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Watt for speaker and Watt for power consumption, Class D and AB

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jst

jst

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Here is what you have with the bridged amp running on 48V into 8 ohms, at the point of clipping (ignoring losses). Red and Blue are the single ended amp voltages fed to speaker + and -. The difference between these divided by 8 ohms gives the green curve, current. So you see your power supply is tasked with providing 6 amp peaks. When running L and R it will be 12 amps. However, after looking at the data sheet of the supply you want to use, I think it can give you those peaks or at least close to it.


View attachment 160517
I havent bought the Meanwell 48v 7.3A , still using brick 48v 5a which i suspect isn't up to the spec. I'll just wait for the multimeter I'm buying to check further tomorrow.

But based on what Raindog123 said, volume matters too, and since 9 o'clock is my sweet spot for listening so I think it doesn't matter much anymore since if more power coming and it's too loud then I will turn it down. I'll just test it for the sake of curiousity.
 
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jst

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Yor maths was right. It could be running in bridge mode but, I suspect it's 150W into 4Ω. You could not sustain 150W into 4Ω both channels driven. 22V * 2 * 5A = 220W.

What do want? A desktop amp to sit next to your PC, along with a pair of speakers or a basic hifi system where you would be sitting a few metres back from the amp and speakers?
I'm using PA speakers/karaoke speakers for my PC, only 1 metre distance from where I sit. Come to think of it, it's too loud lol, bookshelf speaker 6.5 is actually enough from where I'm sitting, kinda regret getting this spker.
 

kchap

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I'm using PA speakers/karaoke speakers for my PC, only 1 metre distance from where I sit. Come to think of it, it's too loud lol, bookshelf speaker is actually enough from where I'm sitting, kinda regret getting this spker.
It seems power is not really an issue. You need a volume control!
 

Raindog123

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I'm getting a multimeter so I'll test it tomorrow how much voltage is running thru my speaker cable at 9'oclock volume.

Totally! You can either measure the current (by getting into the circuit) or voltage (across the speaker or amp terminals). The two are still related by Ohm's law V=R*I (or Vrms=R*Irms). (My point above simply was that the Vout is not the same as the VDC of the power supply.)

Good luck, let us know the outcome! (And don't forget to put your multimeter in AC mode. :) And maybe feed your system with a pure tone...)
 
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jst

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Result is weird I only get 1.9v-2.0v

Multimeter black is put at COM, red at VΩmA, setting is ACV 200.
Then play Sinewave 50Hz, black to speaker negative, red to speaker positive.
lcd shows 1.9-2.0 , how come it's that low ?

Speaker resistance varies from 6.8-7.8Ω
 

Raindog123

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What do you get if you measure your mains from the wall? Like this: :)

DD5A18A7-2296-4284-A172-7CD79415FE8A.jpeg
 
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jst

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What do you get if you measure your mains from the wall? :)
230v
dc is correct 48v , checking from the jack.

speaker impedance when aiyima turned off 6.8, but when I turn on the aiyima it changes to 4.0 ohm lol. So the amp is feeding 4ohm to my 6.8 ohm speaker ?

I use 2 multimeters and both result the same. I'll be getting another one, a clamp multimeter so I can check the current. Shld arrive in 1-2 days.

It's quite fun getting readings from a device lol, as long as it's accurate or close enough. I still wonder about the voltage from speaker only 0.07 -2 , tried dc, only got 0 , but I read that speaker is AC.

----
Tested on Azur 640a , impedance is 3.3ohm, ACA 1.0v , this is weird. I'll just wait for the new multimeter.
 
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Raindog123

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So, if you believe your voltage readings, you output P=Vrms^2/R = 4/6W, or approximately 2/3W. [Which might actually be all you need.]

1) Do you know your speaker sensitivity (in dB)?
2) What is the measured voltage if you play real music at your typical volume?
3) What is your listening distance from the speaker?
 
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jst

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So, if you believe your voltage readings, you output P=Vrms^2/R = 4/6W, or approximately 2/3W. [Which might actually be all you need.]

