subatomic

Hi guys, I built a little board to recieve power from the c64's transformer, and it turned out nice so I thought I'd show it to you: The finished power board, converts the c64 power adapter to 5VDC and 14VDC. Fitting seemlesly with the original c64 power/serial panel, it also has an on/off switch, and two serial ports - each of which is to be used by the banksticks Installed the power board into the c64 case, nice fit, you'd never know it's not a c64 inside by looking at this panel... As you can see it uses Thorsten's optimized PSU circuit design. I plan to use this board for a 4xSID synth embedded in a c64 case with built in active mixer... You can read more details here: http://www.subatomicglue.com/sidl0g/#psuboard

How necessary is the bypass caps? What types of problems do they prevent (what would I notice, if anything, if I didn't use them). For example, the SID module I have from SmashTV didn't have these bypass caps. Would you recommend that I go to the trouble of ordering caps? what does this mean? what exactly does "integrity" mean here... smooth out the power to a better DC supply? thanks...

I agree about headphone amp, not sure about cue for my needs, but maybe you have a killer idea in mind? I think a headphone amp could possibly be done in a separate module, and tap off the above pictured 4x4 mixer outputs. If you want, feel free to extend my design to include the headphone amp. Got some good links in mind? I searched, found a lot of threads, but most seem to advocate using commercial. I just want a simple module I can embed in the SID, customized to the SID (i.e. only 4 channel).

I've also started a topic, and while a few people answered, it wasn't exactly what I wanted, I went ahead and designed a custom simple 4x4 mixer for the SID with balanced outputs, signal routing, panning, and stereo support (with two out 1/4" plugs you can have stereo of any mix of the 4 SIDs). http://www.midibox.org/forum/index.php?topic=5967.0 I'm going to be vectorboarding it very soon. I've already breadboarded it, and it worked well. It has a gain of about 1.5x The only thing it doesn't have is headphone outs, but I think you could tack that on as another module.

I created a Bill Of Materials (BOM) for the mixer here...

created some files I think that will work for the PCB layout, using a paint program (anyone know a free editor that doesn't have restrictions? Eagle was too small)... Here it is, I thnk I might do some more work on the lables, but it should be useable like this... Keep in mind to chop off the bottom so the 1/4 jacks fit flush with the panel. Break out: Front: Back: If this looks non-standard, it's because I haven't done this before, but I think this will work for etching from what I know of it. In the coming weeks, I'll have a friend help me out with the etching (I don't have a kit)... I'll report anything I find once that happens. Keep in mind this is a double sided board, though you shouldn't need through-hole plating. I provided pin spots where you can stick a jumper in to jump the top to the bottom. Just look for the O's that don't have a component associated with it. There's 13 spots... Use some old cut ends from your components or plain wire.

So I created an eagle schematic of the 4in 4out mixer. schematic file also I did some thinking about the PCB layout (freeware eagle was too small to do this) so far this is intended to be perfboard with wire jumpers. I'd like to do a real PCB, but not sure if I'll get around to it since I don't have the equipment... I also answered one of my previous questions. I should use _non-polarized_ electrolytic caps for input/output decoupling... kind of obvious since we're dealing with AC +/- signals. ;)

Ok, here's the updated schematic, let me know if you see any bugs/typos/problems: Now, two last questions, 1.) can someone tell me how to attach the Sleeve output connection? Do I tie Sleeve to ground, or let it hang? NOTE: In testing, the output signal sounds correct, with no noticable differences, with or without ground connected to Sleeve. 2.) for the + and - outputs, what orientation should the polarized caps be? Right now I have the + end of the caps towards the opamp. (see picture). I worry about damaging them... does it matter?

well, lucky today's a holiday (MLK day), so I'm home working on this... so through experimentation I think I'm going to answer my own questions, and post here so you guys can watch, or comment if you care to... So I breadboarded one input and two outputs (using some old LM741's I had laying around). The amp works, though like I predicted I had to update the resistor values on the outputs stage: they ended up changing from 10k and 59k. I also used a 10uf polarized cap on the input instead of the .1uf... Overall gain is 1.4 so you can make it a little hot if you like... keep in mind I have no idea how hot the SID outputs will be so this may need adjusting later... I'll update the schematic when I'm happy with the design. For decoupling ground, here's my results: - I placed a 1uf cap on each balanced output: output+ and output-. - Signal seems to be transmitted regardless of whether the ground is connected or not. It doesn't seem to need a ground. - Interesting observation: only connecting one of the outputs transmits signal, though not as strong as using both. - I notice no loss in signal quality using caps, vs connecting direct. Cool, so looks like the mixer's working, next I'm going to test out more than one input and see how well they mix...

