Commodore Remix

Hi everyone

I've delved back into an old project of mine that I was working on before I was informed about the MIDI Box SID... A hardware SID synthesizer. I'm not doing this to compete with the imense and VERY powerful MIDI Box SID synth, but to take a little different approach to a SID device.

First; the MIDI Box SID to me is very cool, but it has become too complicated for me to make sounds on, especialy with the editor I made in SoundDiver (this is what I use and WANT to use... call me stubborn, I don't care )... it simply has too many parameters to be intuitively programmed.

Second; it is stereo (at least the SammichSID and MB 6582 is). I want a single SID hardware synth, that allow me to use a 6581 SID chip without strange stereo perspectives.

Third; I want a simple device that has just an Audio Out, MIDI I/O, Power switch, and a few LED's for signals... a very small and compact format meant to be controlled entirely by MIDI.

I decided to go from scratch, and build the whole thing on a wishboard from the bottom up... I decided on the PIC MCU (PIC18F452) that I know about from earlier, and by the time of this writing, everything has been set up and is working the way it should... SID is playing a steady sawtooth A4 tone, MIDI I/O is working great. Still afew hardware things is missing, but not that many.

Here is a picture of the "thing" as it stands right now... note that it's a SID 8580 I'm using at the moment (I have most of these to spare, should something go wrong)... also, the KORG Monotron in the picture is just used for it's speaker so that I don't have to blow my analog mixer input if something goes haywire (SID sounds cool through an MS20 analog lowpass filter by the way ):
I've also made the first steps toward the SoundDiver editor that is to be used with this thing... currently only the hardware SID parameters are included as can be seen in the following pucture (at least by those of you who know the specification of SID ):
Right now I'm working on parsing MIDI messages, and complete the System Exclusive specification so that I can get communication going between the editor and the hardware.

That's about it for now... I'm working on this almost every day, and I'll post more comments to this thread along with project progression.

Peace.

Cool stuff, looking forward to seeing the end result. I still have to build my MIDI Box SID synth. I just need the components.

Hi ANX... thanks for stopping by

Well I've been working a bit more on the editor today... also redesigned the whole MIDI parsing routine as I did this in a rather stupid way before... all is up and running again....

One of the things I've been dealing with also, is the fact that I've decided to constrain the memory usage of one patch to only 63 bytes... this means that every single bit is precious, and thus I have to think thoroughly about what goes in to the engine and what does not... and at what bit resolutions... it's back to optimization planning again like in the good old C64 days

Actually I hope to scale the MCU down to a PIC 18f252 rahter than the 18f452... they are identical memorywise exept that it has less I/O pins, but I won't really need them, and it'll allow for the final curcuit board to be smaller I hope.

Also I'm thinking about implementing a single EEPROM chip with 64k of memory, so that I may store patches in this chip... 1024 patches is possible in 64k so it's pretty neat. anyways; it's my intention to make it all a one-board synth with both SID, MCU and EEPROM on the same print... but still some thoughts have to go on this aspect in the future... don't even know what I want to do with this in the end, exept for using it of course.

SOUND UPDATE....

http://razmo.ziphoid.com/MicroSID_Demo.mp3

I've been fiddling with the SID synth I'm working on.... the demo above is only SID8580, exept for the kick drum (Vermona Kick Lancet) and some ping pong delay on the SID.... everything recorded live in multitrack format.

It's currently ONLY the raw hardware parameters of the SID that is being manipulated live (me going crazy on my editor with a mouse on the knobs)... I've not yet started creating any modulation... the filter is not even used in this demo ... I think this demo shows very well that typpical SID sync and ringmod sound between oscillators that it was famous for, and I'm quite impressed how formant like the tones can actually get with this thing.

The project has gotten the name Micro SID, since my goal is a compact, one-SID synth with as few components used as possible... I've already made the schematics for the curcuit boards for it, and is currently looking like this:
Changes will most likely happen, but not much I think... still, the design will be nothing more than a little box with Audio In/Out, Power switch, MIDI In/Out and a few LEDs for signaling stuff.

Coding is still done using a PIC, but I decided to go with the larger of the small 28pin MCU's there is, the PIC 18F2685... it's raw 8-bit assembly coding, even though sometimes I'd wish it was at least 16 bit...

