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Topic: Audible symptoms of amplifier clipping (Read 50967 times) previous topic - next topic
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Audible symptoms of amplifier clipping

Reply #50 –
Quote from: pdq on
First, I would expect the same amount of clipping to be much more audible in test tones than in music if the level of the peaks before clipping is the same for both.


Confirmed. There are two main measures of clipping distortion for which more of the measured quantity indicates stronger audibility:

(1) The percentage of the time the wave is clipped.

(2) The percentage of the amplitude of the wave that is removed by clipping.

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Second, there is no guarantee that an amplifier will clip in exactly the same way as by limiting the peak values in a file. The clipped peaks from an amplifier may be more rounded than the flat-topped peaks in the file, and this could make a significant difference in the amount of generated overtones, possibly making them sound different.


While there is no absolute guarantee, there are strong conditional guarantees. The most important one may be the use of inverse feedback which tends to make the clipping in well-designed amplifiers lead to very similar cleanly clipped waveforms.

Audible symptoms of amplifier clipping

Reply #51 –
Quote from: Rich B on
Listening to a test tone is NOT the same thing as listening to music.


Of course they are not the same, but listening with test tones is not necessarily a stupid or meaningless thing to do.

Where is it written on stone that everything has to be the same for it to be useful?

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If it's easier to isolate the symptoms of amp clipping using test tones then it clearly isn't going to tell me how the clipping might sound with real music.


(1) There is nothing iffy about the fact that hearing clipping (and most other forms of distortion) with test tones is easier. It is essentially a truism.

(2) Again, why does everything have to be based on music? 

Admittedly determining the relevance of hearing distortion while listening to test tones may require some abstract reasoning.

Where is it written on stone that relying on abstract reasoning is a bad thing?

All music is made up of a collection of tones - that is the practical meaning of work by Fourier and Helmholtz in the 18th and 19th centuries.  Those findings have stood the test of time - they are still accepted today.

If a device handles tones of a certain frequency and amplitude well, we have a strong indication that music containing the same tones and amplitudes will also be handled well. 

Distortion at a given amplitude and/or frequency is far more easily heard with a few tones than with music because the tones are simple, continuous and less prone to mask distortion.

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There is a whole lot of stuff happening in the music.


That is true, but comments like that may be called by some: "Hand Waving". One form of Hand Waving is referencing a truism without actually logically relating it to the problem at hand.

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How could you argue otherwise?


Just did. ;-)


Audible symptoms of amplifier clipping

Reply #52 –
Quote from: Rich B on
Quote from: greynol on
  • Rich doesn't like being called out on his bullshit: check


I just think there are more tactful ways to get a point across. I disagreed with your view and you start calling me pathetic. What kind of a moderator are you?




I agree!  Greynol miswrote; in fact you only fit one of the four definitions of 'pathetic'.

http://dictionary.reference.com/browse/pathetic


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pathetic [puh-thet-ik]
adjective
1.causing or evoking pity, sympathetic sadness, sorrow, etc.; pitiful; pitiable:
2.affecting or moving the feelings.
3.pertaining to or caused by the feelings.
4.miserably or contemptibly inadequate



Now run off to your other forums and tell them what mean closed-minded meanies there are at HA.

Audible symptoms of amplifier clipping

Reply #54 –
So to wrap up, if the amp isn't clipping into audible distortion then that means that all forms of distortion will be inaudible from the amp? This happens when the maximum voltage or maximum current has been exceeded.

What we haven't discussed is how protection circuitry would affect the sound. I've been told that amps sometimes employ soft clipping features to prevent damage. Is it not possible for amps to compress the sound at their limits depending on the design?

Audible symptoms of amplifier clipping

Reply #55 –
Quote from: Rich B on
So to wrap up, if the amp isn't clipping into audible distortion then that means that all forms of distortion will be inaudible from the amp?
Wat? That's tautological. (Useless as explained by next comment.)

Audible symptoms of amplifier clipping

Reply #57 –
Quote from: Rich B on
What we haven't discussed is how protection circuitry would affect the sound. I've been told that amps sometimes employ soft clipping features to prevent damage. Is it not possible for amps to compress the sound at their limits depending on the design?


Yes, and this is one of the reasons some people prefer tube amplifiers (not to mention how it is used on purpose in guitar amplifiers).


Audible symptoms of amplifier clipping

Reply #58 –
Quote from: greynol on
It would be if clipping constituted all forms of distortion.


So it's not? I'm talking as far as the amp goes.

If the amp isn't clipping, then what other distortion might be audible from the amp?

Audible symptoms of amplifier clipping

Reply #59 –
Quote from: julf on
Quote from: Rich B on
What we haven't discussed is how protection circuitry would affect the sound. I've been told that amps sometimes employ soft clipping features to prevent damage. Is it not possible for amps to compress the sound at their limits depending on the design?


Yes, and this is one of the reasons some people prefer tube amplifiers (not to mention how it is used on purpose in guitar amplifiers).


I'm talking about AVRs. Is it not possible some incorporate soft clipping circuitry to prevent significant audible distortion from occuring? Rather just compressing the sound, but not being as audibly severe?

Audible symptoms of amplifier clipping

Reply #60 –
Quote from: Rich B on
If the amp isn't clipping, then what other distortion might be audible from the amp?

Linear distortion (look up frequency response) could be a fixed built-in bass boost for example, or bass roll-off ... kinda rare these days.
Nonlinear distortion (look up harmonic and intermodulation distortion) ... this is usually quite low these days too, but there are some exceptions especially among tube amps.
The amp might have processing/DSP features ... these can usually be disabled.

Not a distortion, but high noise floor can be audible too. You might hear some noise when you put your ear next to the speaker.
"I hear it when I see it."

