autocostruzione, circuiti elettronici, building, electronic
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Autocostruzione di Circuiti Audio
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Low power (<30W)
High power (>30W)
Professional audio amplifier circuit diagrams
Other related documents
Headphone amplifier accessories
Application notes and datasheets
Tube amplifier related circuits
Mixer circuit parts
Input
Output
Input and output in same circuit
Other circuits
DI-box is an electronic device for helping to interface electronic
music instruments (like electric guitar and syntetizer) to mixing desks. DI-box is
designed to transfer the sound of your instrument to the mixing console, adding nothing
and taking away nothing. The function of DI box is to convert an unbalanced, high
impedence source, to a balanced, low impedence source for improved noise immunity and to
avoid degradation from long (more than few meters) cable runs. The output of the DI box is
connected to the balanced microphone input of the mixing desk. One of the most important
things a DI has to do is create a balanced signal from an unbalanced signal. Typical terms
you will see are "transformer balanced" and "actively balanced." The
result is a balanced, low impedance send that can travel down a snake without coupling all
manner of noise on a line or instrument level signal. Typical keyboard or other musical
instrument suplies a low impedance, but unbalanced output (which is prone to pick up noise
on long runs).
Generally DI box takes an unbalanced input and (with varying amounts
of isolation depending upon the box) provides a balanced line. It may also provide other
functions - ground lifts, gain pad, etc. Many DI boxes provide also ground isolation which
helps you to get rid of humming caused by ground loops (Hum and buzz are often caused by a
connection between the mixer and ground at the guitar system.) DI-box can be used as a
"splitter" when you plug (say) a guitar pickup in one 1/4" unbalanced jack
and 1 /4" unbalanced patch to the guitar amp into the other.
General information
Simple DI box ideas
Transformer isolated DI box designs
Active Di box designs
Signal splitters
Signal isolation boxes
Signal combining
Conversion between professional and consumer equipments
Other related circuits
A mic preamp boosts the very sensitive low level (millivolts) audio
signal from a microphone to a more usable level, called "line level" (typicaly
from 0.1V to few volts). The mic level signal can easily be degraded by cable length,
cable capacitance, and other such things. A line level signal is vastly more robust, and
is the level used to ship audio around from consoles, to processing equipment, to
recorders or amplifiers.
- 2-wire Remot Microphone
Amplifier - uses special amplifier module from Opamp
Labs
- A High Performance
Transformer-Coupled Microphone Preamplifier
- A Low Noise
Microphone Preamp with Phantom Power Option
- Amplified
Ear - Useful to listen in faint sounds 1.5V Battery operation, includes electret
microphone preamplifier which runs from 1.5V DC and can directly drive 32 Ohms impedance
mini-earphones
- A
Vacuum Tube Microphone Preamp / Direct Box Project - from January 1997 EQ Column,
includes phantom power
supply
- Balanced
mic/line amp with TUBES - uses two 12AU7 tubes in a class-A cathode-driven input
stage, followed by a class-AB1 cathode follower output stage, 6db gain, requires 90VDC and
12VDC
- Balanced Microphone
Preamp Project - simple preamplifier with phantom power
- Balanced Low Noise
Microphone Preamplifier Design - ADI AN-115 (pdf, 78,935 bytes)
- Condenser
microphone hookup
- DIY Speaker Testing
Microphone Preamp
- Dual Phantom Power
Microphone Preamplifier - information and full schematic of a kit available from PAiA Electronics, take also look at the circuit diagram
- ECM Mic Preamplifier
- low noise electret microphone preamplifier
- Electric
Crayons, Anyone? (A Vacuum Tube Microphone Preamp / Direct Box Project) - published in
January97 EQ Column
- IC mic
preamp uses Jensen Twin-Servo topology
- Intercom preamp - a
convenient way of making an intercom is to use a loudspeaker as a microphone
- Jensen
Transformers Application Schematics - includes many microphone preamplifier related
circuits
- JT-13K6-C
in Simple One IC Stage Mic Preamp - 15KB PDF
- Kondensaattorimikrofonin
esivahvistin - simple preamplifier for electret microphone, text in Finnish
- Low Noise Balanced
Microphone Preamp - very low noise, close to the theoretical minimum, high hum
rejection and variable gain with a single rotary pot, similar to that used in many
professional grade mixing desks
- Low Noise
Microphone Preamplifier
- Mic-Pre Pan
Pot Circuit
- Microphone preamp
- very simple two transistor circuit
- Mu Stage Tube Mic
Pre - microphone preamp based on a Jensen transformer and an Alan Kimmel designed
"Mu-mode" gain stage
- PAiA Tube Mic Preamp
- Preamp for low-Z
microphones - This is a low input impedance, high quality pre-amplifier of the sort
that could be used in a stage mixing desk. This circuit is built using diescrete
transistors and uses a dual rail power supply.
