Electronics > Beginners
2 power supplies for a amp
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dazz:

--- Quote from: vol.2 on September 26, 2019, 06:21:01 pm ---
--- Quote from: Zero999 on September 26, 2019, 08:06:19 am ---Yes, that's very true. The original poster should check the power supplies are floating first, before connecting their outputs in series.

--- End quote ---

Thanks. I checked the data sheet and it does look like the - side is tied to ground.

Can you tell me if i can split a 19v switching laptop supply into two so I can power two mono amp boards like the one I linked above?

--- End quote ---

If you're referring to the class D TPA3116s that mariush suggested, I think that's the best way to go. They're a lot more efficient and you will save a lot of trouble, money and energy with those by simplifying the power supply. Not sure what you mean by splitting the power supply to feed two boards, what you would do is to use a singly power supply for both boards, but a laptop brick will probably not  have enough output current for two TPA3116s with 2 ohm speakers.

Do you really need that much power? Because a single stereo TPA3116 board can output 40W+40W with 4 ohm speakers and a single 20V 5A laptop brick

Keep in mind that 100W is not twice as loud as 50W.
vol.2:

--- Quote from: dazz on September 26, 2019, 07:49:11 pm ---If you're referring to the class D TPA3116s that mariush suggested, I think that's the best way to go.
--- End quote ---

I'm referring to this mono board: https://www.ebay.com/p/13016014274

I would two of them for stereo.


--- Quote ---Not sure what you mean by splitting the power supply to feed two boards, what you would do is to use a singly power supply for both boards, but a laptop brick will probably not  have enough output current for two TPA3116s with 2 ohm speakers.

--- End quote ---

I have Bose 141 speakers, they are ~6ohm.

I mean I want to use my 19V power supply to feed both mono boards. I've got a few around, one of them says 4.74A. There was this review that tested the TPA3116 mono board on youtube, and he shows that the boards take about 1.75A each at 20VDC under a 4 ohm load. I am thinking I could get away with splitting the power from the one 4.75A laptop supply to both mono boards. Does this sound right, or am I missing something?

Thanks,


vol.2:
I meant to split the one 19VDC laptop supply to power 2 of the mono TPA3116 boards because I need to power 2 of them for stereo. I don't know if that's safe.

Thanks,

dazz:

--- Quote from: vol.2 on September 26, 2019, 08:14:17 pm ---
I have Bose 141 speakers, they are ~6ohm.


--- End quote ---

Couple of things:
1. Those are 40W speakers, so having a 100W+100W amp makes no sense, unless you want to blow your speakers.
2. If you're gonna be using 6 ohm speakers, you'll never get 100W from one of those boards. The 100W output assumes 2 ohm loads. So you're much better off with a single stereo (BTL, not PBTL) board and a single power supply.
mariush:
It would be safe.

Note that class D power amplifiers like these TPA ones are more efficient, let's say up to 85-90%... compared to class AB that are ~50% or even less.
So if the guy measured the power consumption at 20v 1.75A, that's around 35w in, so assume around 25 watts of actual audio output. Basically, he ran the amplifier at around 2x12-15w.
How much power the amplifiers will use will depend entirely on how much you amplify everything, on your volume knob position, how per-amplified your audio signal is and to some degree depends on the audio speakers and their impedance...

Yes, there's no reason why you couldn't run two mono amplifiers on a single such power supply. Just keep in mind that at very high volumes the two amplifiers may draw high current for brief moments of time and that could cause the power supply to enter in "over current protection" or restart itself ... so you may get "hiccups" (power supply turning on and off)

edit :  I recommend going with my version because you get it in a nice package, with volume control, dc in jacks, input and output connectors and everything.
It's also in the standard configuration of 50w + 50w max, so chances are you're not gonna damage your speakers if you accidentally set the volume to maximum ...
With two of the other (same chip but configured in BTL mode, mono) you may accidentally damage your speakers and you'll also have to do extra DIY (case, add volume control etc etc)
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