How to setup this oscilloscope to test for clipping?

[GabrielPhoto]

Hi!
So I was watching car audio guys using cheap oscilloscopes to set gain so I figured I would try it for home but maybe this device is not enough for home testing?
I am confused like what voltage setting to use for example.
In the end, all I want to see is the sine wave and make sure I am not clipping so any suggestions will be appreciated.
Thanks!

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[Doodski]

Hi @GabrielPhoto.
Set the O-scope for 20 V / division (20 V/div.)
Then use this sine wave generator to feed a 1 kHz sine wave to the amplifier.
Raise and lower the amplifier output till you see clipping occur.
Make a measurement at the clipping voltage level and then you can calculate the RMS Wattage output of the amplifier.

Use formula.>>>
Watts RMS = (Vpeak * 0.707) ^2 / R load
Rload = Resistance of the speaker loads.
Vpeak = the voltage level at clipping.

 

[GabrielPhoto]

Hi @GabrielPhoto.
Set the O-scope for 20 V / division (20 V/div.)
Then use this sine wave generator to feed a 1 kHz sine wave to the amplifier.
Raise and lower the amplifier output till you see clipping occur.
Make a measurement at the clipping voltage level and then you can calculate the RMS Wattage output of the amplifier.

Use formula.>>>
Watts RMS = (Vpeak * 0.707) ^2 / R load
Rload = Resistance of the speaker loads.
Vpeak = the voltage level at clipping.

Thank you, I will try that!!!

 

[DVDdoug]

I'd recommend testing without speakers first. High-power continuous tones can burn-out speakers.

It might clip at a slightly-lower voltage with a speaker load, but that will give you a ballpark idea. If you are close to that with music and speakers you might be clipping but if you are far from the maximum you are not.

It's hard to "see" clipping with regular program material, and you don't know the undistorted waveshape. But you can usually tell if you've hit the voltage limits if you turn it up and peaks don't go any higher.

 

[GabrielPhoto]

I'd recommend testing without speakers first. High-power continuous tones can burn-out speakers.

It might clip at a slightly-lower voltage with a speaker load, but that will give you a ballpark idea. If you are close to that with music and speakers you might be clipping but if you are far from the maximum you are not.

It's hard to "see" clipping with regular program material, and you don't know the undistorted waveshape. But you can usually tell if you've hit the voltage limits if you turn it up and peaks don't go any higher.

As what I am testing is mostly for Bass notes, ie Hovereze, TR devices ...should I still use the 1Khz signal for the check or something lower?
Thanks guys

 

[NTK]

I'd recommend getting a scope with real-time FFT capability. Almost all but the absolute cheapest digital scopes have it. Run a single tone sine wave, such as 1 kHz or another frequency, and look at the spectrum. When you see a quick rise in the harmonics (i.e. increase in harmonic distortions), that's clipping.

Using arbitrary signals (e.g. music) will be more difficult. You'll need to record the source and output and compare them, and will likely require offline analysis.

One thing you must remember: Oscilloscope inputs are ground referenced. The -ve input of the scope is connected to ground. When you hook up the scope to whatever you are testing, you are shorting its -ve output to ground. Make sure what you are measuring is also ground referenced with its -ve at ground potential. You may be able to cheat with non-ground referenced signal with a battery powered unit that is not connected to the AC mains. Or you can use 2 channels and use math function (ChA - ChB) for pseudo-differential measurement. Or you can use differential probes (expensive).

 

[Doodski]

@GabrielPhoto.

I'd recommend testing without speakers first. High-power continuous tones can burn-out speakers.

It might clip at a slightly-lower voltage with a speaker load, but that will give you a ballpark idea.

Excellent point made here^^^.
It will get loud for sure using my method. If you follow @DVDdoug's method of running the amp without loads/speakers connected then you may estimate the clipping level dependent on the amp type and how old it is.
@GabrielPhoto what is the make and model of your amp and how old is it?

 

[Blumlein 88]

Been some time since I messed with an Oscope trying to find clipping. When I did I found it easier to use two closely spaced tones. As an example I made up some tones in Audacity. Real world is likely not to be quite this clean, but will illustrate why I preferred two tones.

Below is a mix of 100 hz and 110 hz. They will go thru periods of adding constructively and destructively. This lets you see the peaks of constructive addition as you approach clipping without having to hard clip the whole waveform. Bottom wave is not clipped. Middle is 1 db clipped and top is 3 db clipped.

 

[DVDdoug]

Or... Measure the approximate peak levels under your "normal loud" listening conditions. Then make a power calculation from the formula Doodski gave you and compare to your amplifier's power rating.

You can't always trust the manufacturer's specs but if you have a 100W amplifier and you're only using 10-20W you are nowhere near clipping.

 

[GabrielPhoto]

@GabrielPhoto.

