gavgomad

It sounds like the question is between building the features into the existing SID v2 (ie. it's in the code running on EVERYONE's SID, whether used or not), or increasing the feature set and compiling a different version of the SID v2 software with substituted code for sending all the oscillator data to the AOUTs.... I think that in my response, I am in agreement with jimp (if I'm reading you correctly, Jim! ;-P).... I would have no problem compiling a .hex file selecting the "AOUT" option I want. I would willingly compile for the added features! Wow TK, I expected that incorporating such features would be a monumental, if not impossible task! To say that I love the way you think is an understatement! ;-) Gav.

Hey TK and all.... This was an interesting quote that I thought I might break out into a separate topic from the MB303 thread in Design Concepts.... TK, this is exciting news to me. As I have mentioned elsewhere, I have dreams of not only turning SID V2 into a controller for a modular synth, but also for a dedicated dual oscillator moog-based synth with patch memories (using all of the LFO and EG facilities of the SID - the arpeggiator etc. are exciting possibilities as well!) - essentially like a Moog Source.... In terms of the features for Key to AOUT.... Realizing some are less doable than others (or simply NOT doable! ;-P) 1) The glide flag for sure... This is more of an issue internal to the SID software itself, as the issue is how the EGs react? 2) Portamento - would be nice if this could be integrated into the KeyCV signal as well, borrowing from the values stored in the SID patch. 3) Multiple AOUTs (or simply an input into the Matrix) - So far, I can see driving a couple of oscillators, maybe three, and it would be nice to feed each separately (ie. pitch derived from their own CV output - to which KeyCV with or without portamento, pitch bend etc. can then be applied). 4) Transpose - Again, from the SID patch data - for driving and storing separate oscillator info, a transpose function would be nice - allows you to use the straight AOUT knobs more as a fine tune? This may not be necessary depending on how many steps are in the AOUT knob functions - you just need to be able to dial up with sufficient accuracy.... It might even be easier to interpolate the Transpose / Fine data from the SID oscillator data to AOUTs 1 and 2, and possibly 3 where a third oscillator is used? Maybe 3 and 4 are realized by flags for voice control - OSC1 to AOUT1, OSC2 to AOUT, OSC3 to AOUT3 and just turn on how many you need? Only one external oscillator, just use one.... Just some thoughts, of course.... Much of the above may be far more detailed than TK wants to get into with the SID software.... ;-) Gavin.

Sorry! My bad.... Just me making things too complicated for myself again! :-X Linear out into CV in feeding the expo converter should do the job.... I like the idea of the equivalent of a Moog Source, plus all the mod goodies in the SID V2, in a nice single rack space.... Will sit nicely next to the Wilba Beast.... ;-) Gav.

Hiya Jim and all! I actually haven't played with the 303 circuit that much - thought it was v/oct as well.... My only interest in weeding in the v/oct support was that so far the best VCO circuits I've found (sounding, not accuracy - v/hz tends to be a bit more stable) are v/oct. Also, I've already got a few really nice moog-clone vco's built and looking for duty!! ;-) I think this is likely far too much coding to include these lookup tables anyway.... But in the best of all possible worlds.... ;-) Gavin.

Just a thought.... On my "to try" list is an MB-SID v2 controlled dual VCO moog-based synth.... The 8 pre-set CVs could be the basepoint for the two pitch CVs, two pulse width controls, vcf cutoff and res, vca, and vc-balance control.... BUT.... They are definitely exponential circuits.... I don't quite know what acreage is left in the MB-SID v2 memory banks, but a lookup table for exponential key follow would eliminate the need for a separate MB-CV.... ;-) I think this is a little more than you might want to tackle seeing as though you've already done so many incredible things with the code for v2, but thought I'd chuck it out there.... ;-) Gavin

Hey Chuck! This project looks fantastic! I hope you'll share the details when it's "street-ready"! Silly question, as I'm new to routers.... Is it possible to route more than one source to a single destination (ie. summing sources)? Keep up the great work, Chuck, and keep us posted!! Gav

STOP THE PRESSES.... Just thinking more about this.... I may have missed some additional genius here.... So rather than the simple binary 0-15 in order, we do a wavetable to set the switches, in the order we want, evenly spaced over a modulation range so that 0-7 or whatever = 4P LP etc.... Then simply set up a modulation destination to the wavetable position, and either modulate with an LFO/EG/Whatever (could get pretty sick!!), or simply assign a knob in the knobs layer as a source? Correction. PURE genius TK! ;-) Now I'd BETTER get to work on a draft of that 3372 board over the holidays! ;-) Gav. PS. Just noticed, by saving that CV, I can now voltage control inputs A and B into the 3372 mixers. Input A will always be the input from the SID belonging to that channel (1=SID 1 Left / 2= SID 1 Right), and Input B can be it's partner in crime. That way, by adjusting the Input B CV, essentially you can create a pure mono mix by combining the AB at equal levels? Plus you get a VCF Pre Gain control for both A and B! ;-) The 3372 is sounding better and better!

