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power up electronic devices with audio amplifier output
power up electronic devices with audio amplifier output
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Old 28th January 2018, 08:25 PM   #11
scottjoplin is offline scottjoplin  Wales
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You're welcome
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Old 29th January 2018, 02:03 AM   #12
Refugee1 is offline Refugee1  United Kingdom
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You would need a rectifier on the output of the amp and an AC signal at the input.
The only way this method could be useful is if you are powering a record player motor built for 50hz on a 60hz supply in order to get the correct speed. A step up transformer would most likely need to be added to the output and you would certainly need an accurate frequency at the input.
We in the UK would have to do it the other way round as our supply is 50hz.
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Old 29th January 2018, 04:12 PM   #13
Joanito is offline Joanito  Portugal
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...So if i rectify, i should be able to drive, let's say, loads equal or above 4 ohms, right ? Like powering a laptop, per example...

And in the beginning of the process of rectifying, the rectifying capacitor is discharged, so the current, in that moment, will exceed the maximum value that the amplifier can provide ?, or not ? How do i find that initial current ?

Last edited by Joanito; 29th January 2018 at 04:36 PM.
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Old 29th January 2018, 06:14 PM   #14
PRR is offline PRR  United States
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"Audio" amplifiers are almost all DC blocking.

The Crown DC-300 was DC coupled through. (No audio person could need 300W those days, the expected user was test labs.)

It was reported that a user with a dead audio mixer power supply put a flashlight battery to the DC-300 input, trimmed the gain for 15V out (actually +/-15V from the two outputs), and the show went on.

Note that you can pick up power supplies for most laptops often far cheaper than any audio power amp. The popular Dell 19V 6A supply was selling everywhere on eBay (genuine Dell, lightly dusty) for $4 a few years ago. It inspired at least one small-commercial product, as well as the MoFo in the Pass section here. Price has recovered to $6, big deal. If you truly fear laptop supply failure, it seems best to get a few of the "right" supplies, than to risk laptop disaster with an improvised supply.
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Old 29th January 2018, 06:26 PM   #15
Joanito is offline Joanito  Portugal
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Hello, it's not just to powering laptops... I found interesting the fact that i can control the tension with the volume pot... and i found interesting that i can power up several electronic devices in case i don't have power supply for them, and i can use the amplifier as an alternative...

Per example, put 12v led lamps flashing... Make a strobe light perhaps... I like to play with this things ;-)

Last edited by Joanito; 29th January 2018 at 06:37 PM.
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Old 29th January 2018, 06:49 PM   #16
Mooly is offline Mooly  United Kingdom
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power up electronic devices with audio amplifier output
Well its great to play with stuff and 'know it can be done' but you also have to be realistic in knowing what is just for fun and what is do-able in theory but no good in practice.

Take your laptop. Suppose you did set up a 100watt amp that runs on -/+50 volt rails to deliver say 19 volts at 4 amps into a laptop.

Think of the heat the amp will dissipate. It would be around 120 watts. Its just not workable.
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Old 29th January 2018, 07:19 PM   #17
Joanito is offline Joanito  Portugal
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ok, thanks
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Old 29th January 2018, 07:27 PM   #18
Joanito is offline Joanito  Portugal
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I also enjoy talking about these things with other people. :-)
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Old 29th January 2018, 07:33 PM   #19
scottjoplin is offline scottjoplin  Wales
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Talking is good. I'm interested about how you are going about trying to learn and your experience with getting information these days, would you mind having a look at this thread here Yet another basic question and please feel free to say anything you like
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Old 29th January 2018, 07:34 PM   #20
Mooly is offline Mooly  United Kingdom
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power up electronic devices with audio amplifier output
Your welcome, and fwiw, these are the sort of things I used to try as a youngster
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