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DIMI 1106/1107 sandwhich face side down on my desk.

DIMI 1106/1107 sandwhich face side down on my desk.

This time I will tell you about the first part of DIMI I have finished. This is a unit of two boards sandwhiched together. Top PCB is board 1107 which is the visible touch pad of DIMI. Straight underneath is PCB 1106 which I like to call the bikini board. This is easy to understand by looking at the PCB etch mask. 1107 does not have any electronics in it. Its function is simply to provide interface for the instrument. 1106 has lamp driver ICs for the number plates, pullup resistors for the keyboard, diode matrix for mapping number plates to 4 bit bytes and DIL sockets for three DIP16 cables that will connect the board to main logic board. Drivers for remaining indicator lamps are located in the main logic board. Similarly keyboard tracking is done in the main logic board that is found underneath 1106/1107 boards.

1106 board etching mask.

1106 board etching mask.

DIMI has eight different PCBs (four boards are identical) and I have made EAGLE CAD versions of all of them. I scanned original PCBs, edited images in GIMP, imported them to EAGLE and then did lots of manual tracing. As the original schematics and etching masks are lost, I needed to do everything from scratch. I will probably make a tutorial about this process at some point. Most of the boards I have etched by hand with help from Olli from Olegtron, but all the files are ready to the factory print as well.

Original DIMI-A board from summer 1970. 1106 board is lifted and 1107 backside revealed.

Original DIMI-A board from summer 1970. 1106 board is lifted and 1107 backside revealed.

As seen from this build footage of the original instrument from 1970, I’m proud to say that the end result is almost identical to the original.

Indicator lamps on DIMI are telephone slide lamps. I didn’t have a clue what they were and I still don’t know exactly where and how they are used. I would be happy to add a picture of an actual device where those are used here. But what I do know, is that they are used either in telephones or telephone exchange and that you slide them to some sort of socket. On DIMI they are hard wired straight to the board, so no sliding here. There are many different brands making these, but the company who manufactured lamps installed on original DIMI happens to still exist, so I ordered bunch of these from Taunuslicht.

Installing laboratory hose bits on 1106.

Installing laboratory hose bits on 1106.

Telephone slide lamps radiate light around them so on DIMI Kurenniemi’s design was to use laboratory tubing bits as a shade. I have to admit that it works nicely and gives the light orange color that the original has as well. I found out that you have to use quite tight tube as the lamps are located fairly close to each other. Lamps barely fit inside and I came up with technique of boiling them to soften them up a bit and then using water and electric spray as lubricant. That allowed me to install the hoses without breaking too many lamps in the process.

Boiling laboratory tube bits.

Boiling laboratory tube bits.

Another funny design solution that gives a nice touch is the magnet holding stylus connector on top of the keyboard. Tiny plate on top of the instrument is actually a keeper plate of small magnet hiding underneath the board. Model railway mini banana plugs are installed on keeper. They function as screw-in connector for stylus leads. Most likely Kurenniemi happened to have only one magnet lying around that he decided to use here, as the other DIMI (the one now in Stockholm) had to do without.

Original keeper plate from Helsinki University Studio DIMI-A.

Original keeper plate from Helsinki University Studio DIMI-A.

Sourcing original vintage magnet turned out to be difficult, but I ordered modern replacement from the same company. Keeper plate of contemporary version is much more boring and does not have the cool Eclipse logo the old one has.


I could easily go on for several pages about the details on this board but I feel it is time to wrap this post up. But at least now it is clear that to actually build a new instrument instead of simply documenting one helps to produce optimal documentation. Already now I have been spending quite a few hours fixing digital files of the bugs and flaws found during the build. If I would build another one, it would be much closer to the original.

To test the board, I hooked it up on Arduino MEGA, did a bit of programming and here you are:

1106+1107 board demo with Arduino MEGA.

Dimi is Reborn!

Dimi is Reborn! Cruising around with my (soon to be) DIMI.

The project of cloning DIMI-A was initiated in the spring of 2014. At that time I was working on a project with Icelandic artist and instrument builder Halldór Úlfarsson on a project involving original DIMI-A. Based on his suggestion I decided to apply funding for making a copy of DIMI-A. Those of you who do not know, DIMI-A is synthesizer by Erkki Kurenniemi and the first synthesizer under DIMI line from the early 1970’s. It is a synthesizer with programmable digital sequencer. I also like to describe it as a tracker [1] without display. I managed to get project funded and started it in 2015, and this article will document the starting point of the project.

