K17 - LM386 Audio Amplifier Module
This Kit is designed as a building block in other projects where a battery-powered, variable-gain audio amplifier is required. Data sheet from National Semiconductor included.

K21 - Two Station Intercom
Simple two wire intercom. Each unit with its own speaker, microphone and amplifier (LM386.) Can be modified to a hard wired "bug". With 4 strand ribbon cable the power can be sent to the remote "bug" unit from the receiving unit.

K26 - Fibre Optic Audio Link
Allows you to send sound through plastic 1mm fibre optic cable. Matched transmitter/receiver pair. Two circuit boards with a microphone at one end and a speaker at the other. 14 feet of fibre optic cable supplied. Will work over 200 meters.

K27 - TDA7052 1W Amplifier Module
A 1W power amplifier building block designed to be part of a larger project needing a low power battery operated amplifier into an 8 ohm speaker.

K47 - LM383 Amplifier Module
A proven & popular power amplifier building block for use in any audio project. Power output is dependent on the supply voltage and load resistance. Over 10W is typical for a 16V supply into a 2 ohm speaker. A 12V supply into a 4 ohm speaker will deliver around 4W. Small heatsink provided.

K48 - Introduction To Class AB Amplifiers
Using amplifier modules is modern, quick and easy but it teaches nothing about how they work. Here is a Class AB amplifier made from individual components which will deliver several watts of power into an ordinary 8 ohm speaker. Gives hands-on learning about cross-over distortion, bootstrapping, complementary pairs, and push-pull. Detailed explanations given.

K50 - 25W Hi-Fi Audio Amplifier Module
This kit contains the essential components needed to build a high fidelity amplifier module using the National Semiconductor LM1875 IC. This kit will deliver 25 watts RMS into 8 ohms at 1% THD. The kit requires a split +/- 25V power supply. Overload protection is provided by on board 2A fuses in each of the supply rails. PCB dimensions are a tiny 53 x 50mm (2.1" x 2"). Heatsink, speaker and cables not included.

K63 - One Chip AM Radio
Complete AM radio on a PCB. Tuned radio frequency front-end, single chip RF amplifier & detector and two stages of amplification of the audio signal into a speaker. All components supplied. Coil prewound. Excellent for schools.

K64 - 120 Second Voice Recorder
Record as many messages as you can in this modern, non- volatile, combined audio processing & memory chip from Information Storage Devices (ISD25120). One button to START/PAUSE & a second button to RESET.

K88 - 10W+10W Stereo Amplifier Module
The TDA2009 is a class AB dual Hi-Fi Audio power amplifier monolithic IC designed for quality stereo applications. This is the standard data book application circuit using a minimum of external components. Each channel is capable of delivering 10 watts into 4 ohm speakers using a 24VDC supply voltage.

K89 - Stereo VU Meter
A simple, low cost stereo VU meter. Two LM3915 dot/bar display driver ICs are used to drive 2 rows of 10 LEDs (4 green, 3 yellow, 3 red) in a moving bar display. Each row of LEDs spans a power range of 0-30 dB in ten 3-dB steps. This VU meter indicates "peak music power" when used with audio amplifiers. Ideal add-on for any of the amplifier kits. Dimensions = 65mm x 42mm

K90 - 3W+3W Stereo Amplifier module
A simple stereo 3 watt per channel amplifier based on the BA5406 power amplifier IC. Minimum component count. Runs on 12VDC power supply. Good general purpose amplifier.

K97 - 4W Amplifier Module
A text book amplifier built around the LM380 IC. It can deliver up to 4 watts into an 8 ohm speaker, depending on the supply voltage. No heatsink required - uses the PCB bottom layer. Soldered directly to the PCB.

K98 - Microphone Preamplifier Module
A preamplifier module to use with an electret or other microphone to boost the signal before feeding into an amplifier. Simple and easy to build using discreete transistors. Runs on 6-12V DC.

K100 - Stereo Preamp/Tone control
A useful addition to any of the power amplifier kits. Extremely easy to built due to the use of a Philips TDA1524A IC. This IC contains all the circuitry required to provide up to 20dB of voltage gain, +/- 15dB of bass and trebble control, channel balance and switchable loudness contour. 12-15VDC supply required. See documentation for full specifications.

