Tripmaster;557737 Wrote: > Hi John > > I'll bite...would it be possible to post a schematic of your favoured > supply? :) > > Thanks
Here is the design: http://johnswenson1.home.comcast.net/stereo/SB_5V.GIF As shown its good for up to 2A load which should be fine for a Touch by itself. If you want to go with an external USB drive its probably best to go with a beefier transformer. The VPS20-2200 should do (with the secondaries in parallel) or if you really want to go with the big monster the VPS20-4000 (secondaries in parallel). The Hammond choke is a little hard to find, but do NOT leave it out, its the heart of the design. With the choke the max current pulse through the transformer is many many times less than it would be if it was just a cap input filter. This radically cuts down on noise sent back into the mains. Also whats going into the regulator is almost a pure sine wave, no high frequency harmonics. This means the regulator can easily filter the ripple out. With a single cap filter there are large amounts of high frequencies going to the regulator. The off the shelf IC regulators are not so great at filtering out these high frequency components, which is one of the reasons for the complicated discrete regulator designs popular with some "audiophole" designs. In this design you are adding a fairly expensive choke ($25-$35) and a simple cheap regulator VS simple cap filter and complex expensive regulator. I went with the simple approach. This is a very carefully tuned designe so be very careful with using different parts, even things such as different brand or model caps can change the behavior significantly. If at all possible I would stick with the specified transformers. They are good quality transformers with high isolation between primary and secondary and don't cost a lot. Its probably going to cost 4 times as much to find a transformer that will outperform these. Have fun, John S. -- JohnSwenson ------------------------------------------------------------------------ JohnSwenson's Profile: http://forums.slimdevices.com/member.php?userid=5974 View this thread: http://forums.slimdevices.com/showthread.php?t=79977 _______________________________________________ Touch mailing list Touch@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/touch
