aion ACHILLES User manual

ACHILLES AMP OVERDRIVE 1
PROJECT NAME
ACHILLES
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Analogman Prince of Tone
A single-channel adaptation of the legendary King of Tone, with a few added features not found in the
original dual-channel pedal.
Amp-like overdrive 1.0.0 (2022-04-08)
BUILD DIFFICULTY
Easy
Actual size is 2.3” x 1.86” (main board) and 1.78” x 0.87” (bypass board).

ACHILLES AMP OVERDRIVE 2
TABLE OF CONTENTS
1Project Overview 8Drill Template
2Introduction & Usage 9Enclosure Layout
3-5 Parts List 10 Wiring Diagram
6Build Notes 11 Licensing
7Schematic 11 Document Revisions
INTRODUCTION
The Achilles Amp Overdrive is based on the Analogman Prince of Tone, the single-channel adaptation
of the King of Tone that was first released in 2012. Unlike the King of Tone, the Prince was designed
for mass production and is assembled in China. As a result, it’s much more affordable as well as being
readily available (the King of Tone has a 4 ½-year waiting list).
The Prince of Tone converts the internal diode DIP switch into an external toggle switch, allowing for
soft clipping, hard clipping or no clipping to be selected without needing to open up the back. It also has
the high gain mod from the King of Tone as standard.
Internally, in addition to the Presence control, there are two DIP switch settings that are new to this
pedal. One of them adds low-mid frequencies to the first gain stage. The other is called “Turbo” mode
that essentially doubles the gain of the second stage, meaning it reaches the clipping threshold sooner
and has more apparent drive on tap.
The Achilles is a direct clone of the Prince of Tone with no modifications.
USAGE
The Achilles has four external controls:
• Drive controls the amount of gain going into the op-amp feedback diode clipping stage.
• Tone controls the treble response via a passive filter.
• Volume controls the overall output.
• Clipping (toggle switch) selects between soft clipping (overdrive), hard clipping (distortion) and no
clipping (clean boost).
There are also three internal controls:
• Presence (trimmer) is an additional passive treble control. The default position is all the way down
(full CCW) and as you turn it up it adds high-end. Noise or hiss will increase as well.
• +Mids (DIP switch) adds low-mids to the signal by increasing the filter frequency of the first op-amp
gain stage.
• +Gain (DIP switch) doubles the gain ratio of the second op-amp stage so that the diodes clip more
easily.

ACHILLES AMP 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—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 1M Metal film resistor, 1/4W
R2 100k Metal film resistor, 1/4W
R3 27k Metal film resistor, 1/4W
R4 33k Metal film resistor, 1/4W
R5 100k Metal film resistor, 1/4W
R6 10k Metal film resistor, 1/4W
R7 10k Metal film resistor, 1/4W
R8 220k Metal film resistor, 1/4W
R9 6k8 Metal film resistor, 1/4W
R10 1k Metal film resistor, 1/4W
R11 1k Metal film resistor, 1/4W
R12 6k8 Metal film resistor, 1/4W
R13 1M Metal film resistor, 1/4W
R14 47k Metal film resistor, 1/4W
R15 47k Metal film resistor, 1/4W
R16 100R Metal film resistor, 1/4W Power supply filter resistor.
LEDR 4k7 Metal film resistor, 1/4W LED current-limiting resistor. Adjust value to change LED brightness.
C1 22n Film capacitor, 7.2 x 2.5mm 10n in some units.
C2 100pF MLCC capacitor, NP0/C0G 750pF in some units.
C3 10n Film capacitor, 7.2 x 2.5mm
C4 1uF Film capacitor, 7.2 x 3.5mm
C5 10n Film capacitor, 7.2 x 2.5mm
C6 100n Film capacitor, 7.2 x 2.5mm
C7 47pF MLCC capacitor, NP0/C0G Not in original pedal, but recommended to prevent high-end oscillation.
C8 10n Film capacitor, 7.2 x 2.5mm
C9 10n Film capacitor, 7.2 x 2.5mm
C10 1uF Film capacitor, 7.2 x 3.5mm
C11 1uF Electrolytic capacitor, 4mm
C12 100uF Electrolytic capacitor, 6.3mm Reference voltage filter capacitor.
C13 100uF Electrolytic capacitor, 6.3mm Power supply filter capacitors.
C14 100n MLCC capacitor, X7R Power supply filter capacitors.
D1 1N5817 Schottky diode, DO-41