- Rane MS 1b microphone
preamplifier circuit diagram - This is a circuit diagram of a commercial high quality
balanced microphone preamplifier. This document is in pdf format.
- Simple
microphone preamplifier - simple one transistor circuit
- Standard
Microphone Preamplifier Input Circuitry - pdf file
- Taos Amp Solid
State Mic Preamp - simple transformerless microphone preamp, includes circuit board
design
- Vintage
Neve Class A Circuit Information - Neve BA283AV Class A Preamaplifier Circuit
- Vocoder Input
Amplifier - This preamplifier has both microphone and line level input options, volume
control and tone control.
Microphone accessories
A phono preamplifer is a device which converts the electrical signal
from phono player to a line level signal. The output of a record player is much lower (few
mV) than a line-output signal, and needs to be frequency-corrected (RIAA-correction) and
amplified to make it usable as other line level signal sources. A typical phono input has
an EQ curve (RIAA) sloping over 40dB from low to high frequency. It also expects an input
of ~3.0 millivolts @1KHz.
- A Better Volume
Control - how to create a log pot that is better than the "real" thing
- A/B
Box Switch Project - A/B boxes can be handy tools for the musician. The simple box
offered here will allow you to switch between two different signal sources going into a
single amplifier. You can also switch a single source to two different destinations.
- Audio
level control with resistive optocouplers - Controlling the level of an audio signal
by means of an applied voltage or current has always been somewhat problematical but often
desirable. . This application note deals with voltage or current controlled attenuators
using optocouplers, primarily in relatively static situations.
- Audio
switching applications for resistive optocouplers - Electronically switching audio
signals can be a more complex matter than it might first appear. Not only are there the
obvious problems of interfacing between your control logic which is running off a 5V
supply and something that is probably controlling a larger voltage swing, but there are
the various imperfections of the switch element to consider, which can degrade your
precious audio signal.
- Bypass
Switch Wiring Diagram - Quite a few effects pedals lack the ability to give you a true
bypass. You can turn the effect off but the signal still goes through some of the effect
pedal's circuitry. Here is a simple circuit that you can build that will allow TRUE
BYPASS.
- CMOS IC
makes low-cost digital potentiometer
- Constant Power
"PAN" Control Circuit for Microphone for Microphone Audio Mixing
- Digitally
control gain over a ±40-dB range - digitally control an amplifier's gain over a
±40-dB range gain resolution of 1.25 dB
- Digital
stereo potentiometer - in pdf format, text in Finnish
- Digital Volume
Control - based on DS1669 Digital Pot IC
- Elektroninrn
potentiometri - electronic potentiometer for audio, text in Finnish
- Fixed
Attenuators - Fixed attenuators can be designed to have either equal or unequal
impedances and to provide any amount of attenuation (theoretically) equal to or greater
than the configuration's minimum attenuation - depending on the ratio of Z1/Z2.
Attenuators with equal terminations have a minimum attenuation of 0 dB. Unequal
terminations place a lower limit on the attenuation.
- Gain
Control - Applications as disparate as test equipment, audio, medical imaging, and
cellular base-station radios need to manage signal amplitudes in the analog domain. This
article tells about those applications.
- Inexpensive
relays form digital potentiometer - build a digitally controllable isolated
potentiometer which can tolerate voltages up to 60V dc
- Improve
FET-based gain control - One problem with standard FET gain-control circuits is
increased noise when you use the FET as a part of a resistive attenuator in series with an
op amp. When you substitute the FET for the gain-setting resistor in a noninverting op-amp
circuit, distortion limits the circuit configuration to applications in which the input
voltage is less than a few hundred millivolts.
