Davo Posted February 5, 2011 Report Share Posted February 5, 2011 Item 150521385822 on ebay is a 12V regulated 500mA power supply for about $10 total. The guy appears to have lots of them. Quote Link to comment Share on other sites More sharing options...
Wilba Posted February 5, 2011 Report Share Posted February 5, 2011 This is a switchmode power supply. I can tell from the pixels and from seeing quite a few switchmode power supplies in my time. The input voltage range (100 - 240V AC) clearly gives it away. Quote Link to comment Share on other sites More sharing options...
Davo Posted February 6, 2011 Author Report Share Posted February 6, 2011 Is that a bad thing? Quote Link to comment Share on other sites More sharing options...
nILS Posted February 6, 2011 Report Share Posted February 6, 2011 A forum search "switchmode" will answer that in fairly great detail :ahappy: Quote Link to comment Share on other sites More sharing options...
philetaylor Posted February 6, 2011 Report Share Posted February 6, 2011 (edited) Usually where audio is concerned, yes. You would find that your SID's have an added whistle or buzz when compared to ones powered with a linear supply. There are audio grade switch-mode supplies but they tend to be much more expensive due to the complexity required to reduce the amount of noise that they generate. Cheers Phil EDIT: Damn nILS beat me to it! Edited February 6, 2011 by philetaylor Quote Link to comment Share on other sites More sharing options...
Davo Posted February 7, 2011 Author Report Share Posted February 7, 2011 Oh crud... Who has a good linear wall-wart? Quote Link to comment Share on other sites More sharing options...
m00dawg Posted February 7, 2011 Report Share Posted February 7, 2011 You can try Goodwill if there is one local to your area. I have found some transformers for pretty cheap there. Look for the ones that typically power amps and things (basically ones that output 10-12VAC, depending on what type of SIDs you will be stuffing in the Sammich). I would look for something around 500mA, though I doubt you would get anywhere near that with a Sammich. I thought I saw a forum post on current draw of a the Sammich not to long ago so you might want to go searching around for that. Having said that, I've run my Sammich on a switchmode PSU. It's not ideal but I haven't had as much audio issues as I thought I would have, though I wouldn't recommend using one for a long period of time or for recording. Quote Link to comment Share on other sites More sharing options...
Wilba Posted February 7, 2011 Report Share Posted February 7, 2011 Oh crud... Who has a good linear wall-wart? Consider this: Quote Link to comment Share on other sites More sharing options...
TK. Posted February 7, 2011 Report Share Posted February 7, 2011 Consider this: are 500mA really sufficient for 2 SIDs + the big variety of LCDs which are used for this project? (some backlights draw only 100 mA, some others 300 mA and more) The result could be, that the input voltage drops below 10.5V, so that the 7809 won't output 9V anymore -> the filter won't work correctly, or there won't be any sound output at all. Another possible effect: the PSU gets hot because it isn't dimensioned for permanently high power consumption. Low-quality PSUs will be damaged over time (1..2 years) if they are used out-of-spec - I had this issue several times in the past. /edit: btw: Best Regards, Thorsten. Quote Link to comment Share on other sites More sharing options...
Davo Posted February 8, 2011 Author Report Share Posted February 8, 2011 Oh well. I'll see just how this PS sounds when I get it, then into the pile-o-stuff it goes. I need to get a real benchtop power supply one of these days. Quote Link to comment Share on other sites More sharing options...
Wilba Posted February 8, 2011 Report Share Posted February 8, 2011 are 500mA really sufficient for 2 SIDs + the big variety of LCDs which are used for this project? (some backlights draw only 100 mA, some others 300 mA and more) The result could be, that the input voltage drops below 10.5V, so that the 7809 won't output 9V anymore -> the filter won't work correctly, or there won't be any sound output at all. I recommend to all builders to keep the backlight pot set to half-way or less... the pot is 50K, changed from official Core spec of 10K, so there is some real current limiting... also there is a header/shunt for powering "high-power" LCD backlights from input power. So in my experience, a 12V AC 500mA power supply is OK, and if you turn the brightness up too much, the current draw will cause voltage to sag and the PIC will reboot (or not boot). When the PSU is regulated, you can choose a higher current rating without any concern, but for unregulated PSUs, going higher than 500mA causes more problems, input voltage will be much higher, thus the voltage regulators will need to dissipate more heat (and powering the backlight from input power becomes more fault-prone). TK, maybe you should turn your LCD brightness down a bit... :thumbsup: Quote Link to comment Share on other sites More sharing options...
TK. Posted February 8, 2011 Report Share Posted February 8, 2011 TK, maybe you should turn your LCD brightness down a bit... :thumbsup: Boyz with big PMUs don't need to reduce the brightness :D Quote Link to comment Share on other sites More sharing options...
m00dawg Posted April 20, 2011 Report Share Posted April 20, 2011 Here is the one I ended up going with from Jameco (US). 12V 1A linear-regulated so that should be enough for even insane LCDs (I would hope). Note that the category says AC-to-DC Switching but the details at the bottom and datasheet indicate it is linear (it is also in the linear section of the catalog page). Happy to finally get away from my switched PSU for sure, though it's more pathological :) I never noticed abnormal noise when using the switcher *shrug* Either way, problem solved. Quote Link to comment Share on other sites More sharing options...
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