Electric Roots BIRMINGHAM PREAMP User manual

Birmingham Preamp @ Electric Roots
Version 1.0
10/19/2020
BIRMINGHAM PREAMP
It's 1969 and something's about to change the game forever: The ground-shaking
dark sound of Heavy Metal is about to take off from Birmingham. Inspired by The
Man of the Riff and the famous Laney Supergroup our Birmingham Preamp is
taking back modern Doom Metal by storm!
59x40mm

Birmingham Preamp @ Electric Roots
Version 1.0
10/19/2020
Knobs
VOL
Controls the output volume
GAIN A
Controls the amount of gain for channel A
GAIN B
Controls the amount of gain for channel B
BASS
Controls the low frequencies
MIDS
Controls midrange frequencies
TREBLE
Controls the high frequencies
BOM
Resistors
R1
1K5
R2
100k
R3
56k
R4
68k
R5
820R
R6
1k5
R7
1M
R8
1M
R9
68k
R10
470k
R11
470k
Capacitors
C1
22nF
C2
22nF
C3
22nF
C4
22nF
C5
220p
C6
270p
C7
220p
C8
220p
C9
220p
C10
22uF(elec)
C11
22uF(elec)
C12
100uF(elec)
Transistors
Q1
SST5457
Q2
SST5457
Q3
SST5457
Q4
SST5457
Diodes
D1
1N4001
Potentiometers
VOL
A100k
GAIN A
A1M
GAIN B
A1M
BASS
A1M
MIDS
A25k
TREBLE
A250k
TRIM1
100k
TRIM2
100k
TRIM3
100k
Other
DPDT
on/on/on

Birmingham Preamp @ Electric Roots
Version 1.0
10/19/2020
Suggestions
Beware of Counterfeit components, if you want quality products, order a kit ,
don’t use ceramic capacitors over 1nF they tend to have microphonic
characteristics in some setups.
Wiring

Birmingham Preamp @ Electric Roots
Version 1.0
10/19/2020
Notes
This PCB requires proper JFET biasing. They need to be biased to around 4,5V but
you can also do it by ear. If you want to bias them correctly, you need to hook up
the PCB to a 9V power supply. Take your multimeter and connect the black
(negative) tip to ground and the positive tip to „Drain“ (Have a look at the
schematic, it’s marked with a „D“).
You can now read the voltage and carefully trim those pots one after another.
CLR is usually 4k7 – 10k. The value depends on how bright you like your status LED.

Birmingham Preamp @ Electric Roots
Version 1.0
10/19/2020
Mods
Try different transistors (SSTJ201)
You can also tweak the tone stack to your liking

Birmingham Preamp @ Electric Roots
Version 1.0
10/19/2020
Schematic

Birmingham Preamp @ Electric Roots
Version 1.0
10/19/2020
License
By buying and using this product you confirm that you have read, understood
and accepted our Terms and Conditions (electric-roots.com/termsandconditions).