If I ordered boards about 6 months ago, would you recommend updating to the latest boards? Or does it matter? I haven't begun soldering yet... I was going to build A, B, and C

Should I add anything to the output of the mixer to decouple the device from ground loops? I've seen other designs add capacitors. If so... - i've seen polarized and non polarized caps used, does it matter? - what value of cap to use (is there some way to calculate it?). I've seen other designs use 1uf, 10uf, 0.22uf, maybe it's based on power xfer? - I can see putting caps on the + and - balanced outs, what about the ground, do I even conect it to the jack? Or just go with + and - to the TRS balanced jack and leave the ground hanging? sorry, I'm not experienced in audio interfacing... does this isolation even matter? (seems it would to me but...)

That's interesting, I hadn't thought of panning, that could certainly be useful. Here, I've modified my frankenstein design to incorporate panning into the 4in 4out router. Note that this design is more simple, it uses DPDT (2 pole, 2 position) switches instead of the 4 position switches of the previous design. With this design, I can assign any SID input to any two channels (AB or CD), and then pan between those channels. This should allow the greatest flexibility, since I can have discreet assignment SID1,2,3,4 -> A,B,C,D or mixed/panned assignments as needed. ->> Could someone with circuit design experience look at this and tell me if the input section will work here? I do expect I might need to adjust some of the resistor values... I wonder if maybe my pan pots should be shorting to ground (like the previous post's stereo mixer diagram) instead of fading between the inputs. I'm going to prototype this one soon, probably with lm741's since that's what I got available. In the end, I plan to use a much nicer amp like the AD823 or OPA2227. UPDATE: the frankenstein grows, I updated the image to use the input section from the stereomixer.gif (previous post), whose panpots tie to ground.

so I'm going to prototype this design soon, and will post results here if I find somethig useful. :-* If good, maybe it could make a good module? 4inx4out audio router...

ah, yes, I had missed that tiny section. :) Ok, so here's what I'm thinking now. I'd like simply 4 outs, just like the nord3: [tt] - outA - outB - outC - outD[/tt] but here's the detail: For flexibility, I want to use switches to route the SIDs to the outs... Maybe a 4 position switch for each SID, not sure. this way I can do any combination of stereo or mono audio out. I have ideas for doing this with standard audio opamps. it shouldn't be too hard... I'm thinking this: http://www.dibsplace.com/design/CIRCATS/opamp04.gif except duplicate the dual opamp section (right hand side) once per output, and then where the 4 inputs joins into one, have that controlled by 4 position switches (one switch per channel)... So doing a little photoshopping, it would be something like this: http://www.subatomicglue.com/sidl0g/audiomixer.jpg - If anyone's already done a design for this, please post here. - If you have comments about the linked circuit, good or bad, also please let me know. I like that the design is for balanced outputs, and it seems simple enough...

What module (if any) does audio mixing? And if none, anyone have a recommended mixer design? I probably just haven't seen the appropriate page that describes this, but if I wanted to have my 1/4" outputs on the back of the synth box be like this (5 plugs total): [tt]- outA - outB - outC - outD - stereoMix (2 sids on left, and 2 sids on right)[/tt] alternatively, I was thinking of just having the 4 outs (outA-D), and having some switches to route each sid to one of the 4 outs. Also, and maybe this answers my question, but where's the design for the LED/Button Matrix thing I see on everyone's midiboxSIDs? Maybe that handles the audio mixing? Sorry, I haven't seen info about the Matrix or how to build/wire it, so I don't really understand it yet (though I'm assuming it does typical LFO type routing?). There's a lot of pages here, and I probably just missed it. Thanks for any links that might enlighten me. :)

if you find out, let us know. I know I'd like to see it... sounds interesting.

thanks for the good replys. lol. I meant what type of encoder is under each knob. (which I think you answered in your next one). I had already found closeups of TK's synth, as well as the large .gif of the panel... :) doing a search on the forums, looks like someone else asked a question about waldorf knobs and apparently we need to ask ALBs directly... thanks for the search term...

