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#1
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A Comparison
Krell 350 Watt monoblocks @ $17,500.00 per pair
350 watts wpc @ 8 Ohms 700 wpc @4 Ohms 1400 wpc @ 2 Ohms Signal to noise = 118db 95 db @ 2.83 V THD = .05% 20 Hz - 20 kHz Input Impedance = 100 K Ohms Input Sensitivity = 2.6v RMS for max power Voltage gain = 26.4 db --------------------------------------------------------------------------------- QSC PLX 3402 Stereo amp $1200.00 700 wpc @ 8 Ohms 1100 wpc @ 4 ohms 1700 wpc @ 2 ohms Signal to noise 107 db THD = .03% 20 Hz - 20 kHz Input Impedance = 6 K ohms Input sensitivity = 1.9 Volts @ 8 ohms Voltage gain = 32 db I figure you get the QSC and either modify it by adding heat sinks or replacing the fans with very quiet ones, and still have saved around $15,000.00 and not be able to hear any difference. If you have a difference of opinion, please provide the technical reason why you disagree that would account for any differences in sound quality. Go ahead Robert, get technical, I'm sure I can find someone to translate if it gets to technical for what you think is my lack of brainpower. |
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#2
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A Comparison
"Signal" wrote in message
OK, so you want people to technically explain audible differences they hear between amps they cannot possibly have compared. Very good! Good job of indicting Robert Morien's incessant childish posturing about QSC amps, Paul. |
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#3
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A Comparison
On Thu, 20 Oct 2005 07:39:07 GMT, "
wrote: Krell 350 Watt monoblocks @ $17,500.00 per pair 350 watts wpc @ 8 Ohms 700 wpc @4 Ohms 1400 wpc @ 2 Ohms Signal to noise = 118db 95 db @ 2.83 V THD = .05% 20 Hz - 20 kHz Input Impedance = 100 K Ohms Input Sensitivity = 2.6v RMS for max power Voltage gain = 26.4 db --------------------------------------------------------------------------------- QSC PLX 3402 Stereo amp $1200.00 700 wpc @ 8 Ohms 1100 wpc @ 4 ohms 1700 wpc @ 2 ohms Signal to noise 107 db THD = .03% 20 Hz - 20 kHz Input Impedance = 6 K ohms Input sensitivity = 1.9 Volts @ 8 ohms Voltage gain = 32 db I figure you get the QSC and either modify it by adding heat sinks or replacing the fans with very quiet ones, and still have saved around $15,000.00 and not be able to hear any difference. If you have a difference of opinion, please provide the technical reason why you disagree that would account for any differences in sound quality. Go ahead Robert, get technical, I'm sure I can find someone to translate if it gets to technical for what you think is my lack of brainpower. As a staunch objectivist, don't you consider your own statement pretty absurd? Please tell us how you can make a statement about difference between these two components without a dbt? |
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#4
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A Comparison
" wrote in message ink.net... Krell 350 Watt monoblocks @ $17,500.00 per pair QSC PLX 3402 Stereo amp $1200.00 I figure you get the QSC and either modify it by adding heat sinks or replacing the fans with very quiet ones, and still have saved around $15,000.00 Ever heard of opportunity cost? It is obvious that you have none but there are folks who will make more than $15K in the time it takes to fiddle with their amp. Even worse they'll be left with no warranty and if the amp ever, for any reason, starts a fire and burns down the building, chances are that insurance won't cover it. These are real choices for some people, just not for you. |
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#5
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A Comparison
"Margaret von B."