- Linear
potentiometer implements logarithmic gain control - trimmer potentiometers are
ubiquitous components and are available in a variety of packages, resolutions, and
temperature stabilities but none of these potentiometers implements anything but the usual
linear function of resistance vs shaft position as useful in many audio applications
- Nine Ways to
Adjust Signal Level - This article describes few different ways to adjust audio signal
level.
- Op
amp linearizes attenuator control response - Professional-audio equipment commonly
uses Analog Devices' (www.analog.com) high-performance, quad-voltage-controlled SSM2164
attenuator. The control response is -30 dB/V, with 0V producing unity gain. Attenuation
increases as the applied control voltage increases in the positive direction. This circuit
extends the range of applications for this versatile chip by providing a simple means of
linearizing the control response. The result is an amplifier with gain directly
proportional to the control voltage.
- Printer
port activates CMOS switches - This cost-effective design provides control for CMOS
switches without the need for an external power supply
- Programmable-gain
amplifier is low-cost - Numerous programmable-gain amplifiers are available, but a
simple solution provides the option of using 256 gain steps with an 8-bit DAC and higher
steps with higher bit DACs.
- Single stage
gives logarithmic gain steps - by placing a variable component in the positive
feedback loop of an op amp, you can vary the gain of the stage logarithmically with
respect to a linear resistance or conductance
- Single
switch controls digital potentiometer - The control of electronic potentiometers in
most today's applications comes from controller-generated signals. However, a significant
number of applications exist that require adjustments using manual, front-panel controls.
This circuit uses one IC, one switch, and 10 discrete components. It implements the
interface of a single DPDT, momentary-contact rocker switch to a DPP (digitally
programmable potentiometer) that has a three-wire increment/decrement interface.
- Tack
a log taper onto a digital potentiometer - idea to convert linear digital
potentiometer to a logarithmic digital potentiometer
- Technical
Secrets of the Crossfader - A crossfader is designed to predictably control the
outputs of two separate mixer channels based on the relative position of the fader's knob
between its endpoints. It's a simple sounding task but there are many different ways the
job can be done, electrically and mechanically. This document describes some of the most
commonly used ones. Most crossfader circuits are implemented in one of two basic schemes.
- Variable-gain
stage uses voltage-output DAC
- VISW 8 x 4 Stereo
audio/video router
- Voice-Over
Circuit - swiches automatically from sound source to microphone when enough sound
comes in from microphone
- Voltage controlled amplifier
- three different circuits
- Voltage
Controlled Audio Panner - variable gain amplifier circuit
Filters and effects
- 10 band audio
equalizer - ascii drawing of simple circuit
- 3
KHz low pass filter plus audio amplifier - circuit uses a switched capacitor filter IC
MF6-50 from National Semiconductor to filter signals with frequencies higher than the 3KHz
needed for voice audio, pdf file
- Adjustable 60Hz
Filter - to filter out any HUM that may be picked up by a noisy power supply or long
wire connection
- "A"
Weighting Filter For Audio Measurements - design based on an old Ampex circuit
- Basic Active
Filter Circuit Blocks
- Closing
the loop deepens notches - Notch filters remove a single unwanted frequency from an
input signal. They are also a vital component of pulse-shaping networks, such as
time-averaging filters.
- Design of Passive
Crossovers
- Five Band Mono
Graphic Equaliser - basic mono unit originally designed for improving the apparent
sound quality when dubbing video
- A Basic
Introduction to Filters - application note on active, passive and switched capacitor
filters, document in PDF format
- Active Filters
- Butterworth, Bessel and Linkwitz filter example circuits and equations
- Audio Graphic Equaliser
- simple 7 band equalizer
- Basic
gyrator design - basic building block of graphic EQ
- Designing A
Pocket Equalizer For Headphone Listening
- Filters
- examples of very many different filter types, good page for filter design information
- Have Ya Ever Been
Too High?? - filter that is intended to take the harshness off some sources of sound
that have an upward response tilt, go to the end of page to find this circuit
- LMC835 -
Digital Controlled Graphic Equalizer IC, take also look at application note
- Multiple Feedback
Bandpass Filter
- Musical Instrument
(Expandable) Graphic Equaliser - standard equalizer plus bonus distortion unit
- Notch
Filter
- Parametric And
Sub-Woofer Equaliser - simple parametric equalizer circuit
- Passive
filters fill the bill at audio frequencies - Low-frequency filters, particularly at
audio frequencies, usually take the form of active filters. These filters eliminate
expensive inductors with windings of many turns. However, passive filters remain a viable
option when you quickly need low-cost prototypes and test pieces.
