300 Watt Subwoofer Power Amplifier - There are some important updates to this project, as shown below. Recent testing has shown that with the new ON Semi transistors it is possible to obtain a lot more power than previously. The original design was very conservative, and was initially intended to use 2SA1492 and 2SC3856 transistors (rated at 130W)with 200W (or 230W) devices, some of the original comments and warnings have been amended to suit. __ Designed by Rod Elliott ESP
555 Timer MonoStable using Pushbutton The two circuits above illustrate using the 555 timer to close a relay for a predetermined amount of time by pressing a momentary N/O push button. The circuit on the left can be used for long time periods where the push button can be pressed and released before the end of the timing period. For shorter periods, a capacitor can be used to isolate the switch __ Designed by Bill Bowden
7 band graphic eqalizer - Audio graphic equalizers are very common as commercial products (for Hi-fi, car audio and stage use) but circuits for them are very rarely published. I didn't design this one but it's really very simple. The details shown are for a 7 band but the principle can be extended to almost any number of bandsif you can find accurate enough components. __ Designed by Richard Torrens
A Better Volume Control - A volume control using a linear pot that is much better than most log pots __ Designed by Rod Elliott ESP
A High-Quality DAB+/FM Tuner, Pt.1 - We know you've been waiting for it and after more than a year in development, we are delighted to present this world-first high performance DAB+/FM stereo tuner design. It has all the bells and whistles of DAB+ in a sleek pro-quality case, with all features accessible by remote control. __ SiliconChip
A High-Quality DAB+/FM Tuner, Pt.2 - Last month, we introduced our new DAB+/FM Stereo Tuner and gave the circuit details. This month, we show you how to assemble the two PC boards and install them into a low-profile steel case. __ SiliconChip
A High-Quality DAB+/FM Tuner, Pt.3 - In this month's final part, we explain how to use the DAB+/FM Stereo Tuner and describe the menu system. We also show you how you can upgrade the firmware if necessary and describe various features of the tuner in detail. __ SiliconChip
Accomodating Offset IF Filters - Digitally synthesized FM tuners normally use ceramic IF filters centered at 10.7 MHz. But the characteristics of individual filters vary. Murata specifies filter center frequency as 10.67 to 10.73 MHz. Outlier filters may make a tuner more susceptible to interference on one side of channel center than the other. __ Designed by Brian Beezley K6STI
Active Subwoofer & Controller - Designed to operate a sub-woofer driver below its resonant frequency __ Designed by Rod Elliott ESP
An Inexpensive Tone Encoder - Figure 1 illustrates an easy circuit that can be constructed with mostly Radio Shack parts on any general purpose circuit board. The only rigid requirement is that capacitor C1 be stable over a wide temperature range. Use only Mylar, Polyester or Metal film for capacitor C1. The frequency is determined by the following formula: FREQUENCY = 1/R1C1The specified values should allow any tone between 100 to 300 Hz. Increase R1 or add another resistor in series with R1 for lower tone frequencies __ Designed by Radio Amateur Society of Norwich
Audio Graphic Equaliser - Audio graphic equalizers are very common as commercial products (for Hi-fi, car audio and stage use) but circuits for them are very rarely published. I didn't design this one but it's really very simple. The details shown are for a 7 band but the principle can be extended to almost any number of bandsif you can find accurate enough components. __ Designed by Richard Torrens
Audio Level Indicator - Audio Amplifier output relay delay __ Designed by Tomi Engdahl
Audio Level Meter - Audio levels can be monitored using a small panel meter with this circuit built from discrete components. The circuit has a flat frequency response from about 20Hz to well over 50Khz. Input sensitivity is 100mV for a full scale deflection on a 100uA meter. Built on two common emitter amplifiers, the first stage has a preset resistor which may be adjusted for a FSD. The last stage is biased to operate at roughly half the supply voltage for maximum ac voltage swing. Audio frequencies are passed through the 10u dc blocking capacitor and the full wave bridge rectifier converts the signal to a varying dc voltage __ Designed by Andy Collison
Audio Tone Controls - Many people at one time or other, regardless of their interest in electronics, have adjusted these controls to suit their preference. Whether its to boost the bass of their favorite CD, cut the noise / static on a talk radio station or compensate for poor loud speaker response, they've reached for the treble and bass tone controls.
Automatic Loudness Control - Simple add-on module Switchable "Control-flat" option __ Contact: Flavio Dellepiane, fladello @ tin.it
AVC Automatic Volume Control - AVC – The featured circuit controls a volume line automatically. It delivers an output voltage of approximately 4 volts peak to peak. This voltage remains relatively constant by input voltages ranging from several hundred milivolts to serveral volts. This electronic circuit is not highly recommended for Hi-Fi __ Designed by Popescu Marian
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