K105 - 18W BTL Audio Amplifier module
This kit contains all the components to build a low voltage, high power, mono 18W Bridge Tied Load (BTL) amplifier module using the Hitachi HA13118. Delivers 18W into 4 ohm at 13.2V. Ideal for running off car batteries. Operating voltage: 8-18V. Speaker & heatsink not supplied.

K106 - 50W Hi-Fi Audio Amplifier module
The heart of this amplifier is a monolithic integrated circuit from SGS-Thomson, TDA7294. It is intended for use as an audio class AB amplifier in hi-fi applications. It has a wide voltage range and output current capability, enabling it to supply the highest power into both 4 and 8 ohm loads.

This module will deliver 50 watts RMS into an 8 ohms at 0.1% THD and is powered by a split +/- 30V supply. A heatsink, rated at 1.4 deg C/W, is required but not supplied. The heatsink can be mounted directly on the PCB.

K126 - Mini-VOX and relay
VOX stands for "voice operated switch". Basically this kit picks up audio via a microphone input, amplifies it and uses it to operate a relay. Sensitivity can be adjusted by an onboard trimpot. Use it to give you hands-free control of things like tape recorders, lights, sirens, etc. Relay contacts rated ar 12/24VDC @ 1A. Based on a circuit published in Silicon Chip, Sep 1994, p31

K139 - Stereo 1W Amplifier module with Volume control
The TDA7053A is an integrated stereo power amplifier IC with volume control input. All work is done internally in the IC. 5 - 18VDC operation. PCB dimensions = 4 x 4.2cm (1.6" x 1.7").

K143 - 6-10W Stereo Amplifier module with Volume control
This kit is a class AB stereo audio power amplifier designed for hi-fi applications using a TDA2005 module. It is easy to construct and has a minimum of external components. The TDA2005 has output current protection and thermal protection. On board volume control. This is the data book circuit which produces excellent sound. Kit requires a supply voltage of 8-18V DC at 1 to 2 Amps.

Maximum power output will only be obtained with a power supply of at least 2A at 15V DC, and using 2 ohm speakers (or 2 x 4 ohm speakers in parallel). However approximately 4W per channel can be obtained with only a 15V DC, 1 Amp supply into 4 ohm loads. The power supply should be well filtered to reduce mains hum.

Specification

DC Input	8 - 18V at 1 - 2A (15 to 30VA minimum)
Power Ouput	> 8W RMS / channel, 2 ohm load, 16V DC supply > 6W RMS / channel, 4 ohm load, 16V DC supply > 4W RMS / channel, 4 ohm load, 12V DC supply
THD	< 0.1% @ 1W, 4 ohm load
S/N Ratio	> 80 dBA
Frequency Response	~ 15 Hz to 50 kHz, -3 dB
Gain	~ 30 dB maximum
Input level	~ 150 mV for full output
Size	75mm x 45mm (3" x 1.8")

K146 - 40 Second Voice Recorder with Looping option July 2008 Special
Record as many messages as you want up to 40 seconds. Recordings are stored in on-board, non-volatile memory. No loss of message(s) when power is removed. One button to START/PAUSE & a second button to STOP/RESET. Features a message looping option that continuosly repeats the first message over and over until stopped. Uses ISD2540 chip from Information Storage Devices.

A63 - 20 Second Voice module
This pre-assembled module measures a tiny 3.5cm x 2cm (1.3" x 0.9"). It uses a chip-on-board device from Vtech. All components are fitted on the PCB, including the pushbutton switches and electret microphone. One button is pressed to record the message. An LED turns on during record. The other button is momentarily pressed to replay the message. A second momentary press during playback will stop the playback. All you have to add is a speaker and 5V DC power.

The record/playback time is determined by a 52K resistor. If you change it to 89K you will get 30 seconds but at a reduced sampling rate. Operating current is 25mA. Standby current is 10 uA. The module comes supplied as you see it in the photo.