- Simple,
Easy Parametric and Graphic EQ's, Plus Peaks and Notches
- Subwoofer Equaliser
Using The Linkwitz Transform Circuit - The Linkwitz transform circuit is a hugely
flexible way to equalise the bottom end of a sealed loudspeaker enclosure. A speaker that
is corrected using this method is flat from below resonance to the upper limit of the
selected driver. The low frequency rolloff point is determined by the parameters of the
transform circuit. Should the enclosure size be too small and cause a lump in the response
before rolloff, this is also corrected. A conventional active crossover network is then
used to divide the subwoofer signal from the main channel signals. Note that there is also
a separate spreadsheet calculator
available for calculating component values for different situations not handled by the
original circuit.
- Tone
Control Circuit - classic Baxendall tone control circuit
- Tone Control
- based on TDA1524A tone control IC
- Tone controls with
2x NE 5532 - check also PCB
design and notes
An audio compressor serves to reduce (or compress) the dynamic range
of the input signal, keeping the level more constant, so that it may be more clearly heard
above background sounds, whether they be noise or accompanying musical sounds. An ideal
compressor introduces little distortion and noise when it is inactive, and controls the
audio level in a way that is pleasing to the listeners ear. >
An audio limiter serves to prevent the signal level from exceeding a
preset limit, and as such is often used to protect a following device from overload. These
can include recorders (both analog and digital), transmitters and power amplifier /
loudspeaker combinations. An ideal limiter introduces very little distortion or noise when
it is inactive, and controls the audio level in a way that is pleasing to the listener's
ear, while keeping tight control over the output level.
Electric guitars use usually stronger in voltage than a microphone
and yet lower than a line-level signal. Typical voltages for these signals are roughly 1
volt for line level signals, and maybe 100 millivolts for a microphone (depends on the
microphone type). The input impedance of guitar ampliifer is high (up to hundreds of
kilo-ohms).
- Analog Music Zone
Guitar Effects Schematics - guitar effects, compressors
- A/B
Box Switch Project - A/B boxes can be handy tools for the musician. The simple box
offered here will allow you to switch between two different signal sources going into a
single amplifier. You can also switch a single source to two different destinations.
- Bypass
Switch Wiring Diagram - Quite a few effects pedals lack the ability to give you a true
bypass. You can turn the effect off but the signal still goes through some of the effect
pedal's circuitry. Here is a simple circuit that you can build that will allow TRUE
BYPASS.
- Digital Echo
Unit - mono unit for producing special effects for amateur dramatics
- Distortion
Effect (for guitars) - three distortion circuit ideas
- Distortion
effect for guitars
- Effect Rack
Unit - contains very many guitar effect unit circuit diagrams
- Effectronics
Schematics - audio processing and effect circuits
- Guitar
Amplifiers - Guitar amplification is a specialised field, where much commonly
understood theory does not apply, and little theory is published. Technically speaking, a
guitar amplifier has a specific type of non-linear gain at its signal extremes, and a
specialised type of limited frequency response. This article collection has lots of
information on guitar amplifiers.
- Guitar
Amplifier Basics - This document tells about the technology of guitar amplifiers.
- Guitar
Amplifiers Overdrive & Distortion Effect Circuits
- Guitar
Effects Boxes - guitar effect schematics and articles
- Guitar Effec Circuits
- Wah, Fuzz and sustain circuits
- Guitar Fuzz
Effect - very compact circuit
- Guitar
Reverb Pedal - circuit for a guitar spring reverb pedal, it has dry, wet, and drive
controls for a wide variety of sounds
- Guitar-related
Circuits - effect circuit collection
- Guitar Vibrato Unit
- Harmony Central -
contains effect information, schematics
and construction tips
- Humbucking &
Noise-Reducing Electronics for guitars
- Improving a guitar
- information on rewiring an electric guitar
- Musical Instrument
(Expandable) Graphic Equaliser - standard equalizer plus bonus distortion unit
- Not Just
Another Headphone Amp - battery-powered musician's practice and monitoring amplifier
for guitar
- Slew
Rate Control - A circuit that limits the rate of change of a signal; a feature of this
design is that the positive and negative rates can be different.
