Tone Control

Agc System For Audio Signals Circuit

This circuit is an AGC system for audio-frequency signals. AGC systems usually consist of three parts: an amplifier, rectifier, and controlled impedance. In this circuit the functions of an amplifier and a rectifier are performed by a single op amp. This makes the system simple and cheap.The...

Tubed Crossovers

You'll find here few ASCII schematics for Heath and Marantz tube crossovers. They were given in L'Audiophile No 11 old sery July 1979. In the same paper there is another tube crossover designed by Gerard Chretien now at the head of Focal i'll try to send an ASCII schematics of that one...

Highpass filters use modified equal-element design

Using a modified equal-element design for a lumped-circuit lowpass filter has several advantages over the well-known equal-element design (Reference 1 and Reference 2). The modified design exhibits superior passband performance with only modest degradation of stopband selectivity. Moreover, the...

Stereo Width Controllers

Sometimes, for a variety of reasons, it would be nice to vary the width of the `sound stage` when listening to stereo recordings. Although technically this is anything but hi-fi, it is a useful addition to PC speakers, or even for the music centre in the listening room.

HiFi preamp with tone control

This preamp and tone control uses the JFET to its best advantage; as a low noise high input impedance device. All device parameters are noncritical, yet the circuit achieves harmonic distortion levels of less than 0.05% with a S/N ratio of over 85 dB.

Alc (Automatic Level Control) Circuit

The rectifier input is tied to the input. This makes gain inversely proportional to input level so that a 20-dB drop in input level will produce a 20-dB increase in gain. The output will remain fixed at a constant level. The circuit will maintain an output level of 1 dB for an input range of +14...

Stereo balancer

This circuit will allow you to set the gain of two stereo channels to the same level. The signal across the two channel-load resistors is sampled by resistors R2. (Values of these resistors will depend upon the power level) For most 20 milliampere LED, use approximately 2 K per watt. (For a...

Wien-bridge-filter

Most audio tone controls affect midband gain, and !bey often create booming or hissing sounds when activated. You can avoid tbese problems by using a dual Wien-bridge filter to provide independent control of tbe treble and bass frequencies. Experiments witb equalizers indicate that tbe optimum...