Practical Electronics – String Ensemble

There were times that building your own Strings Synthesizer (or Strings Ensemble) was an option. We already covered some different DIY projects and here is another one: the Practical Electronics String Ensemble. Below you will find:

  • Some details on this DIY project
  • Sound samples
  • The original Practical Electronics articles (separate pages and a compiled PDF containing the 5 articles).

Some information was reproduced from the blogspot of El Gaucho Andres and of course the original articles from Practical Electronics. Please note that all (c) are with the Author and PE Magazine.


Construction details

The construction details for the String Ensemble were published in Practical Electronics in 1978. It was designed as a version of the ‘string machines’ or orchestral synthesizers that were available at the time to produce a sound which would simulate the whole section of an orchestra. It was designed by Alan Boothman of Clef Products who also designed the Joanna and Band Box. The kit was supplied by Clef Products although Maplin also sold a kit.


The design was four octave based on a top octave generator chip, each note being further divided down by two several times to cover the range. Each note had a separate divide by two chip. The signal was then sent to a diode gate. Each note of the keyboard had a diode gate switch which simultaneously switched four octaves of the note through to the signal processing circuit when a key was pressed. This produced a harmonically very rich signal. A separate diode gate for each note also meant that the instrument was polyphonic. 

This is how the PE String Ensemble sounded:

String Ensemble High Strings new new

The sound then went through a dual delay line with two slow oscillators running a different speeds controlling the delay to give a constantly shifting phase to give the effect of several instruments playing together. Finally the signal was sent to a filter circuit which had switchable filtering to simulate different sections of the orchestra. 

There were filters for high and low strings and also brass and woodwind. These could be mixed together using sliders in any proportion. There were also sliders for adjusting the attack and decay. Finally the keyboard could be split to give a low, medium and high octave setting on the bottom third of the keyboard to accompany the other voices.

The original articles.

Part 1

Part 2

Part 3

Part 4

Part 5

All parts