How much volts and amps required ?

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deletezer

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Joined 2018
#1
I'm making a diy bluetooh speaker. Speakers are two 22w rms 4 inch 4 ohm JBL120SI (44w total I guess). Amplifier Im using is Sanwu HF183 TPA3116 50w+50w. My questions are-

1. How much volts and amps of power should I provide the amplifier to run both speakers at just below their full potential ? Like 40w so that speakers dont produce peak sound and last longer.

2. Also there are various combinations of volts and amps that give the same amount of watts. For eg. a 12V 4A supply gives 48w and 24V 2A supply also gives 48w. Which one will be more suitable and safe for ampli and speakers ?
 
#2
What does the
Sanwu HF183 TPA3116
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amplifier say it needs?
It *must* be somewhere in its user manual, datasheet, spec sheet ot plain "sales" page.
Just feed it what it asks.

Hey, I looked it up for you:
Supply voltage: DC 8 - 26V (DC power supply)
Current: 5A

Amplifier chip: digital amplifier chip TPA3116 with heat sink, stereo, power 2X50W.(More than 24V 3A switching power supply is recommended, it can’t use the transformer to power supply)
Click to expand...

meaning: get an SMPS rated 24V DC, 5A or slightly more.

Easy, huh? 😛
 
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#3
You have two 22W speakers (4 Ohm) and one Sanwu amplifier with two channels, thus one amplifier per 22W speaker. Then, you should not design the supply such that the two amplifiers deliver much more than 22W. You may design for 30W in 4 Ohm.
30W in 4 Ohms requires a supply voltage of 16V.

Two times 30W (30W per channel) means 60W total. Then we multiply the 60W with 1.25 to included generous amplifier losses which result in 75W (minimum).
16V and 75W is a current of just below 5Amp.

NB: Just read Mr. Fahey's posting. You may even supply it with 24V but then the theoretical output power is above 60W per channel in 4 Ohm. Then you need even more current with two 4 Ohm loads. 60W+60W=120W. In such case you should go for an 8 Amp supply. It depends on if you want to limit the amplifier below its potential and the maximum speaker power.
 
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#4
That will work. I know that the amplifier will draw only that much current that it needs. If I supply it with 24V and 5A, it will only take 24v and 2A as per the speakers require (44W). But what will happen if I supply it with 12V and 4A(44W also). Which supply will be the best so the sound output will be around 40w with min. THD ?
 
#7
deletezer said:
Your answer is unclear. Are you telling me to design a 2x30w setup or reduce the power supply ? I wanted to know which combination of power supply ( 12V 4A or 24V 2A ) will be best for my 2x22w setup.
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You put a power limit on an amplifier by setting the supply voltage such that when clipping starts you have reached the power limit you want. After having decided the supply voltage, you calculate the power and current you need.

BUT, as a class D amplifier is actually nothing more than a bipolar Buck-converter, it can convert input power to output power with high efficiency. In other words, the output current from a class D amplifier may be higher than the average input current. It is not like for a class AB amplifier.

Therefore when you want to calculate the current, you calculate it from the maximum output power of the amplifiers (together) and assume an efficiency of around 80% of the amplifiers.

Say you used a 24V/2A supply, you would run into current limitation/overload much before you reached voltage clipping. Normally, current limitation is to be avoided because it is much less precise and may result in the amplifier switching off.
 
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#8
deletezer said:
I have a 20V and 4.5A power adapter(90w). Will it work or will it blow my 44w setup ?
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Your 19.5V/90W laptop supply will work well with the amplifier for music (trivial). If you do testing with a sine-wave and full power, you will run into current limitation at the top.
The reason that music will work well is the "crest-factor" meaning that no (music) signal has a high power content for very long. For short peaks, the energy in the power line decoupling capacitors will supply the current. This is why good decoupling capacitors are important.

With that 20V power supply, your amplifier can deliver more than the 22W specified for the speakers. It is and old discussion what is most safe for the speakers: an amplifier power that exceeds the power of the speakers or an amplifier power below the speaker power.
If the amplifier has more power than the speaker you can overheat the speaker coil even with a clean sine-wave signal. It is rare. If the amplifier has less power, it may start distorting and loose control of the speaker. Such is more likely to damage the speaker.
 
