Wall Wart question

[scottosan]

How much of a difference does the rated current (Ma) make?

[petemoore]

None...almost always...there's enough in a ['small'] 150ma WW to run more than 10 efkts that use 14ma each...I don't recall anyone reporting having exceeded the Ma rating of a WW running Efkts....but I'm sure it's happened.
 as long as the Ma rating of the WW exceeds what your circuit[s draws, you'll be fine.

[niftydog]

for the most part, pete is right. However, it's worth keeping in mind that for unregulated wall warts, the higher the mA rating, the higher the "no load voltage".

Say you have an unregulated 9VDC 3A wall wart running two analogue pedals. The pedals are only drawing maybe 30mA. The voltage the wall wart is producing is very likely to be far in excess of 9VDC and there's potential for problems in that respect.

However, large mA rated wall warts are not common and are usually considered too bulky for our use. However, handy to be aware of this potential pitfall.

[Peter Snowberg]

Keep in mind that more current capability will generally give more stability in output voltage.

Wall warts are generally unregulated so watch out for what the voltage might actually be.

If an adapter is rated at 9VDC @ 150mA, when you don't pull 150mA the voltage may be a few volts higher. You may also have less than 9V by the time you're pulling 150mA.

[scottosan]

Keep in mind that more current capability will generally give more stability in output voltage.

Wall warts are generally unregulated so watch out for what the voltage might actually be.

If an adapter is rated at 9VDC @ 150mA, when you don't pull 150mA the voltage may be a few volts higher. You may also have less than 9V by the time you're pulling 150mA.

I tried 2 different with various voltages.  BOth make some slight humming noise. IS ther any way to get rid of the noise?

[smallbearelec]

Wall-Warts are not well-filtered. At the the price, you can't expect more than the bare minimum. You have a couple of options:

--You can build an add-on box for a WW that contains a larger filter cap and regulator (which will also make the output REALLY quiet).

--You can build a Small Wart.

http://www.smallbearelec.com/Projects/ProjandProd.html

The first solution I offered is really just the business end of a Small Wart; if you don't want to buy one of my kits (which is fine!), the schem and layouts may give you some useful ideas for a bare-bones work-around.