Nebula - thanks for contributing on this! I'm more than happy to have many viewpoints on this, as I'm still not clear on where I want this to go! Please, suggest away! My hope was to get some free discussion from those with an interest in the 3372! ;-) TK - this addition in V2 is what originally drew me to the idea of the multimode vcf, actually.... I must admit, automating mode changes in a wavetable could get SCARY indeed! ;-P The way I see it, TK gives us one POWERFUL synthesizer with an elegant interface, then builds in the possibility for even MORE power (ie. multimode through the switches), but it then becomes OUR responsibility if we want that added power to look more elegant and be more closely integrated into the interface. ;-) I think the puzzle for those of us with 3372s is how to make the multimode function "elegant", as it were.... Right now, you can go into the external switches page, and if you want a 2-pole high pass, take the four switches and go: "on-off-on-on". But maybe its more of a 2-pole band pass you want: "on-on-on-off".... Here's a quick thought.... Keep in mind I'm still at the planning and parts stage.... It should be easy to read the current filter mode from four sets of four LEDs (one for each pair to indicate mode - I think this is sufficient control, while leaving four switches for other effects, external vcf bypass etc.). Maybe a simple four-button solution on the CS that only affects the currently selected SID engine(s) that are dedicated to the four switches? It would be easy enough to do up a little legend on the panel to follow.... Not quite as elegant as what you propose, Nebula, (ie. twist a knob, the LCD reports the mode) but probably at least doable for a programming plebe like me! ;-) Gav.

I agree with you there, Nebula.... My thought was simply that I had a free CV out anyway (once I build the hardware, of course! ;-P), and it would be easier to cycle through the modes with a cv than actually going into the external switch window in the SID architecture and turning on the required x-number of the four switches.... +1 switch if you add a true bypass.... In some ways I regret not sticking with the 2044 given that Seppo's already "on the job" on a board (sounds nice too.... some cmos bypassing it sounds like from your post?), but I couldn't pass up the possibility of multiple modes of the 3372.... My kludgy implementation also falls short in that you still need some sort of hard-wired display for the mode for each voice. If such an implementation made it into the SID architecture, that would be ideal, but my skills are lowly on the programming side. Maybe once I come up with a board for this beast (I can try it without the A/D architecture - it'll be awhile anyway!), some kind soul with a similar interest might meet me halfway and contribute a bit of a code insertion for the SID app.... Basically would require naming of the modes, and linkage of the four switches to act as one total binary output as you step through the modes.... Dunno how many people are looking at 3372s, though, given that absent a group buy (which I was lucky enough to get in on) they're rare and pricey.... I may try a simple 4-Pole LP implementation with bypass switch to start with on the 3372 anyway, so I can get some sound going! ;-) Gav

Hey all! Been off the boards a couple of days, so I didn't see the recent activity.... My thought on the voltage controlled selection of the filter mode was that as the 16 modes are divided (theoretically evenly) across the 10v CV range, there will be a relatively stable voltage range which correlates to a particular mode. Therefore, if I want the 1 pole lowpass option for a particular patch, VOILA! It's storeable as an AOUT setting.... Also, the "phase shift" filters in this design would be quite unique! Basically, in this instance, the 3372 would far outdo the range of options from the SID filter, and still be storable in each patch. Still haven't had the time to bang around with the PCB for such a beast, though... maybe over upcoming hols I can take a stab - my brain needs lots of time, as frankly PCBs aren't my strength! Gav

