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AUDIO AMP + 3KHz FILTER
This circuit is the audio amp section for a complete optical transmitter.
The circuit amplifies and filters the voice audio signals from an electret microphone.
The circuit is described in more detail in the receiver section of Dave Johnson's
Handbook of Optical Through the Air Communications.
Links to electronic circuits,
electronic schematics, designs for engineers, hobbyists, students & inventors:
A DC-Coupled Tube Amplifier With Futterman Output Stage for Dynamic Headphones -
The Futterman output stage in this tube amp offers the choice of DC- and AC-coupled
outputs. The class AB design can output up to 24mW into a 30-Ohm load or nearly 500mW
into a 600-Ohm load. Designed by Rudy van Stratum (Circuit design added
04/05/06)
A Fender-Tone Tube Headphone Amplifier - This tube amplifier with sonic
controls has a paralleled White cathode follower output stage for driving low
impedance headphones. The sonic controls consist of a Fender tone stack (bass, mid and
treble), and ambience and blend controls. Includes simulation files for use with OrCAD
Lite software. Designed by Alex Cavalli (Circuit design added 04/05/06)
A Gainclone for the PC Age - Audio input comes from either the Line-Out of
the PC or an external sound card (described later). A small filter consisting of
680Ω/47pF excludes any RF signals from entering the case. 470nF input capacitor should
have a high voltage rating since...(circuit added 07/08/09) designed by Malcolm
Rix
A Good IR Detector - Some of the companies put two transmitters, one on each
side of the detector, to get a good field of coverage for the front of the 'bot and to
detect left and right. 'Robots, Inspiration to Implementation has a great schematic
that you can use to build one of these. I used all Radio Shack parts for the one I
made and it cost about $10 to build. This detector will NOT detect black flower
pots nor the bottom of boots (grin)....(electronic Circuit added 03/06)
A HiFi Preamp - The PGA2310 is a pretty neat chip. It's capable of
attenuating a stereo source over a 127dB range (-95.5dB to +31.5dB) with 0.5dB steps.
It has a maximum gain error of +/-0.05dB, and THD of 0.0004% at 1KHz. The sweet spot
between THD and noise appears to be between 3V RMS and about 8V RMS....(circuit added
04/05/06)
A JFET-MOSFET Headphone Driver - This amplifier is based on the MOSFET
headphone driver by Greg Szekeres. It has a JFET impedance buffer front-end and a
choke-input power supply. The sound characteristic of the amplifier can be tuned by
adjusting the low pass filter formed with the input capacitance of the MOSFET.
Designed by Richard Murdey (Circuit design added 04/05/06)
A Low-Voltage Class-A Tube Headphone Amplifier - This OTL design features a
high-voltage power supply that is less than half of the one used in the author's first
amp and most other tube amps, but without compromising performance. Designed by
Helmut Ahammer (Circuit design added 04/05/06)
A Musical Distortion Primer - This is an introduction to the basic means of
distorting a signal in a musically useful way. The approach is as non-technical as
possible. I use the simplest signal waveform, a sine wave, to illustrate all
these, although a guitar is much more like a sawtooth than a sine wave. The clipped
waveforms will be shown in their raw state....(Circuit design added 04/05/06)
A Pocket Headphone Amplifier - This is a Chu Moy headphone amp I made. I got
the PCB design from Guzzler from Head-Fi and the original design is very popular and
is here. I changed Guzzler's layout so I could use a Taiwan Alpha pot on the PCB.
These pots a high quality (some say better than ALPS blue velvet) and are available
from Jaycar. You can see the thread here. I also made a DIY Brown dog adapter so I
could use two OPA627 single opamps in a dual opamp socket.
A Pure Class A Dynamic Headphone Amplifier - A high-current output amplifier
for low-impedance dynamic headphones such as the Grados. The amplifier features an new
servo biasing circuit which operates entirely outside the audio feedback loop. The
author includes a balanced-bridge version of the amp for headphones that are wired in
dual-mono as well as instructions for converting a Grado SR80 to dual-mono
operation.... Designed by Kevin Gilmore (Circuit design added 04/05/06)
