aion HORIZON User manual

HORIZON AMP OVERDRIVE 1
PROJECT NAME
HORIZON
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Catalinbread Dirty Little Secret Mk. I
An “amp in a box” drive pedal inspired by the sounds of 1970s Marshall amplifiers.
Overdrive 1.0.0 (2018-09-22)
BUILD DIFFICULTY
Easy
Actual size is 2.3” x 1.86” (main board) and 2.3” x 0.86” (bypass board).

HORIZON AMP 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 Horizon Amp Overdrive is a recreation of the Catalinbread Dirty Little Secret Mk I, a unique drive
pedal that resembles a Marshall amp stack in its response and tone.
The DLS Mk I was the first of three versions, and is often considered the best—or at least, different
enough that subsequent versions should have been released as new pedals. They share some DNA in
common, but they have very different tonestacks and tweakability.
The DLS circuit uses cascaded mu-amps as a foundation. There are no op-amps or clipping diodes. The
clipping signal is generated entirely by the JFETs, giving it a different flavor than diode-clipping-based
overdrives.
USAGE
The Horizon has three controls and two switches:
• Gain controls the signal level before the clipping stage.
• Tone is passive treble cut after the gain stage.
• Level sets the overall output of the effect.
• Rock/Rawk (toggle) changes the filtering in a couple places to give a different flavor to the tone.
• Bright (toggle) allows switching between a few different “treble bleed” capacitors on the gain
control to allow better matching between different types of guitars. This is a modification to the
DLS circuit, but it was recommended by the original designer.
Considered a “foundation” pedal, it’s recommended to use the Horizon as you would use an amplifier in
your signal chain. Boost, compression, drive and wah effects should go before it, and modulation & delay
should go after it.

HORIZON 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 47k Metal film resistor, 1/4W
R3 10k Metal film resistor, 1/4W
R4 1M Metal film resistor, 1/4W
R5 1M Metal film resistor, 1/4W
R6 4k7 Metal film resistor, 1/4W
R7 470k Metal film resistor, 1/4W
R8 200k Metal film resistor, 1/4W
R9 22k Metal film resistor, 1/4W
R10 470k Metal film resistor, 1/4W
R11 1M Metal film resistor, 1/4W
R12 1M Metal film resistor, 1/4W
R13 1M Metal film resistor, 1/4W
R14 4k7 Metal film resistor, 1/4W
R15 22k Metal film resistor, 1/4W
R16 12k Metal film resistor, 1/4W
R17 200k Metal film resistor, 1/4W
R18 47R Metal film resistor, 1/4W
LEDR 4k7 Metal film resistor, 1/4W LED current-limiting resistor. Adjust value to change LED brightness.
C1 47n Film capacitor, 7.2 x 2.5mm
C2 100pF MLCC capacitor, NP0/C0G
C3 220n Film capacitor, 7.2 x 2.5mm
C4 4.7uF Electrolytic capacitor, 4mm
C5 22n Film capacitor, 7.2 x 2.5mm
C6 47n Film capacitor, 7.2 x 2.5mm
C7 470pF MLCC capacitor, NP0/C0G
C8 200pF MLCC capacitor, NP0/C0G
C9 47pF MLCC capacitor, NP0/C0G
C10 220pF MLCC capacitor, NP0/C0G

HORIZON AMP OVERDRIVE 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
C11 4n7 Film capacitor, 7.2 x 2.5mm
C12 47n Film capacitor, 7.2 x 2.5mm
C13 47pF MLCC capacitor, NP0/C0G
C14 10uF Electrolytic capacitor, 5mm
C15 2.2uF Film capacitor, 7.2 x 5mm
C16 33n Film capacitor, 7.2 x 2.5mm
C17 3n3 Film capacitor, 7.2 x 2.5mm
C18 100n MLCC capacitor, X7R Power supply filter capacitor.
C19 100uF Electrolytic capacitor, 6.3mm Power supply filter capacitor.
D1 1N5817 Schottky diode, DO-41
Q1 2N5457 JFET, N-channel, TO-92
Q2 2N5457 JFET, N-channel, TO-92
Q3 2N5457 JFET, N-channel, TO-92
Q4 2N5457 JFET, N-channel, TO-92
Q5 2N5457 JFET, N-channel, TO-92
Q6 2N5457 JFET, N-channel, TO-92
GAIN 1MA 16mm right-angle PCB mount pot
TONE 100kB 16mm right-angle PCB mount pot
VOL 100kB 16mm right-angle PCB mount pot
ROCK DPDT on-on Toggle switch, DPDT on-on
BRIGHT SPDT cntr off Toggle switch, SPDT 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.
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.

HORIZON AMP OVERDRIVE 5
BUILD NOTES
JFET selection
The original DLS circuit uses 2N5457 JFETs. Here’s the bad news: through-hole JFETs are getting very
scarce these days, and the 2N5457 is no exception.
The good news: with JFETs, there is nothing magical about a specific part number. There is wide variance
even within a specific part number, and another part number with similar characteristics will sound
exactly the same.
For the DLS circuit, you’re looking for JFETs with a relatively low VGS(off) (also called VP, for pinch-off
voltage) as that determines when it goes into clipping. The 2N5457 has an average VPof around -1.6V.
Based on these parameters, any of the following JFETs should be comparable:
• 2SK30A-Y
• J113
• PN4393
• 2N5484
Not all of these have been tested, so this is purely based on reviewing the datasheets. There may be
several other types as well. But with JFETs, it’s best to have a variety of options so you have a better
chance of finding something that works.
If you can’t find JFETs with the right specifications, note that just about any general-purpose JFET will
sound good in this circuit. But, you’ll find that something with a higher VPwill go into clipping later,
reducing the total amount of drive available to the circuit and changing the characteristics of the effect.

SCHEMATIC
HORIZON AMP OVERDRIVE 6
GND
1M
1N5817
100uF
100kB
1MA
GND
100kB
+9V
100n
VA
47n
47k
100pF
2N5457
10k
GND
GND
2N5457
2N5457
220n
4u7
1M1M
GND
VA
47R
VA
VA
4k7
GND
22n
47n
470k
470pF
200k
200pF
GND
47pF 220pF 4n7
22k
GND
47n
1M
47pF
GNDGND
2N5457
GND
2N5457
2N5457
10uF
1M1M
VA
GND
VA
VA
4k7
GND
22k
12k
33n
200k
GND
GND
3n3
GND GND
470k
2u2
R1
D1
C19
VOLUME
1
2
3
GAIN
1
2
3
TONE
1
2
3
IN
OUT
C18
C1
R2
C2
Q1
R3
Q2
Q3
C3
ROCKA
A2
A3
A1
C4
R4R5
R18
R6
C5
C6
R7
C7
R8
C8
ROCKB
B2
B3
B1
BRIGHT
2
3 1
C9 C10 C11
R9
C12
R11
C13
Q4
Q5
Q6
C14
R12R13
R14
R15
R16
C16
R17
C17
R10
C15
GND

HORIZON 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
ROCK/RAWK BRIGHTTONE
GAIN
FOOTSWITCHLED
x: +0.85, y: +0.66
ø1/4”
0 1 2
CM
0 1
INCH

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

HORIZON 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
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.

HORIZON 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 (2018-09-22)
Initial release.