Excellent point made here^^^.
It will get loud for sure using my method. If you follow @DVDdoug's method of running the amp without loads/speakers connected then you may estimate the clipping level dependent on the amp type and how old it is.
@GabrielPhoto what is the make and model of your amp and how old is it?

I run a Denon 3800h. I am using two of the LFE outputs (one set to tactile transducer) and they go into a MiniDSP.
From that MiniDSP I am sending 3 of the outputs to a pair of NX6000D and a Buttkicker BKA-1000-4 amp.
The other output is going to a 2nd MiniDSP which is for my subs AND dayton bst-300ex shakers. I got a Crown xls 1002 running the 3 shakers (2 as an 8ohm load on one channel and the other as a 4ohm load on the other channel).
I think that covers the important part.

 

[Doodski]

@GabrielPhoto what is the make and model of your amp and how old is it?

 

[Doodski]

I run a Denon 3800h. I am using two of the LFE outputs (one set to tactile transducer) and they go into a MiniDSP.
From that MiniDSP I am sending 3 of the outputs to a pair of NX6000D and a Buttkicker BKA-1000-4 amp.
The other output is going to a 2nd MiniDSP which is for my subs AND dayton bst-300ex shakers. I got a Crown xls 1002 running the 3 shakers (2 as an 8ohm load on one channel and the other as a 4ohm load on the other channel).
I think that covers the important part.

That is a lot of amp calculations for me. What exact amp will you be testing<?>

 

[GabrielPhoto]

@GabrielPhoto what is the make and model of your amp and how old is it?

I want to test this for the 4 amps mentioned above.
NX6000D(two) , crown xls 1002 and buttkicker amp.
Technically the nx6000D and buttkicker ones are receiving the same signal but with different degrees of boosting and eq from minidsp

 

[Doodski]

I want to test this for the 4 amps mentioned above.
NX6000D(two) , crown xls 1002 and buttkicker amp.
Technically the nx6000D and buttkicker ones are receiving the same signal but with different degrees of boosting and eq from minidsp

OK. Give me a few minutes to gather details and so we can see what kind of peak voltage clipping levels we are dealing with and how loud that would be.

 

[GabrielPhoto]

OK. Give me a few minutes to gather details and so we can see what kind of peak voltage clipping levels we are dealing with and how loud that would be.

Thanks man, really appreciated!!
To give you an idea, one of the NX6000D running my Hovereze that is pretty much only doing from 1hz to 40hz for those drivers.
The one doing HezeBack is doing like 7hz to about 80Hz.
The Buttkicker is doing from about 12hz to 40hz.
The Crown XLS1002 is a bit odd with the shaker but mainly doing from about 10hz to 80hz.
Not sure if any of that matter LOL

 

[Doodski]

@GabrielPhoto

Behringer NX6000D
What loads (R) are there for this amp? (I need to know for calcs.)

Buttkicker BKA1000-P
What loads (R) are there for this amp?

Crown XLS1002
What loads (R) are there for this amp?

 

[GabrielPhoto]

@GabrielPhoto

Behringer NX6000D
What loads (R) are there for this amp? (I need to know for calcs.)

NX6000D
Both of them have a 4ohm load on one channel and an 8 ohm load on the other channel.

Buttkicker BKA1000-P
What loads (R) are there for this amp?

This one is a 4ohm load

Crown XLS1002
What loads (R) are there for this amp?

This one has 4ohm load on one channel and an 8 ohm load on the other channel.

 

[Doodski]

Due to not having the actual units on hand for measurements estimates are required. If any questions just ask.

Behringer NX6000D
Both of them have a 4 ohm load on one channel and an 8 ohm load on the other channel.
4 Ohms per channel, stereo: 2 x 3000 W RMS @ 154.9 V peak @ 38.7 A peak.
8 Ohms per channel, stereo: 2 x 1600 W RMS @ 160.0 V peak @ 20.0 A peak.

Buttkicker BKA1000-P
This one is a 4ohm load.
2 Ohms 1300 W RMS @ 72.1 V peak @ 36.1 A peak.
4 Ohms 920 W RMS @ 85.8 V peak @ 21.4 A peak.

Crown XLS1002
This one has 4 ohm load on one channel and an 8 ohm load on the other channel.
NOTE: I used the max power output spec from the ASR Crown XLS1002 Test Review.
4 Ohms per channel, stereo: 2 x 281.0 W RMS @ 47.4 V peak @ 11.9 A peak.
8 Ohms per channel, stereo: 2 x 150.0 W RMS @ 49.0 V peak @ 6.1 A peak.

 

[GabrielPhoto]

Does it look like the right device settings as per this screenshot?

 

[Doodski]

Does it look like the right device settings as per this screenshot?View attachment 366741

The volts per division (V/div.) on the vertical scale need to be increased and then test for clipping with no loads connected.