API 321 mic preamp schematic - Schematic only, no circuit description. . . [Alan Garren]
Audio preamp - . . .
Audio preamplifier - . . . [Andy Wilson's site]
Audio Preamplifier - A 2 stage audio pre-amplifier with very good performance. This preamplifier has two
direct-coupled common emitter stages and uses series-voltage feedback. The circuit has high input impedance, low
output impedance, voltage gain can be set independently and has low noise levels and good signal noise ratio. . .
. [Andy Collison's website]
Audio Pre-Amplifier - This simple circuit provides good gain to weak audio signals. . . . [Tony van Roon's
Audio PreAmplifier (Reconnsworld) - this is a very easy circuit to build, all parts can be found at the local electronics shop,
no matter how worthless it (the local shop, ) usually is. . . [Andy Wilson's site]
Balanced Low Noise Microphone Preamp - very low noise, close to oretical minimum, high hum rejection and variable gain with a
single rotary pot, similar to that used in many professional grade mixing desks . . .
Balanced Microphone Preamp - As I said in my cheapo digital audio project document, I was going to build a microphone
preamp to attach a Behringer ECM8000 measurement microphone to line input of my minidisc deck. After scanning the
web to see if similar projects existed, I basically found three kinds - ones that used transformers (ie. pretty
expensive to start with) and some even followed those with tubes and another transformer (damn expensive). . . .
[designer does not give his name]
Band 2 PreAmplifier - . . . [Andy Collison's website]
Bride of Zen - The Bride of Zen (BOZ), designed by Nelson Pass and described in The Audio Amateur, 1994, is
a very simple line-level preamplifier which contains only a single medium-power MOSfet per channel (see the
schematic on this page). Mr. Pass has given a very lucid account of the design philosophy. Building instructions
including the lay-out for a printed circuit board can be downloaded from Passlabs. According to mr. Pass, the
variable resistor P102 should be adjusted in such a way that the voltage drop over resistor R108 (in the absence
of an input signal) is 4 Volts. However, in my own homebuilt BOZ I found this to be incorrect. The preamp sounded
good using a cassette deck or an FM tuner as the signal sources. However, using a CD player a nasty form of
distortion occurred during crescendos. . . . [from a.van.waarde's web site]
Build a good GaAs FET preamp for
2 meters, 222MHz or 440MHz - . . .
Car PreAmplifier & Artificial Earth - Especially for car audio installations, can be used for any single supply system. . .
Computer Microphone - This circuit was submitted by Lazar Pancic from Yugoslavia. The sound card for a PC
generally has a microphone input, speaker output and sometimes line inputs and outputs. The mic input is designed
for dynamic microphones only in impedance range of 200 to 600 ohms. Lazar has adapted the sound card to use a
common electret microphone using this circuit. . . [Andy Collison's website]
Dual Mike Preamp power
supply Gerber - . . . [Forssell Technologies/Fred
Forssell or the original designers as shown on the schematic pages]
Dual Mike Preamp
power supply Gerber - . . .
Dynamic Microphone Preamp
- Notice how the transistor bias current flows through
the microphone. A similar circuit can be used with an 8 ohm speaker but in that case you would put it in place of
the emitter resistor. . . [Reverse engineered schematic by Stepan Novotill]
Preamplifier - A low noise pre-amplifier suitable for
amplifying dynamic microphones with 200 to 600 ohm output impedance. . . [Andy Collison's website]
ECM Mic Preamplifier - A microphone amplifier that may be used with either Electret Condenser Microphone (ECM)
inserts or dynamic inserts, made with discrete components. . . . [Designer Andy Collison]
Electret MIC Amplifier - . . . [Andy Wilson's site]
Electret Mic Booster - NOTE:
Must register on this site. . . [Published in Elecktor July/Augu, 2010]
Guitar Preamplifier - This is a circuit for a guitar
preamplifier that can capture mechanical vibrations (any standard guitar pickup) and then convert them into an
electrical signal. The signal is then amplified by an audio amplifier. . . . [© EFY Enterprises Pvt. Ltd. All
FET Preamp Cable - . . .
FM Band PreAmplifier - Here is a high performance RF amplifier for the FM band which can be successfully built
without any special test equipment. The grounded-gate configuration is inherently stable without any
neutralization if reasonably good layout techniques are employed. The output transformer is designed to resonate
with the FET's drain capacitance at about 92 MHz giving the amplifier the highest gain at the low end of the band
where the weaker stations operate. No tuning capacitor is needed as long as the transformer is built precisely as
described . . . [Copyright © 1998 Wenzel Associates, Inc.]
General purchase audio preamplifier based on pair
of 2N2222 transistors - The two small circuits below are
simple pre-amplifiers that can easily be assembled to be used with many of your intended audio projects . Any
similar transistors can be used. The RF potentiometer adjust the negative feed back used to bias to Q1 while Q2
provides for a low impedance output. . . .