1) Do you know your speaker sensitivity (in dB)?
2) What is the measured voltage if you play real music at your typical volume?
3) What is your listening distance from the speaker?
1. spec says 87db for wharfedale 9.2, this DAT speaker (local brand) is 90db
2. 00.2v-00.3v (sine wave 50hz=1-2v)
3. 1 meter


It can't be the aiyima that gives faulty reading, because my azur 640a also only gives 1.0v lol , probably this multimeter is faulty for voltage(but it reads 48v exactly from 48v 5a adapter), i'll wait for the new one in 1-2 days.
 

Raindog123

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00.2v-00.3v (sine wave 50hz=1-2v)

- Sorry, I am not sure I understand your numbers. Is it “zero-point-two to zero-point-three volts”? (Aka 200mV to 300mV?)

- What is the measured voltage if you play 100Hz and 1,000Hz (1kHz) test tones? :)
 
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jst

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- Sorry, I am not sure I understand your numbers. Is it “zero-point-two to zero-point-three volts”? (Aka 200mV to 300mV?)

- What is the measured voltage if you play 100Hz and 1,000Hz (1kHz) test tones? :)
That's as written on the multimeter, but we shld read it as 0.2v , sine wave 50hz= 01.0-02.0v

it reads dc voltage correctly though. (sry for the blurry image but it's readable) ampere varies wildly but highest is 4.0A (from 32v5a)

Screenshot_456.jpg


100hz=1.4v
1khz=0.2-0.3v
 

Raindog123

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I am still confused with the voltage numbers your report. Can you maybe post a pic of the multimeter - the screen and the dial - while taking your measurements? :) I am also curious how you wire the multimeter to measure the [DC] current (your ”amperes“), can you post a pic too?

Again, a couple of [AC] volts is all you might expect while listening a test tone from a 90-dB sensitive speaker at 1m. They should not fluctuate though - jump between 1 and 2 Volts. If they do, something might be wrong with your setting.

It’s 3am here, the family is sleeping. Tomorrow morning I’ll measure my setup, and we can compare numbers…
 
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jst

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I am still confused with the voltage numbers your report. Can you maybe post a pic of the multimeter - the screen and the dial - while taking your measurements? :) I am also curious how you wire the multimeter to measure the [DC] current (your ”amperes“), can you post a pic too?

Again, a couple of [AC] volts is all you might expect while listening a test tone from a 90-dB sensitive speaker at 1m. They should not fluctuate though - jump between 1 and 2 Volts. If they do, something might be wrong with your setting.

It’s 3am here, the family is sleeping. Tomorrow morning I’ll measure my setup, and we can compare numbers…
I just tried using my other system, vintage Sansui AU-555A from 1978, the result is more or less the same, 3 setups and they all produce more or less the same result from 0 - 3v, so it's probably this multimeter is bad. Will try a different brand in a few days, still a cheap one, but it has clamp for AC current.

The AC voltage measurement from speaker isn't fluctuating, it's just I forgot between hz (50-100-1khz) I used, which adapter I used (32v/48v), and the volume setting

Using this Sansui is easier coz the speaker is small and it can hold the black and red probes so my hand is free to turn the volume knob, but still the result is the same, so probably I got a faulty multimeter for AC voltage even though it seems to be measuring other such as dc voltage and impedance correctly. (but it can detect my AC power correctly at 220-230 too lol, weird)

Here's the multimeter I use
Screenshot_457.jpg

Here's the probes, I put red/black probes in the + - of one of the speakers (right speaker)
Screenshot_458.jpg

Now that my hands are free, I can turn the volume knob and take pictures better, even until 12 o clock volume, the voltage is only 3.7 Volt.
I use 100hz coz this small speaker probably got its 50hz cut it produces no sound using 50hz test tone.
The voltage here wasn't fluctuating, I turned the volume higher and took pictures from 7 to 12 o'clock.
Screenshot_459.jpg Screenshot_460.jpg Screenshot_461.jpg Screenshot_462.jpg


