SMP Rails?

imfree707 · 21st June 2011, 02:48 PM

Has anyone seen any modular, that is circuit board-only, Switch Mode PSU's with 120-240V input and +/- Rail outputs for operating Audio Power Amps? A line of these PSU's would be great and could cost less than EI or Toroidal Transformers, these days, and be a Chip-Amp DIYer's dream!!!!

! · 25th June 2011, 01:23 AM

You could use two of the same SMPS in series, though at least the PSU delivering the negative rail would need a floating ground (relative to earth and chassis ground) so you hook them up with PSU #1 having positive rail voltage and negative at earth ground potential, and PSU #2 has positive rail at earth ground (wired to the negative on PSU #1) and its *ground* is no longer ground, it's the negative rail.

It depends on the DIYer whether it would be a DIYer's dream, chip amps have much better PSRR with linear PSU than with SMPS, they will be more accurate with linear and sound artificially "lively" with SMPS... which some people like, but some don't.

Another idea come to mind, use an opamp, voltage divider subcircuit and create a virtual ground between the single rail SMPS positive and negative (again your PSU negative has to be a floating ground, not connected to earth ground in most amp designs).

If you could find the dual rail PSU as a ready made product used in lots of devices, then yes the cost "could" (but wouldn't necessarily be) be lower than EI or toroidal linear PSU, but as you've noted when you inquired - that they are rare in capacities a chipamp DIYer would want - the limited availability means fewer produced, driving up development and manufacturing cost.

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21st June 2011, 02:48 PM	#1
imfree707 diyAudio Member Join Date: Oct 2010 Location: Tenn Loop Ranch, Lebanon, Tn.	SMP Rails? Has anyone seen any modular, that is circuit board-only, Switch Mode PSU's with 120-240V input and +/- Rail outputs for operating Audio Power Amps? A line of these PSU's would be great and could cost less than EI or Toroidal Transformers, these days, and be a Chip-Amp DIYer's dream!!!! __________________ A stiff power supply in a great-sounding amp is always better for you than a stiff drink.

25th June 2011, 01:23 AM	#2
! diyAudio Member Join Date: Jun 2005 Location: Midwest	You could use two of the same SMPS in series, though at least the PSU delivering the negative rail would need a floating ground (relative to earth and chassis ground) so you hook them up with PSU #1 having positive rail voltage and negative at earth ground potential, and PSU #2 has positive rail at earth ground (wired to the negative on PSU #1) and its ground is no longer ground, it's the negative rail. It depends on the DIYer whether it would be a DIYer's dream, chip amps have much better PSRR with linear PSU than with SMPS, they will be more accurate with linear and sound artificially "lively" with SMPS... which some people like, but some don't. Another idea come to mind, use an opamp, voltage divider subcircuit and create a virtual ground between the single rail SMPS positive and negative (again your PSU negative has to be a floating ground, not connected to earth ground in most amp designs). If you could find the dual rail PSU as a ready made product used in lots of devices, then yes the cost "could" (but wouldn't necessarily be) be lower than EI or toroidal linear PSU, but as you've noted when you inquired - that they are rare in capacities a chipamp DIYer would want - the limited availability means fewer produced, driving up development and manufacturing cost.

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