aion Nimbus User manual

NIMBUS DYNAMIC OVERDRIVE 1
PROJECT NAME
NIMBUS
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Maxon®OD-820 Overdrive Pro
A modern reimagining of the classic Tube Screamer circuit, featuring a dual drive/blend control adapted
from the Klon Centaur.
Overdrive 1.0.0 (2021-03-19)
BUILD DIFFICULTY
Intermediate
Actual size is 2.3” x 1.86” (main board) and 1.78” x 0.86” (bypass board).

NIMBUS DYNAMIC 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 Nimbus Dynamic Overdrive is an adaptation of the Maxon OD-820 Overdrive Pro, first released in
2004 as part of Maxon’s Vintage Series alongside the AD-999 Analog Delay, DS-830 Distortion Master,
PH-350 Rotary Phaser, and a few others.
Despite the name, the Vintage Series were not reissues of vintage circuits. The pedals in the series were
released in the same big-box enclosure style they used in the 1970s, but featuring all-new designs,
vintage-inspired with modern improvements.
With its bipolar +/-9V charge pump and dual-pot “gain/blend” control, the Maxon OD-820 Overdrive
Pro actually shares a lot of concepts with the Klon Centaur. They are often compared with one another
in sound, but it is by no means a clone. The OD-820 is actually a little closer to a Tube Screamer with
regard to its clipping diodes and tone control. (Check out this Legendary Tones article from 2004
comparing the OD-820 with the Klon Centaur.)
The OD-820 is the same circuit as the later VOP-9 Vintage Overdrive Pro. The OD-820 has a larger
enclosure that matches the other Vintage Series effects while the VOP-9 is housed in the smaller
standard Ibanez 9-series enclosure.
USAGE
The Nimbus has the same control layout as most overdrive or distortion effects:
• Drive is a dual-gang potentiometer that simultaneously controls the amount of gain in the op-amp
feedback diode clipping stage and blends between clean and drive, similar to the Klon Centaur.
• Tone controls the treble response of the effect. The center point (12:00) is flat. When turned to the
left, it cuts treble, and when turned to the right, it boosts treble.
• Volume controls the overall output of the effect.

NIMBUS DYNAMIC 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 10k Metal film resistor, 1/4W
R4 560R Metal film resistor, 1/4W
R5 62k Metal film resistor, 1/4W
R6 2k2 Metal film resistor, 1/4W
R7 1k Metal film resistor, 1/4W
R8 56k Metal film resistor, 1/4W
R9 100k Metal film resistor, 1/4W
R10 7k5 Metal film resistor, 1/4W
R11 20k Metal film resistor, 1/4W
R12 56k Metal film resistor, 1/4W
R13 1k Metal film resistor, 1/4W
R14 220R Metal film resistor, 1/4W
R15 1k Metal film resistor, 1/4W
R16 47k Metal film resistor, 1/4W
R17 100k Metal film resistor, 1/4W
R18 100k Metal film resistor, 1/4W
R19 1k Metal film resistor, 1/4W
R20 10k Metal film resistor, 1/4W
R21 10k 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 100n Film capacitor, 7.2 x 2.5mm
C2 1uF Film capacitor, 7.2 x 3.5mm
C3 100pF MLCC capacitor, NP0/C0G
C4 100n Film capacitor, 7.2 x 2.5mm
C5 220n Film capacitor, 7.2 x 2.5mm
C6 10n Film capacitor, 7.2 x 2.5mm
C7 220n Film capacitor, 7.2 x 2.5mm