Here's how I measure the current, but it fluctuates wildly, I just capture the highest one, which is 4.35 A , can go as low as 0-2 as well but that's highest captured. There's a dc volt Ampere tester with lcd showing its V and A, though, but I don't have it so I use this method. Seems like it's not that bad if this black brick adapter can produce above 4A with 5A spec.
Screenshot_463.jpg

Should get something like this for knowing dc V and A in probably more acccurate reading.
Screenshot_464.jpg

====

I also have KWH Meter. It's something like this.
5894682_af303c51-7681-4371-bac9-152d168192fd.jpg.webp

And using 48v5a Adapter on my Aiyima A07 plugged into this kwh meter here's what it shows.
0.064Ampere LOL
Screenshot_465.jpg

And here's the Watt , only 6.4
Screenshot_466.jpg

I wonder if it only uses less than 1A and only 6.4W, can I even use something like this LOL ? a 12v 1A adapter.
Can I try it though ? it won't explode or do anything weird, right ?
53084504_4e321641-74df-4070-8aa3-ea7369dd887e_600_600

CA Azur 640a v2 uses 27 watt with volume 10 o'clock and 29watt at 11 o'clock thats already loud enough, standby using 10.8w. Turns out amplifiers are not power hungry.

Screenshot_467.jpg
 
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kchap

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What are you trying measure? If it's the power output you normally do that using test signals and dummy loads. Sending full power tones into the speakers could damage your speakers and send you deaf:) If you use music to measure the output powerthe difference between the average power and pk power can huge, between 20 and 30 dB. Here is a nice output from Audacity Restorer-John's Post #3 It really highlights the difference between the peaks and the average. Measure with the an AC voltmeter you will detect just a a few volts. Use a CRO or a peak level meter and will see 10s of volts.
 
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jst

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What are you trying measure? If it's the power output you normally do that using test signals and dummy loads. Sending full power tones into the speakers could damage your speakers and send you deaf:) If you use music to measure the output powerthe difference between the average power and pk power can huge, between 20 and 30 dB. Here is a nice output from Audacity Restorer-John's Post #3 It really highlights the difference between the peaks and the average. Measure with the an AC voltmeter you will detect just a a few volts. Use a CRO or a peak level meter and will see 10s of volts.
Just measuring realtime voltage sent to speaker by amplifier using normal volume we're comfortable with. You shld try and share your Aiyima A07 with whatever adapter you're using so we can compare our numbers. The same variable we all have would be Aiyima A07 if you have it. I know Raindog123 has it from his posts, he even bought two iirc.

BTW I have a kwh meter and it shows that it only uses 0.06A with Aiyima A07+48v5A and the watt is 6.4Watt (3.2w/ch?) , this thing is for power consumption though, but I can probably assume using it as watt coming out from my speakers. I tried using hairdryer and it jumped to 196watt, so this kwh meter is not wrong.
 
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tonycollinet

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I hope you are not measuring current by putting the probes on the two speaker terminals. If you are, then you are short circuiting the amplifier output through the meter.

To measure current you need to put the meter in line with the speaker wire (disconnect wire from one speaker terminal then have the meter between the speaker terminal and the speaker wire).

Your measurements are not a surprise. This is a very cheap meter, and it's lowest AC range is 200V measuring below 5V is not going to be very accurate at all. (It is rated as 1.2% - if that is a percent of full scale, then you are already at +/- 2V error)

Also - I can't find out if it is a "True RMS" meter - which suggests it isn't. That means it will only measure sine waves accurately. You won't get any sensible measurement of music waveform voltages. (Though I think you are sending sine waves)

Finally speaker power to perceived volume is logarithmic. Typically you will need to go 10x in power to perceive a doubling in volume. So if you (for example) have a 50W amp which at full volume is STUPID loud, then at 5W it will be half of STUPID loud. So a normal listening volume might be just in the 1W to 2W region. SO probably 2-4V at a sensible volume is about right, depending on speaker sensitivity.

Also bear in mind that speaker impedeance varies significantly accross the frequency range. Depending on the frequency of the signal you are sending, and the speaker's complex impedance, it could be as low as 2ohm, or much higher than 10.
 
