middleman

Sold out.

I was following this, and the price was a bit of a shock, considering the price of some of the other replacements (Swinsid & Armsid) and that it is possible to buy a working C64 for less. This puts it out of range for multiple SID project, unless you have deep pockets. However, it might be interesting to consider an FPGA based sound core with multiple ‘personalities’ e.g. virtual analogue, FM, wavetable etc. This would be quite practical by virtue of the ability to reprogram the chip ‘on the fly’. I don’t have the skills for this, but there must be others out there.....

Thanks guys!

May I ask another question? If I wanted to design and build a control surface, to my own specification, is there a suitable project here to modify for this? Where would be a good starting point?

Hi Midiboxers. Total novice question here. Is there any way to add more knobs to the sammich? Instead of having to step through menus to get to the control parameters, I would like to have knobs set up ready to twiddle. Can I buy a midi keyboard like Oxygen 25 and link the knobs that it has to my sammich? Would this require a change to the sammich firmware ? Thanks.

I got the news from igi today. This is fantastic!! I had wanted to build a 6582, but the thought of sourcing sids, or murdering 64's put me right off. The price is very affordable too.

I got a 2204 on ebay, but I havn't tested it yet. Thats another area which needs looking at. Is it possible to program a pic to work as a DSP? or is is necessary to go down the fully blown DSP route? There is a DSP course currently being run in Elector magazine, but with the hardware at £115 its not something to just jump into.

For anyone who has not got a cache of sid's its very hard to get going. Locally 64's are selling for around €80 on average, adn they are not too plentiful. On ebay the postage kills the deal. I got stung a couple of times before I learnt to beware. (for 'untested' read 'dud'.) I have built a Sammitch (brilliant piece of design), but the idea of anything more ambitious is out of the question for me, and most others who are a bit late to the party, due to the net cost of the SIDs A swinsid based MB-6582 with an analog filter bank would be a lovely project, but would definitly need a dedicated pcb in order not to drive a constructor insane. I'll head over to the SwinSid people and see what's happening. If anyone is interested in following this line, keep posting. I don't want to let the dream go just yet!

Yeah, I've been watching the swinsid threads for a while, but development and interest seems to have fallen off lately. I would love to replace the empty sockets in my 64's with something like that, but I get the feeling that without a decent PCB burnt pic service like we have here, it would scarcely be feasible. The FPGA/FPAA route looks very promising, but who has the specialised skills to accomplish this kind of task? What I was thinking is that if some kind of super SID type chip were to be specc'ed out, maybe one of the large scale synth manufacturers would get involved, and this community could benefit with the spin-off. Dunno. Just dreaming really. Now that it is getting so hard to acquire chips, it would be nice if there were a substitute that the community could focus on.

I wonder how much it would cost to get some new sids manufactured? Would you go with the old SID or a more up to date version? Or maybe an up to date version with a SID bit for compatibility? What new features would you include?

Hi fussylizard, in a classic linear design, the large capacitor between the rectifier and the regulator is used as a 'reservoir' to smooth out the rectified AC and to supply the regulator with top up DC, when large load spikes are experienced. Its also a good idea to put a low value resistor in series with the recified and smoothed DC and the regulator. This makes up a passive R/C low pass filter, removing any residual ripple, making the job of regulation easier for the IC. The resistor is usually chosen to match up with the capacitor so as to make the cuttof less than 50 Hz. I forget the math for this, but it should be out there. The other thing to keep in mind is that components are not perfect, and a large electrolytic capacitor will have some resistance. For this reason, it can help to put a smaller capacitor in parallel with the reservoir capacitor.

If you have no desoldering equipment, a quick method is to strip 1 cm of insulation from a piece of multi-stranded wire, loosely twist it and dip the wire into some flux. Heat up the required joint with the iron, and apply the wire. Most of the solder will be pulled up into your wire by capilliary action.

If all you need is +12 -12 & +5 volts and don't mind a little HF, a computer psu will do nicely, especially one from a mini itx or similar (small size). They are cheap, reliable (mostly) and efficient. Add a 9 volt regulator to the +12 volt line and a few passives to clean up any residual HF and you have a very flexible unit.

