Sunday, May 26, 2013

The Clef Products String Ensemble

Here we come with another collaboration from our friend Jeffrey Jones. In this case he talk about the Clef Products String Ensemble a.k.a. PE String Ensemble

"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. 

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 sound was superb, especially considering it used purely electronic means to generate the notes. The top strings were especially rich and vibrant sounding. There was also a socket for the provision of a swell pedal to add extra feeling and realism to the sound.

The kit supplied by Clef was up to their usual high standard. The circuits were printed with the component positions on to make assembly easier and the wiring connections between the circuit boards were also marked. Everything needed to build the kit was available including the keyboard, cabinet and a printed front panel to give a professional appearance.

The building of the kit was generally fairly straightforward with just two exceptions:

The diode gate of each note consisted of twenty components which had to be fitted in the space allowed between each note. To achieve this some components were stacked on top of each other which made soldering quite difficult. Also the fact that each note needed twenty components meant that there were a total of nearly a thousand components just for the diode gates. This was a rather monotonous task.

The other problem was that each diode gate needed four buses to supply it requiring a total of nearly two hundred soldered connections. This was made more manageable by the special enamelled wire supplied with the kit in which the insulation melted upon soldering.

Although there was a lot of work involved in constructing the kit the result was well worth the effort. It worked first time with no problems. In the nearly 35 years which I have had it I have had only two problems with it, a smoothing capacitor failed and one of the top octave generator chips also failed.

I think that this was one of the best electronic instrument kits ever produced but despite this I have never seen any other mention of it on the internet and have never seen one for sale on ebay or anywhere else. I would be very interested to know if there are any other owners (past and present) out there."

Jeff not only made the pictures from his own instrument that you see here, he also he took sound samples so everyone can hear the instrument in its fullness (or you could split into individual files and load it into a sampler to play with it), the sound samples are recordings of all of the C, E and G notes of the top strings covering the full keyboard.

You can hear and download the sound samples here:

Sunday, May 19, 2013

Aliens, Dewtron and stuff

Here is this second article collaboration from a source that wants to remain anonymous, despite this I can tell you that this story is real.

Many of us, synth fans, ask ourselves for why reason synth companies or kit builders in the 80's, went down in business.

Many of us argue that it was caused by the japanese invasion.

But what many of us doesn't know is that the aliens also had something in this business, as was the case for the Dewtron company (it can't be another one that you Dewtron!)

Please take the time to read this weird/funny/strange story about the people of Dewtron and some info about the customer service, you won't regret!

"One day in about 1974 a man knocked on the door of my basement in London. I was in my early 20s and this man was about in his mid-40s. He was dressed in a blue shirt and black trousers.

I thought he was a policeman, but he was not. He had met a friend of mine called Antoinette in Wales and she had suggested he talk to me.

This man was called Nigel Woodfine and he came to talk about his friend Brian Bailey, of Dewtron.

This was a big coincidence because I had already built a Dewtron synth and so had my friend Max Norman.

Then Nigel showed me about 12 typewritten pages. Brian had been possessed by aliens. He was an electronic engineer with no past interest in aliens or UFOs or anything esoteric whatsoever. 

Over a period of about a week he had felt compelled to write down what was dictated to him in the form of automatic writing. Someone else's hand controlled his pen.

The messages in general went along the predictable lines of 'We come in peace to bring you this message etc.' All very interesting, but you could have put it down to the imagination of someone.

But in these pages was one thing which was a specific experiment. I don't have the pages any more, but the message went like this:

'Take a diamond and cleave it in the quadrant mode, so that a beam of light of x angstroms strikes the third axis of the diamond at Y degrees.'

I have forgotten what x and y numbers were.

My father was a PhD in geology, working for BP research, so I showed him but he could not understand exactly how to do the experiment.

As far as I know nothing was done about these messages, but I kept in touch with Nigel for a while and Brian Bailey went crazy trying to understand what it all meant."

Later, the anonymous friend adds:
"The Dewtron synths were very bad because all the circuits were set in brown polyester resin and when they were built they could not be repaired. If you bought 2 VCOs these had to be matched and ordered together. I bought 2 and somehow both were destroyed. I sent them back with Nigel and Brian replaced just one for me, he would not give me both. A one oscillator synth is not much good to anyone."

In the following email, I asked to 'anonymous' why Nigel was sent to him and he reply:
"I am still in touch with Antoinette. I should ask her how she came to send Nigel to me about Brian Bailey of Dewtron. I know Brian went to talk to the people at Porton Down. Porton Down is a government and military research station in Wiltshire who also used to investigate UFO cases, maybe they still do. I don't think they were very interested."

I know, this entry is not very synth related... but you can't deny that this story made you laugh or -at least- put a smile in your face! Oh Dewtron! you have so much to tell us...

Sunday, May 12, 2013

Clef Products (Electronics) Ltd.