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jst

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I hope you are not measuring current by putting the probes on the two speaker terminals. If you are, then you are short circuiting the amplifier output through the meter.
I kinda did, but ppl do that on youtube, in fact I use their method, so many of them use that I've watched a bunch of vid. Nothing is wrong with my speakers though. I don't think black and red probe is connecting, unless it's used as a buzzer or checking connection , but just guessing, this is my first day using a multimeter lol. But even if its used as a buzzer, it won't connect black and red, unless the thing being tested is at fault and somehow connects, which then also connects black and red, while + and - of a speaker is not connected to begin with.

Look at this, it's not me, I screenshot it from youtube vid, many vids do it like that
Screenshot_468.jpg



To measure current you need to put the meter in line with the speaker wire (disconnect wire from one speaker terminal then have the meter between the speaker terminal and the speaker wire).
Ah I see, is it on the Positive or the Negative ?

Your measurements are not a surprise. This is a very cheap meter, and it's lowest AC range is 200V measuring below 5V is not going to be very accurate at all. (It is rated as 1.2% - if that is a percent of full scale, then you are already at +/- 2V error)
Yea it is, but it does the job and I can live with 2v error if the measurement is as I expect like since I use 48v adapter then I would expect it's close to that (5% error), anyway the problem I'm having or trying to solve is not relevant with the price of the multimeter. Ppl on youtube doing the same test using more or less the same model and they have different result.

Also - I can't find out if it is a "True RMS" meter - which suggests it isn't. That means it will only measure sine waves accurately. You won't get any sensible measurement of music waveform voltages. (Though I think you are sending sine waves)

Finally speaker power to perceived volume is logarithmic. Typically you will need to go 10x in power to perceive a doubling in volume. So if you (for example) have a 50W amp which at full volume is STUPID loud, then at 5W it will be half of STUPID loud. So a normal listening volume might be just in the 1W to 2W region. SO probably 2-4V at a sensible volume is about right, depending on speaker sensitivity.

Also bear in mind that speaker impedeance varies significantly accross the frequency range. Depending on the frequency of the signal you are sending, and the speaker's complex impedance, it could be as low as 2ohm, or much higher than 10.

I just want to know how many watts is the sound I'm currently listening/outputted by the amp, at a volume I'm comfortable with.

Anyway, using the probe like you mentioned, is that applies for impedance too or just voltage ? but impedance is different when I try with just the speaker not connected to an amp (6.8-7.8) compared to connected to an amp (stay at 4)


=====

If anyone with Aiyima A07 have the time pls post your result too for comparison.
 
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tonycollinet

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You can't measure impedance with a meter like that (impedance is frequency dependant), just the coil resistance at DC. You also CANNOT measure resistance with the amp connected (as you are also measuring the amp - and even worse if the amp is outputting voltage that will override the measurement)

Ideally you need to find the frequency dependent impedance curve for your speaker, and use a test frequency at which the impedance is around nominal (6 ohms) with a sinusoidal test signal. (This is more likely to be at the higher frequency end - perhaps around 1kHz)

Here is an impedance curve from Amirms recently measured speaker (red curve)

index.php


I'd forget current measurements if I were you - too much chance of damaging something since the meter is a short circuit in current mode.
 

Tangband

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Remember that MOST linear power supplies for power amp are unregulated. Thus needs to have big power capacitors so the supply dont sag under the load.

And most switched mode power supplies are REGULATED. Its more load-friendly. It dont sag as easy. In a well made switched mode regulated supply , there is less need for big capacitance, depending on the high switch frequency ( often 100 kHz compared to the linear 50 Hz ) meaning the capacitor will be refilled much more often than the capacitor in the linear power supply.

In a half bridge switched mode supply thats regulated, you can unfotunately have something called bus pumping.
 
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jst

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I'd forget current measurements if I were you - too much chance of damaging something since the meter is a short circuit in current mode.
Nah, there's something called CLAMP MULTIMETER, you just put the cable inside the circle and it will read the current.
No touching involved.

Screenshot_469.jpg
 
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