Hey all, Well, as it looks like there are a couple group buys for the 3372 which look like they may pan out, I thought I might start a thread on the subject. It was right to the wire whether I was jumping SSM2044 or CEM3372, but the multimode filter possibilities made the decision for me.... Initially, I think I may keep to the basic 4-Pole Low Pass design so that I can get things going sooner than later. I would, however, like to implement the Xpander design further down the road.... I think that some discussion and collective effort in both layers of the project would be helpful? As my 3372s will be going into my full version of the "Wilba Beast", I'm thinking in stereo pairs.... The basic CV controls would be Frequency, Resonance, and VCA for each channel (6/8 CV channels spoken for). I am including a separate pair of VCAs per voice (via an SSM2164; 1/2 2164 per voice) running off of the same CV signal to control feedback. The last CV channel would drive a single ADC (see this link for the general idea: http://m.bareille.free.fr/modular1/vcf_multimode/extrapole.htm) which will control two channels of CMOS switches to derive the filter functions. I figure that with some creativity, the ADC circuitry could be combined with two channels of switched 3372s on a single sided pcb.... My 6582 is going into a three space rack anyway, so I have lots of acreage to play with for stacking purposes. As with any filter design, as we're going for CPU control, the inputs can be drastically pared down.... Anyone else toying around with the 3372 out there? Gavin.

Hey All, As I'm slowly amassing the parts for my SID, since I am in full blown parts amassing mode :P, I am also thinking about a nice submixer project based on the MIDIBox Mixer. I thought it might be interesting to revive some discussion on the MB Mixer project by lylehaze and pilo, give some of my ideas on what I'd like to do, and get some feedback from others (including the creators themselves!).... This project is ideal for a keyboard submixer - for mixing your individual stereo SID channels, MBFM, filters, other keys etc. The basic design is there for the mixer (level, pan etc. depending on the number of ICs), however there are a couple features which would be excellent for live purposes.... I think TK already alluded to possible storage of "scenes" as patches, and I think that this would be a critical option for live. Additionally, and similar to the implementation of analog switches in the new SID software, I was thinking about implementing a switching system for routing to external effects (or, if you prefer, VCFs etc.), perhaps two switches (two destinations) per channel, and depending on some hardware configuration, the switches could route the signal either in series or parallel.... To give some idea, here is what I'm thinking of doing for each channel.... Once processed with the PGA chip, each signal is fed to the two (or more, if you wish!) switches. In my two switch scenario, the first switch would be parallel, out to a delay line - dry continues down the chain, and the return from the delay line is mixed in at the final summing amp. The second switch (which would not have an impact on the first send) would redirect the signal completely from the dry channel input to the final summer, redirecting the signal to a stereo-modified chorus unit (Boss Dimension Clone), which would have its own input to the final summer. Theoretically, if one needs fewer than 16 stereo inputs, additional PGA chips could be placed in a different location in the chain to handle fx return duties, with storable results. There's lots of panel space given the low requirements for the MB Mixer, so each channel could have its own tact switch and led for each send (or, alternately, if more sends are desired, maybe someone could do a button/LED matrix for each?). Ideally, these switches would connect to DINs, and the LEDs to DOUTs, all ready for storage, and easily viewed on the panel. Concept I'm good at, hardware I'm not bad at, but coding is pretty rough.... ::) To keep things modular, I think I could put together a design for each set of four stereo channels using four quad SPDT switches (DG333As or similar) for two sends (or, reconfigure it as four stereo switches for two channels). As the system is dependent on summing amps, where you pull the signal for the switches will determine if it is a parallel or series send. Maybe set up some jumpers on the board so that the signal from the previous switch is either sent down the line to the next, or a separate input is fed in through the jumper pin when a cable is connected. LOTS of possibilities! Also, as each switch can be wired independently, you could, for example, have the logic signal for send 1 switch the output of the PGAs to your VCFs - Channel 1 to its own pair of VCFs, Channel 2 to another etc.... Just wire the output back in to the chain prior to the other sends at the jumper points! This board could also conceivably be used to directly control signal routing in other projects (SID etc., which already has slots in the patch for switches). So what are people's thoughts? Does this sound excessive or worthwhile? Any ideas? I'm still in idea stage myself (busy fall at work!), but I'm starting to ponder the possibilities.... ;) Gavin

Hey all! Just to clarify, JH's clone is of the 2040 and not the 2044. The 2040 is THE Holy Grail VCF on a chip, if not THE Holy Grail VCF period. Fat, warm, and the Xpander switch trick can be used to get any number of responses out of it. The quality of the ICs was notoriously sketchy (no output protections, so one false move and ZAP!), and they're unobtainium now (lest you look REALLY hard and have a minimum of $40 US to splurge on a single IC!). 2044 is a GREAT chip, but only 4-Pole LP, and totally different filter topology than the 2040 (brought in to replace the 2040 as Moog sued - I guess Bob was concerned about being "out-phatted"? ;D) The discrete version looks great, but requires CLOSE matching of the trannies, and accordingly is expensive if you are using pre-matched pairs (see the MOTM version, which is based on the JH clone). Looking forward to that 3372 page Wilba! A 2044 is a better 4-Pole LP, but to have an Xpander filter with VCA x8? I'm up for some of that! :D Gavin.

