Jaicen

That's something that i've been thinking of doing. Would a passive heatsink prolong the life of something like a 6581 that runs very hot, or would that need something like a fan?

Tonight, I finally got around to testing three different SID 6581's i'd acquired from a very generous friend, against the one that came inside my own C64. Two of the SID's had really good aggressive filters that had a really nice range, and two had quite smooth dark filters. Strangely, two of the SID's that were the least similar were manufactured exactly the same time (week 22, 1984). However, the thing that I find most interesting is that the one I prefer that's the most aggressive and resonant is in the smaller package, manufactured in Taiwan. The other week 22 SID was manufactured in Korea. This lead me to wonder wether the place of manufacture had anything to do with the quality of the sound produced. Don't get me wrong, i'm not saying that Korean SID's don't sound good. I've got a second Korean SID which has a pretty nice filter, though less aggressive than the Taiwan. This is an 84, but week 36 so later manufacture. All I was wondering really, was of all the 6581's this community uses, which ones do YOU prefer ie; Week:22 Year: 1984 Manufacture: Taiwan Package: Small Plastic Interestingly, my third choice SID is a REV4, wk19 1984. Although the filter is smooth and has a decent range (more so than 2284 number 2, least favourite), it just lacks that bite and resonance of the other two. It does run much cooler than the Taiwan though, which is a concern for me.

Unbelievable man! TK, this is THE synth now! V2 seems to me to be a quantum leap away from the original MBSID design, it's so powerful I don't know what i'm going to do with myself!

I'm the other way around mate, well actually, I find it all a nightmare!! Hehe, but seriously, something that works like a guitar mult-fx thing would be just fine. Have a set number of pre-sets which are editable via JSynthLib on the PC, and scroll through them using up/down and maybe bank buttons on the pedal. I could live without any other controls on the pedal itself, although a CV in to control filter cutoff or pulse width would be nice.

Yeah i'm down with the small size, but don't forget that humans have quite large feet, so you'll need to make the enclosure pretty big anyway, i'd say at least 6x4" if you want a pair of footswitches, MIDI and audio jacks and a display. Keep up the good work though, i'm excited by this thing (even though I don't have the facility to burn ATMEGA stuff :( ). With regards to your challenge, I have a pretty good Idea what i'd like to house one in, but firstly could you explain in more detail the capabilities of this thing? Your initial posts have been a little vague!

Looks like an interesting design, could be very useful with my GR-20. I'd planned to use a minimalist MBSID, but this might be a better option. I'm thinking you program patches on a PC, then scroll up and down them using footswitches?? Personally, I don't think you'd be able to fit many traces underneath the SID itself if you want the PCB to be easily home-made. If you're going for manufactured PCB's, there's no real reason not to use a two layer board. Those are just my thoughts, but so far looks like some good work!

Sweet, cheers! When you do get it breadboarded, i'd appreciate your thoughts on how well it performs, I don't currently have any CV equipment to test it with. I think i'm going to go for another PCB layout soon, not really happy with the first one i've done, but it's all progress!

I'm guessing you're not going to be using my PCB, bearing in mind that I haven't checked it for errors just yet. I don't suppose you'd be able to part with one of those CEM's would you?? I'd like to have a two voice module, i'd planned to use the CEM3396 for a little extra variety, but that's not so easy to integrate into a modular system.

Yeah, seems to be a very clean sounding synth. It does make me a little nostalgic for early 90's gaming! Not that far removed from my beloved Megadrive (for obvious reasons!). Hey Prof, did you get anywhere with that TB clone? I don't know if you got my last message a while back about a bulk-buy of the components but i'm still interested.

Yeah, the distortion occurs because the EXT in is always routed to the VCA. If you turn the filter off, the extra gain not dropped throught the filter will overdrive the VCA.

How's this then! I've knocked up a quick and dirty layout for the CEM3394 module. The circuit is from:http://www.ori.org/~aaronc/synth/CEM3394_V2.pdf click I didn't really plan it all that well, so I ran out of room for the CV inputs to pins 6, 7 and 8, but they're just straight CV in's pretty much, so I just added pads for external pots or whatever. I think since the whole thing comes in at 3.6 x 2.1 inches, it's not a bad job for a dirty hack ;) Any thoughts or suggestions are more than welcome!

