Circuits & Schematics Audio

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 ...

When a system's specifications call for a lowpass filter with a steep frequency-cutoff characteristic, an engineer can opt for a “brick-wall”- filter design that features a sharp transition band. For example, in an FM ...

At the end of the DI for a Simple log-scale audio meter (Ref. 1), I promised to show how to upgrade it to work better. With these fixes, it now has near-digital performance, with faster response and smoother operation. Even this supersized version ...

While refurbishing an ageing audio mixer, I decided that the level meters needed special attention. Their rather horrible 100 µA edgewise movements had VU-type scales, the drive electronics being just a diode (germanium?) and a resistor. ...

A question that arises frequently in audio and signal processing applications is this: How can I control gain on dual channel (e.g., stereo) inputs simultaneously with only a single knob? Of course, an obvious solution would be to simply use a dual ...

Low-frequency filters, particularly at audio frequencies, usually take the form of active filters. These filters eliminate expensive inductors with windings of many turns. Both analog and digital active filters are most compatible with large-scale ...

The sample and hold circuit (Figure 3) is considerably more complex than the oscillator. This is unfortunate but unavoidable. It's the S/H that gives this design its speed (fast settling time) and very low distortion, and it's very unlikely ...

Introduction As discussed in the article [ 1 ], although a sinewave is the simplest possible waveform, it is also one of the hardest to generate in pure form. Any impurity represents distortion, and that means added harmonics that make very low ...