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i heard that class d amplifiers a lot of them are putting out square waves and that isnt good at all and i also heard people only blox up subs becasue of that just wondering if that is true or not and why would an amp produce a square wave anyways? It does becasue of distortion from what i understand but from what i hear from most companies is they just automatically produce them without tthe distortion. someone please explain i am confused. Posts: 404 | From: Canada | Registered: Nov 1999
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No Amplifier "produces" square waves. Square waves are D.C.(Direct Current) like a battery, and a switch, either on or off. An amplifier makes sine waves A.C. (Alternating Currrent) larger. When the amplifier has exhausted it's resources, such as the ability to produce clean power, the amplifier stops for a brief milisecond, which is seen on a scope as a rounded, square wave. Because the top of the rounded A.C. wave is lopped off. And that is "Clipping", which occurs ONLY when you overdrive the amplifier, by excessive volume levels, or exessive signal input due to mis-adjusted gain controls, and when the amplifier is given a less then desireable resistance load. And that goes for ALL amplifiers, from Class A-Z.
------------------ E.C. Wuz here
Posts: 1057 | From: Vancouver, British Columbia, Canada 'eh | Registered: May 1999
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well harrison labs ade an amp which was just thrown out of the competition circuit at the last usac even it was a class hl amplifier and it pout out 10000 watts it was called a drag queen and it put out square waves and when a signal clips it should put out a square wave am i right we hooked up an oscilloscope to the amplifiers at our ashop while tuning a vehicle before and some notes were producing square wavws according to the oscilloscope due to clipping.
Posts: 404 | From: Canada | Registered: Nov 1999
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If you break down the class D amp you have a power supply (not unlike a a/b power supply), a preamp section (also not unlike a/b counter- part), the drive section that process's the analog into the pulse modulated signal, the power output section that delivers the kind of current that the sub needs, and the filter that turns the 'quared off'waves coming out of the finals into a more smooth sinewave-like signal. Yep, pre the output filter is nasty square wavey guys. The output filter is a cap and coil or multiples thereof that only allow the modulation of the square waves to come out and thus audio.
'Where there's a will there's a wall' 'Would you like a little SQ with your SPL?'
Posts: 926 | From: Sugarland, Tx | Registered: May 1999
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Tech man I hear you are good at this iam good to for only being in the game 4 years if that but coiuld you explain that better to me please?
Posts: 404 | From: Canada | Registered: Nov 1999
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If I may clarify with the following. Harman/Kardon used a famous way to market their amplifiers. Set up an amplifier on a scope, and signal generator as input. They would show how well the amplifier produced the exact signal, and whatever deviation from the original signal. All amplifiers operate on D.C, and recieve and amplify A.C., which is what we hear. I don't listen to a scope, and certainly try to avoid continuous sine waves from a signal generator. In essence what you saw was the same thing.
------------------ E.C. Wuz here
Posts: 1057 | From: Vancouver, British Columbia, Canada 'eh | Registered: May 1999
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sorry to give you guys such a hassle here but what did i see in easy speaking terms that any joe shmoe would understand becasue i am having trouble grasping this. I saw the amplifier square off on a lot of frequencies we actually had an ascilloscope and a test tone generator hooked up to his car stereo amplifier all at the same time and it showed a lot of squared off waves. Posts: 404 | From: Canada | Registered: Nov 1999
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Hey benthebass... Did you do your scope examination with or without a speaker load? At high or low volume? Which model amp?
A few things to know about class D design. They often won't output a very linear signal if there is no load on it. They are often frequency sensitive, ie: They shift phasing as you go through the range of frequencies and the filter is more effective in it's design range than outside leading to harsh sound outside the design range. It's possible to make class D 20 to 20,000 compatible but difficult and not very versatile. (can't just put any speaker on it) to the best of my knowledge) Peavey did make a music reinforcment series of amps (deca) that were class D of a sorts that played most of the range but the distortion spechs were just satisfactory. JMO.
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It was a phoenix gold zpa 0.5 and jl 18 w6 4 zpa 0.5 in total and 4 jl 18 w6 in total but we got lots of square waves except for the peak in the vehicle came out nicely curved and rounded.
