2 Designs for Class D Power Supply - Which One?
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 Class D Switching Power Amplifiers and Power D/A conversion

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 12th May 2006, 03:51 PM #31 bck2diy   diyAudio Member   Join Date: Aug 2004 Location: Da Bronx Sorry for the confusion :-) I calculated for a scenario of about 60V DC between one of the rails and GND: 1. Using a 10k resistor to bleed, say, 2x10,000uF capacitors would require the resistor to be rated atleast 1/2W (double that to 1W) and it would take about 35 minutes 2. Using a 1k resistor for the same would require the resistor to be atleast 4W (double - 8W) but the time taken would drop to about 4 minutes I am going for a longer discharge time so my final choice would be closer to option 1 (use a 2W or higher rated resistor as you suggested). -bck2diy
 12th May 2006, 05:26 PM #32 richie00boy   Did it Himself diyAudio Member     Join Date: Nov 2003 Location: Gloucestershire, England, UK I would just use a small power resistor across the terminals and de-rate it, i.e. use a 1W resistor but choose the resistance such that it only dissipates 0.5W. You don't need to it discharge quicker than a good few minutes. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, modules and more.
sx881663
diyAudio Member

Join Date: Nov 2003
Location: so. ca.
Discharging caps

Quote:
 Originally posted by bck2diy Sorry for the confusion :-) I calculated for a scenario of about 60V DC between one of the rails and GND: 1. Using a 10k resistor to bleed, say, 2x10,000uF capacitors would require the resistor to be rated atleast 1/2W (double that to 1W) and it would take about 35 minutes 2. Using a 1k resistor for the same would require the resistor to be atleast 4W (double - 8W) but the time taken would drop to about 4 minutes I am going for a longer discharge time so my final choice would be closer to option 1 (use a 2W or higher rated resistor as you suggested). -bck2diy

Discharging to safe levels and not to zero is what you are after. The times you stated are much longer than to a safe level. Even 6 time constants should be conservative and would give a time value 1/2 what you called out. This exercise does give one a good feel of just how much energy is stored in these caps. Certainly not something you want to dump across your test probe!
Roger
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 13th May 2006, 11:53 PM #34 Andrew Hume   diyAudio Member   Join Date: Jul 2005 Location: New Jersey synchronicity strangely, i am in the exact same boat. i have a circuit quite similiar to your last one, although i am using some 42000uF 90V caps i have lying around. for what it is worth, i am slowly grinding my way through making a small PC board for everything other than the big caps (standard "use anything from the Mouser catalog" project). although i am unsure when they would be ready (i intend to use a commercial pc fab), i'd be happy to share them with you. andrew
Bgt
diyAudio Member

Join Date: Jan 2005
Location: NL, Voorschoten
Quote:
 Originally posted by bck2diy so a single transformer does provide good channel separation (soundstaging) if the bridge circuit is done correctly? Do I correctly understand what you're saying?
Just to show you the wiring layout of a 1 transformer stereo amp. with superb soundstage. I use this for the UCD amps. and the Coldamps.

http://www.grotel.nl/photo/wiring%20...d%20stereo.jpg
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Kind regards,
Bert

 21st May 2006, 11:37 AM #36 Bgt   diyAudio Member   Join Date: Jan 2005 Location: NL, Voorschoten This grounding scheme did not work for me, was to much humm and a lot of crosstalk. Touching the input cable changed my soundstage completely.(UCD400's had increased gain) http://www.grotel.nl/photo/wiring%20...%20stereo2.jpg Just waiting for Coldamps new SMPS(model30) when finished and to try them. __________________ Kind regards, Bert

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