- Spring Reverb
Unit For Guitar
- Stage Center
Reverb Unit - simple spring reverb unit
- The
GEO-Fex collection of vintage and new-design effects and musical related DIY
- The Guitar Effects Oriented Web Page
- FAQs and circuit diagrams
- The Guitar Effects Oriented Web Page
- Home of the Guitar Effects FAQ, the Tube Amp FAQ, the Tube Amp Debugging Page, and
"The Technology of" effects series.
- The
Technology of the Tube Screamer - The Tube Screamer series of distortion/overdrive
boxes from Ibanez has a reputation that has led them to pass into musical urban myth.
Helped along with Stevie Ray's use of them, the TS 808 and TS 9 have been sought after and
traded up to astronomical prices. All the members of the TS family share a common
technical design, with the similarities vastly overwhelming the differences. This document
describes the technologies used in them.
- The
Technology of Wah Pedals - The stock "wah" pedal has been around since at
least the early 60's. This thing produces a distinctive tone that is well loved by the
expressive guitarist. What a wah does is clear - it is either a bandpass filter or an
overcoupled lowpass filter that exhibits a resonant peak just at its lowpass rolloff
frequency. The resonant peak can be moved up and down in frequency by the player, and this
makes for a striking emulation of the human voice making a "waaaah" tone, or its
tonal inverse, "aaaooow".
- Vox AC30 Guitar
Amplifier Simulator
- Simple Surround
Sound Decoder - three simple surround decoder circuit ideas
- Surround Sound
Decoder MK1 - designed to extract the rear channel from Dolby-encoded film
soundtracks, very simple design
- Surround Sound
Decoder Mk2 - fully featured surround decoder
- The PTI SD-PL1
surround sound decoder - This circuit takes a stereo audio input from any true stereo
source and outputs 4- or 5- speaker surround sound. The effect is claimed sounds
ridiculously similar to Dolby ProLogic, but this implementation is no way near the full
Dolby ProLogic (this implementation is more like very simple basic Dolby Surround
decoder).
S/PDIF
NOTE: The digital output of a typival PC CD-ROM is generally at TTL
levels, roughly 0 and 5 volts. This is different from SP/DIF standards, which are +/-
about half a volt. However, many SP/DIF inputs include means for eliminating the mismatch
in DC levels and they can also easily withstand the extra voltage.
SCMS
DAC
Signal conversion
Equipment modifications
Misc
VU meters
- -30dBm to +30dBm
Audio Level Meter - circuit with balanced input and adjustable gain to drive needle
type VU meter, uses special amplifier module from Opamp
Labs
- Audio LED VU meter -
built around discrete components
- Audio
Millivoltmeter
- Audio
Output Level Meter - This unit is designed for monitoring the audio output level
across a loudspeaker when carrying out alignment of radios.
- High-resolution
volume-unit meter simplifies CD recording - CD digital-recording decks typically have
peak-reading-only volume-level meters. This feature is adequate to prevent clipping but
does a poor job of reading the average volume, or loudness, level. A high-resolution,
average- (not peak-) reading volume-unit meter produces an accurate reading of loudness.
- LED Audio VU Meter
- logarithmic scale with 3 dB steps, based in LM3915 IC
- Led
Bar Audio Power Meter - This is a 10 led logarithmic (3dB steps, 30dB full scale) LED
audio power meter built using LM3915 driver IC. This page explains in detail how to build
it and how it works.
- LM3916N bar graph
driver - datasheet in pdf format, drives a 10 LED bar graph with VU proportions
(3dB/step)
- Peak
Reading Audio Level Meter - indicates peak audio response on an analogue meter,
similar to a tape recorder recording level meter
- Peak
Reading Level Meter Using Indicator Tubes - Indicator tubes are well-suited for use in
fast, accurate level meters for monitoring tape recordings or power amplifier output
levels.
