Laptop Charger As Power Source

[Andrew Heck]

I realize that all wall worts are not made the same, so is a laptop charger a good, quiet, low interference source of DC power? If so, I’ve wondered now for a while, what of ground in a DC circuit that’s not rectified from AC such as a battery powered head amp for MC phono signal boost? And how ‘bout the two prong wall wort? Does the negative (common?) act as ground? Asking for a friend...
Thanks in advance for your efforts to type an enlightening answer, thus making me slightly more dangerous in the ways of circuitry.

 

[sKiZo]

Ida know about low noise, but they are handy. I'm using a 12v 6a monitor brick to power an HD Radio auto head here in the home system and no complaints, but that's just FM. No problems, but I'm not just using the RCA outs on the head into my receiver and the inboard amps aren't being used, so not much of a load.

 

[Lavane]

Some wall warts can be marginal when it comes to delivering current needed to power a device. The laptop bricks tend to deliver more amperage than some wall warts. That's a thin thing. I would think laptop chargers are better filtered than a cheap wall wart as well. I replaced a couple wall warts with laptop chargers and with one little headphone amp it did get rid of a very slight buzz.

 

[BinaryMike]

I’ve wondered now for a while, what of ground in a DC circuit that’s not rectified from AC such as a battery powered head amp for MC phono signal boost? And how ‘bout the two prong wall wort? Does the negative (common?) act as ground?

"Ground" or circuit common can be the negative or positive side of a battery or any other power source. It's whichever side is convenient for the engineer's purpose, or it can be the common terminal of a power supply that delivers both positive and negative output voltages.

The output of a wall wart is "galvanically isolated" or electrically floating like a battery relative to its AC input terminals, so that either side of the output cable can used as ground in the load circuit.

Does that help?

 

[Andrew Heck]

"Ground" or circuit common can be the negative or positive side of a battery or any other power source. It's whichever side is convenient for the engineer's purpose, or it can be the common terminal of a power supply that delivers both positive and negative output voltages.

The output of a wall wart is "galvanically isolated" or electrically floating like a battery relative to its AC input terminals, so that either side of the output cable can used as ground in the load circuit.

Does that help?

Thank you. That gives me a great place to start researching. I appreciate it.

 

[Shadowdog]

I think it's being done over at diyaudio on a kit SS amp they are selling.

 

[KingBubba]

People in the class D amp group here are known to use laptop bricks all the time, including myself.

 

[Bob]

It's an excellent power source. you can buy boards on eBay that ups/downs/duals the
voltage to drive just about any circuit.

it's also good for heaters, just wire them up to use the standard output or use an Ebay
board to change the voltage.

 

[Pio1980]

Laptop power supplies are
an excellent source of power when used in a prescribed manner. Please consult your technician if you have any questions about whether laptop power supplies are for you.
(May inject hash noise or interfere with radio reception or cause anxiety and/or death. Discontinue use and consult your technician if any of of these symptoms occur)

 

[Guest159]

Nelson Pass uses laptop chargers for his ACA amp kits. I'd recommend checking out the threads for the ACA at diyaudio.com and diyaudiostore.com to see what chargers they're using. I know they've used a couple different ones. I believe one is 18V and the newer one is 24V. Don't quote me though.

 

[SX550]

People in the class D amp group here are known to use laptop bricks all the time, including myself.

Same, made a few little amps and used cheap laptop bricks to power them just fine.

 

[Farmhand]

I haven’t yet dared to try this with a Lepai 2020. Will an 18v brick kill a 12v amp or will it just supply what’s being drawn?

 

[Pio1980]

Voltage supply level is constant, current draw varies to demand up to capaciity of supply. Do *not* use voltage higher than rating for device!

 

[Poultrygeist]

I've used a variety of laptop psu's with class D amps, DAC's and preamps with good results. I've had better results with a linear regulated psu such as this inexpensive Pyramid.

 

[Pio1980]

I've used a variety of laptop psu's with class D amps, DAC's and preamps with good results. I've had better results with a linear regulated psu such as this inexpensive Pyramid.

View attachment 1365508

The little regulated 12VDC range supplies supplies are good here for these preamps, the higher voltages for Class D power amps tend to negate the cost advantage past a certain point. Say, 6-10 amp at 19-36 VDC. You do not get anything close to rated power into an 8 ohm speaker at 12V with the 311# series chips. You need the higher voltage to take advantage of the power reserve they offer into less than highly efficient speakers.