I just swapped my Roland MKS-70 for an SCI Six-Trak. I felt that I needed an American VCO poly in my collection. There aren’t many affordable ones available, but the Six-Trak is one. I also have a Roland JX-10 which is the keyboard version of the MKS-70.
Design wise, it’s kind of a strange combination of 80’s high tech and 70’s vintage. While it has the classic Sequential Circuits logo and solid wood sides, it has a “digital” user interface. You select a parameter number on a keypad and set the value with a pot. This is probably a big reason for why it’s not more expensive, kind of like same thing with the Roland JX:s. However, it’s actually very easy to work with, and there’s a nice template for Ctrlr available. The Six-Trak has a very good midi implementation – each parameter is can be controlled by midi CC (!) and not sysex which was the common and annoying way back then.
The cosmetic condition is very good on this one, I heard it was previously owned by the guy who managed SCI imports to Sweden back then.
Soundwise, it’s not a Prophet 5. Compared to the Roland Juno-6, which also is a one oscillator poly, the Six-Trak sounds very weak. To come alive, some external effects like chorus and reverb is recommended. There are no built in effects.
However, there’s a unison mode that definitely turns the Six-Trak to an monophonic monster! This mode can make it deliver extremely fat leads and basses.
I just upgraded the firmware in my newly bought MKS-70 from 1.03 to 1.08. I’m not actually sure what the differences are, but since I have the possibility to program EPROMs there was no reason not to.
However, the engineers at Roland decided to put the EPROM in a position that makes it impossible to pull it straight out. The EPROM is located at the mainboard in the bottom of the MKS-70 and marked with an A. The two voice cards (same as used for the JX-10) are stacked upon that. It is possible to fold away those cards, but a lot of cables has to be detached. I should mention that there each voice card also has an EPROM, these are didn’t have to be upgraded.
The TOP853 couldn’t burn the TC57256D-20 EPROM that are used in the MKS-70 and JX-10. My advice is not to buy the TOP853 if your’re going to use it for programming. The GQ-4X did it after I added a custom line to a new text file called customdevices.txt
I know it’s a bit insane, but I got a very good deal and bought an MKS-70. The MKS-70 is the rack version of JX-10. The JX-10 contains two JX-8P. So at the moment, I have a total of five JX-8P engines!
It seems to be fully working, has a few scratches on top and the front panel looks very nice. However, when booting it and pressing the VALUE button the screen read “Ver 1.03 FINAL JX”, which is not the last version of the firmware. Regarding “FINAL JX”, it’s kind of strange because it was not the last JX synth produced (JX-1 was the last one, though it’s not analog) and it was not the last firmware version either. Just like on the JX-10, the firmware was very buggy on the MKS-70, but they got it all sorted out with version 1.08. I’ll have to open the MKS-70 and check what kind of EPROM it uses.