alchemist Posted July 29, 2014 Report Share Posted July 29, 2014 Hello, I am following that thread, and I am quite lost. Wouldn't be a good idea to provide sample schemas for 5v/9v/12v outputs, DC or transformer input(s), and the best options regarding the number of core and SID modules? Quote Link to comment Share on other sites More sharing options...
Shuriken Posted July 29, 2014 Report Share Posted July 29, 2014 (edited) Unfortunately it is not that easy. It all depends on what regulator you use and so on. For the 78xx regulator the following table applies: Output-voltage Outputcurrent Transformervoltage V 100 mA 1 A 2 A V 2 78L02 - - 5 3,3 78L33 7833 - 9 5 78L05 7805 78S05 9 6 78L06 7806 - 9 7,5 - - 78S75 9 9 78L09 7809 78S09 12 10 78L10 - 78S10 12 12 78L12 7812 78S12 12 15 78L15 7815 78S15 15 18 78L18 7818 78S18 18 24 - 7824 78S24 21 of 24 The parts need to be adapted to current and voltage. With a low voltage (below 5 V) C1 can be decreased to 1000 µF. With voltages above 15 V en 1 A, C1 needs to be 4700 µF. With currents above 1 A moeten the diodes need to be replaced by 1N5401's. C4 needs to be applied if the wiring between powersupply and appliance exceeds ±15cm Partlist: C1 = 2200 µF/35 V (see text for remark) C2, C3 = 100 nF C4 = 10 µF/35 V (see text for remark) Br1 = 4x 1N4002 of 1N5401 (see text for remark) Vr1 = 78xx T1 = trafo Edited July 29, 2014 by Shuriken Quote Link to comment Share on other sites More sharing options...
Hawkeye Posted July 29, 2014 Report Share Posted July 29, 2014 (edited) Great post, Shuriken! That clears up all the confusion of the possible combinations! :-) skunks, regarding your question Hawkeye, I just looked at your calculations again and wondered, why 9V AC input for MB-6582 in PSU Option A is considered OK even with plain 7809 (non-LDO) ?I make an assumption that it worked in your case because your transformed was good enough (25VA) to sustain 9V AC under load. You are right, skunks, in the MB6582 Power Option A, the 9V AC are rectified and then directly sent into the 7809 - this differs from TKs "optimized circuit" with many MBSID modules. Also, you and Shuriken are right - under certain circumstances (e.g. the AC wall voltage being low), the 7809 non-LDO vreg might deliver a bit lower voltage than desired, when fed by 9V AC + recitifer diodes. But, I think, in this special case, this is ok for the analog part of the SIDs (only opamps and stuff), and a slightly low voltage (e.g. 8.5V) would still sound good. Also, the dropout voltage of a vreg depends on the amps being drawn - and probably the 9V rail is not very demanding (only a few opamps), even in a fully loaded MB6582 with eight 9V SIDs. But Shuriken´s recommendation to normally feed a 7809 with 12VAC + rectifier diodes is solid - or to use a more modern LDO vreg. Many greets, Peter Edited July 29, 2014 by Hawkeye Quote Link to comment Share on other sites More sharing options...
alchemist Posted July 29, 2014 Report Share Posted July 29, 2014 Thank you, Shuriken ! Now I have to chose the best output, then the switchers for the 2 other voltages. Quote Link to comment Share on other sites More sharing options...
skunks Posted July 30, 2014 Author Report Share Posted July 30, 2014 Hawkeye, thank you for giving your complete view on "why 9VAC worked" from different perspectives. It's more clear now for me. Shuriken, Did you provide power with a transformer? I tried both, transformer and switching PSU (from dead printer). As you advised I set LM2596 output voltage to 8v. And it helped. Thanks :-) Now LM2596 presence is not audible. And it's input doesn't have to be regulated, at least why care about it's input if you have to regulate it's output anyway. Shuriken, you assembled so much useful info in one post! Is transformer voltage in that table AC? C4 needs to be applied if the wiring between powersupply and appliance exceeds ±15cm Where it's better to apply it? In powersupply box or after that long wires? Now I have to chose the best output, then the switchers for the 2 other voltages. According to my tests you may even choose cheap LM switcher but have to use 78xx afterwards in order to cut noise. Quote Link to comment Share on other sites More sharing options...
skunks Posted July 30, 2014 Author Report Share Posted July 30, 2014 Hello, I am following that thread, and I am quite lost. Wouldn't be a good idea to provide sample schemas for 5v/9v/12v outputs, DC or transformer input(s), and the best options regarding the number of core and SID modules? I just remembered one thing to add to Shuriken's post. Especially if you are dealing with multiple separate MB CORE and SID modules (not MB-6582 where there are easy pre-built PSU Options). 1. Bypass bridge rectifiers if you are using DC as input (more about it in this ) in order to avoid shifted grounds 2. Avoid ground loops (grounds must not be connected more then once) I found a little improvement on my noise level when removed ground connection coming in ribbon cable between Core and SID module and put a separate thick wire. Quote Link to comment Share on other sites More sharing options...
Shuriken Posted July 30, 2014 Report Share Posted July 30, 2014 I cannot take credit for the table. It's an article on a dutch website (circuitsonline.net) The pcb is also there. Yes the transformer voltage is in AC (haven't yet seen DC transformer :wink:) C4 needs to be applied in powersupply box. As for the LM2596, you could experiment with faster diodes (MUR120) to rectify. And a big capacitor in front of it. Quote Link to comment Share on other sites More sharing options...
skunks Posted July 30, 2014 Author Report Share Posted July 30, 2014 There were actually 2 big capacitors (2200uF and 1000uF) in front of it. Thank you for faster diodes idea. Quote Link to comment Share on other sites More sharing options...
jrp Posted August 8, 2014 Report Share Posted August 8, 2014 (edited) the 7809 non-LDO vreg might deliver a bit lower voltage than desired, when fed by 9V AC + recitifer diodes. But, I think, in this special case, this is ok for the analog part of the SIDs (only opamps and stuff), and a slightly low voltage (e.g. 8.5V) would still sound good. i cannot recomend this. Linear regulators will be very unhappy in such a case. It is not that the regeulator can adapt in a mannor: "Ok, i need to drop 3V, so i just adjust myself to 8.5V." The Voltage will drop, yes, and the regulator will be fighting and sweating, not being able to do what it´s supposed to do: Stabilize voltage and get rid of any ripple. It will lead to hum and possible failure. For non demanding circuits (not this one!) it would then be better to go without a regulator altogether. Don´t try this with your sid though. Also, to be safe it is common practice to account for 10% mains variations. If you measure voltage and the regulator is a little of, just check the voltage at it´s input. These Parts have tolerances, so you might be getting 8.7V from 12v. That would be fine. Edited August 8, 2014 by jrp Quote Link to comment Share on other sites More sharing options...
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