Circuits & Schematics - Audio

In the first part ( Ref. 1 ) of this Design Idea (DI), we saw how to use the TDA7052A (or similar) power amp to build a minimalist siren-type power oscillator, and also, having looked at that device’s distortion characteristics under various ...

When audio power amplifiers oscillate, the result is often smoke, perhaps with a well-cooked PCB and a side order of fried tweeter. This two-part Design Idea (DI) shows some interesting ways of (mis-)using a common power amp to produce deliberate ...

The circuit in Figure 1 adds a soft muting switch with power-up/power-down muting to a line-level audio circuit. R 4 , C 1 , and JFET Q 1 quietly ground a signal in 100 to 200 msec when you close S 1 or release it when you open S 1 . Potentiometer ...

In Part 1 of this Design Idea [ 1 ], we saw how a standard electret microphone capsule can be persuaded to detect infrasonic signals down to a fraction of a Hertz by adding some fairly simple equalization. In this second and concluding part, we ...

Electrets aren’t only used as audio pickups. For decades, they have been employed in security systems to detect unexpected changes of air pressure within rooms, while more recently they can be found in vapes as suck-sensors (or, more ...

Introduction In general, muting and/or signal switching is done by relays, FETs or CMOS analogue switch ICs. All have limitations, but a little known technique that really doesn't look like it could ever work is to use bipolar transistors. The ...

It’s easy to mute a balanced signal line. Simply short the terminals or break the signal path. But when the line is unbalanced (single ended) and the output has strong dc bias, trying to mute the circuit with these methods will affect the ...

Despite the title, this DI does not describe a gadget to tell you when to don your shades, but instead features a useful add-on to (analog) audio kit. Built into a mixer, for example, it will show when the output of any stage is approaching ...

In Part 1 ( Ref. 1 ) of this article, we briefly looked at the Wien bridge oscillator before homing in on the bi-quad filter as our best candidate for an oscillator capable of giving 0.0001%/ 120 dB distortion, and showed its full circuit. Treating ...

Over the years, the Design Ideas (DI) column has featured many interesting oscillators, but none that I can recall was specifically designed to produce a really clean sine wave. Putting that omission together with the need to rebuild my old ...