4W
R11 10k Metal film resistor, 1/4W
R12 470R Metal film resistor, 1/4W
R13 100k Metal film resistor, 1/4W
R14 22k Metal film resistor, 1/4W
R15 22k Metal film resistor, 1/4W
RPD 2M2 Metal film resistor, 1/4W Input pulldown resistor.
LEDR 4k7 Metal film resistor, 1/4W LED current-limiting resistor. Adjust value to change LED brightness.
C1 470n Film capacitor, 7.2 x 3mm
C2 150pF MLCC capacitor, NP0/C0G
C3 100n Film capacitor, 7.2 x 2.5mm
C4 4u7 bipolar Electrolytic capacitor, 5mm Can also use polarized (oriented according to silkscreen).
C5 1n5 Film capacitor, 7.2 x 2.5mm
C6 100n Film capacitor, 7.2 x 2.5mm
C7 2n2 Film capacitor, 7.2 x 2.5mm
C8 56n Film capacitor, 7.2 x 2.5mm
C9 56n Film capacitor, 7.2 x 2.5mm
C10 10uF bipolar Electrolytic capacitor, 5mm Can also use polarized (oriented according to silkscreen).
C11 10uF bipolar Electrolytic capacitor, 5mm Can also use polarized (oriented according to silkscreen).
C12 100uF Electrolytic capacitor, 6.3mm Power supply filter capacitor.
C13 47uF Electrolytic capacitor, 5mm Reference voltage filter capacitor.

THULCANDRA BOOST/OVERDRIVE 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
C14 100n MLCC capacitor, X7R Power supply filter capacitor.
D1 1N5817 Schottky diode, DO-41
D2 BAT46 Schottky diode, DO-35
D3 1N914 Fast-switching diode, DO-35
D4 1N914 Fast-switching diode, DO-35
D5 BAT46 Schottky diode, DO-35
D6 1N914 Fast-switching diode, DO-35
D7 1N914 Fast-switching diode, DO-35
Q1 2N5088 BJT transistor, NPN, TO-92 Original part number is BC849C, SMD type. 2N5088 is an equivalent.
Q2 2N5088 BJT transistor, NPN, TO-92 Original part number is BC849C, SMD type. 2N5088 is an equivalent.
IC1 LM833 Operational amplifier, DIP8
IC1-S DIP-8 socket IC socket, DIP-8
TREBLE 250kB 16mm right-angle PCB mount pot
BASS 25kB 16mm right-angle PCB mount pot
MID 10kC 16mm right-angle PCB mount pot
GAIN 1MB 16mm right-angle PCB mount pot
VOL 100kB 16mm right-angle PCB mount pot
LED 5mm LED, 5mm, red diffused
IN 1/4" stereo 1/4" phone jack, closed frame Switchcraft 112BX or equivalent.
OUT 1/4" mono 1/4" phone jack, closed frame Switchcraft 111X or equivalent.
DC 2.1mm DC jack, 2.1mm panel mount Mouser 163-4302-E or equivalent.
BATT Battery snap 9V battery snap Optional. Use the soft plastic type—the hard-shell type will not fit.
FSW 3PDT Stomp switch, 3PDT
ENC 125B Enclosure, die-cast aluminum Can also use a Hammond 1590N1.

SCHEMATIC
THULCANDRA BOOST/OVERDRIVE 5
BAT46
1N914
GND
1M
1N5817
100uF
1MB
10kC
GND
250kB
100kB
25kB
+9V
100n
VA
22k
22k
47uF
GND GND
VB
470n
10k
1M
VB
LM833
LM833
VA
GND
150pF
1N914
18k
100n
1k8
GND
4u7
1n5
GND
GND
100n
470k
VB
2n2
18k
56n
10uF
100k
2N5088
VB
VA
10k
GND
10uF
470R
100k
GND
RPD
D1
C12
1
2
3
GAIN
1
2
3
MIDBOOST
1
2
3
TREBLE
VOLUME
1
2
3
1
2
3
BASS
IN
OUT
C14
R14
R15
C13
C1
R1
R2
IC1A
2
3
1
IC1B
6
5
7
84
C2
D2 D3
D4D5
R3
C3
R4
C4
C5
C6
D6 D7 R5
C7
R6
C8
C10
R10
Q2
R11
C11
R12
R13
GND
1k2
2N5088
VA
10k
470k
VB
56n
GND
R7
Q1
R8 R9
C9

THULCANDRA BOOST/OVERDRIVE 6
DRILL TEMPLATE
Cut out this drill template, fold the edges and tape it to the enclosure. Before drilling, it’s recommended
to first use a center punch for each of the holes to help guide the drill bit.
Ensure that this template is printed at 100% or “Actual Size”. You can double-check this by measuring
the scale on the printed page.
Top jack layout requires the use of closed-frame jacks like the Switchcraft 111X. Open-frame jacks will
not fit in layouts with 5 or more knobs due to the placement of the DC jack.
LED hole drill size assumes the use of a 5mm LED bezel, available from several parts suppliers. Adjust
size accordingly if using something different, such as a 3mm bezel, a plastic bezel, or just a plain LED.
0 1 2
CM
0 1
INCH
x: -0.775, y: +1.71 x: +0.775, y: +1.71
ø9/32” ø9/32”
x: -0.775, y: +0.41
ø9/32”
x: 0, y: +1.71
ø9/32”
x: +0.775, y: +0.41
ø9/32”
x: 0, y: -1.20
ø15/32”
x: -0.775, y: -1.20
ø5/16”
CENTER (0,0)
125B
BASSMIDBOOSTTREBLE
GAINVOLUME
FOOTSWITCHLED
ø3/8” ø1/2”
0.385”
0.625” 0.625”
ø3/8”
OUT DC IN

THULCANDRA BOOST/OVERDRIVE 7
ENCLOSURE LAYOUT
Enclosure is shown without jacks. See next page for jack layout and wiring.
125B

THULCANDRA BOOST/OVERDRIVE 8
WIRING DIAGRAM
125B
IN +VGND N.C. N.C. OUT
PCB
IN
GND +V +V JACK GND JACK
OUTIN
GND GND PCB
OUT
Shown with optional 9V battery. If battery is omitted, both jacks can be mono rather than one being stereo.
Leave the far-right lug of the DC jack unconnected.

THULCANDRA BOOST/OVERDRIVE 9
LICENSE & USAGE
No direct support is offered for these projects beyond the provided documentation. It’s assumed
that you have at least some experience building pedals before starting one of these. Replacements and
refunds cannot be offered unless it can be shown that the circuit or documentation are in error.
All of these circuits have been tested in good faith in their base configurations. However, not all the
modifications or variations have necessarily been tested. These are offered only as suggestions based
on the experience and opinions of others.
Projects may be used for commercial endeavors in any quantity unless specifically noted. No
attribution is necessary, though a link back is always greatly appreciated. The only usage restrictions
are that (1) you cannot resell the PCB as part of a kit without prior arrangement, and (2) you cannot
“goop” the circuit, scratch off the screenprint, or otherwise obfuscate the circuit to disguise its source.
(In other words: you don’t have to go out of your way to advertise the fact that you use these PCBs, but
please don’t go out of your way to hide it. The guitar effects industry needs more transparency, not less!)
DOCUMENT REVISIONS
1.0.0 (2019-10-18)
Initial release.