Let's build a "perfect" MOS SID (6581)

...and how to do so...
User avatar
aciddose
KVRAF
12289 posts since 7 Dec, 2004

Post Tue Oct 08, 2019 1:42 pm

The linked thread is about a full spice schematic/netlist that models the SID filter + amplifier analog stages.

I've decided to "spam" this thread linking to a past thread in the instruments forum in case it was missed back then. At the time I couldn't decide the best forum to post it in. I should also make sure the thread is linked in SID-related threads related to the sidplay open source library and similar locations as well.

viewtopic.php?f=1&t=526480
Free plug-ins for Windows, MacOS and Linux. Xhip Synthesizer v8.0 and Xhip Effects Bundle v6.7.

User avatar
aciddose
KVRAF
12289 posts since 7 Dec, 2004

Re: Let's build a "perfect" MOS SID (6581)

Post Tue Oct 08, 2019 2:20 pm

I've wondered whether it might be possible to match the timbre using NJFETs for the input buffer and VCRs and NPNs for the other transistors, or whether the NMOS curve is too unique and an NPN model would end up far too linear.

Variations on approximated discrete SID-filters would be a really cool project. I wonder if the modular crowd might be interested in PCBs + parts kits?

I suspect the 6581 SID filter might be one of if not THE most distorted filters ever :)
Free plug-ins for Windows, MacOS and Linux. Xhip Synthesizer v8.0 and Xhip Effects Bundle v6.7.

User avatar
justin3am
KVRAF
10817 posts since 7 May, 2006 from Southern California

Re: Let's build a "perfect" MOS SID (6581)

Post Tue Oct 08, 2019 3:25 pm

No need for three of the same topic in different sub-forums. If you would like this thread moved, we can do that but otherwise lets try to keep the discussion in one place.

User avatar
aciddose
KVRAF
12289 posts since 7 Dec, 2004

Re: Let's build a "perfect" MOS SID (6581)

Post Tue Oct 08, 2019 7:48 pm

Well, the question is whether the SID can be considered an instrument (it can't really) and where the content of the thread would be most accessible to those most interested in it.

DSP / development would make more sense if it were focused on a software re-implementation. So posting there was probably not too useful. DIY here makes sense from the perspective of electronics projects since the main content is a ltspice schematic used to simulate the circuit. Hardware would make sense due to any SID-based hardware being most likely the sole application of this stuff.

The DIY aspect may make sense... if there is any interest in the idea. I'd like to make an attempt myself although I can't see it happening any time in the next year or so. Possibly next year... if I do make any modified schematics/models I'll post them here though.
Free plug-ins for Windows, MacOS and Linux. Xhip Synthesizer v8.0 and Xhip Effects Bundle v6.7.

User avatar
justin3am
KVRAF
10817 posts since 7 May, 2006 from Southern California

Re: Let's build a "perfect" MOS SID (6581)

Post Wed Oct 09, 2019 8:01 am

Cool, I would certainly be interested in your progress. :tu:
If you decide that you would like to have the thread moved later, we can do that.

I don't know about the modular crowd in general but I'm definitely interested in a PCB (I can source my own parts). If you want to aim a product specifically at DIY Eurorack, you might think about designing a front panel for it too; there is a white paper which contains panel specs on the Doepfer website.

I find that there is demand for DIYsynths but it's mostly coming from folks who will try to find someone to build the module for them. There are a number of professional kit assemblers who advertise their services on the Muffwiggler forum. I think there could be demand for the x0xbox equivalent of a SID based synth. ALM Busy Circuits has their SID Guts module but I think that's a BYOIC affair.

User avatar
Skupje
KVRist
476 posts since 26 Oct, 2018

Re: Let's build a "perfect" MOS SID (6581)

Post Sun Oct 13, 2019 2:54 am

Think the DIY application makes sense since it has an analog filter section.

Return to “DIY: Build it and they will come”