arnhey Posted May 15, 2015 Report Share Posted May 15, 2015 Hi there, first of all, I would like to thank Thorsten for developing this awesome project idea! Right now I'm planning to bild my first MidiSid, which is my first Midibox Project as well. I have decided to order the Kit-Set that contains the MBHP_CORE and the MBHP_SID from Mikes Midishop. I do not have the original C64 power supply, because I bought the 6581 on Ebay without anything else. My Question is about the power supply that is provided along with the kit. Do I need an extra PSU for the 12V supply for the 6581 or is the power source able to supply the SID chip as well? Sorry if this is not the right place for this question. Cheers, Arnhold Quote Link to comment Share on other sites More sharing options...
jjonas Posted May 16, 2015 Report Share Posted May 16, 2015 Now it's been a few years since I bought stuff from Mike, but I don't think he provides power supplies with the kits he sells. Are you intending to buy this item: MIDIbox SID 8580 / 6581 (Art.-Nr.: Set-005)? Quote Link to comment Share on other sites More sharing options...
latigid on Posted May 16, 2015 Report Share Posted May 16, 2015 This should really be a sticky topic, but: the best practise is to use a high-current linear PSU outside of the box and replace the 7805 with a modern switching Vreg. You can then use linear Vregs (7809 or 7812) to supply power to the SIDs. Quote Link to comment Share on other sites More sharing options...
arnhey Posted May 16, 2015 Author Report Share Posted May 16, 2015 (edited) Now it's been a few years since I bought stuff from Mike, but I don't think he provides power supplies with the kits he sells. Are you intending to buy this item: MIDIbox SID 8580 / 6581 (Art.-Nr.: Set-005)? That's the one I want to buy. In the partlist you have this entry and this seems to be a PSU: 1 Poweranschluss-Buchse wall adaptor (power supply) Edit: I just realized that this is not a PSU, but just an adapter. I still don't know what kind of adapter it is. So now my question is what is the best way to supply the SID chip and the Modules. This should really be a sticky topic, but: the best practise is to use a high-current linear PSU outside of the box and replace the 7805 with a modern switching Vreg. You can then use linear Vregs (7809 or 7812) to supply power to the SIDs. What is the difference between a modern voltage regulator and a linear Vreg? Edited May 16, 2015 by arnhey Quote Link to comment Share on other sites More sharing options...
ilmenator Posted May 16, 2015 Report Share Posted May 16, 2015 The main difference is that switching type voltage regulators dissipate a lot less heat. Very often they come as a drop-in replacement, i.e. with the same footprint as a linear vreg, but without the metal part that attaches to a heat sink. Switching vregs are usually more expensive (factor 5-10). Quote Link to comment Share on other sites More sharing options...
latigid on Posted May 16, 2015 Report Share Posted May 16, 2015 ^^ yep! An upside of this is that they also use less power (i.e. higher efficiency). Generally people stick to linear regulators for audio as the noise can be problematic. But the technology is improving all the time. Quote Link to comment Share on other sites More sharing options...
arnhey Posted May 16, 2015 Author Report Share Posted May 16, 2015 Thank you for all your quick responses. First I will use a metal cooler (Reichelt: V 5801B) and attach it to the Voltage regulator and maybe I will later try a switching Vreg. In the walkthrough the recommended range of the PSU is 14-15V AC. Is there a Problem If I use 14-15V DC? The rectifier converts AC to DC, doesn't it? Quote Link to comment Share on other sites More sharing options...
jjonas Posted May 16, 2015 Report Share Posted May 16, 2015 (edited) The cooling element looks too small to me. I tried to have a core+LCD and two 6581s powered from a 12VDC switching PSU, but the stepdown to 5VDC for the core+LCD was too much. Stepdown from 9VDC was manageable with the thermal sink I used (it was bigger than what you plan on using), but I wouldn't call even that the optimal solution. If you're going to step down from 15DC to 5DC using a linear regulator, and the core+LCD (which I think you will need eventually) consume something like 500mA (if I recall right), the regulator would need to burn (15DC - 5DC) * 0,5A = 5W worth of power. If I'm reading correctly the cooling element data provided at reichelt.de for the thermal sink you intend to use, it would heat up to well over 100 degrees celsius with 27 degrees Kelvin per Watt of power dissipation. (In other words: if room temperature is 20C, the thermal sink will heat up to 47C when it dissipates 1W of power; to 74C when it dissipates 2W etc.). A rule of thumb I read somewhere: if the regulator (or thermal sink) is too hot to touch for more than a few seconds, you should rethink how to do it. Edited May 16, 2015 by jjonas Quote Link to comment Share on other sites More sharing options...
arnhey Posted May 17, 2015 Author Report Share Posted May 17, 2015 Thank you for your help! I now ordered a bigger coolervand hope it is sufficient enough. Quote Link to comment Share on other sites More sharing options...
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