aion Cirrus User manual

CIRRUS DYNAMIC OVERDRIVE 1
PROJECT NAME
CIRRUS
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Ibanez®ST-9 Super Tube Screamer
An updated version of the Tube Screamer featuring a frequency-adjustable midrange boost that can be
placed either before or after the drive stage.
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).

CIRRUS DYNAMIC 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 Cirrus Dynamic Overdrive project is a clone of the Ibanez ST-9 Super Tube Screamer, an incredibly
rare Tube Screamer variant only produced from 1983-84. It’s essentially a stock Tube Screamer with an
added stage, a semi-parametric midrange control that delivers a fixed boost at a variable frequency.
The ST-9 was introduced near the end of the original run of the 9-series and was quickly discontinued
along with the rest of the series. However, the circuit reappeared the next year in 1985 as part of the
Master Series, this time called the STL Super Tube. This series had broader distribution and so the STL
version is much easier to find.
Curiously, the STL version made one major change to the circuit: transplanting the mid-boost stage after
the clipping instead of before, where the original ST-9 put it before. There are no other changes to the
circuit, but there is a notable difference between pre-clipping and post-clipping mid boost.
The Cirrus project incorporates both versions, allowing the mid-boost section to be placed either before
or after the clipping using an on-board slide switch. (This is the main update from the original 1590B
version of the Cirrus, which uses on-board jumpers to set the mid-boost location but can’t be toggled.)
In addition to the mid-boost slide switch, the Cirrus also includes a clipping diode switch so you can
select between three different sets of diodes.
USAGE
The Cirrus has the following controls:
• Drive controls the amount of gain in the op-amp feedback diode clipping stage.
• Bite is a semi-parametric midrange control with fixed boost.
• 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.
• Clip (toggle switch) selects between three sets of diodes: 1x silicon (stock), 2x silicon, and LEDs.
• Mid EQ (slide switch) selects the location of the mid-boost section, either before the drive stage
(ST-9 mode) or after (STL mode).

CIRRUS 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 1k Metal film resistor, 1/4W
R2 510k Metal film resistor, 1/4W
R3 220k Metal film resistor, 1/4W
R4 7k5 Metal film resistor, 1/4W 1k5 if using 20kC midrange pot. See build notes.
R5 7k5 Metal film resistor, 1/4W 1k5 if using 20kC midrange pot. See build notes.
R6 10k Metal film resistor, 1/4W
R7 51k Metal film resistor, 1/4W
R8 4k7 Metal film resistor, 1/4W
R9 1k Metal film resistor, 1/4W
R10 10k Metal film resistor, 1/4W
R11 220R Metal film resistor, 1/4W
R12 1k Metal film resistor, 1/4W
R13 1k Metal film resistor, 1/4W
R14 510k Metal film resistor, 1/4W
R15 10k Metal film resistor, 1/4W
R16 10k Metal film resistor, 1/4W
R17 470R Metal film resistor, 1/4W
R18 10k Metal film resistor, 1/4W
R19 10k Metal film resistor, 1/4W
R20 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 47n Film capacitor, 7.2 x 2.5mm
C2 1uF Film capacitor, 7.2 x 3.5mm
C3 5n6 Film capacitor, 7.2 x 2.5mm 27n if using 20kC midrange pot. See build notes.
C4 15n Film capacitor, 7.2 x 2.5mm 68n if using 20kC midrange pot. See build notes.
C5 1uF Film capacitor, 7.2 x 3.5mm
C6 47pF MLCC capacitor, NP0/C0G
C7 47n Film capacitor, 7.2 x 2.5mm
C8 100n Film capacitor, 7.2 x 2.5mm

CIRRUS DYNAMIC OVERDRIVE 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
C9 220n Film capacitor, 7.2 x 2.5mm
C10 1uF Film capacitor, 7.2 x 3.5mm
C11 100n Film capacitor, 7.2 x 2.5mm
C12 1uF Film capacitor, 7.2 x 3.5mm
C13 47uF Electrolytic capacitor, 5mm Reference voltage filter capacitor.
C14 100uF Electrolytic capacitor, 6.3mm Power supply filter capacitor.
C15 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
D7 1N914 Fast-switching diode, DO-35
D8 3mm LED LED, 3mm, red diffused
D9 3mm LED LED, 3mm, red diffused
Q1 2N5088 JFET, N-channel, TO-92 Original uses 2SC1815-BL.
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
DRIVE 500kA 16mm right-angle PCB mount pot
TONE 20kW 16mm right-angle PCB mount pot
BITE 100kC dual 16mm dual pot, right angle Original ST-9 uses 20kC, but values have been scaled for 100kC. See
build notes for more information.
LEVEL 100kB 16mm right-angle PCB mount pot
MIDEQ 4PDT slide Slide switch, 4PDT, E-Switch
EG4208
CLIP 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.

