PROJECT NAME APERTURE BASED ON BUILD DIFFICULTY Ampeg Scrambler Easy

EFFECT TYPE DOCUMENT VERSION Octave-Up Fuzz 1.0.0 (2021-07-02)

PROJECT SUMMARY A legendary octave-up fuzz effect with a blend control that makes it great for bass guitar.

Actual size is 2.3” x 1.86” (main board) and 1.78” x 0.86” (bypass board).

APERTURE OCTAVE FUZZ 1 TABLE OF CONTENTS

1 Project Overview 7 Enclosure Layout 2 Introduction & Usage 8 Wiring Diagram 3-4 Parts List 9 Licensing 5 Schematic 9 Document Revisions 6 Drill Template

INTRODUCTION

The Aperture Octave Fuzz is an adaptation of the Ampeg Scrambler, an exceptionally rare octave-up fuzz pedal originally released in 1969. It’s said that fewer than 2,500 units were produced, and today the originals typically sell for over USD$1,000 on the used market. The Scrambler is an octave-up fuzz in the vein of the Superfuzz, fOXX Tone Machine and Octavia— although all four circuits use their own techniques to generate the octave, so they all sound different. Due to its largely un-filtered bass content and clean blend control, the Scrambler is particularly good for bass guitar, as you would expect from a company that primarily makes bass equipment. Ampeg reissued the Scrambler in 2005 in a vintage-style enclosure. According to Analogman, these reissues are very faithful to the originals, but not identical. In 2017, the Scrambler was again reissued, this time in a modernized enclosure and including a treble control and output volume, and marketed as a “bass overdrive” with no mention of fuzz. It’s not known how accurate these circuits are to the original, but they have received mixed reviews and are not regarded to sound like either the old ones or the 2005 reissues, so it is likely that the resemblance is in name only. The Aperture project is faithful to the original 1969 Scrambler, with the addition of an optional volume boost stage as well as a master volume control at the end. The original unit suffers from excessively low volume, so the make-up gain stage from the Univox Superfuzz has been adapted for this circuit. With the gain boost disabled and the Volume knob at full, the circuit is 100% identical to a vintage Scrambler.

USAGE

The Aperture has the following controls:

• Texture is sort of a gain control, but not in the traditional sense of clipping or compression.

• Blend sets the ratio between clean and effect.

• Volume is the master output volume control. It is disabled unless boost mode is engaged.

• Boost (toggle) enables or disables an optional gain stage at the end of the circuit.

APERTURE OCTAVE FUZZ 2 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 ) 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 , 1/4W

R2 1M Metal film resistor, 1/4W

R3 4k7 Metal film resistor, 1/4W

R4 2k2 Metal film resistor, 1/4W

R5 470k Metal film resistor, 1/4W

R6 4k7 Metal film resistor, 1/4W

R7 220R Metal film resistor, 1/4W

R8 8k2 Metal film resistor, 1/4W

R9 220k Metal film resistor, 1/4W

R10 220k Metal film resistor, 1/4W

R11 1k Metal film resistor, 1/4W

R12 470R Metal film resistor, 1/4W

R13 47k Metal film resistor, 1/4W

R14 47k Metal film resistor, 1/4W

R15 100k Metal film resistor, 1/4W

R16 15k Metal film resistor, 1/4W

R17 1k Metal film resistor, 1/4W

R18 10k Metal film resistor, 1/4W

R19 100R 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 10n Film , 7.2 x 2.5mm

C2 4.7uF Electrolytic capacitor, 4mm

C3 100uF Electrolytic capacitor, 6.3mm

C4 22uF Electrolytic capacitor, 5mm

C5 4.7uF Electrolytic capacitor, 4mm

C6 4.7uF Electrolytic capacitor, 4mm

C7 1uF Film capacitor, 7.2 x 3.5mm

C8 1uF Film capacitor, 7.2 x 3.5mm

C9 1uF Film capacitor, 7.2 x 3.5mm

APERTURE OCTAVE FUZZ 3 PARTS LIST, CONT. PART VALUE TYPE NOTES C10 1uF Film capacitor, 7.2 x 3.5mm

C11 100uF Electrolytic capacitor, 6.3mm Power supply filter capacitor.