Dreamer, did you see any prices on this site?

Cheers guys, that sounds like good counsel. I'm going to place my order with SmashTV on the weekend, then break out the soldering iron when the parts arrive. This place is really excellent, and the combination of hardware, software, DIY and funny sounds is a powerful draw for me. I have another couple of projects in mind, and the advise that I've got on this one is really encouraging for the future. Much appreciated.

Say your pot has three tags. The one in the middle is the 'wiper'. If you set the knob to the middle of its travel, then measure between one tag and the middle one (the wiper) you will get a resistance. Now measure between the wiper and the other tag, you will get another resistance. If the pot is linear, both will be about the same. If the pot is a 'log' pot one will be much larger than the other. This is because log pots are often used for volume control, so that the apparent increase in sound level matches the response of the human ear.

The old portable (luggable)c64 used a switched mode psu for all voltages. Personally, I would use a switchmode for the +5v (digital) supply as HF has no effect here, plus you get the benefits of higher efficiency (lower heat and electricty bills) smaller size and more ouput per euro. There is no need to filter when used for this purpose. They normally include over voltage and short circuit protection as standard. I would not take a DIY approach to switchmode design, as the internal voltages are significantly higher than mains levels. Even after switch-off they can deliver lethal currents. In a commercial design, all components are caged for this reason. By all means build a linear psu for the audio portions of the circuit. When building, it is a good idea to first solder up the mains side of the transformer, and then tape off or otherwise insulate the bare tags before continuing. I have used the LM723 voltage regulator in combination with a power transistor for linear regulation in the past. You can set the voltage precisely if you want, and also set your own current limits. It has better line and load regulation than fixed voltage regulators too, which is important with analog synths.

OK. Decision made. If I read it right, the core 8 has 8 analogue inputs. That's plenty for me to start with, so no need for an AIN module. A visit to Smash TV tells me I need to choose a device number. Problem: I don't know what Sammitch's device number is (is it the same as channel? in which case it it device 1) Also, is it necessary/desirable to have a lcd display? The display in Sammitch was invaluable when it came to fault finding. If so, which type is easiest for a noob to source and hook up? Sorry for all the basic questions, I'm sure that once I get my sea legs I will be able to return the favor. Edit: found the page with all the lcd stuff http://www.midibox.org/dokuwiki/lcd just in case someone else needs it. My eyes are going square reading all the docs. Very educational. This place is like a goldmine for info, but you sure have to do a lot of digging :)

Thanks for putting the options so clearly, Peter. What I think I'll do is to go with your option b, but using a breakout box to house the additional controls, so as to preserve the Commodore keyboard as intact as possible (unfortunately it has a couple of additional holes that were made to accomodate the midi out socket :( Never mind. One additional request, would it be best to use the core 8 or the newer LPC 17 module? I would like to stay as up to date as possible, even if it is a little more expensive, and have it in the back of my mind to build more projects in the future.

Thanks for the replies, this is just the sort of info I need! The keyboard i am using is a Commodore unit, originally intended for use with the C64 Sound Expander. It has been modded for its current function using a pic based midi circuit from Tom Scarff. I have also been thinking about taking the harder (but more satisfying) route of adding some control features using a Core module plus AIN and DIN modules. How feasible is this, and do you know of anyone else who has gone down this route and might be able to advise a beginner?

I have a basic (key down only - no velocity sensing) midi keyboard which I plugged into the back of my Sammitch and it just worked - no problems. Now I am thinking of buying a controller with more features, such as touch sensitivity, pitch bend etc. Will any keyboard just work with my Sammitch, or is it necessary to perform some configuration, and if so, can anyone help or point me in the direction ?

I have just completed a SammitchSid, kit supplied by Wilba. It works brilliantly and exceeds my expectations. It is over 15 years since I used a hot soldering iron, and can honestly say that it is the best documented electronics build that I have ever done. I had previously attempted a couple of Practical Electronics designs in the 80s, but gave up because of problems that I encountered. Despite the superb quality of the kit and instructions,I would, however, not reccomend this project to an absolute beginner. It would be better to learn to solder and then build some small projects first. Then come back an build the beast!!