Integrated Synthesizer renovation

I was fortunate to receive funding to renovate Kurenniemi’s Integrated Synthesizer in 2017. The work began in the fall of 2017 and concluded in the summer of 2018. This is not a comprehensive record of the process, but rather a collection of posts that I originally shared on the project’s Facebook page.

20180108

New Power Supply Unit for Integrated Synthesizer. I am not comfortable operating the instrument on its original power supply, which was designed according to specifications from the early 1960s. Therefore, I created a new power supply based on Power One units, incorporating Over Voltage Protection (OVP) to ensure that a malfunctioning power supply will not damage the original instrument. I had to modify the other unit to provide ±6V, with the OVP activating at 6.5V. Erkki designed the synthesizer to allow for the connection of an external power supply without any modifications to the instrument—very clever!

20180113

The new power supply is now operational. It connects via an octa plug and banana connectors, with no modifications made to the synthesizer.

20180201

I am redoing the patch cables in my lab. Helsinki University Studio acquired a VCS3 in early 1971, and since both matrixes are from the same manufacturer, the pins have become mixed at some point. In the integrated you mainly use shorting pins (not visible in the picture), while the pins similar to those of the VCS3 are used as patch cables. As you can see, all of them once had cables installed, which is also evident in some photos and film footage from the 1960s. I will rewire a couple of cables and start figuring out the patching tomorrow. By the way, these pins are quite expensive; there are a couple of hundred euros on the table! The white, red, and green ones in the container are likely from the VCS3, as they do not have drilled holes.

20180202

First program! This is a simple one using four flip-flops in a scale-of-two configuration. I have connected the output of a harmony generator to one flip-flop and then chained the four flip-flops together. The result is the generation of sub-octaves of the original sound. Next, I will tackle something more complex.

20180206

I have taken a couple of days off from intense 60’s digital logic. I calibrated and fine-tuned the VCS3 at Helsinki University (just for fun!) and am now building a table for Integrated. Let’s see how it turns out!

DAW of the 1960’s!

20180416

There are a few knobs and switches on the front panel of the IS. The mixer should have included a set of mute switches, which were never originally connected. Later, someone removed them from the panel, stealing half of the switches and leaving only empty holes. I found a couple of remaining switches in the studio. After some research, I discovered that these switches are extremely rare. They were only manufactured in the early 1960s and were also used by Brian May in his Red Special guitar. There appears to be a community dedicated to creating their own Red Specials, and there is a project underway to produce new clones of the original switch. Since the switches on the IS are not connected, I only needed the visible part for aesthetic purposes. Kind individuals from the UK (thanks, Timothy!) who are working on the clones generously sent me their 3D-printed prototypes of the actual handle part of the switch. They look great! If by any chance you happen to have these Jean Renaud switches—or any rotary switch from this manufacturer, as the original contacts are the bottleneck in producing the cloned switches—please let us know!

20180417

I accidentally discovered this folder in the studio library, and it is the most fascinating find ever. It contains all the receipts for purchases made at the studio during 1964 and 1965. Until now, the timeline for the construction of the IS has primarily relied on hearsay and interviews conducted many years later (although there are a few compositions created with the equipment and some other sources as well). However, this folder provides hard evidence, making it extremely valuable for establishing accurate timelines. Here is the shipping list for the Sealectro matrices from August 1964. After a quick browse, I also found a receipt for the parts for the frame from April 1964, indicating that the build most likely began in the summer of 1964. I need to delve into this material more closely and try to determine when individual modules were constructed.

20180425

New aluminum side panels have been completed! The original panels are missing, with only the bottom one remaining. I am now considering whether they should be painted or left as is. I believe the original color was a creamy white, similar to the bottom panel. They also look quite good in their untouched state.

20180515

CV summing problem on this board. Can you identify the issue (one wire that was never soldered)? Otherwise, we are ready to close up the instrument, as the work is nearly complete.

20180608

We are quite close to the moment when we can declare the patient cured. However, there are still a few minor issues to address. This must be one of the most minimal voltage-controlled oscillators (VCOs) I have ever encountered! It features a PNP-based relaxation circuit, calibrated as a low-frequency oscillator (LFO), and it surely produces a lovely sawtooth wave vibrato when used properly.

20180619

With summer holidays approaching, I am excited to announce that the generator unit of Kurenniemi’s synthesizer has been restored to its original condition from 1968. This has been one of the most rewarding projects I have undertaken so far. The renovation would not have been possible without the support of the Alfred Kordelin Foundation, so a big thank you to them! There is still some paperwork and documentation to complete, and if anyone has a knob similar to the one missing from the lower right, please let me know! I hope to return to the studio for some recordings after the summer. Next stop: DIMI-6000?