DIY PROJECTS
CV/Gate Sequencer (finished)
I finished this project two years ago shortly before KORG released their SQ-1. My design supports three Channels, each with Analog CV and Gate Outputs. Sequences could be 32 steps long and 12 can be stored in a non-volatile memory. Each step could have an unique gate-time length. The design is controlled by an Arduino Micro. The User interface is made of 12 Digi-switches and 5 Potentiometers. I've also integrated a Real-time recording feature and syncing with an analog clock input. Gate Voltages could be commonly switched from 5 Volt to 12 Volt, and could be individually muted and inverted.
VS RAM-Cartridge (finished)
Still ongoing project. A RAM-Cartridge for the Prophet VS. If it will work one day ... it supports 1600 sounds in 16 switchable Banks, each with 100 sounds. In sum there is room enough for all available memory banks and for your own sounds as well. The Design based on an Arduino Mini, features an 7-Segment Display and two Digi-switches as User Interface. Aluminium housing which fits in the existing VS Cartridge Slot.
Update 2016/10/27 :
One step forward ! With a little help from an original RAM Card it was possible for me to figure out Sequentials "secret" Data-Bytes :o) ... one bit by the other ... pure oscilloscope work ... pure fun !!! Now it will be correctly detected as a RAM Card and it is possible to switch over from internal to external memory.
Really funny about this topic ... later on I realized that there is a existing function in the OS that let you initialize a fresh RAM Card (Hold ENTER and press 8) to achieve exactly that this bytes will be written automatically. But I think I'm one of the few guys on this planet who knows the exact memory location ;o)
Update 2020/05/27 :
Wow ... after 4 years it needs the worldwide corona crisis to finished this project. In between the market offers two very similar products with mostly the same specs. But for me ... mine is definitly the best looking one :o)))
Memory Extension and Floppy-Emulator for the Sequential Prophet 2000 (stopped unfinished)
I got this great sampler as a cool birthday present this year :o) After checking and repairing some smaller issues I think it should be a good idea to extend the sample-RAM up to the possible maximum of 1 M-Words. Currently it got the standard size of 256 k-Word. I check the schematics and see that it could easily be extended. The sequential developers implemented a socket inside, and some versions of factory memory expansions combined with a new floppy disk are available in the past. I decided to design my own expansion that will add 768 k-Words of extra RAM to the Sampler.
The design based on the usage of cheap available 30Pin-SIMM Memory modules ... after I found a source for this outdated SIMM-sockets, I started to setup my prototype board. But then I ran in a unexpected problem ... only 6 of the 8 voices will play correct. Two voices plays the sample only with very strange sounding errors. After some investigation work I realize that the Voice Controller Chips (a 40 Pin custom made sequential circuit I-624) could be the source of the problem. Each of this chips handle two of the 8 voices of the Prophet ... so it could be possible that one of mine got a problem. As I already said ... 6 voices are working correct so the extended sample RAM itself can't be the problem and all 8 voices will work flawlessly if the samples are located on the base 256k-Word Memory. To get a clearer view on it I decide to rearranged the position of the 4 chips ... in general a good idea to confirm that the voice controller itself is the problem. But ... i got a really unexpected result ... each time I rearranged the chips I got other faulty voices ... sometimes more than 2 voices are not working correct. It seems so, that there is another reason for this behaviour and at the moment I haven't any good idea about what this could be.
The problem with custom made chips is ... they are seldom and very expensive. A set of 4 "new old stock" custom chips from a well known american supplier of sequential circuits spare parts will cost round about 300$. Add taxes and shipping costs for a customer in germany and it is ... let's say ... a little bit unattractive :o)
So I decided to stop this project and wait for another good idea. Maybe one reader of this text could give me a helpful hint then contact me via E-Mail (refer to the impressum). Hint's, Help or opinion's about this topic are appreciated !
To solve the upcoming storage problems that will automatically occur if you have bigger samples, I decided to swap the original floppy with a USB Floppy-Emulator. The standard units from gotek, modded with a Flash-Floppy Software, Rotary Encoder and this tiny OLED Displays work fine in my Roland Samplers S-50 and S330. This mod will work flawlessly ... the flashfloppy firmware detect the correct format and make loading and saving to a breeze ;o)
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