Power amp output

Thread Starter

PaPiャSly

Joined Dec 25, 2022
47
When i hooked up my multimeter to check output voltage of the subwoofer it can reach 17v while playing a 49hz audio @my set gain
"no speaker was connected on this tes"

Whuzi audio ZK TB21 power amp class d 200w 50w*2 R&L 100w subwoofer rated input 12-24 5a

Amp power input was 20v @ 5A

Now when i connect my subwoofer and raise the volume and reach 12v i hear some high tone which is resolved by lowering the volume

My concern is:
Is it clipping or my sub is undermatched with my amp
 
Last edited:

MisterBill2

Joined Jan 23, 2018
18,176
There is a lot of information missing relative to answering your question.
Was the 20 volts and five amps the power that your amplifier was drawing? Or was that what was feeding into the input? AND what sort of amplifier? Not brand or model, but stereo, guitar, PA amp, or car sound booster? What power rating??
 

Thread Starter

PaPiャSly

Joined Dec 25, 2022
47
Iv
There is a lot of information missing relative to answering your question.
Was the 20 volts and five amps the power that your amplifier was drawing? Or was that what was feeding into the input? AND what sort of amplifier? Not brand or model, but stereo, guitar, PA amp, or car sound booster? What power rating??
I have edited my thread, hope ut helps answering my question
 

MisterBill2

Joined Jan 23, 2018
18,176
At that power level and that low a frequency there will probably be mechanical non-linearity (clipping), and that will produce harmonic energy that you could hear. There might also be electrical non-linearity such as clipping or just harmonic distortion without actual true clipping. Non-linear operation certainly produces harmonics, even if there is no actual clipping.
 

Thread Starter

PaPiャSly

Joined Dec 25, 2022
47
At that power level and that low a frequency there will probably be mechanical non-linearity (clipping), and that will produce harmonic energy that you could hear. There might also be electrical non-linearity such as clipping or just harmonic distortion without actual true clipping. Non-linear operation certainly produces harmonics, even if there is no actual clipping.
Here are some sound exmples, there are some phone mic distortion so disregard the high pitch

https://drive.google.com/file/d/1G89ggT0eAIetq_kfb4bW_a-S46ANF9EA/view?usp=drivesdk
 

BobTPH

Joined Jun 5, 2013
8,813
It sounds like a case of inflated specifications to me. Assuming a 4Ω speaker, that is only 36W of output power. A scope would help to tell you what was happening.
 

MisterBill2

Joined Jan 23, 2018
18,176
At fairly loud listening levels my MARANTZ 2235 produces no audible distortion. And that is from a not quite current device. And operation without any speakers connected is not within the specification of most amplifiers, so none of the specifications are applicable, anyway.
 

Audioguru again

Joined Oct 21, 2019
6,673
Google shows a ZK TB21 amplifier using two Texas Instruments TPA3116 power amp ICs.
When the supply is only 20VDC, the two stereo outputs produce 52W each into 4 ohms with severe 10% clipping distortion or 38W with low distortion.
The subwoofer output has the two TPA3116 channels in parallel producing 105W into 2 ohms with severe 10% clipping distortion or 78W with low distortion. Editted

The amplifier uses class-D switching with LC filters on its outputs then it should NEVER be operated without a load because then its series LC filters are a dead short at its switching frequency and the IC is being destroyed.
Your amplifier might now produce a low level tone after being damaged. Maybe the power supply was a switching type that is now damaged and is producing a low level tone.
 
Last edited:

BobTPH

Joined Jun 5, 2013
8,813
When the supply is only 20VDC, the two stereo outputs produce 52W each into 4 ohms with severe 10% clipping distortion or 38W with low distortion.
The subwoofer output has the two TPA3116 channels in parallel producing 105W into 4 ohms
That is a pretty good trick, paralleling two amps to get twice the power into the same load. Still trying to figure out how that works.

Okay, it can, but only of the single amp was current limited to half the current the speaker needed.
 

Thread Starter

PaPiャSly

Joined Dec 25, 2022
47
Google shows a ZK TB21 amplifier using two Texas Instruments TPA3116 power amp ICs.
When the supply is only 20VDC, the two stereo outputs produce 52W each into 4 ohms with severe 10% clipping distortion or 38W with low distortion.
The subwoofer output has the two TPA3116 channels in parallel producing 105W into 2 ohms with severe 10% clipping distortion or 78W with low distortion. Editted

The amplifier uses class-D switching with LC filters on its outputs then it should NEVER be operated without a load because then its series LC filters are a dead short at its switching frequency and the IC is being destroyed.
Your amplifier might now produce a low level tone after being damaged. Maybe the power supply was a switching type that is now damaged and is producing a low level tone.
Oh i didn't know that, thanks a lot for this info
 

MisterBill2

Joined Jan 23, 2018
18,176
The destruction done by vastly overdriving speakers, especially with RAP, is impressive, and complete. And actually quite amusing! after telling two kids not to play that stuff too loud, they did it anyway, and the destruction was more thorough than could have been done any other way. Cones shredded and voice coils torn loose and melted to the pole piece. And at last, quiet so others could talk.
 
Top