This project did not come out of nowhere. I have been studying Kurenniemi instruments for more than ten years. I have written several articles about them [2, 3, 4, 5]. Latest one, focusing on DIMI-A and DICO was recently released by The MIT Press[6]. I have also been performing with the original instruments on numerous occasions, even together with Kurenniemi himself.

Digital City (from left Mikko Ojanen, Erkki Kurenniemi and Jari Suominen (Thomas Carlson did not fit to this picture) live in Koko theatre 2005.

Lineup Kurenniemi named Digital City two seconds before the concert. From left Mikko Ojanen, Erkki Kurenniemi, me and Thomas Carlson (who did not fit to this picture). Kokoteatteri 15 January 2005.

Now back to our main subject. Here is an extremely short version of the history of DIMI-A. Kurenniemi (with his team) started to work on the instrument during winter 1969-1970. The instrument was finished during summer 1970. DIMI-A was given name DIMI (after digital music instrument) and soon afterwards renamed to DIMI-A after development of the next instrument, DIMI-O, started. Two almost identical versions of DIMI-A were made. One DIMI was sold to Helsinki University Electronic music studio, where it is still in use today. The second one was sold to Swedish composer Ralph Lundsten, who used it for few years and then donated it to the collections of Musikmuseet in Stockholm (currently merged with Swedish Museum of Performing Art). [7, 3, 2]

Ralph Lundsten shows kids how to play DIMI-A (while his copy was still working) and some other Kurenniemi synths (in Swedish).

The most important reason to pick DIMI-A of all Kurenniemi instruments as main subject of this project is that while being the most iconic of all Kurenniemi instruments, it is the instrument with least information available. All other Kurenniemi instruments have fairly complete documentation. This can include schematics, timing charts, sketches, part lists and so on. But for DIMI-A there are none. During last ten years I have tried unsuccessfully to source them with Kurenniemi and few others. It is highly likely that documentation has existed, but currently we do not know if it still exists or if it has been destroyed at some point. The plot thickens when you lift off the the keypad board and have a look inside. More than 100 IC circuits, most of them without markings as they have been wiped away with acetone. Effort has surely been taken to protect ones intellectual property.

Studying historical instrument as this is not just about electronics. It is also about the history. In case of DIMI-A it is about the history of (Finnish) electronic music, Finnish underground scene and the history of technology. There are many stories to be told about the instrument. Some of them you will find by simply looking at the finished instrument. It has an aeroplane power cable between its power supply and the actual instrument. It has a model railway banana connector connecting probes to the modified magnet keeper plate. The fact that the circuits are wiped and the schematics are missing are a hint of another story.

Finnish composer Jukka Ruohomäki and Erkki Kurenniemi with the finished instrument at the Helsinki department of musicology.

Finnish composer Jukka Ruohomäki and Erkki Kurenniemi with the finished instrument at the Helsinki department of musicology.

DIMI-A is linked to the founding of Digelius Electronics Finland but was finished before founding of the company. Instruments made before DIMI-A were built in the premises of Helsinki University Studio. Few existing photographs of the finished instrument are also from the University studio. However the instrument was most likely built in the premises of another electronic instrument company, Elektromusiikki Oy [8]. Elektromusiikki was company selling mostly electric organs, electric accordions and discotheques (”two turntables and a microphone”) and was run by Jouko Kottila, who would also be one of the founders of Digelius Electronics Finland. Elektromusiikki was also a place were many key figures of Finnish underground scene were hanging out at that time, but nowadays very little is known about the place.

The difficulties in projects like this is that even if the original instrument was not built that long time ago, 45 years is still a long time. It is such a long time that memories of the people involved start to fade and melt together; someone might remember clearly working on instrument on some location with someone, but what the actual instrument was and what the actual location was might not be so clear anymore. People don’t simply remember. Ask me about the project I have done few years back and I would not be able to tell you much.

Technology obviously plays an important role in a project like this. Companies producing electronic components and mechanical parts did not spend too much effort on documenting what they were doing and when. True to even most legendary IC circuits is that in many cases their birthday is not known [9]. These are only few examples. Reverse engineering an electronic device with very little documentation and tens of wiped ICs is another remarkable problem, even though it is much easier nowadays than it used to be. And was not impossible even back in the day.

The point of actually building a working copy of the instrument might seem pointless. But it is the actual work that forces you to pay attention to the details that might be trivial or not. Trying to source a component might reveal why it was chosen in the first place. Kurenniemi might use some bit as it really made sense. Or maybe it just was available? Or it just happened to by at hand? The beauty is in details. And when you are building a copy of a synthesizer from scratch you really need to check every detail, there are no shortcuts.