wrote in message " wrote in message ink.net... Krell 350 Watt monoblocks @ $17,500.00 per pair QSC PLX 3402 Stereo amp $1200.00 I figure you get the QSC and either modify it by adding heat sinks or replacing the fans with very quiet ones, and still have saved around $15,000.00 Neither are required. QSC amp fans aren't *that* noisy, and if they are a problem its easier just to put them out of ear shot. Since they aren't $15k amps, the *need* to put them on display is vastly reduced. Of course this shoots the $#@!! out of what $15k amps are *really* about, and that's bragging rights. Ever heard of opportunity cost? It is obvious that you have none but there are folks who will make more than $15K in the time it takes to fiddle with their amp. Good thing that there's no need to fiddle with QSC amps. |
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#6
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A Comparison
"Signal" wrote in message ... " emitted : Krell 350 Watt monoblocks @ $17,500.00 per pair 350 watts wpc @ 8 Ohms 700 wpc @4 Ohms 1400 wpc @ 2 Ohms Signal to noise = 118db 95 db @ 2.83 V THD = .05% 20 Hz - 20 kHz Input Impedance = 100 K Ohms Input Sensitivity = 2.6v RMS for max power Voltage gain = 26.4 db --------------------------------------------------------------------------------- QSC PLX 3402 Stereo amp $1200.00 700 wpc @ 8 Ohms 1100 wpc @ 4 ohms 1700 wpc @ 2 ohms Signal to noise 107 db THD = .03% 20 Hz - 20 kHz Input Impedance = 6 K ohms Input sensitivity = 1.9 Volts @ 8 ohms Voltage gain = 32 db Where are the frequency response plots? Why would you need them? Isn't it all about the sound? I figure you get the QSC and either modify it by adding heat sinks or replacing the fans with very quiet ones, and still have saved around $15,000.00 and not be able to hear any difference. If you have a difference of opinion, please provide the technical reason why you disagree that would account for any differences in sound quality. OK, so you want people to technically explain audible differences they hear between amps they cannot possibly have compared. Very good! Some people here seem to think all they have to do is listen and you can make a judgement with just one listen and no comparison blind or otherwise. |
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#7
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A Comparison
"dave weil" wrote in message news  On Thu, 20 Oct 2005 07:39:07 GMT, " wrote: Krell 350 Watt monoblocks @ $17,500.00 per pair 350 watts wpc @ 8 Ohms 700 wpc @4 Ohms 1400 wpc @ 2 Ohms Signal to noise = 118db 95 db @ 2.83 V THD = .05% 20 Hz - 20 kHz Input Impedance = 100 K Ohms Input Sensitivity = 2.6v RMS for max power Voltage gain = 26.4 db --------------------------------------------------------------------------------- QSC PLX 3402 Stereo amp $1200.00 700 wpc @ 8 Ohms 1100 wpc @ 4 ohms 1700 wpc @ 2 ohms Signal to noise 107 db THD = .03% 20 Hz - 20 kHz Input Impedance = 6 K ohms Input sensitivity = 1.9 Volts @ 8 ohms Voltage gain = 32 db I figure you get the QSC and either modify it by adding heat sinks or replacing the fans with very quiet ones, and still have saved around $15,000.00 and not be able to hear any difference. If you have a difference of opinion, please provide the technical reason why you disagree that would account for any differences in sound quality. Go ahead Robert, get technical, I'm sure I can find someone to translate if it gets to technical for what you think is my lack of brainpower. As a staunch objectivist, don't you consider your own statement pretty absurd? What's absurd is bad mouthing a brand of amps without any kind of comparison. Please tell us how you can make a statement about difference between these two components without a dbt? I don't think you honestly do that for any amp, yet people do it here all the time. I do think it would be a great test to do, since the cost of the QSC is not out of reach for someone with a bit of discipline, the way a Krell is, and you don't have to hire a forklift to move the QSC which is made for touring and therefore ruggedly built and has twice the power, there's no reason at all to assume it wouldn't be as transparent as the Krell. |
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#8
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A Comparison