Hi all.... Usually I don't do a "me too", but just in case this is a more official "speak up or lose out", I'm in for a full base kit with PICs.... No rush, of course - Canada Post is slow as death with my board and SIDs anyway, and I'm still deciding what the final feature set of my box will be.... ;) Gavin

That virtual beer is waiting for you when you finish off this board as well, Seppo! ;D Does your implementation of the linearizing function work comfortably with 13600s as well? I know they're harder to find, but I have a TON of them.... ;) Thanks for all your work, and looking forward to seeing the results! Gavin.

Hey Jaicen! True, there are some excellent discrete filters out there which would beat out many of the CEM and SSM chips.... Moogs etc. I actually plan on an MB based project to control and switch between stereo sets of discrete filters, actually! That being said, with discrete, you have a number of problems if you are looking at multiple channels - Most important of which are differing component tolerances (voices WILL differ somewhat!), and for my situation, SIZE. THE most tantalizing discrete filter for me right now is, strangely enough, a discrete recreation of a chip - the SSM2040. Eight of those bad boys would be amazing, but those will be BIG boards, with LOTS of components of different tolerances, not to mention how they'll react individually when they heat up in a closed space together.... Doug Curtis and Dave Rossum were brilliant in getting their designs onto a chip, and eliminating many of these variables. Accordingly, in those nice old polysynths, you don't cycle through eight voices with the same sound, and get: Bop - plonk - doink - bowwww.... I exaggerate a bit, but you get the idea! ;-P .... Ah, but that's the FUN of analog in my estimation, and why analog filters marry so well with the SID! ;-P Cheers, Gavin.

Apologies, Seppo (and NLX!!) That's what I get for skimming to catch up - saw your PS and latched on to the 2164.... Excited to hear about the dual 2044 board! Wow, almost missed that! I may need to send you virtual beer for designing half of my synth! (I'd send real, but I think any decent beer would not be healthy by the time it reached you, and you probably have better there!) ;) Maybe my task will be to handle the 2164 design? I plan on including some analog bypass switching as well, so perhaps there is somewhere where I can modestly contribute - and more my speed - I am a true rookie at PCB layouts! ;) I'm fighting for space in my box - Wilba base board, and trying to get all that other stuff as well, all into a two-space case with enough room for all that silicon and voltage to breathe! UGH! Thanks for all of your efforts as well, Seppo! Gavin.

