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#275308 - 10/16/09 09:56 PM Re: B&K Receiver for M80's [Re: Zimm]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10411
Charles, you're still not getting the point that what those writers termed "clipping" was nowhere near actual clipping.
_________________________
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#275329 - 10/17/09 12:17 AM Re: B&K Receiver for M80's [Re: Zimm]
fredk Offline
axiomite

Registered: 12/06/07
Posts: 7217
Loc: Canada
 Quote:
Don't sell out damn it, too many are counting on you to resist upgraditis!

I'm not selling out, I'm just being fickle. ;\)
_________________________
Fred

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Blujays1: Spending Fred's money one bottle at a time, no two... Oh crap!

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#275351 - 10/17/09 11:40 AM Re: B&K Receiver for M80's [Re: JohnK]
Zimm Offline
connoisseur

Registered: 12/08/08
Posts: 1361
Loc: New Orleans
 Originally Posted By: JohnK
Charles, you're still not getting the point that what those writers termed "clipping" was nowhere near actual clipping.

No, John, you are still not getting the point that I don't believe the major forces in the industry would allow their hand-picked PR mags (as most allege) to publish scientific reports from 1999 to 2009 saying some of their models clip the signal when, in fact, they don't. I think ad dollars would dry up over night.

I guess what you meant to say was I'm still not believing in your opinion. That is true, on this point. I have no problem believing that .016 THD can be caused by a short duration high amplitude frequency being clipped (flattend across the very top) - whether I can hear it or not.

Nor do I have a reason to doubt lab reports that show at near 100 watts my receiver could clip the signal and cause 1% THD. And I certainly have no reason to think almost every publisher in the industry is ignorant of the meaning of the word Clip, but that you have it right. Sorry, I just don't know you that well.

I love a good conspiracy story, but such a leap demands more meat on the bones.
_________________________
Panny 3000 PJ, 118" Carada, Denon 3300, PS3, Axiom QS8, PSB 5T, B&W sub, levitating speaker wire

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#275357 - 10/17/09 01:04 PM Re: B&K Receiver for M80's [Re: Zimm]
fredk Offline
axiomite

Registered: 12/06/07
Posts: 7217
Loc: Canada
Some clarification please:
My current understanding of clipping in an amplifier is that it is a hard limit related to the maximum amplitude of a signal that can be reproduced. If your amp has a maximum amplitude limit of 10 thats all it can produce. The more you try to push beyond this limit, the longer the signal is in clipping and the longer the signal is in clipping for. The transition from beautiful music to harsh distortion is a rapid one over a range of a few watts.

What the magazine implies is that clipping is a soft distortion of the top of the wave as opposed to a hard limit. Which view is correct?
_________________________
Fred

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Blujays1: Spending Fred's money one bottle at a time, no two... Oh crap!

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#275360 - 10/17/09 01:20 PM Re: B&K Receiver for M80's [Re: fredk]
Zimm Offline
connoisseur

Registered: 12/08/08
Posts: 1361
Loc: New Orleans
Don't know. But the way i understand it is this: if 1% of the area inside the cone of frequency (on scope) is clipped off the top, then you have a certain level of distortions compared to the original. Let's call it .001%. But as the cone gets higher or wider more of the area of the cone is above the clipping point. Let's say 10% of the total signal making that freq cone is now clipped off. The resulting distortion is higher because a higher percentage of the original source signal is not being reproduced - i.e., more of the signal is clipped off. So you can easily have clipping causing .0016, then .08, then .1, then 1% as the signal gets louder and the amp must clip more and more of the original information.
_________________________
Panny 3000 PJ, 118" Carada, Denon 3300, PS3, Axiom QS8, PSB 5T, B&W sub, levitating speaker wire

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#275362 - 10/17/09 01:31 PM Re: B&K Receiver for M80's [Re: Zimm]
fredk Offline
axiomite

Registered: 12/06/07
Posts: 7217
Loc: Canada
 Quote:
Don't know

But this is at the heart of the matter. If you understand the physics of clipping, you know exactly how it manifests itself.