I've been searching around on the forums and in the SID pages on the main site, and I can't seem to find the answer to these questions: ??? what type of encoders are used here? http://www.ucapps.de/midibox_sid/midibox_sid_cs2.jpg I count 15 knobs total, can someone give me a rundown on what each knob is in this particular SID box? I want to know about detented/non-detented and does the encoder have a switch? I'm trying to figure out which encoders to order from smash's shop. It would be nice if Part C's BOM would mention if "switched" enoders are nessesary or optional, and if they're used in the "original" (see picture) design. ??? Am I correct that there are only encoders in this picture? (Step C makes it sound like no pots are used). http://www.ucapps.de/midibox_sid/midibox_sid_cs2.jpg ??? Does someone have a complete BOM for the pictured design? Including all I/O jacks, etc... http://www.ucapps.de/midibox_sid/midibox_sid_cs2.jpg I noticed that the IO jacks (i.e. audio/midi) were not listed in the MidiboxSID PartA/B/C sections. What else has been omitted? ??? Does someone have a link/part#/make&model to the long tact switches used here? I'm in the US... http://www.midibox.org/midibox_sid_photos/10.html ??? Got a link to those enoder knobs? Or something similarly sized?

so I was wondering is it user configurable, or do you have to hack the hardware again to configure it? i.e. what's the mechanism to configure it.... I'm starting to suspect I should read elsewhere on the forums about using a joystick to get ideas, maybe it's a standard thing... ;) ok, i figured that. but I wanted to know specifically about this synth's configuration. how he has the buttons, in the knobs or separate? I didn't see separate... The pictures are tiny and grainy. sorry :(

I like it, do you have a higher res front view of the panel so we can see what everything does and how they work? Is the joystick reconfigurable, or always on cutoff/res? On the knobs that have three functions below them (white, yellow, orange colors), how do you switch functions? Is it a knob with button built in? The three lights above one of the knobs, I think it's the osc lights, how do you change those? So this is a c64 case painted black? Where did you get the knobs? Same as the big encoder knob?

I ordered from Centsible a week ago, and just today recieved a tracking number for 2 6581 SID chips that apparently have been tested to work. Centsible sent them out today... He also says he is (now) out of the 6581's and will be marking the website, but should be getting more at a later date. Commication was pretty good, promptly answering questions about a day later with email. For those of you trying to get the 8580's Maybe try ordering 6581's? Maybe they're easier to get?? no idea...

I now have a tracking number for 2 6581 SID chips that apparently have been tested to work. Centsible sent them out today... He also says he's out of the 6581's and will be marking the website, and will be getting more at a later date. Commication was pretty good, promptly answering questions. I only ordered about a week ago, so this was pretty fast turnaround. It probably helped him out that he just went to a c64 show, but still, I'm happy. Hope they arrive working. ::) UPDATE: they arrived stuck in black conductive foam. Pretty quick

That's interesting. Though, I ordered the 6581 chips, not the 8580 chips people were having troubles with. Also, centsable did send an email saying they had one 6581 chip for me, and the second they could probably get from the c64 conference they were going to. I'll check back with them to see what's up. Good to know though, thanks.

Check here too... http://www.avishowtech.com/midibox/wiki/index.php?pagename=MIDIboxSIDFAQ#QA3 I ordered a couple from centsable recently...

I'm starting to realize that "16 gauge" is a little thinner than I was thinking so the baking pans might not be ideal. I have played with 16 gauge steel sheet and it did seem good enough. So maybe 16 would still be ok, but it'd be the thinnest I'd go. I've not tried aluminum to know if it's more bendy than steel... So... what's a good thickness to use for the front plate? What's common? I noticed Schaeffer sells 1mm, 2mm, 3mm, 4mm thicknesses... So maybe that's the range... Right now I'm thinking I'll do acrylic/plexiglass with photopaper on the back of it for custom printed graphic. It's a cheap way to prototype, and if I love it I can immortalize it by buying something expensive.