GOD CITY INSTRUMENTS Gorilla Glasses V1.0 User manual

God City Instruments – Gorilla Glasses V1.0 Build Guide
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GOD CITY INSTRUMENTS – Gorilla Glasses V1.0 Build guide
The God City Instruments (GCI) Gorilla Glasses is a DIY friendly version of the GCI Ape Eye pedal which uses a
common DIP-08 single op amp running at +/- 9VDC instead of Ape Eye’s discrete op amp running at +/- 15VDC.
The sound is full, dynamic, and expressive, holding its own against many beloved boutique overdrives.
Experienced builders will recognize the topology as a Fetzer Valve style Jfet boost in front of a Distortion+ /
DOD250 style distortion circuit. This PCB has been designed to be an easy build with minimum components,
yet still offer the builder enough flexibility to tailor the tone to their own tastes.
Regarding the TC7660H, this is a charge pump which inverts +9VDC to -9VDC, allowing for +/-9V (18V total)
operation. This can be substituted for TC7660SCPA, but some capacitor value changes are required. Check
data sheets prior to making this substitution.
Regarding C9; If an older single op amp is used, it may require an external compensation cap. In that case,
populate C9. This is not required for most current op amps.
If a clipping diode switch is desired, omit D1, D2 and D3 and run wires from the D3 position to a switch for off-
board clipping diode options.
To bias the Jfet, set a DMM to detect DC voltage in the appropriate range, connect the black probe to ground
(typically dropping it in one of the enclosures threaded holes is adequate) and the red probe to the VD pad.
Apply power to the pedal. Adjust trim pot until DC voltage reads 4.5v. You can further adjust by ear while
playing.
This pedal is an easy build, but this guide is intended for people who have some experience building pedals.
Component sourcing, component identification, assembly techniques, wiring stomp switches, etc. is not
covered. The GCI Brutalist Jr. assembly guide has helpful information for less experienced builders. That guide
can be found here:
http://www.kurtballou.com/brutalistjr/
Available separately is the GCI 3PDT utility PCB for PCB pin 3PDT footswitches. This PCB makes footswitch
wiring quick and easy. Not compatible with solder lug style switches.
Don’t forget to connect the ground pad of the PCB to the ground lug of the input, output, and DC power jacks!
Due to the scope of this project, technical support is not available. However, consider joining the GCI DIY PCB
Builders group on Facebook to get advice from and share your work with other builders. We require that all
group members agree to the rules before being accepted into the group.
https://www.facebook.com/groups/2454786551255317/
Component values for the PCB as well as some alternate values are listed below. This is a BOM for the PCB
only. Resistors and diodes are 6.3mm leg spacing, film and ceramic capacitors are 5.08mm leg spacing, and
electrolytic capacitors are 2.54mm leg spacing. I/O jacks, DC jack, switch, enclosure, and knobs are not listed.
The schematic and a drill template for a 125B (1590N1) sized enclosure are also attached.

God City Instruments – Gorilla Glasses V1.0 Build Guide
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Part
Value
Description
Substitute
Notes
C1
2.2n
film capacitor
C2
10n
electrolytic capacitor
4.7n-22n
Input high pass
C3
10u
film capacitor
4.7u-22u
Affects Jfet gain
C4
22n
film capacitor
10n-0.1u
Interstage HPF
C5
0.1u
MLCC
C6
100u
electrolytic capacitor
C7
0.15u
film capacitor
0.1u-0.22 u
Affects tightness of bottom end. Bigger is looser.
C8
150p
MLCC
100p-470p, Polystyrene
Drive circuit low pass filter. Bigger is warmer.
C9
30p
MLCC
33p, none
Required for externally compensated op amps
C10
0.1u
MLCC
C11
1u
MLCC
C12
0.1u
MLCC
C13
100u
electrolytic capacitor
47u-220u
Power filtering
C14
1u
film capacitor
0.47u-4.7u
Coupling cap
C15
1u
film capacitor
0.47u-4.7u
Coupling cap
C16
1u
MLCC
C17
1u
MLCC
C18
3.9n
film capacitor
2.7n-4.7n
Affects range of tone control
CLR
4.7k
1/4 watt resistor
1k-10k
Affects LED brightness
R1
1M
1/4 watt resistor
R2
6.8k
1/4 watt resistor
R3
2.2M
1/4 watt resistor
R4
100R
1/4 watt resistor
R5
1k
1/4 watt resistor
R6
100k
1/4 watt resistor
R7
1M
1/4 watt resistor
R8
4.7k
1/4 watt resistor
R9
470R
1/4 watt carbon resistor
Metal
Carbon is more resilient to power supply issues
R10
1.8k
1/4 watt resistor
1k-2.7k
Smaller increases gain and tightness.
R11
10R
1/4 watt carbon resistor
Metal
Carbon is more resilient to power supply issues
R12
10R
1/4 watt carbon resistor
Metal
Carbon is more resilient to power supply issues
R13
4.7k
1/4 watt resistor
D1
1n5818
Schottky Diode
D2
1n5818
Schottky Diode
D3
RED
3mm LED
Yellow, Green
Affects clipping symmetry
D4
1n5818
Schottky Diode
D5
1n5818
Schottky Diode
D6
1N5818
Schottky Diode
LED
L1
3mm LED
IC1
LM741
Op Amp
TL071, NE5534, LF356
Pin compatible single op amp capable of 18v supply

God City Instruments – Gorilla Glasses V1.0 Build Guide
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IC2
TC7660H
Charge Pump
TC7660SPCA
Adjust power supply caps accordingly
Q1
J201
Jfet
J113, MPF5102, 2n5857
Pin compatible Jfet
Q_BIAS
25k
Trim Pot
20k-100k
Affects bias range
VOL
A100k
16mm Pot
A50k
GAIN
A250k
16mm Pot
CLIP
A5k
16mm Pot
TONE
B100k
16mm Pot
B25k, B50k
Affects range of tone control
S
PAD
Send to PCB
L+
PAD
LED+
L-
PAD
LED-
R
PAD
Return from PCB
V
PAD
9V input
VD
PAD
Jfet bias test
G
PAD
Ground

God City Instruments – Gorilla Glasses V1.0 Build Guide
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God City Instruments – Gorilla Glasses V1.0 Build Guide
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0.3125
0.125
0.50
0
0.829
1.379
1.929
3.828
0 0.559 1.309 2.059
0.375
0.50
0 0.772 1.309 1.847
0
0.454
0.914