Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › CMOY's virtual ground: Which PSU?
New Posts  All Forums:Forum Nav:

CMOY's virtual ground: Which PSU?

post #1 of 10
Thread Starter 
So I've been trying to build an AC adapter-powered CMOY. Because of the CMOY's virtual ground, these adapters need to be isolated - the AC side needs to be electrically isolated from the DC side by a transformer. I recently realized, after several fried chips, that the laptop power brick I've been trying to use is in fact a "switch-mode" power supply, which is probably not isolated and thus shorting out the virtual ground (i.e. not allowing the CMOY's ground to float at a voltage half-way between the + and - rails being put into the chip).

I want a good, regulated power supply, but I'm having trouble telling which might be "switch-mode" instead of "linear regulated," which are apparently isolated.

Will something like this solve my problems? Or something like this?

Does anyone have recommendations for cheap, linear-regulated power supplies for the CMOY? Note that I'm not grounding anything to the chassis and the DC jack is isolated, so that isn't what's causing the short.
post #2 of 10
The power supplies you linked are WAY above what you could ever need, like WAY WAY WAY over.

You can buy an Elpac regulated power supply at about 500mA and it'll power pretty much any solid state amp you could build until you get to the Gilmore designs or ones that require dual secondary transformers.

Personally though, I would suggest getting any cheap $5 wallwart you have lying around your house and simply building a TREAD, it'll be MUCH better than a commercial regulated psu.

Most other regulated DC wallwarts are pretty crappy for noise, go with an AC-AC wallwart and build a regulator.
post #3 of 10
2 amps, holy sh**.

Yeah, a little too much.
post #4 of 10
I got one of these. http://www.allelectronics.com/cgi-bi...R_SUPPLY_.html works fine.

You really need to test these things since it rarely says if it is isolated or not. You use test for continuity from either AC prong to either DC output. It you get continuity from any combination of AC->DC then you are not isolated.

Whatever you do buy you should test it. Even if it is the one I linked above. It's surplus, so they may not all be identical.

Read the section on power supply on Tanget's site for the Pimeta. http://www.tangentsoft.net/audio/pimeta/pguide.html
post #5 of 10
That first one you linked to is probably linear, the second one has AC output and is therefore not usable without addtional rectification and regulation. Since the first one has only a two-prong AC plug, it won't short anything out as long as the power supply's chassis doesn't touch the cmoy's tin or virtual ground. The 2A output current rating is overkill for a cmoy.

That said, why not use the tried-and-true Elpac WM080-1950-760 linear 24V wallwart? It is fully isolated, the cmoy should work fine with the higher voltage and will give you more output voltage swing capability as well. This is available from Allied Electronics.
post #6 of 10
aestuo, I think you'd better find out what cause that short problem before replacing power supply. Because, that doesn't looks like power related problem, but it looks like circuit problem like cold joint or wrong wiring.

Cmoy does not requires whole lot of power. You don't need 2A.
Any wallwart b/w 9~24V/300mA or higher will do the job without problem. Linear or switching, Regulated or not, doesn't really matter. That means basically any wallwart... like those wallwarts that comes with answering machine, phone, etc... will work. I am sure you have at least one in your house unused.
post #7 of 10
Thread Starter 
Thanks for the Elpac suggestion. Yes, I was a fool for not getting a multimeter first and testing continuity. I'll save Tangentsoft's TREAD boards for an upgrade after I get my CMOY working. This is my first electronics project.
post #8 of 10
Thread Starter 
This Elpac WM220 has +12 and -12 dual-supply, and it seems to cost the same. Can I power the chip directly with this? It might be switch-mode but that shouldn't matter now as the ground will no longer need to float. Are there any problems with this besides the potential noise?
post #9 of 10
Quote:
Originally Posted by aestuo View Post
This Elpac WM220 has +12 and -12 dual-supply, and it seems to cost the same. Can I power the chip directly with this? It might be switch-mode but that shouldn't matter now as the ground will no longer need to float. Are there any problems with this besides the potential noise?
It is definitely switch mode. Potentially there is noise, and using this means you should eliminate the rail splitter in the cmoy. You will need a mini-DIN connector instead of a barrel type socket on the amp. You won't need the 5VDC output of this supply.
post #10 of 10
If you wanted to get a dual +/- 12 V from Elpac which is also a linear, there's the WM113 series. You can choose between a wall-mount version and a "table top" version which has an AC side cord as well as a DC side cord. It's actually a triple output supply, but you can ignore the 5 V output. It's a bit expensive, but not horrible, all things considered.
New Posts  All Forums:Forum Nav:
  Return Home
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › CMOY's virtual ground: Which PSU?