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Power Supply specs question...?? Turntables
Old 17th September 2011
  #1
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Power Supply specs question...??

Hey all...

Easy question for your electrical gurus...

Many power supplies are rated at 12volts output. However, some have a milliamp rating also. For example, some will say something like... 12v - 1200 m/a. Is the m/a spec. going to make or break a compatibility?

I have a unit that asks for a 12v power supply. Will any 12 v. supply do the trick, or should I match the m/a specs. too?

Thanks for any help with defining these specs!
Old 17th September 2011
  #2
Registered User
Abolutely ... current is measured in Amperes or amps for short. Milliamps are one thousandth of an amp - so a 1000mA PSU is also a 1 amp PSU.

The factor of Volts and amps gives Power.

Supplying the correct polarity Power at the right voltage is absolutely critical, so this means current is critical.
Old 17th September 2011
  #3
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Quote:
Originally Posted by Kiwi View Post
Abolutely ... current is measured in Amperes or amps for short. Milliamps are one thousandth of an amp - so a 1000mA PSU is also a 1 amp PSU.

The factor of Volts and amps gives Power.

Supplying the correct polarity Power at the right voltage is absolutely critical, so this means current is critical.
Herein lies a conundrum, however, as my unit has simply a "12volt" label on the back, with no mention of m/a. I have several power supplies here with differing m/a specs. What gives with this??? How can I choose a supply, given your suggestion?

Thanks for input!
Old 17th September 2011
  #4
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Rick Sutton's Avatar
 

If the unit that the power supply feeds does not have the required amperage marked on it, it should be searchable. By the way, don't forget.........12 volts can be either AC or DC.
As far as matching the amperage spec, you should use a supply that gives at least that......going to a larger amperage supply is also acceptable.
Old 17th September 2011
  #5
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Quote:
Originally Posted by Rick Sutton View Post
If the unit that the power supply feeds does not have the required amperage marked on it, it should be searchable. By the way, don't forget.........12 volts can be either AC or DC.
Hmmm... Well, now that you point this out... it says "12VDC", so that brings up more questions. What be this? Special kind of supply?

Also, when you say "searchable", do you mean simply... Google it?? The owners manual says little more than I know.

You guys rock!
Old 17th September 2011
  #6
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Rick Sutton's Avatar
 

Quote:
Originally Posted by Mr. Kelly View Post
Hmmm... Well, now that you point this out... it says "12VDC", so that brings up more questions. What be this? Special kind of supply?

Also, when you say "searchable", do you mean simply... Google it?? The owners manual says little more than I know.

You guys rock!
What exactly is this unit that you need a supply for?

And one more thought......you need to know the polarity of the input if it is a DC supply. The polarity should be marked where the power input is on the unit. Also there are several different sizes of plugs. You gotta figure all this stuff out before you plug anything into that unit or you could be in a boatload of trouble. This is why most people contact the Mfg and just get a replacement supply.

BTW....Kelly, I visited your website and really liked what you are doing. Great music and I was struck by how excellent the recordings were.
Old 17th September 2011
  #7
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Quote:
Originally Posted by Rick Sutton View Post
What exactly is this unit that you need a supply for?

And one more thought......you need to know the polarity of the input if it is a DC supply. The polarity should be marked where the power input is on the unit. Also there are several different sizes of plugs. You gotta figure all this stuff out before you plug anything into that unit or you could be in a boatload of trouble. This is why most people contact the Mfg and just get a replacement supply.

BTW....Kelly, I visited your website and really liked what you are doing. Great music and I was struck by how excellent the recordings were.
Thank you for your interest in helping solve my supply dilemma! I purchased a ART Headamp 5 from Ebay, but the seller forgot to send the supply. So, to avoid having him have to ship the supply, I figured I'd just try to find one I already have. Herein lies my conundrum. I do have VDC supplies, but they're all labeled w. m/a specs, while the unit does not.

The unit does not show any polarity info... just a socket labeled "12VDC". That's it.