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#10
deletezer said:
But what will happen if I supply it with 12V and 4A(44W also).
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You don't supply it with "12V and 4A". You supply 12V and then it will draw whatever current matches the speaker impedance and signal level. Be aware that the speakers and hence the amp do not know that the speakers are 44W; all they know is the speaker impedance. There will be an optimum supply voltage: below this you get less output, above this you may damage the speakers or the amp. At this voltage the amp will draw a particular current at max output; your PSU needs to be able to supply this.
 
#11
The amp rating is not something you supply, but as we call "availability or capable-of".

Amps is a rating that is the result of a voltage across a given impedance/resistance(your amplifier has impedance/resistance.) You control the factors of U(voltage) and R(impedance), with I (current) as a result. And boom, ohm's law. 😛

Hence, your power supply is 'capable of providing 4A'. If you exceed that limit, your supply will either blow up or go into protect mode.
 
#12
FauxFrench said:
Your 19.5V/90W laptop supply will work well with the amplifier for music (trivial). If you do testing with a sine-wave and full power, you will run into current limitation at the top.
The reason that music will work well is the "crest-factor" meaning that no (music) signal has a high power content for very long. For short peaks, the energy in the power line decoupling capacitors will supply the current. This is why good decoupling capacitors are important.

With that 20V power supply, your amplifier can deliver more than the 22W specified for the speakers. It is and old discussion what is most safe for the speakers: an amplifier power that exceeds the power of the speakers or an amplifier power below the speaker power.
If the amplifier has more power than the speaker you can overheat the speaker coil even with a clean sine-wave signal. It is rare. If the amplifier has less power, it may start distorting and loose control of the speaker. Such is more likely to damage the speaker.
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I understood everything,but still didn't find my answer. Sorry for not knowing but you are saying that overpowering the amplifier than what speaker need will overheat the coil and under powering will create distortion at higj volumes. In that case what volt and amp of power supply should I use so that it doesn't creates much distortion in high volumes and will not overheat speaker coil. Again my ampifier supports 50w+50w or a totalspeakers. rms but all I wanted it to do is drive my two 22w 4ohm speakers. Mr. FAHEY said to use 24V and 5A supply(120w) but that will completly overpower the amp than what is needed(44w). Just tell me what you recommend me to supply it with ?
 
#13
I proposed 16V and 5 Amp and that is what I would use. One amplifier channel for each 22W speaker.

I wrote "...may overheat...". If you leave a 22W speaker with a constant amplitude signal causing 40W in the speaker for a long time, the speaker coil will (slowly) heat up and may in the end burn. For music with transients lasting perhaps 100ms, the speaker coil will not get excessively hot due to the thermal mass and no damage is caused.

If the supply voltage is lowered to an output power such that clipping occurs at 10W, the music signal will more frequently run into clipping. At heavy clipping (heavy distortion) the amplifier looses control of the speaker movement such that the coil may deviate from its correct linear movement in the narrow magnet air-gap and the coil may strike the magnet. Such may cause permanent mechanical damage even at a power considerably below the rated power of the speaker.
 
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#14
Thus, both an amplifier limitation above and below the rating of the speaker can cause damage to your speaker but for two different reasons.

Personally I would choose 30W amp power for a 22W speaker. This corresponds to 16V/5A with a BTL coupled class D amplifier.
I would have no hesitation in using a 20V (19.5V) supply I already had available for normal music.

Understand the power rating of a speaker such that it is a power level the manufacturer guarantees the speaker can stand for long with a clean input signal. In reality it can stand more. It is not so that above that level the speaker is just burned in a moment. The magnet strike is more unpredictable because it happens in a fraction of a second.
 
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#15
You sir FauxFrench are a genius and answered all my questions. Thankyou. But I couldn't find a 16V and 5A power adapter. Since the ampli can't take power from transformer. I will have to use power adapters such as a laptop charger. These are the options available near to the supply you recommended (16V and 5A. 80w). -

20V and 4.5A 90w
20V and 3.25A 65w
19V and 4.7A 90w
19.5V and 2.31A 45w
19V and 3.16A 60w
19.5V and 3.34A 65W
15V and 5A 75w

Which one should I use ?
 
#16
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