I most certainly am!! I imagine that those one-chip solutions would allow for a complete CEM synth on one pcb of about A5 size. Originally, I was looking for a way to clone the SH-101, and apart from the sub-oscillator, this should get pretty close i'd imagine.

Having done a little more research, I think I may actually be able to complete this project! The CEM3394 is completely voltage controlled, so it should integrate nicely with the MBCV. I'm going for a modular design, which means I'll start by building the MBCV with LCD and multiple CV-outs, then build the ADSR and LFO's into their own seperate modules. This synth is not going to have any pre-sets or anything, it'll be completely Knobby with patch leads for routing. Proper old-skool! So, with that in mind, this is the feature list i'm planning for: 1x CEM3394 module (VCO, VCF and VCA) 1x 3x envelope modules (PIC Based ADSR, 3 envelopes in one module) 1x Dual LFO modules (PIC Based, as above) 1x MBCV module At some point i'm also planning to add a CEM3396, but since this requires an actual square wave frequency input rather than a CV to control the frequency, this is proving a little harder to work out.

Not to mention the SID, if you applied 12V to the 5V line, that's going to be dead too.

Generally, if it's small and has transistors, it's switchine. Linear PSU's tend to be much larger with big-ass chunks of Iron. For example, virtually all cell-phone chargers will be switching PSU's.

Yeah, I was following all that a while back, but it's been awful quiet since then! I think i'll just use this as a starting point, http://www.ori.org/~aaronc/synth/CEM3394_V2.pdf which is basically ripped from the datasheet, and hook it up to an MBCV. However, MBCV has no ADSR, so I guess i'll probably have to use the two gate outputs and build a seperate ADSR module to power the VCO & VCA. EDIT: Scratch that, this guy has done all the work for us! 1-chip VCA plus a 1-Chip VCO & VCF and i'm sorted! http://www.tomwiltshire.co.uk/sdiy/envgen.html

I've just stumbled on a 3396 and a 3394 so I bought them just in case (you know how it goes ;) ). I'm thinking i'll just design something simple and drive it from an MBCV if there's nothing currently in development. I was just wondering if anyone had been busy designing a synth to use these little beauties! I remember that Stryd was working on something, but that was late last year so perhap development has stalled. So, any news ?

FINALLLY!! Not only is it a tracker capable of playing through a real Megadrive, but it runs on a PC so it's easy and fast. I'm going to get myself knee-deep in this soon enough! I've also got a ZX Spectrum +3, I wonder if this tracker will work on that? That would be very cool, because the +3 has integrated MIDI input, so I might be able to find some software to get it sync'd. Justice I say!

Oh you just had to didn't you! I've just got my head around the old one!

Can't you just rip TK's wavetable code from the SID and use that??

Come now, it really wasn't that hard ;) http://www.meadowfield.freeuk.com/synth/arp.html

Agreed! I would say however that the dynamic range is not really an important concern for me. In machines like the 505 and 626 (probably the 7x7 boxes too), the the samples are hard limited to maximize the volume and reduce the signal to noise ratio. The natural envelope of the hits are then restored after the conversion to analogue. If a similar scheme was adopted, it would allow much greater flexibility in terms of pitch and dynamics, as well as noise specs. I think it's important to note that if you pitch up the samples, it will reduce their length so the envelope is also affected.

As above, it's probably working off the +5v line coming from the MIDI connection. The power button would be connected to the external inputs, so the MIDI power wouldn't be affected by it.

That looks really nice Altitude, what kind of price are they going for? I think a rack mounted SID only really makes sense if you're not using a full CS. I think it would be a little cramped otherwise.

Have you shorted all the pins on J4? I'm not sure that's right, you only need to short the audio in pin of the SID to ground. Actually, you shouldn't short it, you should wire in a large cap (>1uF) to ground, because there's a DC offset on the Audio in pin, which can mess up the VCA if it's shorted to ground.