January 2017

High-performance Stereo Valve pre-amplifier (Part 1)

This stand-alone stereo valve (vacuum tube) pre-amp is based on the Currawong Amplifier (November 2015-  January 2016 issues) but features a new power supply that runs from a low-voltage DC supply. Uses two 12AX7 dual triodes.

It has very good performance (especially for a valve preamp), with low distortion and a very high S/N ratio of 105dB. Optional mixed output for use with musical instruments. Easy to build on one PCB.

Design considerations are published this month, with construction and assembly given in Part 2 next month.

High voltage design suitable for experienced constructors

High-visibility 6-digit LED GPS Clock (Part 1)

This 6-digit clock really does shine a light on the time! Using 56mm-high seven segment digits, the time can be clearly seen from a distance thanks to its high-visibility display. It can be set to show the time in various colours and has an optional GPS module for automatic time setting, time zone and daylight saving. A 7-day alarm is built in. The article includes a useful discussion on various display characteristics.

Circuit board construction is described this month with final testing and assembly given in Part Two’s article in next month’s issue. PIC microcontroller-powered.

5-element Yagi antenna for DAB radio

 Please take note

Friends at Silicon Chip magazine have informed us of a small error in the 5-element Yagi DAB Antenna project. In the upper left of Fig.1, the point where the folded dipole connects to the boom is labelled ‘A’, when it should be labelled ‘F’. For those of you building the antenna, a corrected diagram can be accessed here (PDF)

Digital audio broadcasts tend to be either all or nothing with virtually no middle ground. This 5-Element Yagi antenna (aerial) will improve radio reception in weaker-coverage areas and could even let you receive DAB signals where none are currently detected!

Our project is half the size of the FM Antenna (EPE October 2016 issue) and includes all constructional details, drawings and photos to enable this super-powerful DAB aerial to be built.

Introducing the Arduino
Part 12: Wi-fi and the Internet of Things

The final part of our practical Arduino primer explores choices for wireless networking and the ESPDuino microcontroller that neatly combines Arduino compatibility with an ability to connect to a wireless network. Configuring the ESPDuino’s IDE is described along with a simple IoT environmental monitoring system.

Electronics Building Blocks

How to build a 6A/ 24V power supply on the cheap, by using imported modules readily available online.

Also in this issue:

• Techno Talk – how China’s rural heartland is evolving to trade online
• Net Work – are bricks-and-mortar stores meeting the Internet challenge?
• Circuit Surgery – current mirrors for high-side current measurement
• PIC n’ MIX – PICs and the PICkit3 – a beginner’s guide (part 8)
• Interface – first look at the BBC Micro Bit
• Audio Out – amplifier power supply techniques
• Max’s Hot Beans – some VR gizmos, books and gadget recommendations

In next month’s issue:

Solar MPPT Charger and Lighting Controller (Part 1); High-performance stereo valve preamplifier (Part 2); Turntable strobe;  High-visibility 6_digit LED GPS Clock (part 2); The Micromite (Part 1).