SP-303 DSP Reverse Engineering Crusade

[gym_prof]

Anyone interested in being part of my crusade to reverse engineer the SP-303 effects DSP algorithms? I extracted a binary image of the firmware/OS for a 303 (forum won't let me attach the file format but I can email it to you). I'm planning on building up a grammar for said code to deconstruct the DSP portion. Long term goal would be to build a standalone effects unit that uses the original algorithms and DAC architecture. I love these little magic boxes, and use them almost daily in my own music stuffs. I know it's a bit of a silly project, but I've reverse engineered more challenging devices before. I'm an electrical Engineering student studying in California.

To move forward I'm thinking I'll need an original service manual to find the specific CPU/DAC chips being used, RAM/bus information, and DAC filter/preamp schematics.

Once I have the CPU chip nailed down I should be able to track down an op-code list and work from there on the firmware/kernel hex.

If it sounds like a project you're interested in being part of or can help out with DM me! It's a pet project at the moment but I'd love to shoehorn it into a college CPE project if I make some progress.

Got high-res pictures of the CPU board chips??

[Crane]

Here is the Boss SP-303 service manual.
http://www.nquabayre.com/wp-content/upl ... Manual.pdf

I have a sp-505 open right now (basically the same as the 303) not sure what pictures of the chips are going to do for you but I will take them if wanted.

The only sought after algorithm of the sp 303 was the vinyl simulation "vinyl sim" which has already been created in a software format for the same price as buying a 303 or sp-505.

I commend you for your crusade, but if anyone wants an effects box from roland......They already have it and have signed up on the forum.

Good luck

[gym_prof]

You pose a fair point about the effects unit argument. Thank you for the service manual! I'll probably dig into it a bit more knowing what DSP chip is used. I had no idea someone had actually reverse engineered the vinyl-sim, I was under the impression they were all constructed somewhat arbitrarily on the sound rather than the original code.

[PeteSasqwax]

I had no idea someone had actually reverse engineered the vinyl-sim, I was under the impression they were all constructed somewhat arbitrarily on the sound rather than the original code.

I was always under this impression too.

Is this in reference to Vulf Comp or is there something else? Personally I'd love to see it available as a plugin for iOS devices but I've just bought a 303 to solve that issue the long way round

I'm totally down to help if I can, although I'm not sure in what capacity I would be of use.

[ghost bazz]

To the OP...

This sounds like a great project. Does your expertise extend to understanding the language of the OS, and potentially modifying it to add functionality in an updated version?

[zindan]

has the vinyl sim really been reverse engineered? like exactly?? which software?
that algorithm has always left me dumbfounded, shit is so perfect but i have absolutely no idea how the fuck it works

-edit-

also has anyone reverse engineered the 404 equalizer? curious what kind of curve that shit does, i love it

[7million]

Sounds interesting I was trying to do this for the 404SX to change the pitch shift so it behaves more like the 202 (slows down or speeds up sample - traditional style)

I considered using mess (MESS 0.148u1)
https://www.youtube.com/watch?v=ulQo5SjNTaQ

correct me if Im wrong but if we emulate the chipset in mess we can run the OS and it would be running the code so therefore we might be able to interrogate it from mess & a pc that way?

otherwise I know the firmware update
sp404sx_up.bin

is written in C++

Screen Shot 2020-05-05 at 11.28.15 am.png (42.92 KiB) Viewed 38995 times

I also wanted to see if we can change the behaviour of the trim marker points since it only allows +30 or -30 at a time for start and end points.

I am also trying to reach out to a developer at Roland

[Ill Green]

Old thread, but I am interested in this feat. Any updates?

For some reason, the service manual is not available in my region, I really want to know the chips used. Most IC chips have an oscillating-resistor (ROSC) which can be hacked to be used as Pitch/Speed. Technique consists of removing the resistor from the IC's ROSC input and replacing it with potentiometer between 100k to 200k. 100k are easy to find but with a 200k, you have a very wide range of pitch.

I would be stoked to have a 5th knob for pitch on my SP-303

[abuse_it.s_ok]

i think its using the echo delays pitch function, but i remember it sounding dull and muffled when it was done on a 404, not unusable, but would prefer having something else to do that job for me, a 202 or a 224 maybe with all its extras