I wish Tom Cumberland visited these boards.
_________________________
Fred

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Blujays1: Spending Fred's money one bottle at a time, no two... Oh crap!

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#275372 - 10/17/09 03:46 PM Re: B&K Receiver for M80's [Re: fredk]
ClubNeon Offline
connoisseur

Registered: 02/06/09
Posts: 3448
Loc: Western Maryland, USA
The further pushed into clipping the higher the Watts Root Mean Squared output of an amplifier. Because RMS measures power over time, a sine wave which just kisses the peak will spend less time at full power than a DC signal which is held there.

This hard clipping, when the amp has no more to give, doesn't get any louder because DC holds the cone still. The harsh change in movement into and out of the clip is what causes the audible harmonic distortion.

At the very first signs of clipping, the 0.016% point in this example, there's still some additional amplitude to be had (especially with non-test tones) because of the way the capacitors and transform can handle instantaneous demands vs. continual.
_________________________
Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
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-Chris

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#275393 - 10/17/09 07:19 PM Re: B&K Receiver for M80's [Re: ClubNeon]
fredk Offline
axiomite

Registered: 12/06/07
Posts: 7217
Loc: Canada
OK, you kinda lost me. Who am I kidding, you completely lost me.

So, at 70 some odd watts the receiver was just barely clipping, but you could still apply another 30 watts before reaching the hard clipping limit?
_________________________
Fred

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Blujays1: Spending Fred's money one bottle at a time, no two... Oh crap!

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#275396 - 10/17/09 07:55 PM Re: B&K Receiver for M80's [Re: fredk]
ClubNeon Offline
connoisseur

Registered: 02/06/09
Posts: 3448
Loc: Western Maryland, USA
"Hard clipping" was probably a poor word choice, but it's hard to come up with a way to say it. Maybe some examples.

It's possible to come up with a test tone which is demanding enough of power to keep the caps from building up a full charge, and the current flow has saturated the transformer's core. At this point the peaks of the output waveform start clipping. This is all the power that can be moving through the amp to the speaker at any instance in time. Turning the volume up higher will result in a higher power RMS reading, but the instantaneous power reading will be no higher. It is just the amp is spending more time at its peak output. Instead of just the absolute peaks being clipped some of the lower portions of the signal have gone to DC too.

The other example is a passage which is nearly silent, the caps have a good charge built up, the transformer is far from saturation. Then a shot rings out. This spike in the output can exceed the the level of that continuous bombardment mentioned above.

Most content is more like the second example. A few small peaks with most of the signal not being very demanding. So you may not have a huge power reserve, but you can exceed the levels of what one gets with a test signal. As you turn up the volume further where the amplifier is reaching its limits for this content, the loss of a few little peaks is hardly noticeable. As that happens the lower portions are still getting louder and taking more power to reproduce. It's not until more of the signal is clipped that you think things are starting to sound harsh, and (hopefully) back off a little.

I still don't know if I'm doing a good job describing this. Maybe if you think of sound as being made of lots of little instances, but the power readings are taken with that averaged over time. The more time spent at higher output levels the higher the Watts RMS reading. So if even the tiny peaks are clipping because the amp can't exceed the current flow at that instant in time, it doesn't mean that more power can't be applied to bring more parts of the signal up in level.
_________________________
Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs
-Chris

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#275400 - 10/17/09 08:29 PM Re: B&K Receiver for M80's [Re: ClubNeon]
fredk Offline
axiomite

Registered: 12/06/07
Posts: 7217
Loc: Canada
Ah, ok. The article Zimm pointed out is a continuous output test and this was the only instance I was thinking about. It is in this instance that I thought that clipping becomes 'hard' so that you can't get clipping at .o16%THD. Is this correct?

I understand what happens with program material and that often you only get clipping of very small parts of the signal.
_________________________
Fred

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Blujays1: Spending Fred's money one bottle at a time, no two... Oh crap!

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