C12 100n MLCC capacitor, X7R Power supply filter capacitor.

D1 1N5817 Schottky , DO-41

D2 OMIT The factory schematic shows this diode as 1N456, but says it is not used.

D3 1N456 diode, DO-35

D4 1N456 Rectifier diode, DO-35

D5 OMIT The factory schematic shows this diode as 1N456, but says it is not used.

D6 OMIT The factory schematic shows this diode as 1N456, but says it is not used.

Q1 MPSA14 Darlington , NPN, TO-92 Substitute. Original uses 2N5306.

Q2 2N3904 BJT transistor, NPN, TO-92 Substitute. Original uses BC169B.

Q3 MPSA14 Darlington transistor, NPN, TO-92 Substitute. Original uses 2N5306.

Q4 MPSA14 Darlington transistor, NPN, TO-92 Substitute. Original uses 2N5306.

Q5 2N3904 BJT transistor, NPN, TO-92

OCT. 10k Trimmer, 10%, 1/4" Set to about 40% rotation (11:00) for stock circuit.

TEXT. 10kB 16mm right-angle PCB mount pot

BAL. 50kB 16mm right-angle PCB mount pot

VOL. 50kB 16mm right-angle PCB mount pot

BOOST DPDT Toggle , DPDT

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.

APERTURE OCTAVE FUZZ 4 SCHEMATIC

+9V VA

D1

1N5817 C12 C11 VA

100n 100uF VA F 8 u 1 C k 8 0 1 1 GND GND R k k 5 4 0 7 1 1 0 4 R R

VA VA 1 0 F F 9 1 u u 1 BOOST_A BOOST_B C 1 1 C VA VA E C A1 Q5 B1 B N 2 VA k A2 B2

A 2N3904

0 OUT 1 3 3 7

GND L 6 k 5 A3 B3 1 k A 1 E R k 6 E 4 R B R 5 1 F M B B 3 U 1 7 R u

k VA k U T 1 C k 2 2 0 0 L 7 X 1 0 k 9 1 5 M 1 O 4 5 E 2 1 R R 1 R V T 2 D D n 1 1 1 0 C 1 k k 3 5 0 7 Q1 Q3 Q4 1 7 IN R 4

R GND 7 5 MPSA14 4 u 7 C MPSA14 2 4 u k 3 6 4 C 2 0

R4 2 D GND GND 8 2 0 D D M k 1 P

M Q2 2 R R 1 8 R R 2 2k2 2N3904 2 R 2 7 GND 3 0 1 k R 7 4 R 4 D2 C3 C4 GND GND GND 7

R 100uF 22uF

220R C6

GND 3

4u7 E V k A 0 2 T

GND GND GND 1 C O 1

D2, D5 and D6 left empty in original units. GND The factory schematic shows them, but indicates that they are omitted.

APERTURE OCTAVE FUZZ 5 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.

INCH 125B 0.385”

0 1 0.625” 0.625”

ø3/8” ø3/8” CM ø1/2” OUT DC IN

0 1 2

VOLUME TETURE

x: -0.65, y: +1.71 x: 0.65, y: +1.71 ø9/32” ø9/32”

BOOST BALANCE

x: -0.85, y: +0.66 x: 0, y: +0.66 ø1/4” ø9/32”

CENTER (0,0)

LED FOOTSWITCH

x: -0.775, y: -1.20 x: 0, y: -1.20 ø5/16” ø15/32”

APERTURE OCTAVE FUZZ 6 ENCLOSURE LAYOUT

Enclosure is shown without jacks. See next page for jack layout and wiring.

125B

APERTURE OCTAVE FUZZ 7 WIRING DIAGRAM

IN GND +V N.C. N.C. OUT

PCB GND +V +V JACK GND JACK GND GND PCB IN IN OUT OUT

125B

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.

APERTURE OCTAVE FUZZ 8 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 (2021-07-02) Initial release.

APERTURE OCTAVE FUZZ 9