Soldering a USB instead of DC input.

[Hoads2047]

Hi,

I am making an AMP for my PC as a school project.

Only thing is most of the kits are DC powered and i need it to be USB powered.

Can i solder the USB chord to where the DC socket should be?

 

Thanks.

[Hackentosher]

Uh yeah should be fine as long as your project uses 5v and probably less than 2 amps.

[dany_boy]

If the amp works with 5v and draws less than 1A, then it should be perfectly fine.

[TrigrH]

Should be alright if its 5v and less than 0 amps.

 

(jk just counting down for the memes)

[mariushm]

Most audio amplifiers like working with higher voltages. With only 5v coming from the USB port, the audio amplifiers may not work or their output will be really low, like at most 0.5w to 1w of audio power.

 

My advise would be to find some wall wart adapter and power your audio amplifier from 9v or 12v ... or you could even find some old laptop adapter and power your audio amplifier from 16.5 ..18v if the circuit can tolerate such high voltage. Laptop style 12v adapters are also very cheap and easy to find, because they were used with LCD monitors, with tablets, with small laptops , xbox consoles etc ..

 

For regular wall wart adapters, they mostly use standard barrel jack connectors, with either 2.1 or 2.5mm ID (internal diameter) and 5mm or 5.5mm OD (outer diameter)... all of these are very easy to find  (or you can cut buy a pair plug and receptacle  and cut the plug from the adapter you plan to use and install the plug you want)

 

 

[unknownmiscreant]

8 hours ago, mariushm said:

Most audio amplifiers like working with higher voltages. With only 5v coming from the USB port, the audio amplifiers may not work or their output will be really low, like at most 0.5w to 1w of audio power.

 

My advise would be to find some wall wart adapter and power your audio amplifier from 9v or 12v ... or you could even find some old laptop adapter and power your audio amplifier from 16.5 ..18v if the circuit can tolerate such high voltage. Laptop style 12v adapters are also very cheap and easy to find, because they were used with LCD monitors, with tablets, with small laptops , xbox consoles etc ..

 

For regular wall wart adapters, they mostly use standard barrel jack connectors, with either 2.1 or 2.5mm ID (internal diameter) and 5mm or 5.5mm OD (outer diameter)... all of these are very easy to find  (or you can cut buy a pair plug and receptacle  and cut the plug from the adapter you plan to use and install the plug you want)

 

 

Would definitely recommend this, and a simple 5v relay can be operated off USB, so the AMP turns on/off with the computer. Just make sure the AMP is capable of running for extended periods without anything bad happening.

On 8/4/2017 at 5:26 PM, Hoads2047 said:

Hi,

I am making an AMP for my PC as a school project.

Only thing is most of the kits are DC powered and i need it to be USB powered.

Can i solder the USB chord to where the DC socket should be?

 

Thanks.

Be careful with USB ports, as a max of 1A can be drawn from the port, however this must FIRST be negotiated by the device. The default output of a USB port is 100mA, and if the device draws more than this without negotiating first, the computer can think of it as 'faulty' and will remove power from the port.

[Kered124]

Surely he should be okay with something like an LM386? I have used 6v battery packs to power these with no issues. The datasheet says 4v can run the IC.

 

http://www.ti.com/lit/ds/symlink/lm386.pdf

 

I think it will work as long as you aren't expecting very high volumes. Also- using two USB sources in parallel for double the current would greatly benefit you.( If it is safe to do so...? I don't see why it wouldn't be, but i'm sure someone here knows the answer to that.)

[mariushm]

From that datasheet, page 6 ..

 

 

With 6v input, the mono amplifier will barely be able to output 0.2 watts of power while dissipating about 0.1 watts of energy... so in essence, it's about 60% efficient.

Even with 12v input, the LM386 can onlyh produce around 0.8w of power without horrible distortions (3% THD) - at 10% THD it can do 1w maybe but it would sound horrible.

 

-----------------

 

Something very easy to make would be an audio amplifier based on TDA2050 - they're discontinued as they're ancient but they should still be easy to find and there's also lots of chinese fabs still making them.

 

TDA2050 likes higher voltages, you get best output with +/- 25v or +50v  (the amplifier can be powered with negative and positive power supplies, or with a single power supply) but it will still produce sound with as little as 10v on the input (so that makes it easy to power with a 12v from computer, or with a ~18v from a laptop adapter).

 

 

On the right axis you have the voltage (split power supply, +/- voltage, so for single power supply you multiply that by 2)

So for let's say 12v (+/-6v), this mono chip will only do about 2-3 watts but if you power it with around 18v (let's say from laptop adapter) it can probably do close to 10 watts (i'm looking at the +/- 10v point) and if you use a transformer to produce +/-15v or +/- 20v, you'll get 20w or more of good quality sound (0.5% THD, way better compared to LM386's 3% THD)

Or maybe you can buy a +48v power supply from eBay (lots of these were used for telecommunication, phone stuff, power over ethernet switches, so they're cheap) or from reputable stores and then you'll have up to 40w of audio per channel with suitable cooling of the chips (or they'll burn up).

 

The chip is a mono amplifier, so you basically need to make the same circuit twice :

 

 

The pictures in the datasheet are scanned badly (it's that old chip, they scanned the pictures to put them in pdf, so i drew over some spots that could have confused beginners on the right) .. split power supply design is more straight forward, really basic, but like i said, it's easier to find a 12v or higher power supply, than make one using transformers and bridge rectifiers and so on.

 

And don't forget.. the chip MUST BE HEATSINKED ... and separate heatsinks for each chip. The chip's only around 70% efficient, so if you output 10w of audio, it will make 3-4 watts of heat, and the chip by itself can maybe dissipate maybe around 1w of heat only. Heatsink is required to not blow it up.

 

Here's a bunch of circuits with it : http://www.eleccircuit.com/tda2050-amplifier-stereo-35w-75w/

 

Here's a hi-fi project with it , but it uses split power supply mode so you can't use an atx power supply with it: http://diyaudioprojects.com/Chip/DIY-TDA2050-Hi-Fi-Chip-Amplifier/

 

You need to use transformer with two secondary windings to get negative and positive voltages (but you don't really need to make that power supply so "beefy" and to use so expensive parts)

Any transformer with 2  secondary windings and at least 6v AC on each winding (at max 18v AC)  will work for a cheap amplifier based on the project at the link above

 

Here's an idea... want to be the cool guy at school, make a 5.1 amp using 6 of these chips and power it from a laptop adapter/xbox power supply anything that can do more 12v or more. You'll have 5-10w per channel which should be enough to make the sound heard in classroom.

 

 

A relatively similar audio chip that's also easy to work with would be LM1875, but this one needs at least 16v (or +/- 8v, and can handle up to 60v) to function  ... see datasheet for single power supply schematic or google for projects made with this chip : http://www.ti.com/lit/ds/symlink/lm1875.pdf