aion ANDROMEDA User manual

ANDROMEDA NATURAL OVERDRIVE 1
PROJECT NAME
ANDROMEDA
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Nobels ODR-1 Natural Overdrive
A unique overdrive pedal whose complex drive tone earns it a spot on the pedalboards of many Nashville
studio musicians.
Overdrive 1.0.2 (2020-10-29)
BUILD DIFFICULTY
Intermediate
Actual size is 2.3” x 1.86” (main board) and 2.3” x 0.86” (bypass board).

ANDROMEDA NATURAL 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 Andromeda Natural Overdrive is a recreation of the Nobels ODR-1, a somewhat obscure pedal
from Germany that nonetheless is considered a “secret weapon” among Nashville studio musicians.
The primary complaint of the ODR-1 is that it has way too much bass with no way to dial it out. To that
end, this project incorporates a variable bass control inspired by the Timmy and Zendrive. The stock
tones are still there with the knob all the way up, but now you have the option to dial it back.
Looking at the schematic, you can see a stark difference with Japanese-designed pedals (i.e. most Ibanez
& Boss circuits). This is German engineering at its finest—tons of odd-value resistors and capacitors
forming very precise filters and signal shaping. This is not a particularly simple build, but it’s very
rewarding and well worth the effort.
The new 125B version of the Andromeda has a new layout but is otherwise identical to the earlier
1590B version. No features were added or removed.
USAGE
The Andromeda has four controls:
• Gain controls the amount of gain from the op amp that is fed through the feedback clipping diodes.
• Spectrum is a very non-standard tone control of sorts. You can pan between a 700 Hz lowpass filter
and a 5 KHz high-pass filter, which is mixed with a fixed 2.1 KHz frequency boost (upper mids). This
control is much more complex than your standard high-cut or Tube Screamer style tone control.
• Bass allows you to adjust the bass response of the circuit. The stock ODR-1 circuit is the equivalent
of having the Bass knob turned all the way up.
• Level sets the overall output of the effect.

ANDROMEDA NATURAL 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 33k Metal film resistor, 1/4W
R2 1M Metal film resistor, 1/4W
R3 3k3 Metal film resistor, 1/4W
R4 2k7 Metal film resistor, 1/4W
R5 10k Metal film resistor, 1/4W
R6 1k8 Metal film resistor, 1/4W
R7 820R Metal film resistor, 1/4W
R8 1k5 Metal film resistor, 1/4W
R9 12K Metal film resistor, 1/4W
R10 39K Metal film resistor, 1/4W
R11 10K Metal film resistor, 1/4W
R12 12k Metal film resistor, 1/4W
R13 5k1 Metal film resistor, 1/4W
R14 2k2 Metal film resistor, 1/4W
R15 150K Metal film resistor, 1/4W
R16 3k3 Metal film resistor, 1/4W
R17 1k2 Metal film resistor, 1/4W
R18 43K Metal film resistor, 1/4W
R19 10K Metal film resistor, 1/4W
R20 20K Metal film resistor, 1/4W
R21 4k7 Metal film resistor, 1/4W
R22 22K Metal film resistor, 1/4W
R23 5k1 Metal film resistor, 1/4W
R24 1k2 Metal film resistor, 1/4W
R25 150K Metal film resistor, 1/4W
R26 150K Metal film resistor, 1/4W
R27 15K Metal film resistor, 1/4W
R28 15K Metal film resistor, 1/4W
LEDR 4k7 Metal film resistor, 1/4W LED current-limiting resistor. Adjust value to change LED brightness.

ANDROMEDA NATURAL OVERDRIVE 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
C1 68n Film capacitor, 7.2 x 2.5mm
C2 22n Film capacitor, 7.2 x 2.5mm
C3 120pF MLCC capacitor, NP0/C0G
C4 82n Film capacitor, 7.2 x 2.5mm
C5 2.2uF Film capacitor, 7.2 x 5mm
C6 2.2uF Film capacitor, 7.2 x 5mm
C7 2n7 Film capacitor, 7.2 x 2.5mm
C8 82n Film capacitor, 7.2 x 2.5mm
C9 1n Film capacitor, 7.2 x 2.5mm
C10 22n Film capacitor, 7.2 x 2.5mm
C11 27n Film capacitor, 7.2 x 2.5mm
C12 100n Film capacitor, 7.2 x 2.5mm
C13 8n2 Film capacitor, 7.2 x 2.5mm
C14 560pF MLCC capacitor, NP0/C0G
C15 8n2 Film capacitor, 7.2 x 2.5mm
C16 4n7 Film capacitor, 7.2 x 2.5mm
C17 82n Film capacitor, 7.2 x 2.5mm
C18 1uF Film capacitor, 7.2 x 3.5mm
C19 2.2uF Film capacitor, 7.2 x 5mm
C20 470n Film capacitor, 7.2 x 3.5mm
C21 1uF Film capacitor, 7.2 x 3.5mm
C22 100uF Electrolytic capacitor, 6.3mm Power supply filter capacitor.
C23 47uF Electrolytic capacitor, 5mm Reference voltage filter capacitor.
C24 47uF Electrolytic capacitor, 5mm Reference voltage filter capacitor.
C25 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
D4 1N914 Fast-switching diode, DO-35
D5 1N914 Fast-switching diode, DO-35
D6 1N914 Fast-switching diode, DO-35 Optional. Bridge the jumper pads between D6 and D7 for the stock
ODR-1 circuit.
D7 1N914 Fast-switching diode, DO-35 Optional. Bridge the jumper pads between D6 and D7 for the stock
ODR-1 circuit.