DIMI is Born promo single

DIMI is Born 7″ was essentially a Finnish version of Switched on Bach. It did not help to boost sales at all and only two DIMI-A units were produced and sold. Here is weird fan made music video of the a-side.

More updates will follow!

This research project is funded by Finnish Cultural Foundation. Outer space photo was taken by Veera Knuuti and Digital City live picture by Kati Heickell.


[1] Wikipedia. Music Tracker. url: (visited on 11/04/2015).

[2] Jari Suominen. “ Erkki Kurenniemi’s Electronic Music Instruments of the 1960s and 1970s”. In: Erkki Kurenniemi – A Man From The Future. Ed. by Maritta Mellais. Finnish National Gallery, Central Art Archives, 2013. url:

[3] Mikko Ojanen and Jari Suominen. “ Erkki Kurenniemen sähkösoittimet”. In: Musiikki 3-4 ( 2005). url:

[4] Kai Lassfolk, Mikko Ojanen and Jari Suominen. “ DIMI-6000: An Early Musical Microcomputer by Erkki Kurenniemi”. In: Proceedings of the International Computer Music Conference. Athens, Greece, 2014. url:

[5] Mikko Ojanen et al. “ Design Principles and User Interfaces of Erkki Kurenniemi’s Electronic Musical Instruments of the 1960’s and 1970’s”. In: Proceedings of the International Conference on New Interfaces for Musical Expression. New York City, NY, United States, 2007, pp. 88–93. url:

[6] Kai Lassfolk, Mikko Ojanen and Jari Suominen. “ Interaction of Music and Technology: The Music and Musical Instruments of Erkki Kurenniemi”. In: Writing and Unwriting (Media) Art History. Ed. by Joasia Krysa and Jussi Parikka. The MIT Press, 2015. Chap. 19. url:

[7] Erkki Kurenniemi. “ Private interview (MP3) by Mikko Ojanen and Jari Suominen at Helsinki University Electronic Music Studio, Vironkatu”. June 2004.

[8] Jouko Kottila. “ Private interview (MP3) by Mikko Ojanen and Jari Suominen at Helsinki University Electronic Music Studio, Topelia”. June 2014.

[9] Brian Santo. 25 Microchips That Shook the World. 2009. url:
(visited on 10/27/2015).


My version of DIMI-S or Sexophone. Each player will need to hold on of the one of the metal pieces at the corners.

My version of DIMI-S or Sexophone. Each player will need to hold on of the one of the metal pieces at the corners.

This is project I have been planning to do for a long time. As an expert on Erkki Kurenniemi’s electrical music instruments I have had a chance to try out most of these weird beasts. The very instrument in question is DIMI-S, which Swedes call Kärleksmaskin (a love machine) and us Finns Sexophone. Sexyphone is my AVR based pocket version of this synthesizer.
Original DIMI-S in Kiasma. At the front the white noise gate unit I built for this instrument for Kurenniemi exhibition in Kiasma.

Original DIMI-S in Kiasma. At the front the white noise gate unit I built for this instrument for Kurenniemi exhibition in Kiasma.

Kurenniemi built two DIMI-S instruments. Today another unit is located in Kiasma museum in Helsinki, while the second one is in busy use at composer Ralph Lundsten’s studio in Stockholm, Sweden. Instruments differ a bit from another and original schematics exist only of the unit still located in Lundsten’s studio. My instrument attempts to mimic the functionality of Lundsten’s instrument. If you are fluent in Swedish, this instrument is thoroughly discussed in fine article by Jörgen Städje. I also happen to have the original schematics of this instrument in my possession which came in handy for sorting out some minor details.

Basic principle of the instrument is following. Instrument can be played alone, but more players, the merrier. Each player will hold one metallic knob in hand (sometimes also handcuffs have been used). By this they will be connected to the circuitry of the instrument. When they will touch each other, instrument will be playing notes and melodies.

Handcuffs may be used with Sexyphone.

Handcuffs may be used with Sexyphone.

My instrument is designed to be portable, so one can easily take it with to bar or where ever people usually touch each other. Four metallic screw bits at the corners will substitute as metallic knob. As long as all players will touch one of these with the other hand, touches will be tracked. One can also install handcuff electrodes to the corners when more dramatic setup is preferred. The instrument can either be heard through two piezo speakers (one for bass and one for treble) or line out through mini jack output.

The original instrument is equipped with light organ unit. My version substitutes this with a smaller system of six LEDs.