Posts: 404 | From: Canada | Registered: Nov 1999
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I believe Infinity had a few full range class D's that were standard issue in Vector awx3's(?). I remember a cool feature on these some years ago in a car audio mag, as&s, ca&e or csr (i think csr)
cya
------------------ Jeff President, Sweet Sounds Inc. Team Sweet Sounds is gathering information....all are welcome Authorized Dealer for Cerwin Vega, Image Dynamics, Clarion Pro Audio, Stinger, Hifonics, Digital Designs, Memphis and more.....
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benthebass8 the rounded curves in the car is A.C, sine waves, the square waves are D.C. , the A.C. is amplified "piggyback" on the D.C. wave in the amplifier. Just like F.M uses a 19KHz carrier wave to send a signal. But you end up hearing A.C. (am I close TechMan?)
------------------ E.C. Wuz here
Posts: 1057 | From: Vancouver, British Columbia, Canada 'eh | Registered: May 1999
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You called it SSA It's a CSR with the Infinity class D amps.. I've still got it here somewhere..
Posts: 5348 | From: Nash-Vegas, TN | Registered: May 1999
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Well first, the zpao.5 is a A/B or quasi a-a/b design so d is not relevent. The square waves are probably clipping. They would only happen at certain notes if the amp were turn up close to it's limit since the sub changes impedance at different frequencies. It was probably clipping. You were playing pretty loud right? And you know you were playing sine waves right? Some music purposefully distorts the wave form (even clipping it) in order to color the bass.
SSQ Bose also made some cool full range class D's. Many installers may have seen them already They are the speakers in those plastic boxes with the amp built in (4 wires) The amp has a shield can on it with lots of holes and there isn't a heat sink. The power fets were glued to the circuit board and there was 1 or 2 ic's with quite a few pins on them.
I'm not sure I'm understanding you analogy ELI. Of course any clipping you see on what should be sine wave like forms coming out of a playing amp will appear like the tops were cut off of the waves. I do believe they call wave forms AC still even if the are a pure square wave or triangle wave. FM is a carrier at whatever the frequency. This is shifted up and down in frequency to the music. Then for stereo a sub carrier at 19khz distance is shifted for a second channel's audio. Maybe you can help me understand your analogy.
'Where there's a will there's a wall' 'Would you like a little SQ with your SPL?'
Posts: 926 | From: Sugarland, Tx | Registered: May 1999
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Tech, I was making the analogy of a carrier wave idea, I felt that there was some confusion, and tried to simplify. Basicaly saying that the square wave seen was test signal only. and that amplifiers do not "produce" square waves the way it was thought, rather a clipped sine wave, which "resembles" a square wave, as you described. Thanks for the technical re-adjustment.
------------------ E.C. Wuz here
Posts: 1057 | From: Vancouver, British Columbia, Canada 'eh | Registered: May 1999
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I'm going to chime in with something. I may be wrong, but here goes anyway. Someone (I know who it is) said on this forum that a clipped signal is pure DC. I think that is horse****, amplifiers dont put out DC unless there is something seriously wrong. He was trying to make the argument that a clipped signal will blow a speaker because its "DC" and that during that portion of the signal, the voice coil will heat and not be able to dissipate it's heat due to it's not moving due to the DC it is seeing. I think that is total crap. No matter what, unless there is a major meltdown in the amplifier, the speaker will not see enough DC to cause overheating of the coil from a clipped signal, unless it is a sinewave that is clipped or something like that. I believe his theory only applies to true DC operation, like hooking up your 12V car battery to the speaker or something similar. Just because the AUDIO output wave form is clipped doesn't necessarily mean the output AC waveform is clipped. I think this cat is a total idiot, but who knows, I may be. And no, it wasn't Tech, Eli, Dukk, or any of our regulars. You know who you are!
------------------ STILL waiting to hear a GOOD pair of HLCD's!!
If it dont fit, force it... if it breaks, it needed to be replaced anyway...
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For the record... Any waveform that crosses over from a current flow from one direction to another is AC, no matter the waveform. If it goes from 0 to x volts and back to zero then it's pulse DC. If it goes from a + peak across zero to a negative peak then it's AC. It can look like a square wave, triangle wave of a groovy wavey wave but it's ac. The current flow can't change directions and be DC. Just for clarification.
I do believe that there is argument for both the sharp edges in a clipped signal and the fact that driver movement is paused for a moment in either peak of a clipped waveform contributing to a blown driver. Just my opinion on that part.