NIMBUS DYNAMIC OVERDRIVE 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
C8 10pF MLCC capacitor, NP0/C0G
C9 220n Film capacitor, 7.2 x 2.5mm
C10 1uF Film capacitor, 7.2 x 3.5mm
C11 22pF MLCC capacitor, NP0/C0G
C12 1uF Film capacitor, 7.2 x 3.5mm
C13 47uF Electrolytic capacitor, 5mm Reference voltage filter capacitor.
C14 10uF Electrolytic capacitor, 5mm Charge pump capacitor.
C15 100uF Electrolytic capacitor, 6.3mm Inverted supply filter capacitor.
C16 470n MLCC capacitor, X7R Inverted supply filter capacitor.
C17 100uF Electrolytic capacitor, 6.3mm Power supply filter capacitor.
C18 100uF Electrolytic capacitor, 6.3mm Power supply filter capacitor.
C19 100n MLCC capacitor, X7R Power supply filter capacitor.
D1 1N5817 Schottky diode, DO-41
D2 1N914 Fast-switching diode, DO-35
D3 1N914 Fast-switching diode, DO-35
Z1 1N4742A Zener diode, 12V, DO-41
Q1 2N5457 JFET, N-channel, TO-92 Original uses 2SK246. Can substitute any general-purpose audio JFET.
IC1 JRC4558D Operational amplifier, DIP-8
IC1-S DIP-8 socket IC socket, DIP-8
IC2 JRC4558D Operational amplifier, DIP-8
IC2-S DIP-8 socket IC socket, DIP-8
IC3 TC1044SCPA Charge pump, DIP-8
IC3-S DIP-8 socket IC socket, DIP-8
DRIVE 250kB dual 16mm dual pot, right angle
TONE 20kW 16mm right-angle PCB mount pot
VOL. 100kA 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
NIMBUS DYNAMIC OVERDRIVE 5
GND
2M2
1N5817
100uF
20kW
100kA
+9V
100n
VA
10k
1M
100n
2N5457
10k
VB
VB
VA
GND
1uF
250kB
560R
62k
GND
JRC4558D
JRC4558D
JRC4558D
JRC4558D
VA
-VA
100pF
1N914
250kB
2k2
100n
GND
1k
220n
56k
GND
100k
GND
GND
10pF
56k
1k
7k5
10n
220n
20k
GND
220R
1k
VA
-VA
220n
GND
1uF
47k
GND
GND
20pF
100k
1uF
100k
1k
GND
10k10k
GND
47uF
GND
TC1044SCPA
100uF
PWR_GND
-VA
470n
100uF
PWR_GND
10uF
GND PWR_GND
1N4742A
IN
OUT
RPD
D1
C18
TONE
1
2
3
VOLUME
1
2
3
C19
R1
R2
C1
Q1
R3
C2
DRIVE_A
1
2
3
R4
R5
2
3
1
IC1A
84
6
5
7
IC1B
2
3
1
IC2A
6
5
7
IC2B
84
C3
D2
D3
DRIVE_B
1
2
3
R6
C4
R7
C5
R8
R9
C8
R12
R13
R10
C6
C7
R11
R14
R15
C9
C10
R16 C11
R17
C12
R18
R19
R20R21
C13
1
2
3
4 5
6
7
8
IC3
C15 C16
C17
C14
Z1
GNDGND

NIMBUS DYNAMIC 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 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.
0 1 2
CM
0 1
INCH
x: -0.65, y: +1.71 x: 0.65, y: +1.71
ø9/32” ø9/32”
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)
125B
VOLUME DRIVE
TONE
FOOTSWITCHLED
ø3/8” ø1/2”
0.385”
0.625” 0.625”
ø3/8”
OUT DC IN

NIMBUS DYNAMIC OVERDRIVE 7
ENCLOSURE LAYOUT
Enclosure is shown without jacks. See next page for jack layout and wiring.
Note: The upper pads for the dual-gang gain potentiometer appear to be cut in half. This is intentional!
It’s called a plated half-hole or castellated hole, and it’s used so that the PCB can lay flat across the pots
instead of angling upward to make room for the dual pot.
Solder it like you would if they were normal pads, but bend the small set of pins forward slightly so they
make contact with the edge of the pads. The solder will flow easily into the half-holes.
125B

NIMBUS DYNAMIC OVERDRIVE 8
WIRING DIAGRAM
125B
IN +VGND GND 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.

NIMBUS DYNAMIC 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 (2021-03-19)
Initial release.