PKN XD4000 Test Results |
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Speaker Sol
Young Croc Joined: 15 September 2009 Location: Ireland Status: Offline Points: 1320 |
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Does this happen when the RMS Voltage reaches it's max or when peak voltages cross a threshold? What I am asking is, does a short burst peak distort when it passes the RMS point, or does this only happen when the amps RMS power is near it's max? Thanks.
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S DeXter
Young Croc Joined: 12 May 2008 Location: Moon Status: Offline Points: 1268 |
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It was clipping at the 0db @ 8ohm and -5db @ 4ohm because the lights are driven from the input signal.. The power supply runs out of current (inducing the ringing) before it hits its max voltage. This is all with the red AGR LED off. But as you say on a real world signal (not a sig. gen), there should be enough juice available from the caps to stop this from being an issue. I would assume the 6000 is similar, although we have not had it on the bench. Edited by S DeXter - 16 May 2010 at 11:19pm |
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Enjoy your self...... It's later than you think.......
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ceharden
The 10,000 Points Club Joined: 05 June 2005 Location: Southampton Status: Offline Points: 11776 |
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Just in case anyone is interested, the 'ringing' you see when the signal approaches clip is not oscillation as with a linear amplifier. It is an artifact common to class D amplifiers (albeit some better than others) and you'll find that the 'ring' is at the carrier frequency (switching frequency) of the class D output stage. It looks a lot worse than it actually is.
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S DeXter
Young Croc Joined: 12 May 2008 Location: Moon Status: Offline Points: 1268 |
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Did look a bit like a tweeter killer (although i doubt these power amps will rarely be used for that application). Edited by S DeXter - 16 May 2010 at 11:52pm |
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Enjoy your self...... It's later than you think.......
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The Builder
Old Croc Joined: 03 January 2010 Status: Offline Points: 3107 |
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Also see Joke.
Big language, English
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It just is.
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ArthurG
Young Croc Joined: 03 May 2004 Location: France - China Status: Offline Points: 976 |
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well a good class D amp has no ringing. Waveforms should be clean and they are solution to avoid this bad behavior (like using a limiter below a certain duty cycle). The rings affects the sound quality when the amp is driven hard. In fact, with all respect due to PKN, these guys seem to be excellent in their core competence, ie SMPS, but they lack a little bit in class D design. It doesn't mean that the amp is bad, quite the opposite as it's one of the best switching offer around with real long term power output. Thus they offer tremendous value for money, kudos to the PKN engineers But if you are looking at a good sounding amp, then its not the best choice...
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U.Viktor
Young Croc Joined: 04 May 2010 Status: Offline Points: 716 |
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We have also measured PKN 4000 and 6000 before using them. So that ringing behaviour is much less serious because you need to measure by a true differential oscilloscope probe! Applying standard 'A-weighed' filters the situation is even better, harmonic disortion is bellow 0,4% at clipping...
Anyway most of the amps are much worst for the speakers in case of clipping.
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U.Viktor
Young Croc Joined: 04 May 2010 Status: Offline Points: 716 |
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There is another thing what nobody really speaks about.
What if the load is a SPEAKER not a Resistor? So the switching amps have great advantage not too sensitive to REACTIVE loads (like the Speakers), I meant everything is completely different on reactive loads and resistive testing is just means a little information about an amp... I have seen my own eyes when a super-high-end analog amp (0.00001% THD on ressistors) connected to speakers and made weird waveforms while a cheap switching amp was almost perfect..
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darkmatter
Old Croc Joined: 26 February 2005 Location: LDN Status: Offline Points: 2425 |
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Some interesting reading:
http://focus.ti.com/analog/docs/analogtechdoc_hh.tsp?viewType=mostuseful&rootFamilyId=57&familyId=20&docTitle=class&docCategoryId=1 |
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Speaker Sol
Young Croc Joined: 15 September 2009 Location: Ireland Status: Offline Points: 1320 |
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So let's see. A few more questions and I appreciate that no one is really that familiar with this amp yet, but advice is appreciated.
Full bridge class D? This means each channel is already running in bridge? This means that a 4ohm load is really split into a pair 2ohm loads? The amp is stable into 2ohm load but at decreased power and risk of overheating. So how will this amplifier cope with speakers such as the Stasys X , which drop to 3.5 bellow 40hz? (Also worth noting that according to the MacroTech 9000i build in load monitor, the impedance drops to below 3ohms at 30hz, But this may not be accurate). Many Thanks |
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levyte357
The 10,000 Points Club Joined: 10 May 2004 Location: UK, London Status: Offline Points: 11743 |
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Can assure you, any amp that can drive 2x Turbomax per channel all night, full tilt, playing roots, without smoking or thermalling is a real 4 ohm amp, as you can best believe that load will be dropping well below 4 ohms stereo at times. |
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"Who am I? I'm the guy who does his job.. You must be the other guy".
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U.Viktor
Young Croc Joined: 04 May 2010 Status: Offline Points: 716 |
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As I heard from the manufacturer only the LC PKNs are Class-D,
they have modified Classic-D circuitry and XD and XE is something different. A 3000W/4OHM amp is far better than a 3000W/2OHM. Isn't it?
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