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2010 FiveFish Studios
For comments & corrections about this guide, please email [email protected]
www.fivefishstudios.com
X-12 Microphone Preamp Kit
Diodes
Diodes are semiconductor devices that permit current flow only in one direction. Think of it as a one-
way valve.
The X-12 preamp kit uses 2 different kinds of diodes.
1.
The first type of diode we’re using is the SIGNAL DIODE. They have glass body, and used
around the relays and the soft-start phantom power.
2.
The second type of diode we use is the General Purpose, Rectifier Diode. They are black, with
a white/silver band. They’re used for the local on-board voltage regulator as protection
diodes.
NOTE: Diodes have polarities just like electrolytic capacitors. One side is denoted as the ANODE (or
positive side) and the other side is the CATHODE (or negative side). If you soldered these diodes in the
wrong position, your phantom power or preamp may not work. Follow the band markings on the PCB
silkscreen layout.
Transistor
We’re using a transistor as a switching device in the X-12 Mic Preamp Kit. The transistor
has (3) legs, the Collector, Base and Emitter terminals. Looking from the top, the transistor
has a half-circle shape, like a half-moon.
Take note when inserting transistors that you do not insert them backwards. Otherwise,
phantom power will not work, and possibly even ruin the transistor. The flat side should be
facing to the right.
Grayhill Selector Switch
The X-12 uses a sealed, high-performance, high-quality, 12-position, Grayhill selector switch.
It’s the RED Selector switch
below.
Some boutique preamp manufacturers also use Grayhill selector switches for their preamps. They are durable, reliable, have a
nice solid feel to it, and provide good resistance to RF Interference. This switch will be the most commonly used/abused
mechanical device on the X-12 preamp. I want this part to withstand being turned and turned and turned and is just one of the
expensive parts in this kit.
LED-Illuminated Push Button Switch
The X-12 also use a high quality, PCB mounted LED-Illuminated Push Button switch. From left to right, the functions are 48V
Phantom Power, -20dB Pad, and Polarity Reverse. Each switch has it’s own color. If you re-arrange the switches, make sure to
re-arrange the LED current-limiting resistors too.
