Reference earphones
There are 3 basic types of earphones, each with their set of benefits and problems. Small transducers that are inserted into the auditory canal. This leaves onl...
Vacuum tube audio amplifier
Where can you obtain a 12AX7 tube, you ask These tubes are very popular for use in the "preamplifier" stages of many professional electric guitar amplifiers. Go...
Musical keyboard as a signal generator
An electronic musical keyboard as a source of variable-frequency AC voltage signals. You need not purchase an expensive keyboard for this - but one with at leas...
Whistle Responder Schematic
Some 20 years ago it was common to see small key-holders emitting an intermittent beep for a couple of seconds after its owner whistled. These devices contained...
Voice Bandwidth Filter
This circuit passes frequencies in the 300Hz - 3. 1kHz range, as present in human speech. The circuit consists of cascaded high-pass and low-pass filters, which...
USB Powered Audio Power Amplifier
This circuit of multimedia speakers for PCs has single-chip-based design, low-voltage power supply, compatibility with USB power, easy heat-sinking, low cost, h...
Room Recorder
My wife was working on a doctoral dissertation and needed to do some field work involving personal interviews in various settings. What would be the best way, t...
Quality Stereo Wireless Microphone or Audio Link
This stereo FM wireless microphone also makes a great quality audio link. We tested it to beyond 50 meters and it was rock solid. It`s certainly not the first w...
Pushbutton Relay Selector
This circuit was designed for use in a hifi showroom, where a choice of speakers could be connected to a stereo amplifier for comparative purposes. It could be ...
Preamplifier For Soundcard
This circuit can be used for inductive pick-up elements and dynamic microphones Most soundcards have a line` input and one for an electret (condenser) microphon...
Phono Preamplifier
In recent years, following CD`s introduction, vinyl recordings are almost disappeared. Nevertheless, a phono preamplifier is still useful for listening old viny...
Multimedia RIAA Preamplifier
Even if a large number of album titles once available on vinyl are now, little by little, being proposed as CDs, not all are available and far from it. You may ...
Multi-Melody Generator With Instrumental Effect
This melody generator can generate various English and Hindi tunes as also instrumental effects. Various modes of melodies can be selected through DIP switches....
Mini Guitar/Bass Amplifier
Tiny, portable Guitar Amplifiers are useful for practice on the go and in bedroom/living room environment. Usually, they can be battery powered and feature a he...
Mini Audio Signal Generator
A small audio test generator is very useful for quickly tracing a signal through an audio unit. Its main purpose is speed rather than refinement. A single sine-...
Loudspeaker Protector Monitors Current
This circuit uses a 0. 1O 1W resistor connected in series with the output of a power amplifier. When the amplifier is delivering 100W into an 8O load, the resis...
IR Music Transmitter and Reciever
Using this circuit, audio musical notes can be generated and heard up to a distance of 10 metres. The circuit can be divided into two parts: IR music transmitte...
Guitar Control
IC1A op-amp is wired as an inverting amplifier, having its gain set by a three ways switch inserting different value resistors in parallel to R4. This input sta...
Modular Preamplifier Switching Center
This module can be a necessary addition to the Modular Preamplifier Control Center when more than two sources need to be connected to the preamplifier chain. Fo...
FM Wireless Microphone
Here is a very simple, inexpensive and interesting project which provides lot of fun to a home experimenter or hobbyist. This simple transmitter can transmit sp...