"Margaret von B." wrote in message ... " wrote in message ink.net... Krell 350 Watt monoblocks @ $17,500.00 per pair QSC PLX 3402 Stereo amp $1200.00 I figure you get the QSC and either modify it by adding heat sinks or replacing the fans with very quiet ones, and still have saved around $15,000.00 Ever heard of opportunity cost? I must admit I've not heard that phrase. Explain please. It is obvious that you have none but there are folks who will make more than $15K in the time it takes to fiddle with their amp. How smart do you need to be to connect an amp to a preamp? Even worse they'll be left with no warranty and if the amp ever, for any reason, starts a fire and burns down the building, chances are that insurance won't cover it. These are real choices for some people, just not for you. The QSC has a 6 year warranty, their products have been favored by pros for 30 years, so I doubt that a fire is a very real consideration. What kind of cheap ass insurance company would not cover such an event? |
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#9
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A Comparison
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#10
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A Comparison
On Thu, 20 Oct 2005 16:14:39 GMT, "
wrote: "Signal" wrote in message .. . " emitted : Krell 350 Watt monoblocks @ $17,500.00 per pair 350 watts wpc @ 8 Ohms 700 wpc @4 Ohms 1400 wpc @ 2 Ohms Signal to noise = 118db 95 db @ 2.83 V THD = .05% 20 Hz - 20 kHz Input Impedance = 100 K Ohms Input Sensitivity = 2.6v RMS for max power Voltage gain = 26.4 db --------------------------------------------------------------------------------- QSC PLX 3402 Stereo amp $1200.00 700 wpc @ 8 Ohms 1100 wpc @ 4 ohms 1700 wpc @ 2 ohms Signal to noise 107 db THD = .03% 20 Hz - 20 kHz Input Impedance = 6 K ohms Input sensitivity = 1.9 Volts @ 8 ohms Voltage gain = 32 db Where are the frequency response plots? Why would you need them? Isn't it all about the sound? So, how do they sound compared with each other? I figure you get the QSC and either modify it by adding heat sinks or replacing the fans with very quiet ones, and still have saved around $15,000.00 and not be able to hear any difference. If you have a difference of opinion, please provide the technical reason why you disagree that would account for any differences in sound quality. OK, so you want people to technically explain audible differences they hear between amps they cannot possibly have compared. Very good! Some people here seem to think all they have to do is listen and you can make a judgement with just one listen and no comparison blind or otherwise. And some people think that you don't even have to LISTEN at all. |
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#11
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A Comparison
" said:
Krell 350 Watt monoblocks @ $17,500.00 per pair 350 watts wpc @ 8 Ohms 700 wpc @4 Ohms 1400 wpc @ 2 Ohms Signal to noise = 118db 95 db @ 2.83 V THD = .05% 20 Hz - 20 kHz Input Impedance = 100 K Ohms Input Sensitivity = 2.6v RMS for max power Voltage gain = 26.4 db --------------------------------------------------------------------------------- QSC PLX 3402 Stereo amp $1200.00 700 wpc @ 8 Ohms 1100 wpc @ 4 ohms 1700 wpc @ 2 ohms Signal to noise 107 db THD = .03% 20 Hz - 20 kHz Input Impedance = 6 K ohms Input sensitivity = 1.9 Volts @ 8 ohms Voltage gain = 32 db One of the things that I noticed immediately is the ability of the Krell to deliver twice the power (meaning current) in half the load, up to 2 ohms. I suspect that even in 1 ohm the figure would be close to the required 2800W, be it for a brief period of time. The QSC has only marginally more power into 2 ohms (not that those insanely high wattages have any meaningful use, you will note). Also, the current doesn't double with half the load. This means the Krell has a stiffer power supply, despite the lower average wattage. It is a true constant voltage source. The input impedance of the QSC amp is rather low, something to keep in mind when driving it directly from an opamp's output. The input sensitivity should have nothing to do with the output load impedance, is this a typo, a mistake or does the amp use such a high amount of global feedback that the load has influence on the input? In the latter case, problems might arise with strongly reactive loads, and this may make for a different sounding amplifier. I also noticed the DF isn't specified. There are more issues to discuss, but that would require more information about both amps, and, preferably, the schematics. -- "Audio as a serious hobby is going down the tubes." - Howard Ferstler, 25/4/2005 |
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#12
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A Comparison
"ScottW" wrote in message