- Simple
circuit forms peak/clipping indicator - This simple peak detector is the result of a
need for a single-5V-supply, level/clipping indicator for a multimedia-PC sound system.
The design is unique in that it detects both stereo channels on a single peak-hold
capacitor. All the adjustments in the circuit simultaneously apply to both left and right
stereo inputs. The output is suitable for driving a bar-graph display or for
analog-to-digital conversion and display with a microprocessor. The circuit operates as a
dual positive-peak-detector circuit.
- Sound Level
Meter - one chip replacement for the standard analog meters, based on LM3915 audio
level IC
- Stereo VU Meter -
A simple, low cost stereo VU meter that uses two LM3915 dot/bar display driver ICs to
drive 2 rows of 10 LEDs moving bar display, pdf file
- Three-Level
Audio Power Indicator - Battery-operated 3 LED display that connect it to loudspeaker
output
- Understanding
Peak-Reading Meters - includes one example circuit diagram
- VU And PPM Audio
Metering - circuits using analugue needle meters
- VU Meter
- 5 led VU meter, in pdf format, includes circuit board, text in Finnish
- VU Meter Amplifier
- VU Stereo
Meter - will indicate the volume level of the audio going to your speakers by lighting
up LEDs, based on LM3915 IC
Decibel meters
Filters needed in audio mesurements
The problem of measuring audibility of sounds is complicated by the
nonlinearity of human hearing. The frequency dependence of human hearing is described by
the Fletcher-Munson Curves. The Fletcher-Munson Curve explains the non-linear response of
the human ear ensitivity to pure tones, but in practice, many sound sources are anything
but pure. The apparent loudness of a frequency mix is not necessarily a simple combination
of responses to individual frequency bands. Owing to the complexity of operation of the
human ear, it is not possible at present to design an objective noise measuring apparatus
to give results which are absolutely comparable, for all types of noise, with those
obtained by subjective methods. In an attempt to account for human hearing sensitivity in
a standardized way so that measurement instruments can be compared, the International
Electrotechnical Commission (IEC) issued Standard IEC 651 (1979). This standard identifies
four application types (types 0 through 3) and three weighting curve characteristics (A, B
and C). Historically, the A, B, and C weighting networks on a sound level meter were
derived as the inverse of the 40, 70 and 100 dB Fletcher-Munson curves and used to
determine sound level. The lowest curve repesents the threshold of hearing, the highest
the threshold of pain. The A-weighting characteristic is most widely used, and though
originally intended for low-level sounds, it is commonly applied to higher sound levels as
well.
Testers
Distortion measurements
Other measuring circuits and notes
- 1 kHz
Audio Oscillator - This circuit consists of a CMOS square wave oscillator on a
frequency of approximately 1 kHz. The RC filter, which has a roll-off frequency of 500 Hz,
filters the harmonics, providing a sine-wave output. The oscillator has many uses,
sidetone circuits in transmitters and signal injectors for audio tests are just two.
- 3 Channel
Spectrum Analyzer - This 3 channel 15 LED spectrum analyzer can be used as an addition
to any audio amp project. It produces fantastic displays on three LED bars that can be
individually adjusted for any particular frequency range.
- DIY Speaker Testing
Microphone Preamp
- Measuring
Input and Output Impedance - input or output impedance of any two terminal network or
electronic equipment can be determined by measuring the small signal ac currents and
voltages
- Simplified
Measurement of Output Impedance - suitable for measuring audio circuits
- Spectrum Analyzer
and Equalizer Designs - for audio frequencies, article first appeared in the February
1982 issue of Recording-engineer/producer magazine
- A Better Volume
Control - use linear potentiometer and one tran resistor to make almost logarithmic
response curve
- Amplifier Thermal
Protection and Shutdown Circuit
- Amplifier
Timer - Turns-off your amplifier when idle for 15 minutes, fed by amplifier
tape-output
- Ask
the Applications Engineer - a collection of articles from its "Analog
Dialog" newsletter in pdf format from Analogue
Devices, useful info for people designing ADC and DAC systems
- Audio Auto
Shutoff - purpose of this circuit is to automatically turn off any device plugged into
its power outlets after a certain period of time of silence
- Circuit
combines power supply and audio amplifier - This circuit can helpful if you must
transfer dc power and audio over a pair of copper wires. The circuit uses only one IC, the
well-known LM317, a low-cost power-supply regulator. Using this chip, you can modulate the
adjustment-pin input with the audio signal from an electret condenser microphone,
connected between the output and the adjustment terminals of the IC.