Well, I pack up half way through my lengthy message and fire up at work this morning with three new posts covering some of what I was going to say! Then I edit my post, and again, new posts already covering stuff! I guess I'm losing my originality! ;-P I've played with a few of these chips in non-SID situations, and will cut and paste my subjective thoughts below.... ;-) Seppo, GREAT to hear that you're doing a 2164 board. Right now, for a 4x2 SID system, my plan is to go with an AOUT per voice (I won't say hurry up.... but.... :P) an SSM2044 each for left and right channel, and a 2164 to handle final VCA duties left and right, as well as feedback VCA left and right (to the SID input, with an on/off switch). Unwieldly to do 4 stereo voices on one single board, but was going to do two voices per board and stack them in my case. Soooo.... NLX's combo AOUT and 2164 board would be SWEET, and only leave me with quad or octal 2044s to design! ;D Now, thoughts on filters.... YMMV! ;) The 3320 is a solid chip, and I personally would prefer it over a '78 or '79 by reputation (again, I haven't personally played with either the '78 or '79, but they were in many later instruments which I found to be more "clean" sounding). That being said, the 3320 is often accused of being "neutral" sounding.... It is THE non-Roland sound of the early to mid-eighties (same chip in most of the american poly synths of the eighties). BUT is also responsible for the multi-mode filter on the Synthex and for the pure BEEF that is in my beloved Oberheim.... If used right, the 3320 sounds quite good indeed. There are some nice schematics for these, and tips for their use on the net. Still figuring our what to do with the couple I have! ;) The 3372 is not as "warm" a filter as the 3320 (IMHO remember! ) but has built in VCA and is readily configured into a multimode filter (think OB Xpander etc.). These are becoming fairly scarce though, as is noted in earlier posts, and Xpander users are in need of replacements so unless you are using any of the special features of this chip, there are others out there better suited, more "dinosaur" friendly, and probably the '78 and '79 are fairly close in sound (speculation on my part from comments of others and minor playing time on an ESQ-1, which I liked very much!). My preference right now (already given away above!), even though it is ONLY a 4-pole lowpass (no other modes possible) is the SSM-2044. Not as good as a 2040 (which I own, but not enough of them for my SID box and ULTRA rare!), but pretty beefy and I would say subjectively "warmer" and more "organic" than a 3320. 2044s are also pretty plentiful right now, again, as noted, and are reasonably priced. So your initial question.... I like the 3320 - Google up the "emulator archive" diy section for the choice of value for the caps in the circuit to sound more Oberheim vs. Prophet vs. Digisound. There is also a nice schematic on the net for a switchable low pass / band pass using the 3320 (look up OG2 - Scott Bernardi's site). My impression is that later CEM's ('78 and '79) sacrificed a bit of quality (ie. analog "girth") for accuracy and features that made them a better match with digital controllers. If you are running multiple voices and want each voice to sound exactly the same, this may be a positive feature to you. Overall, which you choose will depend on your goal. All of those mentioned made it to the production stage because they offered something different. For fatter and warmer, the SSMs are tough to beat. You sacrifice a bit of stability, though. For solid operation, multiple modes and stability, the CEMs are a great choice. The 3320 may be the "right up the middle" choice if you want a bit of both - then again, that's what Sequential, Oberheim and others did in the eighties, and while there are those who applaud them for it, there are still others who curse and swear To HEAR the difference.... SSM 2044s were used in the Korg Polysix and Trident (among others; early Fairlights and PPGs used them too). I know of a few sites with Trident samples if you google for mp3s, and that will give you an idea of that chip. The 3320 is easier, but depending on which synth it was used in, can be a chameleon - Best and widest range of examples are Oberheim OB-8 or Xa, Sequential Prophet-5, Elka Synthex. The '78 and '79 were, if I recall, used in some of the Ensoniq synths (ESQ-1 / SQ-80), and some late model Sequential stuff (VS, perhaps the 2000/2002 series samplers?). As always, the mileage of others may vary! Hope my two cents help! Gavin

Thanks for the additional info! I'll keep my eyes peeled for the .brd! I'm looking at using 8 SSM 2044s, seeing as though they seem to be relatively available at present, which are comfy on +/- 15 and +/-12V. Of course, there will be AOUT modules (likely one for each stereo voice), and I plan on using 4 SSM 2164 quad VCAs - one per stereo voice, for final VCA (L/R), and feedback VCA (L/R). I think the 2044s aren't TOO hungry, so the 12V rails should be OK? I'll get my calculator.... ;-) Still getting all the other goodies together.... I actually contemplated using my hi-end bench PSU (consists of a custom Plitron toroid from a Bryston amplifier, coupled with two Bryston regulator boards providing (presently) +/- 12V and +/- 15V, but there would still be the inevitable problem of getting the +5V and +9V without adding line noise or incinerating the regulators (although undocumented, I believe the voltage on the secondaries is upwards of 20-24V - should check this for sure), as well as size - the toroid is 4.5", and the two regulator boards are about 4"x4.5", each with their own chassis mounted rectifier, on which each board sits.... Details details.... ;-P Thanks again for the help! Gavin.

It's amazing how you find interesting information that you SHOULD have noticed originally and remembered for later.... ::) Just discovering all the interesting tidbits about NortherLightX's PSU design, as I have been struggling with getting a good PSU to supply not only the SID and cores, but a BARRAGE of external VCFs.... A couple questions.... Apologies if I've missed anything dealt with in another thread.... Firstly, for NortherLightX.... Your "official" PSU thread seemed to fizzle awhile back.... What were your final thoughts on the design, and did you ever get a .brd file together? I would be MOST interested, as your design looks excellent! ;) Secondly, and more for the North American contingent who may have tried this supply.... Any suggested value substitutions? I seem to recall that fuse values may change etc., but not being a power supply expert myself, I thought I'd run it by the pros - or at least far more "with it" amateurs than myself! ;) Cheers and thanks! Gav.