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I have to respectfully disagree, Audiophyle.. I am sure I am not the person you were talking about since I posted this on another forum, did not say that an amp put out pure DC, and I am as regular as anyone on here, but this is a copy of what I posted on another forum. I belive this is an at least partially correct theory: "One more opinion to this thread. Both excessive power AND distortion can kill a speaker. Power can destroy a speaker if you crank it and exceed the voice coils thermal power rating for a long period of time continuously. Distortion(as in clipping) CAN destroy a speaker in the following manner. When you play an amp to high and keep asking for more, the amp will send a distorted signal to the speaker. The speaker only reproduces what is sent to it, right? So you have an amp sending a partial square wave to a speaker. With a clean signal, a speaker helps cool itself by the alternating motion forcing air over the voice coil, this is the reason you can send more power than the speaker is rated for IF it is clean, unclipped power(to a point) and not have the speaker burn, as long as the suspension is not bottomed and overstressed. Now, what's at the top and bottom of a square wave? DC, which speakers REALLY don't like. This is what hurts the speaker. With DC in the signal, there is no movement after the flat part of the signal, so the voice coil does not move, taking away partially the ability of the speaker to cool itself by sending air over the VC/polepiece. The thing that compounds this is the fact that the amp is sending THE HIGHEST power through the speaker at this point, so what you basically have is a voice coil that is being heated up in the same way as stove coil element, with diminished ability to cool itself as it is designed t.! These are just some ways to point out that both sides are right. I read the article in the mag to and got a laugh out of that part.. I have seen a lot of under powered speakers destroyed..." How else can you expalin speaker in sealed boxes(taking away the element of playing below Fb in a ported box) being underpowered being destroyed? I have seen it(And done it) myself. This would make a good debate topic Then again, I may have made myself out to be a complete MO-RON with that, but I never claimed to know everything
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It's easy to have something taken out of context 'eh Buzz? It's happenned to me, just used the "wrong word" for lack of a better one at the moment. Just like you used the words "partial square wave" in your description. It can lead to heated posts and wrong impressions, I'm sure you know what your'e reffering to, just like I did when I er.. mis-worded what I wanted to explain. But as long as everything gets clarified, all will be quiet(or loud) on the western front.
------------------ E.C. Wuz here
Posts: 1057 | From: Vancouver, British Columbia, Canada 'eh | Registered: May 1999
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Buzz, it was NOT you! I wouldn't say something like that about a respected poster on this board. The point of this other bozo's post was that even an unclipped square wave will blow a speaker. I dont think that's impossible, but at the same time I have to think it's highly unlikely. Yes, the speaker is seeing a squarewave on an AC carrier, but, since it's on an AC carrier, I dont believe it could hold the woofer at excursion long enough to cause the aforementioned heating of the voicecoil. Guess that makes sense. Anyway...
------------------ STILL waiting to hear a GOOD pair of HLCD's!!
If it dont fit, force it... if it breaks, it needed to be replaced anyway...
posted
Thanks Audiophyle I missed the post you are talking about, I will have to search around and see what this guy said about that.. I agree a voltage is AC or DC and you have something really wrong if your amp is putting out pure DC, I've seen that happen too. I was referring to the clipped part of the wave as more of a short "DC pulse" (guess that's what I'm trying to call it) riding on an AC waveform and not a pure DC or pure square wave in my post. Actually Bill O. had an interesting idea about this a while back(when he was here) about square waves. He mentioned(maybe KOB did too) something about the extra stress placed on woofer components when you accelerate the cone from rest to full power and back instantaneously, as opposed to increasing voltage/current over the course of a smooth sine wave period.I got to thinking about this and i would think they might have a point, as force is mass times acceleration, and you drastically increase acceleration of the cone when playing a square wave through a woofer, raising force on the system. Of course this has nothing to do with the "blown woofer amp clipping thoery" that was mentioned but I was typing this and just remembered it. It just makes me wonder what the mechanism is for blowing woofers under these conditions...
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Buzz, I think DQ knows what happens when you accelerate a woofer to xmax to quickly! Go look at the pic of her exploded IDQ woofer in "it could only happen to me!"....
------------------ STILL waiting to hear a GOOD pair of HLCD's!!
If it dont fit, force it... if it breaks, it needed to be replaced anyway...
