Can't Find 18 VAC Power Supply over 500mA- Help and Advise, Please

  • Thread starter Thread starter stevieb
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stevieb

Just another guy, really.
Want to power some number of Presonis MicPre's. We have several of them, but are short of the wall-warts. Mouser has 18VAC wall warts, but the MicPre's power requirements are 1000mA; Mouser's most powerful is only 500mA. We would prefer to have ONE power supply to drive them all (about six to twelve) that has the amperage to do the job. Mouser sells no such animal. A fixed output would be prefered, but a variable or multiple-output power supply would be okay.

Anybody know of a source?

Will we have to build it ourselves? If so, sobeit- source for plans?

thanks.
 
stevieb said:
Want to power some number of Presonis MicPre's. We have several of them, but are short of the wall-warts. Mouser has 18VAC wall warts, but the MicPre's power requirements are 1000mA; Mouser's most powerful is only 500mA. We would prefer to have ONE power supply to drive them all (about six to twelve) that has the amperage to do the job. Mouser sells no such animal. A fixed output would be prefered, but a variable or multiple-output power supply would be okay.

Anybody know of a source?

Will we have to build it ourselves? If so, sobeit- source for plans?

thanks.
Click to expand...

You don't need plans for VAC, it's just the transformer. You need a 12A 18VAC power transformer. I would stick a fuse on the 120V side as well--2A ought to do. A power switch is nice. And a box of course, with a power plug and 12 18VAC outs.

Something like this, although you might flip through the catalog for something cheaper:

http://www.mouser.com/Search/ProductDetail.aspx?qs=atHKiefXm7QYrUMaWLuvSA==
 
mshilarious said:
You don't need plans for VAC, it's just the transformer. You need a 12A 18VAC power transformer. I would stick a fuse on the 120V side as well--2A ought to do. A power switch is nice. And a box of course, with a power plug and 12 18VAC outs.

Something like this, although you might flip through the catalog for something cheaper:

http://www.mouser.com/Search/ProductDetail.aspx?qs=atHKiefXm7QYrUMaWLuvSA==
Click to expand...


You could find something cheaper, but the toroidal would be nice from a noise point of view.

I'd be willing to bet you could make a nice 18VDC switching power supply. Unless the preamp needs multiple voltages (which I'm guess is not the case), it won't have a transformer, and the DC will pass through the rectifiers just fine. If you put the PS in another rack (or even another room, though you'll need some pretty heavy cable to keep the heat losses down - if you are going to run them all on one pair, 12 gauge would likely be enough, but I'd go with 10 gauge if you are going any distance) you would get some improvement in signal to noise ratio. Maybe not enough to go through the bother - OK, almost certainly not enough to go through the bother - but some improvement none the less. Of course, you'd void the warranty, but I do that on just about every piece of electronics I own.

You'll have to excuse me - I've been having fun making power supplies for a bunch of stuff lately. Either way, you definitely want a fuse on the wall power. A power switch is a good way to save some money, because you don't use any power when it is turned off, but if you have everything on a power conditioner or some such that you turn off you'll be fine.


Light

"Cowards can never be moral."
M.K. Gandhi
 
It's much easier to buy a switching supply than build; those are complicated beasties. It would be about $70-$80, usually. They would be in the Mouser catalog too. But if the preamps are running a voltage multiplier circuit for phantom, DC won't work--the phantom voltage would drop to 18V.
 
Hey Stevie,
Just google 18VAC Power supply.....M-Audio even makes a 3.5 amp one.
Probably pretty pricey.....
18VAC is standard Security Panel power. Usually 1-Amp.
Here is one I found at VETCO for $21.40 Each
Good luck!
 

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mshilarious said:
It's much easier to buy a switching supply than build; those are complicated beasties. It would be about $70-$80, usually. They would be in the Mouser catalog too. But if the preamps are running a voltage multiplier circuit for phantom, DC won't work--the phantom voltage would drop to 18V.
Click to expand...



Whoops! I didn't even think of that. You're almost certainly right.


Light

"Cowards can never be moral."
M.K. Gandhi
 
Light said:
Whoops! I didn't even think of that. You're almost certainly right.
Click to expand...

It does make an interesting point about power supplies though--the reason why switching supplies are popular is because they only need really small transformers, and they are efficient. A 12A transformer for a linear supply needs to be huge (I think the unit I linked was 5" diameter), with some thick & expensive copper, which is required to keep the efficiency at a reasonable level.
 
Do you have any charity shops around?

See if you can talk to the guy who tests the electrical equipment.

I work at a charity shop myself and we have buckets full of any kind of power supply you can imagine. They'll probably charge you a buck.
 
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