Sequential Circuits MultiTrak

Device type	Keyboard synthesizer
Purchased when	around 1989-1990
Purchased where	from a friend of a classmate
Price including S&H	400.00 DM (around 200.00 EUR) + around 90 EUR for the spare parts
Condition when purchased	defective
Current condition	working
Status	in use

The Sequential Circuits MultiTrak (or Model 615) if one of those synthesizers from the 80s, that had to be polyphonic and cheap. It's a simple synthesizer without a knobs array but just one data entry knob and a parameter matrix. It's quite comfortable to program and sounds good.

6 voices
1 VCO (sawtooth, triangle, square with variable pulsewidth)
1 VCF, can be modulated by LFO and/or VCO
1 VCA
1 LFO, selectable waveforms triangle and square
1 VCO EG (invertable)
1 VCF EG (invertable)
1 VCA EG
1 6-track sequencer, 4 separate sequences
1 arpeggiator
Can use splits/layers, and even is capable of being multi-timbral with some tricks.
Velocity can influence LFO (vibrato intensity), VCF (cutoff) and/or VCA (amplitude)
Unison mode to fatten up the sound by playing all 6 voices parallel (there are funny combinations of less voices for unison in combination with stacks possible, didn't check out everything for now, without a manual, this thing is not too easy to use with such special functions).

This is one of the rare items in my studio which really has a story, and took a lot of influence to the fact that i started the new hobby, collecting synthesizers and using them. It all begun around 1989-1990, when a friend of a classmate asked me if i can fix this synth. He got the schematics of the MultiTrak, and i had a look into it. It didn't take long to see that 2 custom chips (one logic array and the keyboard scanner, a mask programmed microcontroller) and the firmware EPROM have gone due to an overvoltage caused by a broken linear voltage regulator. I don't know if this regulator burned due to construction problems or due to experiments with the power supply, as i got the synth without power supply. As i had no chance that time to get the custom parts for the synth, the owner sold me this thing for 400 DM (around 200 EUR, that time it was a lot of money for me as i was still in education), i took it because of the velocity capable keyboard, which felt lots better than my DX21 i had that time. I said to me "the time comes where i will fix this synth, in worst case with a selfmade MCU and modifications of the digital part".

Today, i'm kind of happy i never had the time and patience to redesign the digital part. In 2004, i found the EPROM image of the MultiTrak somewhere in the web. Fine. So just 2 of 3 puzzle parts missing. After a while of searching, i found WineCountry. I immediately created a PayPal account (the easiest way to pay from Germany to USA) and ordered those 2 parts there. At first, i accidentally got the logic array for a TOM, but immediately after my complaint, WineCountry sent me the right part with no further costs and told me to do what i want with this TOM chip (if anyone from Germany needs one, contact me :). Okay, good service, and the about 50 EUR i paid including shipping was not too much. So about 07/2004 i got all special parts i needed.

Then again some time went away as just dropping the chips into the synth didn't fix it. The next time i had enough free time to have a closer look at this was around 09/2005, where i took time, multimeter, soldering iron and checked out everything a bit further. I found another 2 TTLs and the CPU (a Z80-A) to be broken. I took the Z80-A from a ZX Spectrum (he will get it back somewhen :), had the rest around in different versions, glued everything together and - heared the first tones from it. That time, with a 2x6V power supply, it worked so far. Okay. Time to take the last step.

I again ordered some parts, all together about 40 EUR, to fix the rest. Replaced the TTLs by correct types, cleaned up everything (every single key, the whole construction), removed rust, cleaned pots, and built a file power supply, which looks like it could be original. Lots of work, but after putting everything together, recalibrating the DACs, i had a fully working MultiTrak.

I just need some original looking screws now, have to bend a pot (the axis is a bit bent), clean the master volume pot again, and then it's like new. Because of all this work, i think i will never give this really fine synth away. And for another reason: I had that D-110 and that DX21 and played around with them rarely. I never got real fascination with those synths, the DX21 sounded funny, but not really fat, the D-110 had fine strings and pads, but also there is missing a real kick. Was okay for some standard drums also. But then i got this MultiTrak and things changed immediately. Starting with the first working result of my rebuild efforts, in 09/2005, i loved to play around with this quite simple analog synth. It didn't take long that i needed more stuff. Checking out the prices at eBay, seeing, that all those things don't really cost too much money if you want some mainstream stuff, i started to build up a small home studio. You can read more about this in the small stories of the other items in my studio. Nothing else will have that much to tell :)

What you won't see in the other items: The first success on the MultiTrak lead to purchase of a keyboard stand, a nice keyboard seat and lots of cables.
This synth is quite simple with just one VCO, but due to some other funny features, you can get impressive sounds from it. Especially in unison mode, it is quite good for bass lines, but also usable for good pads or screaming leads.

To see the repair history, continue reading the following pages.

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