ANDROMEDA NATURAL OVERDRIVE 5
PARTS LIST, CONT.
PART VALUE TYPE NOTES
Q1 2N5457 JFET, N-channel, TO-92 Commonly-available substitute. Original uses BC264D.
Q2 2N5088 BJT transistor, NPN, TO-92 Commonly-available substitute. Original uses 2SC2362G.
IC1 JRC4558D Operational amplifier, DIP8
IC2 JRC4558D Operational amplifier, DIP8
IC1-S DIP-8 socket IC socket, DIP-8
IC2-S DIP-8 socket IC socket, DIP-8
GAIN 250kA 16mm right-angle PCB mount pot
LEVEL 50kA 16mm right-angle PCB mount pot
SPECT 25kB 16mm right-angle PCB mount pot
BASS 50kC 16mm right-angle PCB mount pot Modification. Turn it all the way up for the stock ODR-1 circuit.
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.

ANDROMEDA NATURAL OVERDRIVE 6
BUILD NOTES
Bass Control
Most drive pedals will cut bass before clipping the signal. The classic benchmark is the Tube Screamer’s
720Hz filter, and most drive pedals are somewhere in this range.
The stock ODR-1 does not have very much bass-cut, and so in most rigs, it has an enormous low end
that doesn’t work very well. This is the biggest complaint about the circuit and is the fatal flaw in an
otherwise exceptional design.
Fortunately, it’s an easy problem to solve. By adding a Bass control to allow the bass to be cut down to
reasonable levels, the Andromeda becomes an incredibly usable drive effect. And with the knob all the
way up, it’s exactly like the stock ODR-1 circuit.
If for some reason you do want to leave off this control, you can jumper pins 2 and 3 of the Bass pot to
eliminate it entirely.
Clipping Diodes
The ODR-1 circuit uses both soft clipping diodes (op-amp feedback) and hard clipping diodes (signal to
ground). The hard clipping diodes clip the signal pretty aggressively, and as a result, they remove some of
the character of the effect.
The Andromeda has been modified to have two extra diodes, D6 and D7, in series with the existing hard-
clipping diodes. It’s recommended to use these. However, they are not on a switch that allows them to
be toggled in and out, so they can’t be added and removed on a whim.
If you don’t want to use the additional diodes, you can either run jumper wires across them or you can
just bridge the two jumper pads to the immediate left of D7.

SCHEMATIC
ANDROMEDA CLASSIC OVERDRIVE 7
1N5817
100uF
GND
+9V
100n
VA
33k
2N5457
1M
GND
15K
15K
GND GND
3k3
GND
68n
2k7
10k
22n
GND
120p
250kA
82n
1k5
820R
12K
1k8
2n7
GND
39K 10K
82n
1n
12k
GND GND
22n
5k1
43K
25kB
27n
100n
8n2
2N5088
150K
3k3
2k2
GND
GND
1k2 20K
10K
560p
4k7 8n2
GND
22K
5k1
4n7
82n
1k2
50kA
150K
150K
GND
JRC4558D
JRC4558D
JRC4558D
JRC4558D
GND
GND
GND
470n
47uF
50kC
1uF
47uF
GND
GND
GND
VA
VA
VA
VA VB
VB
VB
VB
VB
VB
VB
2u2
2u2
1uF
2u2
D1
C22
IN
OUT
C25
R1 Q1
R2
R27
R28
R3
C1
R4
R5
C2
C3
GAIN
1
2
3
C4
R8
R7
R9
R6
C7
R10 R11
C8
C9
R12
C10
R13
R18
SPECTRUM
1
2
3
C11
C12 C13
Q2
R15
R16
R14 R17 R20
R19
C14
R21
C15 R22
R23
C16
C17
R24
LEVEL
1
2
3
R25
R26
2
3
1
IC1A
6
5
7
IC1B
84
2
3
1
IC2A 6
5
7
IC2B
84
D3
D2
C20
D5
D4
C23
BASS
1
2
3
C21
C24
C6 C19
C18
C5
D7 D6
JUMPER
GND

ANDROMEDA NATURAL OVERDRIVE 8
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, 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
LEVEL GAIN
SPECTRUM BASS
FOOTSWITCHLED
x: -0.65, y: +1.71 x: 0.65, y: +1.71
ø9/32” ø9/32”
x: -0.65, y: +0.41
ø9/32”
x: 0.65, y: +0.41
ø9/32”
0 1 2
CM
0 1
INCH

ANDROMEDA NATURAL OVERDRIVE 9
ENCLOSURE LAYOUT
Enclosure is shown without jacks. See next page for jack layout and wiring.
125B

ANDROMEDA NATURAL OVERDRIVE 10
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.

ANDROMEDA NATURAL OVERDRIVE 11
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
1.0.2 (2020-10-29)
Updated links for new website.
1.0.1 (2019-07-28)
Removed RPD from parts list. (Not used in this circuit.)
1.0.0 (2018-08-22)
Initial release.