Hey everyone, I have a question that I am sure someone (or everyone) here could answer for me.
I have a wireless microphone system Shure ULXP4 Shure ULXP4
I can’t find the power supply which is 14 - 18V 550 mA
I don’t want to kill the mic system and I don’t have time to order the proper power supply as I need to use it for a gig tomorrow.
How important is the mA rating? I have an adapter that is 12V 400 mA.
(I actually used this adapter by mistake last time I used the system and it worked. I did so by accident as the 12V 400 mA power supply is branded Sure so I thought it was the correct one. I just noticed now that it’s the wrong one.)
I also have another adapter with the correct polarity and the size of the plug is much more snug. It is 15V 1500 mA.
Is it better to have the correct Volts or mA?s
I really don’t understand the mA rating or the implications of using higher or lower than rated.
My understanding is that the 15V 1500 mA one is just fine for permanent use, because I am under the impression that while the minimum mA matter, the device will only draw the mA that it needs, if the adapter has a larger number than needed, and the voltage is very important to get right, so your 12v/400mA is not good at all to be using.
I’m just guessing, so wait for the authoritative answers to show up.
Many people are confused by amperage ratings and what they mean when it comes to power supplies and replacements.
One easy way to look at it is this:
Voltage is provided by (or pushed) by the power supply.
Amperage is taken by (or pulled) by the device being powered.
In other words, while the voltage is a constant and should match, the amperage is something that varies based on the device’s need. Your computer will “pull” more amps when it’s working hard than when it’s not. The voltage will remain the same regardless.
The amperage rating of a power supply is the maximum number of amps that it’s able to provide if needed.
Thus, as long as you replace your power supply with one that is capable of providing as much or more amps than the previous supply, you’ll be fine.
If you replace the power supply for some reason with one that has a maximum amperage rating that is less than the previous and less than what your device actually requires, then you may end up with a burnt out or (at least) overheating power supply, and the device itself may not function, or may not do so well.”
Looks like I am good to go on the adapter that is 15V 1500mA and the the polarity matches!
Depends if the output voltage is regulated. If yes, then make sure your replacement adapter is also regulated, and the current rating on the replacement is greater than the original. Eg, if 14V 500mA on the original, 14V 600mA would work fine, 400mA maybe not so much.
If not, if the output isn’t regulated, then the actual output voltage of the adapter depends on the load, so 14V 500mA might be 21.5V with no load at all, dropping to about 18V at 250mA, about 14V at 500mA, and so on.
Of more concern would be the connector, making “shure” (haha) it’s the right size and polarity.
How do I tell if the power supply is regulated?
In the manual the power adapter is described as “the supplied AC adapter or certified 14–18 Vdc (550mA) replacement supply.”
The one I would like to use says DC 15V 1500 mA Max 23W
Fesso as long as the volts are correct, the excess amperage is fine. The device will only draw as much as it needs as you noted in your earlier post. :+1:
Unregulated PS’s without a load will test at a higher voltage than is specified on the unit, then drop into spec when used. Most devices are made to allow for this but if regulation is required those few extra volts could cause trouble. Low amperage can cause devices to not operate or to not operate correctly but generally won’t harm a device. I save all the working wall-warts I come across and use them to replace dead ones, and I’ve found that getting close to the called-for specs is almost always good enough as long as you meet or exceed the amp requirement. Most PS’s die because the device manufacturer saves money by providing a PS which barely supplies enough amps, so where I can I use a bigger one for replacement. One thing to watch for is whether the PS output is AC or DC because they come both ways. Using an AC one where DC is required is a guaranteed fail.
Commercial wall power supplies are rated @ +/- 10% so your fine
with the voltage on the higher voltage wall PS. The article you found is correct about amperage.All loads can be broken down to a single resitance and thats what the power supply sees, thus load only pulls what it was desighned to pull… unless its a variable load but that doesnt seem to be your case.
Constant Voltage supplies (classic PSUs/most wall adapters) are rated at their nominal voltage output, which they'll keep withing safe tolerances at up to their maximum current output, but obviously they'll try to provide up to their maximum real current rating and then shut off or die in The Magical Smoke Show). LoL! :-))
The current output they provide mostly depends on load impedance (V/R, V is output voltage and R is Rload + Rsupply). They are supposed to precisely provide what the load requests, within their operating conditions.