rutgerv

I have a few more practical questions regarding the new SID V2 hardware setup, that perhaps Thorsten (or Wilba!) can help out with: 1. How are the two SID modules connected to a single Core? I assume that the regular SID connection is still used, but to which pins of the PIC is the second SID connected? 2. How is the AOUT supported? Is the idea that each core (master or slave) has two SID's and it's own AOUT module for modulating external effects? Or is only the Master Core the one that supports the AOUT? 3. Do the custom switch settings in the V2 SID require a DOUT module? Or is it possible to use the AOUT gate outputs for switching? 3. If I'm correct the Core for SID V2 requires a PIC18F4685, but can the MidiBox FM also use this PIC for it's Core? Greetings, Rutger

If you ever find a bunch of CEM's for a reasonable price i'd be very interested. The reason I wanted to start building the MidiBox is because I want to learn about programming PIC's. I'm a student in artificial intelligence (so experienced in programming) and familiar with analog electronics, but i have never programmed a PIC. I was hoping to gather experience with this project to be able to construct a PIC controlled poly analog synth somewhere in the future.... For now I'm focussing on the Rick Jansen implementation of the Moog filter. I noticed some differences between the Moog filter schematic and the PCB that Thorsten used to create the demo on www.ucapps.de. On the picture of the PCB I noticed less IC's and more transistors. I assume that the LM3046 NPN-array is left out in this design and that manually matched transistor pairs are used. With a good matching procedure this can even lead to better results of the expo converter and the filter, besides, buying a bunch of transistors may be cheaper. I will be using a simple transistor matching circuit by Jim Patchell to select transistors. I changed the NPN transistors in the ladder from BC109 to BC549 (easily available and cheap at Reichelt.de). Oakley uses the same transistors in the Moog Super Ladder filter module. I also intend to use a LM13700 (also available through reichelt) for the CV control over the resonance. Only half of the LM13700 is used, so I think that I will make a stereo filter on a single PCB to use the other half of the LM13700. I changed op-amps to TL074 and TL072. The best news: the electronic components of the new design should be less than 10 euro's for a mono version of the filter (this is without pots, connectors and PCB). I was thinking about adding a CV parameter (or just a switch) to control the amount of gain on the input op-amps, just like Thorsten did manually, or maybe a seperate drive circuit that drives a nice sounding transistor. Greetings, Rutger

Building Oberheim filters might be more difficult, since most famous oberheims used Curtis chips that contained the entire filter. The CEM filter is not produced anymore, but if you're lucky, you could find some on the internet. Or ask Thorsten...I believe he had a bunch of them ;). Greetings, Rutger

Hi, thanks! I understand. I'm willing to try and program additional AOUT or DOUT (I assume that you need this for the 8 custom switch flags to output) support if I got the basics working with this filter. I just finished the drawing of the Moog schematic by Rick Jansen in Eagle and modified the Resonance feedbackpath allow CV control over the resonance. I also changed the choice of op-amps to ones that are easier to find (i.e. Reichelt). All op-amps are TL074 or TL072 now. In the resonance cv control circuit I used half of an LM13700 OTA. My intention is to make at least two circuits of this filter on one board (i.e. stereo) and see if everything works alright. I haven't still figured out how many filters I would like to make eventually. Just a stereo filter on the output is very nice, but it would also be great to have more filters (i.e. one for each SID). That would make a more polyphonic synth, but it would also require that each SID+CORE sends it's specific envelope generator voltage to the AOUT. Can you give a little insight on to which CORE the AOUT has to be connected to support the 8 custom parameters you spoke about? Is it only the Master CORE? Or can each CORE have it's own AOUT module with these 8 custom parameters? In other words. Are those 8 custom parameters meant for an ensemble or for each patch within an ensemble? Greetings, Rutger ps. Getting more and more excited about this! And of course I will share schematics and boards as soon as I got something working. If the Moog filter work good and Rick Jansen agrees, perhaps it would be interesting to make it available as a kit for expanding the SID synth. But it's a little soon for that I guess ;).

Thank you Thorsten, for sharing so much of the new design info. That allows me to start working on the filter right away! I'm working on a redesign of the filter of Rick Jansen, that supports cv controlled resonance and cutoff, to be able to store all settings of this external filter in a MBSID patch. Initially I'm making a stereo version that is controlled by only 1 resonance cv and 1 frequency cv, but perhaps with the new MBSID V2 it would be interesting to make actually 4 or maybe 8 filters to work with 4 or 8 sids at true polyphony. With four SID's it should be possible to create a 4-voice synth with 3-osc per voice. With 8 SID's the same should be possible with 8 voices but this requires 8 additional AOUT outputs (and support in the patch structure). If 8 sid's are used for stereo doubling a 4-voice polyphonic synth the AOUT outputs could be routed to both left and right channel versions of the filter... This would result in a true stereo 4-voice 3-osc poly synth..... nice ;). Another thing I was thinking about (but maybe Thorsten already covered that) is some sort of mixing system controlled by the patch structure, that would allow panning settings of the 4 or 8 independant SID's through only left and right outputs. But again, this requires many AOUT outputs. Greetings, Rutger

Why don't you use a desoldering pump? It requires some practice, but you can safely remove an entire IC with it.

Hi everyone, that sounds really nice!!! After having built this: http://www.orpheo.nl/dutch/index.php?mainframe=rsynthsite.php, i'm settings things up for new project. I would like to create a 4xSID and 1xFM MidiBox with two or maybe even four (for dual stereo) Moog filters in it, but I was wondering how to incorporate this into the system. Do you think it's possible to let one of the PIC cores handle those filters? I was thinking that the AOUT module could control resonance and frequency cv's and maybe even a drive parameter, but I'm not certain if it is technically possible to save the settings for the 'external' filter with every patch on the SID synth. I'm not scared of programming, by the way (I study artificial intelligence), but I'm not familiar with assembler. Greetings, Rutger ps. Now I'm thinking about it...maybe it would be a cool idea to create a totaly seperated Core and AOUT module to function as a multi effect with it's own programs. The SID master core could then simply send a 'program change' to this effects core and handle a stack of analog effects (filters, phaser, BBD flanger/chorus).... Of course i'm not thinking about the costs, but hey....please allow me to have this fantasy ;)

Hi, I read some posts on the external analog filter (Moog or CEM) that could be connected to the SID (V2) and the FM MidiBoxes...The sounds I heard were very cool, but I was wondering if someone knows if the CV that is sent to this filter is stored with each patch! Can I completely recall settings that include this external filter from both SID and FM MIdiBoxes? And can the each patch store a steady CV (to keep the filter partly closed for instance) as well as a modulation routings to this external filter? Greetings, Rutger

Hi Enrico, I think this drop of 1dB when the filter is active is done on purpose. It is probably to prevent clipping when the resonance is up. Greetings, Rutger