ups.com Origional document reference: http://www.qscaudio.com/products/amps/plx/plx.htm 6K ohm input impedance isn't ideal and may cause problems with many a source. Other than older vacuum tubed preamps, its hard to think of any. Most modern (less than 20 year old) vacuum tube and SS preamps will handle 2 volts into a 6 K ohm just fine. Most will put out upwards of 10 volts into a 10K load, for example. But most disconcerting is the very strange input sensitivity spec. 1.9V @ 8 ohms? Are they implying that input sensitivity varies with output load impedance? That will cause FR variance with any speaker having a non-flat impedance curve (virtually all but active speakers). What they are saying that this is the input sensivitity for rated output with a 4 ohm load. The rated output power varies with load impedance, and the rest follows. So that begs the question already raised... why isn't FR specified? It is, in a part of the original document that Mike didn't post. |
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#13
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A Comparison
"Sander deWaal" wrote in message
" said: Krell 350 Watt monoblocks @ $17,500.00 per pair 350 watts wpc @ 8 Ohms 700 wpc @4 Ohms 1400 wpc @ 2 Ohms Signal to noise = 118db 95 db @ 2.83 V THD = .05% 20 Hz - 20 kHz Input Impedance = 100 K Ohms Input Sensitivity = 2.6v RMS for max power Voltage gain = 26.4 db --------------------------------------------------------------------------------- QSC PLX 3402 Stereo amp $1200.00 700 wpc @ 8 Ohms 1100 wpc @ 4 ohms 1700 wpc @ 2 ohms Signal to noise 107 db THD = .03% 20 Hz - 20 kHz Input Impedance = 6 K ohms Input sensitivity = 1.9 Volts @ 8 ohms Voltage gain = 32 db One of the things that I noticed immediately is the ability of the Krell to deliver twice the power (meaning current) in half the load, up to 2 ohms. I suspect that even in 1 ohm the figure would be close to the required 2800W, be it for a brief period of time. The QSC has only marginally more power into 2 ohms (not that those insanely high wattages have any meaningful use, you will note). Also, the current doesn't double with half the load. This means the Krell has a stiffer power supply, despite the lower average wattage. It is a true constant voltage source. Just shows that Sander is easily snowed by raw specsmanship. It's pretty well known in the industry that the Krell ratings sheet has been juggled by Krell. The 8 ohm power rating was backed off, to create the impression that it is an ideal amp and puts out twice the power into 4 ohms. If the Krell amp were rated more conventionally based on those tests that Sander's buddy Middius hates, there would be a different story. The input impedance of the QSC amp is rather low, something to keep in mind when driving it directly from an opamp's output. Most conventional audio-grade opamps have absolutely no problem driving a 1K load to 5 volts rms, let alone just 2. Ditto for modern preamps, whether vacuum tube or SS. The input sensitivity should have nothing to do with the output load impedance, is this a typo, a mistake or does the amp use such a high amount of global feedback that the load has influence on the input? In the latter case, problems might arise with strongly reactive loads, and this may make for a different sounding amplifier. I also noticed the DF isn't specified. Shows that Sander can't see that the amps input sensitivity is scaled to its output ratings into various load impedances. There are more issues to discuss, but that would require more information about both amps, and, preferably, the schematics. Looks like having Sander comment on power amps is like engaging the proverbial loose cannon. Taking technical comments about SS amps at face value from a tube advocate like Sander is very risky. |
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#14
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the mckelviphibian stinks thusly
The mckelviphibian stunk thusly:
" wrote in message ink.net... Krell 350 Watt monoblocks @ $17,500.00 per pair ----------------------------------------------------------------------- I put in a dotted line to separate myself from the awful stink. What's the IM for each of these? What is the damping factor? What is the slew rate, not measured under small signal conditions, but, say, half way to the rails? What is the power supply capacity of each? I have, on occasion, heard Krell amps, but not under ideal conditions. However, it would be hard to imagine a Krell sounding worse than a QSC, to which I have had considerable exposure. Does anyone know if the QSC amp uses "blameless design"? IOW, does it use active current sources? Does the QSC have a regulated output supply? This feature has been a mainstay of Krell design. Contrary to what the mckelviphiban stinks, I am not a subjectivist. I do believe my ears can tell me alot, however, without the necessity of blind testing. |
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#15
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A Comparison