Worse-case scenario (which hopefully, won't be too bad) is that the seller will send along the supply. Best-case, I'll figure out what I can use here and save him the trouble!


Also... and most importantly... Thank you BOATLOADS for your thoughtful comments about my website recordings! You made my day!
Old 17th September 2011
  #8
Lives for gear
 

are you talking power supply or wallwart ?
the biggest amp rating you can buy should work fine
if the voltage plug and polarity are correct

if the voltage etc matches plug it in
if it doesnt melt you are okay
WARNING: do this at your own risk !!!!!!!!!

it should work
but no guarantees
Old 17th September 2011
  #9
Registered User
You should be able to find a user manual for this that will tell you the current rating you need. I googled and found some clowns providing the manuals if you complete a survey or IQ test - I don't trust them not to run malware, so you can risk this at your own peril.

Logically - this device powers 5 headphones. A decent headphone amp needs to provide about half a watt per pair, so if you expect to run 5 pair at full volume, you might need as much as 2.5 watts = 2500 milliWatts. At 12 Volts, you need 2500/12 = 208.3 milliamps.

That's a rough guess of output power - and electronic devices are far from 100% efficient (they get hot). So to be safe I would double that.

I would look for approx 500mA - but if you can buy a 1000mA or even 2000mA, I would do it. More is better - because the device will only draw as much as it needs. Generally, it improves the bass response if there is more than sufficient current.

The biggest problem I find is getting the right sized connector ... it's frustrating how many sizes there are that look similar but just don't farkin work.
Old 23rd September 2011
  #10
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Okay.... a week later... I got a power supply from the fellow who sold me the unit. It's not the stock supply. I'll get over it.

However, the supply seems under powered at 150 m/a. I'm going to use one that I have that's much higher output capacity, as has been suggested.

I don't have a handle on the polarity. The supply I have shows negative in the center and positive on the outside ring. Make sense? The unit shows no polarity. Manual isn't helpful.

Any thoughts? Just get a supply and run with it???
Old 24th September 2011
  #11
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Rick Sutton's Avatar
 

double post
Old 24th September 2011
  #12
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Rick Sutton's Avatar
 

Quote:
Originally Posted by Mr. Kelly View Post
Okay.... a week later... I got a power supply from the fellow who sold me the unit. It's not the stock supply. I'll get over it.

However, the supply seems under powered at 150 m/a. I'm going to use one that I have that's much higher output capacity, as has been suggested.

I don't have a handle on the polarity. The supply I have shows negative in the center and positive on the outside ring. Make sense? The unit shows no polarity. Manual isn't helpful.

Any thoughts? Just get a supply and run with it???
Kelly, you have to make sure the polarity is correct. So you have the supply from the seller in your possession and it does work on the headphone amp? If so, what is the polarity on the output of that supply? ( I can't tell from your post if you are referring to the larger supply or the one from the seller)

Do you own a voltmeter?

Here's a pic of a Head4 which clearly shows the polarity of the DC connector. Can't find squat for the 5. If it were me I'd measure the polarity (if not marked) of the seller's supply if it works and then use the larger supply with a proper connector and polarity wired the same. In a pinch I'd cut the connector off the smaller supply and wire it to proper polarity on the bigger supply. If I had any questions about the actual rating of the headamp I'd contact tech support at Art and get the info.
Attached Thumbnails
Power Supply specs question...??-large_art-headamp-4-3.jpg  
Old 24th September 2011
  #13
Lives for gear
 

Thank you, Rick, once again!

Both power supplies I have, plus a few others, have both polarities. Is it such that the "incorrect" polarity will simply not work with this unit? I've resisted just plugging the things in to see if they'd work. I'm exercising rare caution to prevent from frying the thing!

I do have this little "multimeter" device that seems to be able to measure A/C-D/C, ohms, and dB. Sadly, all that I have ever used for has been to test batteries! What did you have in mind for this thing???
Old 24th September 2011
  #14
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Rick Sutton's Avatar
 

Kelly,
Check your PM's
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