I was originally going to go for a 20x2 blue LCD, but the CFAH2004A-YTI-JP does look that much brighter and "PLED-like", and who knows what the extra two lines might come in handy for later on. I'd be in for one! Gav.

Hey TK! That was purely my intention - I know you have lots to do before you can even think SID V2! ;-P Besides, I don't think my panel and form will change too much from my mock-up; only whether or not I can make the switches programmable or not (drop that decade counter! :P) This is great news. Hopefully this can make life a bit easier for you as well - for example, if more than one person wants a filter switch or distortion switch, once the code is done once, it can be shared amongst the forum and inserted into those slots as desired. ;) This would be fantastic if there is enough room in the PIC! I assume the stereo effects would be implemented using a second SID per voice? In the interim, I was planning to build a Boss Dimension-C clone into my box when I finally get around to heating up the iron.... Won't do tap delays, but will be wide indeed! :) Thanks again, TK, for all your hard work! ;D Gav.

This would be ideal. As I say, be it a distortion or noise gate, be it a switchable send/return bypass to an effects box, be it a multi-bit switch to toggle for various VCFs, be it a separate external VCA control - if there were some "generic" parameter slots for AOUT and DOUT controls which could be flagged on and off for our own purposes (we could go in to the code, name the parameters ourselves"), then with a couple building blocks of code, a lot of customization might be possible without interfering with the global platform. My hardware skills are better than my coding so the coders might be able to correct my stupidity, but it would seem to me if there were slots in the voice architecture, then by naming and defining the parameter behaviour (ie. my "filter select" would, in theory, work the same way as the SID VCF mode control - one button, leds rotate through the options), then directing the parameter to an AOUT or DOUT destination, you would be set. From a coding perspective though, this degree of openness may be a bit of a challenge?

Hey all! I know there's a long wait until TK can even THINK of V2 SID let alone crazies like me with more ideas, but there seems to be a little more discussion going on in here as of late on new features and thought I'd throw out some ideas of my own.... This is my first post of any real substance, but I'm an age-old lurker from Canada whose been plotting my entry into the MIDIBox fray for some time! Thanks TK and others for making these projects so amazing! I have a couple ideas to throw out for the wishlist discussion.... CMOS switch control - Driving CMOS switches from a steady output from a DOUT module. There could be multiple uses here. First and foremost, to select between outputs of maybe four external VCFs (I'd like to build multiple options into my box; Moog, Korg, EMS etc., as they all respond differently). Also, this could be used as an on/off bypass for effects like distortion etc. It would be nice to have a couple of single bit configurable switch controls, and maybe one 2 or three bit control for filter selection built into the voice structure of V2.... AOUT features - Except in one respect, the MB-SID has, in my view, made the MBCV redundant: 1v/oct tracking. Aside from the fact this would be useful to track an external 1v/oct synth using the built in glide/bend/lfos/envs etc., it would be nice to have this facility for properly controlling 1v/oct vcfs (moog etc.). I know there was a problem with the lookup table not fitting into the V1 SID code.... Is this possible now with the new PIC? It would be great to use all those interpolating modulators with an external synth too.... Another AOUT feature that would be great if it were implemented in some dedicated fashion in the voice architecture would be an external VCA. There are great cheap VCAs out there to solve the SID volume glitch (a MiniMoog VCA clone can also introduce some very nice overdrive!) ;-) Trigger Out - As a "gravy" item.... If the AOUT can handle 1v/oct with glide, bend etc., the final nail in the MBCV would be to have gate outs and a clock output (with programmable divider). These would also be useful for controlling external modulators for use with the SID itself (again, not to mention making the SID module useful for external synth fun!) I have a little preliminary panel sketch of the 1U rack project I'd like to do to indicate what I mean (if there's any interest I'll post... once I find out how to post an image!! ;-P). If worse comes to worse, I'll probably implement the CMOS switching anyway using a 4013 decade counter - it just won't be programmable. ;-) Anyway, just some food for discussion! I'm probably thinking a single voice unit with a full AOUT for my needs right now, but if somebody wants to build multiple VCFs, there's no reason you couldn't implement different filter selections into a multiple SID module as well! ;-) Thanks for reading, and keep up the really creative work, all! Gav.