aion Parhelion User manual

PARHELION VINTAGE OVERDRIVE 1
PROJECT NAME
PARHELION
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Boss®OD-1 OverDrive
A precursor to the Tube Screamer, known for being the first overdrive effect to utilize diodes in a
negative-feedback arrangement for clipping purposes.
Overdrive 1.0.1 (2021-04-02)
BUILD DIFFICULTY
Easy
Actual size is 2.3” x 1.86” (main board) and 1.78” x 0.86” (bypass board).

PARHELION VINTAGE OVERDRIVE 2
TABLE OF CONTENTS
1Project Overview 7Drill Template
2Introduction & Usage 8Enclosure Layout
3-4 Parts List 9Wiring Diagram
5Build Notes 10 Licensing
6Schematic 10 Document Revisions
INTRODUCTION
The Parhelion Vintage Overdrive is based on the Boss OD-1 OverDrive, originally released in 1977 as
one of their first compact pedals alongside the SP-1 Spectrum and PH-1 Phaser.
The OD-1 is notable for being the first overdrive effect to utilize diodes in an op-amp’s negative
feedback loop for clipping purposes. Like the Distortion+, it lacks a tone control, but most who play
through it say it doesn’t need one.
The OD-1 had two different versions. The original 1977 version used the Raytheon RC4303 quad
op-amp (called the “quad version”). The second version from December 1980 used a single 4558 dual
op-amp (the “dual version”) and changed the input & output buffers to transistor emitter followers as a
cost-savings measure, as in most of their later pedals. The original quad version is said to sound better
and is what the Parhelion project is based on.
While the RC4303 is long out of production, they can still be found without too much trouble. They
share a standard pinout with other quad op-amps such as the LM324 and LM348, so there are many
other options that will perform similarly.
The Parhelion has two toggle switches allowing for a little more flexibility. A clipping switch selects
between three different sets of diodes, and an EQ switch changes the gain structure of the op-amp
clipping stage for higher gain and more bass.
Note: The legacy 1590B version of the Parhelion was called the Corona. The updated version was given a new
name upon release in 2021 for obvious reasons.
USAGE
The Parhelion has the following controls:
• Drive controls the amount of gain in the op-amp feedback diode clipping stage.
• Volume controls the overall output of the effect.
• Clip (toggle switch) selects between three sets of diodes: 1x silicon (stock), 2x silicon, and LEDs.
• EQ (toggle switch) selects between two different tones: stock mode (similar to the Tube Screamer)
and another mode with slightly higher gain and less bass cut.

PARHELION VINTAGE 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 1k Metal film resistor, 1/4W
R2 220k Metal film resistor, 1/4W
R3 10k Metal film resistor, 1/4W
R4 33k Metal film resistor, 1/4W
R5 4k7 Metal film resistor, 1/4W
R6 3k3 Metal film resistor, 1/4W
R7 10k Metal film resistor, 1/4W
R8 10k Metal film resistor, 1/4W
R9 10k Metal film resistor, 1/4W
R10 4k7 Metal film resistor, 1/4W
R11 470k Metal film resistor, 1/4W
R12 470R Metal film resistor, 1/4W
R13 100k Metal film resistor, 1/4W
R14 33k Metal film resistor, 1/4W
R15 33k Metal film resistor, 1/4W
R16 100R Metal film resistor, 1/4W Power supply filter resistor.
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 47n Film capacitor, 7.2 x 2.5mm
C3 47pF MLCC capacitor, NP0/C0G
C4 47n Film capacitor, 7.2 x 2.5mm
C5 330n Film capacitor, 7.2 x 2.5mm
C6 18n Film capacitor, 7.2 x 2.5mm
C7 1uF Film capacitor, 7.2 x 3.5mm
C8 100n Film capacitor, 7.2 x 2.5mm
C9 1uF Film capacitor, 7.2 x 3.5mm
C10 47uF Electrolytic capacitor, 5mm Reference voltage filter capacitor.
C11 100uF Electrolytic capacitor, 6.3mm Power supply filter capacitor.
C12 100n MLCC capacitor, X7R Power supply filter capacitor.

PARHELION VINTAGE OVERDRIVE 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
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
D7 (jumper) Jumper for stock OD-1.
D8 3mm LED LED, 3mm, red diffused
D9 3mm LED LED, 3mm, red diffused
IC1 LM348N Operational amplifier, quad, DIP-14 Original uses Raytheon RC4303AP. LM348N is a close substitute.
IC1-S DIP-14 socket IC socket, DIP-14
DRIVE 1MA 16mm right-angle PCB mount pot
VOL. 10kB 16mm right-angle PCB mount pot
CLIP SPDT cntr off Toggle switch, SPDT on-off-on
EQ SPDT on-on Toggle switch, SPDT on-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.
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.

PARHELION VINTAGE OVERDRIVE 5
BUILD NOTES
Clipping diodes
The original OD-1 used asymmetric clipping, with one diode in one direction and two in the other. An
extra diode has been included on the Parhelion in case you want to experiment with other clipping
options, but for the stock mode you will want to jumper D7.
The “up” position of the toggle switch engages this mode, while the “down” position is adapted from the
Tube Screamer (one diode in each direction).
If you include D7, the clipping will be symmetrical, but at a higher threshold that could be described as
slightly more open or transparent.

SCHEMATIC
PARHELION VINTAGE OVERDRIVE 6
GND
2M2
1N5817
100uF
GND
+9V
100n
VA
LM348N
LM348N
LM348N
LM348N
1MA
10kB
1k
220k
10k
33k
4k7
10k
10k
10k
4k7
470k
470R
100k
100n
47n
47n
18n
1uF
100n
1uF
1N914
1N914
330n
3k3
GND
47pF
GND
VB
VB
VB
VB
VB
VB
VA
33k
33k
47uF
GND GND
VB
100R
IN
OUT
RPD
D1
C11
C12
IC1A
2
3
1
IC1D
13
12
14
6
5
7
IC1B
9
10
8
IC1C
DRIVE
1
2
3
VOLUME
1
2
3
R1
R2
R3
R4
R5
R7
R8
R9
R10
R11
R12
R13
C1
C2
C4
C6
C7
C8
C9
D2
D3
D4 D5
D6D7
C5
R6
C3
411
EQ
2
3 1
D8
D9
CLIP
2
3
1
R14
R15
C10
R16
GND

PARHELION VINTAGE 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.
0 1 2
CM
0 1
INCH
x: -0.65, y: +1.71 x: 0.65, y: +1.71
ø9/32” ø9/32”
x: -0.65, y: +0.41
ø1/4”
x: 0.65, y: +0.41
ø1/4”
x: 0, y: -1.20
ø15/32”
x: -0.775, y: -1.20
ø5/16”
CENTER (0,0)
125B
ø3/8” ø1/2”
0.385”
0.625” 0.625”
ø3/8”
OUT DC IN
VOLUME DRIVE
EQ CLIP
FOOTSWITCHLED

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

PARHELION VINTAGE 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
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.

PARHELION VINTAGE 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 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
1.0.1 (2021-04-02)
Corrected D7 in parts list, which should be jumpered for the stock OD-1 circuit.
1.0.0 (2021-03-19)
Initial release.