Audible symptoms of amplifier clipping

Reply #61 –
Quote
Nonlinear distortion (look up harmonic and intermodulation distortion) ... this is usually quite low these days too, but there are some exceptions especially among tube amps.


So an amp that is not clipping might still have audible nonlinear distortion?

Audible symptoms of amplifier clipping

Reply #62 –
Quote from: Rich B on
So an amp that is not clipping might still have audible nonlinear distortion?


Unless I've forgotten how to read, is that not what xnor just wrote!?

Audible symptoms of amplifier clipping

Reply #63 –
There are some, yes, that for example produce 1% at 10W into 8 ohm. There are even tube amps that produce 5% at 10W. This distortion is not just at the lower end but also in the mids, where our hearing is more sensitive.

edit: but usually the problem is clipping. Combine the wrong amp (low power output or not designed for low load impedances) with the wrong speaker (low sensitivity, low impedance) and you will get into trouble.
"I hear it when I see it."

Audible symptoms of amplifier clipping

Reply #64 –
And just to be clear, it is very easy these days for a competent engineer to design and build an amplifier for which all forms of distortion, short of clipping, are inaudible under normal operating conditions.

Audible symptoms of amplifier clipping

Reply #66 –
Quote from: Rich B on
No word on his SPL levels, but hopefully I'll have some information soon.

It's been three weeks, and this post came just a day after you said you'd ask "him," indicating that it was in progress.

Well?!?

Audible symptoms of amplifier clipping

Reply #67 –
Quote from: Rich B on
If the amp isn't clipping, then what other distortion might be audible from the amp?
Rich,

Have you ever heard any distortion of any kind (excluding frequency response variations) from any amp that wasn't,

a) defective?
b) over-driven?

I have not.

Quote from: Rich B on
I'm talking about AVRs. Is it not possible some incorporate soft clipping circuitry to prevent significant audible distortion from occuring?
To some extent, yes. If you round-over the peaks instead of chopping them off square, there are fewer added harmonics.

I have no idea if that feature is available in any AVRs.  I've seen high-power pro amps with limiters, and some McIntosh amps have limiting.

But obviously, you are changing (distorting) the wave shape and if you "push it" far enough you'll start to hear it.  Again, this is something you can play-with yourself with an audio editor and a limiter effect.  (I think Audacity's default limiter is simply a hard-limiter that clips, so if you are using Audacity you might want check that and maybe use a different plug-in.)

Note that a limiter normally has to kick-in before you actually hit the maximum...  That means the waveform has to start getting re-shaped (distorted) somewhere around -3dB or -6dB (with 0dB referenced to clipping).    The exception would be with a digital file, or with a delay where you can "look ahead" and only process the signal where it would otherwise be clipped.


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Rather just compressing the sound, but not being as audibly severe?
Limiting is a kind of dynamic compression.  i.e. You are reducing (compressing) the dynamic range by reducing the difference between the "loud parts" and "quiet parts".

In fact, if you buy a hardware compressor, you are usually buying a "compressor/limiter".

Audible symptoms of amplifier clipping

Reply #68 –
Quote from: pdq on
And just to be clear, it is very easy these days for a competent engineer to design and build an amplifier for which all forms of distortion, short of clipping, are inaudible under normal operating conditions.


And for a not-unreasoanble price, one can obtain such an amplifier that is sufficiently powerful to seriously damage just about any loudspeaker designed for home use before it clips.

Audible symptoms of amplifier clipping

Reply #69 –
Quote from: Rich B on
If the amp isn't clipping, then what other distortion might be audible from the amp?


Amps aren't the only source of distortion in audio systems. Speakers and human ears generally have far more distortion.

Audible symptoms of amplifier clipping

Reply #70 –
Quote from: pdq on
And just to be clear, it is very easy these days for a competent engineer to design and build an amplifier for which all forms of distortion, short of clipping, are inaudible under normal operating conditions.


I'm pretty sure this has been stated to RichB at least once in all his questions and not learning.

Audible symptoms of amplifier clipping

Reply #71 –
There are now many cheap amplifiers in the market, made in China, that have quoted THD/N of 10%. At about half the power specified for the amp, this comes down to 1% or less.
What is this distortion? Is it damaging to the speakers as well as to the sound quality?

Audible symptoms of amplifier clipping

Reply #72 –
I'm guessing this is just normal clipping such as most amps will exhibit when driven too much. Nothing special, probably just a method so they can print a higher Wattage on the box.

Audible symptoms of amplifier clipping

Reply #73 –
You mean those cheap class-d amps? Those numbers specify the max output power "marketing style", that is well in clipping territory.

Output power at 0.1% THD+N (or if not available then at 1% THD+N) will give you a better idea of what the amp is capable of. If you're into high fidelity then you probably don't want to operate the amp in this range where distortion rapidly rises.

Damage? Well, it's not impossible if you seriously push the amp over 10% all the time.
"I hear it when I see it."

Audible symptoms of amplifier clipping

Reply #74 –
Quote from: Gecko on
I'm guessing this is just normal clipping such as most amps will exhibit when driven too much. Nothing special, probably just a method so they can print a higher Wattage on the box.

That's what I thought about the marketing thing - just confirming that the 1 to 10% is nothing but clipping.

Quote from: xnor on
You mean those cheap class-d amps? Those numbers specify the max output power "marketing style", that is well in clipping territory.

Damage? Well, it's not impossible if you seriously push the amp over 10% all the time.

Right, I do mean those - but the damage would happen in the case of any amp pushed past its capability. The problem with this kind of marketing is of buying an amp that isn't powerful enough for the application, unless one reads and understands the entire spec.