ACHILLES AMP OVERDRIVE 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
D2 BAS33 Switching diode, DO-35
Original uses MA856 diodes. The BAS33 is the closest available diode
currently in production.
D3 BAS33 Switching diode, DO-35
D4 BAS33 Switching diode, DO-35
D5 BAS33 Switching diode, DO-35
IC1 JRC4580D Operational amplifier, DIP8
IC1-S DIP-8 socket IC socket, DIP-8
MODE 2-pos. DIP DIP switch, 2-position
PRES. 50k trimmer Trimmer, 10%, 1/4”
DRIVE 100kB 16mm right-angle PCB mount pot
TONE 25kB 16mm right-angle PCB mount pot
VOL. 100kA 16mm right-angle PCB mount pot
CLIP DPDT cntr. off Toggle switch, DPDT on-off-on
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.
FSW 3PDT Stomp switch, 3PDT
ENC 125B Enclosure, die-cast aluminum Can also use a Hammond 1590N1.

ACHILLES AMP OVERDRIVE 5
BUILD NOTES
Clipping diodes
The Prince of Tone uses MA856 diodes, which clip at a slightly higher threshold than standard silicon
diodes such as 1N914 (approximately 0.82V compared to 0.7V). These diodes are long out of production
and have almost entirely disappeared from the old-stock market, likely all bought up by Analogman and
other cloners.
The BA282 and BA283 are very close to the MA856, and were the popular substitute among builders
for awhile... until they dried up too.
Now, the closest option is the BAS33. These clip at around 0.8V, still significantly higher than the 1N914
and only slightly lower than the MA856. We’ve compared the curves on a Peak DCA75 and confirmed
that they closely match the MA856 across the current test range.
The only problem is that the BAS33 went end-of-life in early 2022. Availability is still high, but
eventually they’ll join the ranks of the others.
Clipping switch
The DPDT on-off-on switch allows for three settings: soft clipping (diodes in op-amp feedback loop),
hard clipping (diodes to ground after the second op-amp stage) or no clipping (all diodes lifted). If you do
not need the clean boost setting, you can instead use a DPDT on-on switch.
However, note that since the diodes are shared between the two settings and “relocated” in each
position, you cannot use an on-on-on switch to use both sets of diodes or it will cause issues with the
circuit.

SCHEMATIC
ACHILLES AMP OVERDRIVE 6
GND
2M2
1N5817
100uF
GND
+9V
100n
VA
100kA
25kB
100kB
22n
JRC4580D JRC4580D
VA
GND
100pF
100k
1M
VB
27k
33k
10n 10n
GND
10k
100n
VB
220k
6k8
1k
10n
VB
6k8
50kB
10n
VB
VB
1uF 1uF
1M
GND
10k
47k
47k
GND
100uF
GND
VB
1uF
VB
100k
100R
1k
47pF
IN
OUT
RPD
D1
C13
C14
VOLUME
1
2
3
TONE
1
2
3
DRIVE
1
2
3
C1
2
3
1
IC1A
6
5
7
IC1B
84
C2
R2
R1
R3
R4
C3 C5
R6
C6
R8
R9
D4 D5
D2D3
R10
C8
R12
PRESENCE
1
2
3
C9
C10 C11
R13
SW1B
3 4
SW1A
1 2 R7
R14
R15
C12
C4
CLIPPING A
A2
A3
A1
B2
B3 B1
CLIPPING B
R5
R16
R11
C7
GND

ACHILLES AMP OVERDRIVE 7
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 assumes the use of closed-frame jacks like the Switchcraft 111X. If you’d rather use
open-frame jacks, please refer to the Open-Frame Jack Drill Template for the top side.
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.
x: -0.65, y: +1.71 x: 0.65, y: +1.71
ø9/32” ø9/32”
x: -0.85, y: +0.66
ø1/4”
x: 0, y: +0.66
ø9/32”
x: 0, y: -1.20
ø15/32”
x: -0.775, y: -1.20
ø5/16”
CENTER (0,0)
ø3/8” ø1/2”
0.385”
0.625” 0.625”
ø3/8”
OUT DC IN
125B
VOLUME
CLIPPING TONE
DRIVE
FOOTSWITCHLED
0 1 2
CM
0 1
INCH

ACHILLES AMP OVERDRIVE 8
ENCLOSURE LAYOUT
Enclosure is shown without jacks. See next page for jack layout and wiring.
125B

ACHILLES AMP OVERDRIVE 9
WIRING DIAGRAM
125B
IN +VGND N.C. N.C. OUT
PCB
IN
GND +V +V JACK GND JACK
OUTIN
GND GND PCB
OUT

ACHILLES AMP OVERDRIVE 10
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 cannotbe 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 (2022-04-08)
Initial release.