CIRRUS DYNAMIC OVERDRIVE 5
BUILD NOTES
Mid-boost resistor & capacitor values
The original ST-9 and STL used a 20kC dual pot for the midrange control. This value is hard to find, at
this time only available from Tayda Electronics in straight-pin knurled shaft format. It can be made to
work for this PCB, but it’s not easy.
Fortunately, this type of parametric filter can easily be adjusted for different potentiometer values. In
fact, most other circuits that use this type of parametric EQ use 100kC—for example, the Lab Series L5
Preamp and the Pearl OD-05 Overdrive.
Accordingly, for this project, the surrounding values in the parametric filter have been modified so
you can instead use a 100kC dual pot, which is much easier to find. By increasing the resistor values
and reducing the capacitor values in the mid-boost section by a factor of 5, it will preserve the same
frequency characteristics.
If you do find a 20kC potentiometer and want to use it, here are the original values:
• C3: 27n
• C4: 68n
• R4: 1k5
• R5: 1k5
Boost level
The Ibanez ST-9 Super Tube Screamer product manual says that the midrange supplies a +25 dB boost.
However, some who have played it have noted that it doesn’t sound like it’s anywhere near +25 dB, and
in fact others have calculated it at +8 dB, which seems more accurate.
If you don’t feel like +8 dB is enough, the gain boost can be adjusted by increasing the difference
between C3 and C4. The only side effect is that in this type of parametric circuit, by increasing the
frequency gain, you also increase the Q (width). If the Q is too wide it won’t sound very good at all.
To get the full 25 dB with the same available frequency range, use the following values:
• C3: 5n6
• C4: 270n
If you want more than stock but not that much more, use the values from the Pearl OD-05, which at +15
dB is right in the middle:
• C3: 4n7
• C4: 68n
Note that these are changes from the 100kC adjusted values, not the stock 20kC values. Scale
accordingly if using a 20kC boost pot.

SCHEMATIC
CIRRUS DYNAMIC OVERDRIVE 6
1N914
D2-3
1N914
D4-7
D8-9 LED
GND
2M2
1N5817
100uF
GND
+9V
100n
VA
100kB
500kA
20kW
100kC 100kC
47n
1k
510k
1uF
220k
5n6
7k5 7k5
15n
1uF
10k
51pF
51k
1k
10k
100n
GND
1k
220n
GND
220R
1uF
1k
GND
100n
510k
2N5088
10k
GND
10k
470R
1uF
GND
47n
4k7
GND
GND
VB VB
VB VB
VB
VA
VA
VA
GND
GND
47uF
10k
10k
VB
GND GND
100R
IN
OUT
RPD
D1
C14
C15
LEVEL
1
2
3
1
2
3
DRIVE
IC1A
2
3
1IC1B
6
5
7IC2B
6
5
7
IC2A
2
3
1
TONE
1
2
3
1
2
3
BITEB
1
2
3
BITEA
C1
R1
R2
C2
R3
C3
R4 R5
C4
C5
R6
C6
R7
R9
R10
C8
R12
C9
R11
C10
R13
C11
R14
Q1
R15 R16
R17
C12
C7
R8
CLIP
2
3
1
84
84
C13
R18
R19
R20
SW1B
5
6
4
SW1C
8
9
7
SW1D
11
12
10
GND

CIRRUS DYNAMIC 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, 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
TONE BITE
LEVEL DRIVE
FOOTSWITCHLED
CLIP
x: 0, y: +1.06
ø1/4”
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”

CIRRUS DYNAMIC OVERDRIVE 8
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

CIRRUS DYNAMIC 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.

CIRRUS DYNAMIC 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
1.0.0 (2021-03-19)
Initial release.