- Class A
Amplifier Design
- Class
D audio-power amplifiers: Interactive simulations assess device and filter performance
- Class D amplifiers are much more efficient than other classical amplifiers, but their
high efficiency comes at the expense of increased noise and distortion. You can assess the
frequency- and time-domain characteristics of a Class D amplifier, including the output
filter, using online simulations.
- Class-T
Digital Audio Amplifier Evaluation Board using Digital Power Processing Technology
EB-TA2020 from Tripath Technology - This application note describes a diigtal
amplifier which operates from 13.5V power source and outputs up to 20W por channel power.
The application note is in pdf format.
- Designing
With Opamps - Audio design has for many years relied on a very small number of opamp
types. The TL072 and the 5532, numbers that will be immediately familiar to anyone
involved in audio electronics, have dominated the small-signal scene for many years. There
are however other opamps, some of which can be very useful, and a selected range is
covered here.
- DIY
class A amplifier chassis & massive heatsink
- EDN
ears-on project: Listening to Class D - You needn't look further than Class D audio
amplifiers to find a technology whose proponents tend toward exuberant advocacy at best
and bald-faced hype at worst. Although these ICs are not yet the be all and end all of
audio amplification that their makers would have you believe, they are remarkably
good-certainly more listenable than the clamor about them.
- George
Krilov audio schematics page - page is about transistor audio power amplifiers,
contains articles about power amplifiers shematics, design, construction and SPICE
simulation, page is partially in English and partially in Russian
- Guitar Effects FAQ
- Jensen
Transformers Application Schematics - many practical circuit ideas using audio
transformers
- JT-115K-E90
"Sync" Conversion for Magna-Tech 69C Repro Amplifier - sync track tape head
preamplifier
- Load Sensing
Automatic Switch - apply power to the entire audio system by turning on one item,
simple circuit
- Loudspeaker
Protection and Muting - information and circuits
- Main principles
of amplifier wiring - how to wire operational amplifier circuits
- Mixed
feedback drive circuits dor audio output transformers - using feedback eliminates
transformer distortion and primary resistance
- Mosfet Power Amplifiers
- A discussion of the benefits of the lateral Mosfet output devices used in todays High
Power audio amplifiers
- NE555 drives a
speakes: Pulse Width Modulation Amplifier
- Optocoupler
Application Guide - Resistive optocouplers, comprising a LED coupled to a
photoresistor, have some unique advantages as control elements in analog audio circuits.
- Philips
SAA1099 Sound Generator
- Proper
Grounding Inside Equipment Avoids Ground Noise Coupling (aka"Pin 1 Problems")
- 15KB PD
- Pushing the Limits of
Audio Power Amplifiers
- Removing
the "DC Thump" from Audio Circuits
- Signal Detecting
Auto Power-On Unit - switches on relay when detects sound input
- Sheldon's Audio
Designs - audio DACs and tube amplifiers
- Simplest Ever
Amplifier Bridging - a design for a simple add-on bridging adapter for stereo power
amplifiers
- Simulation Electronique SPICE -
some hifi circuits and simulation of them using SPICE, text in French
- Soft-Start Circuit
For Power Amps - redusces the current spike large transformers take when switched on
- Subtleties count in
wide-dynamic-range analog interfaces - transporting high-dynamic-range analog signals
from one piece of equipment to another is not a trivial task, this article gives some help
to it
- The ALTMANN
"SPLIF" Amplifier Topology - something about how to get some of the feedback
out of our HIFI amplifiers
- Thermo-Fan To Keep
Your Amp Cool - fan controller which controls fan based on temperature
- Using Current Sources,
Sinks & Mirrors In Audio - Integral to most audio amplification systems, the
current source and current sink are indispensable.
- Variable Amplifier
Impedance - idea of being able to vary the output impedance of a power amplifier
Misc circuits
Here you can find links to some ICs which mightr be useful in audio
projects.
A/D and D/A conversion
Audio controlling
Recording and playback
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