Sähkökvartetti DF controller
This build is a replica of the original DF controller of Sähkökvartetti (Electric Quartet). Original controller was lost at some point. Replica is 100% operational and is now hooked up on the original Sähkökvartetti.
This controller is part of two Sähkökvartetti subsystems: viulukone (violin machine) (also ‘resbass’ (travel/portable bass)) and laulukone (singing machine). Electronics of these systems are located in the Sähkökvartetti main rack; the controller only houses two pots and two switches. In total , laulukone has seven parallel signal paths, and this controller controls one of them.
There is not a great deal of footage featuring the original controller. All the footage I found were from new bits and documentaries made by YLE back in the day. The color of the controller box can only be guessed, but most likely it was light grey or white. Below are all shots I was able to source.
After the first image was shot, the longer shaft on pitch potentiometer was installed, allowing easier operation. Controller is not seen in Ungdom för helvete, released in September 1969, but one year later in the show in Vanha, viulukone is clearly working. Laulukone is not working anymore at this phase, but the reason most likely is a broken microphone preamp. As far as I know, Sähkötapahtuma show in Vanha is the last Sähkökvartetti show.
The original controller is built in a weird shaped box, possibly without a back plate. It looks like it could be from a model railway power supply or something like that, but I have not been able to figure out what it actually is. Potentiometer knobs are similar to ones on melodiakone 2 and filter controllers. Push button is most likely similar to one Kurenniemi used on DICO a couple years later. The acrylic cube on the tip of the extension arm is most likely cut from the acrylic bar. Underneath the filter controller is a longer section of acrylic bar which would roughly match the size of the cube.
I didn’t try to do 100% replica, but I did try to get dimensions roughly right so the controller would feel like the original when held in hand. I eyeballed a hammond box that would be closest to the size of the box based on the images above. Couldn’t source similar potentiometer knobs either, the ones I used are the closest to the size and shape I could find. Extension arm I took from an old handbag and used transparent dice as a cube.
The existing schematics of Sähkökvartetti are somewhat vague and far from complete. Schematics only give the pinout of the connectors, not the actual circuit. To confirm the pinout, I reverse engineered the circuit on the PCB.
The circuit consists of three parts. The first part is a clock generator circuit. It consists of an UJT oscillator clock driving a 2-bit counter (MC790P). Knob on the controller is setting the frequency of the oscillator.
The second part is the viulukone sound generator. It sums the outputs of the counter together to create a 2-bit ramp waveform. Generator is gated with an opto-isolator.
The third part is the actual laulukone digital filter (DF). It consists of a bank of four first order low pass filters. Counter clock is used to cycle through these filters, enabling one filter at a time (consistent with Kurenniemi’s memories from 2002). Output is then fed to the output of an opamp buffer.
This build was supported by Talking Machines / Kone Foundation.
- YLE. “M. A. Numminen – mies Somerolta”. 1996. url: https://svenska.yle.fi/a/7-887810 (excerpt)
- Jukka Ruohomäki. Private telephone interview. 2020.
- YLE. Sähkökvartetti Bulgariassa. Excerpt from “Maailma lähikuvassa”. PROG_2009_00142688. Broadcast date: 09/30/1968. url: https://areena.yle.fi/1-50219735 (visited 04/06/2022).
- YLE. “Otto Donner /15min”. Broadcast(?) date: 02/24/1969.
- YLE. Erkki Kurenniemi tietokonemusiikista. Excerpt from “Ihmisen uudet mahdollisuudet”. PROG_2009_00121250. Broadcast date: 03/27/1969. url: https://areena.yle.fi/1-50113320 (visited 6/4/2022).
- YLE. “Ungdom för helvete”. Ung 69. 2.9.1969. url: https://areena.yle.fi/1-50191266 (visited 04/06/2022).
- Erkki Kurenniemi, Jukka Ruohomäki and Sähkökvartetti. Sähkötapahtuma Vanhalla. 11/17/1970. Audio recording. Unreleased.
- Sähkökvartetti: Excerpt from a live performance. “Avantometric Attachments 2002”. Mediataideyhdistys Avanto ry. 2002. (excerpt from).
- Kullervo Aura and Erkki Kurenniemi. Sähkökvartetti documentation. 1968.
- Erkki Kurenniemi. “Sähkökvartetti EK 020807 — 020826”. Restoration memo. 2002.
- Jari Lehtinen. Sähkökvartetti.txt. Restoration memo. 2002.