In the next entries I will be publishing some information about Clef Products Ltd. (sometimes called Clef Electronics). This company had very interesting kits, some of them were ahead of their time, but badly marketed. I have a couple previous post about Clef, look for the Clef tag.

I've found this web with profuse information about Clef and the kits they were selling at that time:

In conversation with our friend Jeffrey Jones about Clef, he recalls:

"As regards Clef I have met Alan Boothman twice, once at an electronics exhibition where he had a stand displaying the piano and string ensemble, and once when I went to his premises to pick up the cabinet for the piano. He was always very friendly and helpful. I also had contact from someone who used to work at Clef. He was advertising to buy a String Ensemble about two years ago. I contacted him and he gave me a valuable insight into the company which I can share with you."
Sure we will enjoy what you have to told us Jeff! He also sent this old Clef two-page catalog pictured here:

I made this chronological list of Clef instruments/kits:
  • 1972 - PE Electronic Piano (Practical Electronics, sep 1972 to jan 1973)
  • 1975 - Joanna (PE Joanna - Practical Electronics, may to sept 1975, may 1977)
  • 1976 - Sound Design (updated Joanna) (Practical Electronics, mar 1976 pg.215?)
  • 1978 - String Ensemble (PE String Ensemble - Practical Electronics, mar to july 1978)
  • 1978 - Electronic Piano (88 keys, 72 keys and 'Stage Piano', three versions of an updated Joanna)
  • 1979 - Master Rhythm (PE Master Rhythm - Practical Electronics, dec 1980 to jan 1981)
  • 1979 - Band-Box (PE Bandbox - Practical Electronics, nov 1981to feb 1982)
  • 1982 - Microsynth (aka. uSynth and later B30 Microsynth - Practical Electronics, jun to aug 1982)
  • 1984 - PDSG
I don't know if Clef had more than those instruments/kits mentioned here. From all of it, there are so little info on the web, so, with the help from some friends, in the following posts we will be talking about some of this rare instruments.

Saturday, May 4, 2013


After some months of delay I finally found some time to post the first collaboration here.
The following article came from my good friend Jeffrey Jones who built an MINISONIC, the original, el nĂºmero 1, the mark I. We both found that there is almost nothing of information about this synth on the web, so Jeff therefore wrote about his experience with the MINISONIC.

Minisonic 1

The original minisonic was designed to be as cheap as possible to allow more people to be able to own a synthesizer. All of the circuits were designed to be as cheap and simple as possible. The unit did not even have a keyboard but used a stylus and keys etched on a printed circuit board to operate. It used batteries to avoid a power supply. The whole synthesizer was built around three fairly small printed circuit boards. The kit consisted of the circuit boards and components but nothing else. The constructor therefore had to make a cabinet and etch the keys onto a PCB. On the plus side the synthesizer was very cheap and even allowing for the cabinet other extras the cost was about one tenth of that of the ETI4600 which was available as a kit at about the same time. Additionally the modules were connected by patch cords which made it very flexible.

The PCB's were very easy to construct and the unit worked first time. The obvious drawback was having to make your own cabinet and keyboard. Additionally the patchcord system required a lot of wiring from the PCB's to the front of the cabinet and the provision of sockets.

In use there were a number of problems which would be expected in a unit this cheap. The stylus keyboard was very hit and miss, it was difficult to hit the right note cleanly and there was an obvious gap between lifting from one note to another. Intermitting connection of the stylus also made notes a bit unstable.

The unit that I made covered four octaves but it was not possible to set up the span of the oscillators to cover this range in tune. In practice the keyboard could only be used over two and a half octaves. The sample and hold circuit was quite basic resulting in a drift in tune with fairly long notes. The tuning of the oscillators was not very stable and could drift even during the playing of a single tune. 

One other strange problem was to do with the way the minisonic generated a trigger pulse. It used a high frequency oscillator signal which was sent to the stylus and was detected from the keyboard. This allowed a single stylus contact to generate control voltage and trigger pulse. Holding the stylus and wearing headphones allowed the high frequency signal to be transmitted to the keyboard before actually touching it. This generated a trigger pulse to operate the synthesizer resulting in the previous note being heard.

On the plus side the original unit had two oscillators which could be used to modulate each other. The patchcord system allowed for great flexibility enabling many modules to be connected in different ways. The ring modulator was also a bonus. 

In conclusion the original minisonic synthesizer was a good introduction to sound synthesis and great for producing a wide range of sounds. It was not however very practical for playing tunes. I passed it to a friend who used the basic circuits to build a Minisonic 2. This had none of the problems of the original.

For those of you that don't know what synth we're talking about, here you can find a website with the scanned pages from the Practical Electronics magazine (nov 1974 to mar 1975) including the erratas:
Tim Stinchcombe - PE Minisonic articles ( )

Thanks Jeff! I also encourage others to share info about electronic musical instruments not easily found on the web.