I also decided to drop the use of an EEPROM chip for 64k of ekstra memory... mainly because the MCU has more than enough space for patches, and it can program into it's own program memory, so that I can use this for storing patches... with the PIC 18F2685 I got 96k of flash program memory, and I simply won't use all of that space for the player routine.

More updates as things progress...

nice teaser demo

A little update in the last demo (press link above)... I've implemented an ADSR envelope on the SID's filter now, and it can be heard in the update on two bass-lines... kick is still Vermona Kick Lancet, but the added snare is SID too

Enjoy... more to come when I've done something new...

Allright.... I've been coding a bit more on the Filter envelope, but the main stuff I've been on is the SID envelope bug... I needed to make a Hard Restart to avoid the SIDs buggy timing on beginning of notes.

A normal delay with the SID is approx. 33ms (that's what I've read at least... others say 60ms, but I believe this is in a C64 context). I've decided to clock the SID at 2MHz instead of the "normal" 1Mhz (yes yes... I know that a real C64 is clocking it a tiny bit slower), which then allow me to drop the latency to half (16ms)... in the future I'll be experimenting with a clock rate of 3.33MHz, just to see if I can get this latency even further down.

I made yet another small demo, using the new code with latency and the use of SID's hardware envelopes on the oscillators... but this time I've included other instruments as well (other synths)... SID is playing only ONE of the tracks in this demo... you'll have to guess which one

http://razmo.ziphoid.com/WhatsSID.mp3

http://razmo.ziphoid.com/SID-CORE.mp3

Another demo showcasing the software Filter Envelope in action... switching of different filter modes also and a bit of resonance tweaking ... I feel that the envelope is behaving pretty good now, sounding analog enough.

I also changed some note triggering code, because I implemented the Hard Restart inside the MIDI interrupt... the thing hanged when I did this, so now all triggering is left to the main code and things work.

More demo's as things progress...

http://razmo.ziphoid.com/FeedbackSID.mp3

A small demo of SID when the audio output is fed back into it's input via a potmeter (set at maximum in this demo)... it's the same feature as with the MIDI Box SID... kind of chaotic in nature, and you have to experiment, but in the end you get some really nice results that you've never heard SID produce before

In this demo, SID is the fast harcore blade-like bassline... the other instruments are other synths.

Whoa this sounds phat.

LMan wrote:Whoa this sounds phat.

Yup!... you can do some nice things with this feedback trick

I redesigned the ADSR envelopes for both the filter and volume... actually I dropped using the SID's internal hardware envelopes on the oscilators since the ADSR bug is impossible to work around in a way I can accept.

I decided to control the volume register instead, but this gives me only 16 steps as it's only 4 bits wide... I did manage to get this changed into a 5bit one instead by using a little trick. I can use the sustain parameter as a second volume register in realtime as long as I only decrease the value in it (so I only have 4bits resolution in the attack phase)... so by setting the combination of sustain and volume register properly, I can have 32 steps instead which is much much better... when the SID's ADSRs are set as 0,0,15,0 it works 100% as it should (no bug) and it works as a simple gate... but as the sustain parameter can be modulated in realtime it works as a semi-volume register. This of course means that you cannot use the SID's hardware ADSR on individual oscillators anymore, but as this is a monosynth anyways, it does not matter... I prefer the tight timing of MIDI more.

Other than that, the ADSR envelope code itself has been changed to give better and more bouncyness... I believe I've reached the ultimate ADSR for this project now.... tjek it out here:

http://razmo.ziphoid.com/ADSR_Showcase.mp3

Bassline heavily inspired by The Overlord's "Sundown" tune...

Excellent job Razmo!!

Analog-X64 wrote:Excellent job Razmo!!

Thanx ANX ... just doing my best, and have not lost interrest in the project still which kind of surprise me a bit

One advantage is, that I'm developing small snippets of code that I'll save for future projects... this way I have code for an ADSR, LFO, Arpeggiator etc. that I can improve upon in the future and make new projects faster... at current everything has to be done from scratch.

My next project, hopefully will be that of interfacing the YM2164 FM chip from Yamaha... the same FM chip used in the KORG DS-8 and Yamaha FB-01 FM synthesizers, and hopefully the code from this project can be reused in some places. This chip, along with the compatible 2151 is to my liking one of the best sounding FM chips Yamaha has made, and is yet another Synth-on-a-Chip kind of thing... another interresting chip for future projects is the analog CEM3396 chip which is also a synth-on-a-chip.