Control by sound may be very useful, not just on a robot but also for a bit of home automation, for example, a sound-activated light responding to a knock on the door or a hand clap. The lig... Read more
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 have treasures in your collect... Read more
In this circuit, Op-Amp operates in the closed loop. Input is applied to the Inverting terminal and output is fed-back to the inverting terminal as voltage shunt feed-back. The polarity of t... Read more
Designs for audio amplifiers with DC coupling to the load are not often encountered these days, even though they offer definite advantages. One advantage is that there is no need for the com... Read more
Just recently the author had cause to make an MP3 player for a 93-year old recently moved to a nursing home. There, radio reception turned out to be hopeless, mainly owing to interference fr... Read more
Designs for good-quality headphone amplifiers abound, but this one has a few special features that make it stand out from the crowd. We start with a reasonably conventional input stage in th... Read more
The technical demands on microphones used with radio equipment are not stringent in terms of sound quality: a frequency response from around 50 Hz to 5 kHz is entirely adequate for speech. F... Read more
Many new devices require a headphone connection, but due to the high level of integration and miniaturisation there is usually little room left. The low supply voltage and/or battery voltage... Read more
This acoustic sensor was originally developed for an industrial application (monitoring a siren), but will also find many domestic applications. Note that the sensor is designed with safety... Read more
Superheterodyne receivers have been mass-produced since around 1924, but for reasons of cost did not become successful until the 1930s. Before the second world war other, simpler receiver te... Read more