Arny Krueger wrote: "Sander deWaal" wrote in message " said: Krell 350 Watt monoblocks @ $17,500.00 per pair 350 watts wpc @ 8 Ohms 700 wpc @4 Ohms 1400 wpc @ 2 Ohms Signal to noise = 118db 95 db @ 2.83 V THD = .05% 20 Hz - 20 kHz Input Impedance = 100 K Ohms Input Sensitivity = 2.6v RMS for max power Voltage gain = 26.4 db --------------------------------------------------------------------------------- QSC PLX 3402 Stereo amp $1200.00 700 wpc @ 8 Ohms 1100 wpc @ 4 ohms 1700 wpc @ 2 ohms Signal to noise 107 db THD = .03% 20 Hz - 20 kHz Input Impedance = 6 K ohms Input sensitivity = 1.9 Volts @ 8 ohms Voltage gain = 32 db One of the things that I noticed immediately is the ability of the Krell to deliver twice the power (meaning current) in half the load, up to 2 ohms. I suspect that even in 1 ohm the figure would be close to the required 2800W, be it for a brief period of time. The QSC has only marginally more power into 2 ohms (not that those insanely high wattages have any meaningful use, you will note). Also, the current doesn't double with half the load. This means the Krell has a stiffer power supply, despite the lower average wattage. It is a true constant voltage source. Just shows that Sander is easily snowed by raw specsmanship. It's pretty well known in the industry that the Krell ratings sheet has been juggled by Krell. The 8 ohm power rating was backed off, to create the impression that it is an ideal amp and puts out twice the power into 4 ohms. If the Krell amp were rated more conventionally based on those tests that Sander's buddy Middius hates, there would be a different story. The input impedance of the QSC amp is rather low, something to keep in mind when driving it directly from an opamp's output. Most conventional audio-grade opamps have absolutely no problem driving a 1K load to 5 volts rms, What good is that if 1.7 V will drive the QSC to clipping into a 4 ohm load? let alone just 2. Ditto for modern preamps, whether vacuum tube or SS. But not all. I have a CD that didn't like it. As I said before (and Arny snipped cuz he couldn't address it), that low input impedance probably leaves the passive attenuator pres out. The input sensitivity should have nothing to do with the output load impedance, is this a typo, a mistake or does the amp use such a high amount of global feedback that the load has influence on the input? In the latter case, problems might arise with strongly reactive loads, and this may make for a different sounding amplifier. I also noticed the DF isn't specified. Shows that Sander can't see that the amps input sensitivity is scaled to its output ratings into various load impedances. BS... Sander's right and only cheap ass amps whose max output voltage diminishes as a function of load need do this. You say Krell underrates their 8 ohm capability... I say QSC overrates theirs. Which would you prefer.. an underrated amp or an overrated amp? ScottW |
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#16
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A Comparison
" wrote in message ink.net... Krell 350 Watt monoblocks @ $17,500.00 per pair 350 watts wpc @ 8 Ohms 700 wpc @4 Ohms 1400 wpc @ 2 Ohms Signal to noise = 118db 95 db @ 2.83 V THD = .05% 20 Hz - 20 kHz Input Impedance = 100 K Ohms Input Sensitivity = 2.6v RMS for max power Voltage gain = 26.4 db --------------------------------------------------------------------------------- QSC PLX 3402 Stereo amp $1200.00 700 wpc @ 8 Ohms 1100 wpc @ 4 ohms 1700 wpc @ 2 ohms Signal to noise 107 db THD = .03% 20 Hz - 20 kHz Input Impedance = 6 K ohms Input sensitivity = 1.9 Volts @ 8 ohms Voltage gain = 32 db I figure you get the QSC and either modify it by adding heat sinks or replacing the fans with very quiet ones, and still have saved around $15,000.00 and not be able to hear any difference. If you have a difference of opinion, please provide the technical reason why you disagree that would account for any differences in sound quality. **I'm sure someone would, but you have not listed all the technical specs available for each amp. Here's a few which are absolutely necessary: * Frequency response plots when driving a simulated speaker load. * Square wave response at various frequencies, when driving highly reactive loads. * IMD figures. * Output impedance figures, plotted from 20Hz to 20kHz. * Et al. -- Trevor Wilson www.rageaudio.com.au |
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#17
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the mckelviphibian stinks thusly
"Robert Morein" wrote in message ... The mckelviphibian stunk thusly: " wrote in message ink.net... Krell 350 Watt monoblocks @ $17,500.00 per pair ----------------------------------------------------------------------- I put in a dotted line to separate myself from the awful stink. What's the IM for each of these? What is the damping factor? What is the slew rate, not measured under small signal conditions, but, say, half way to the rails? What is the power supply capacity of each? I have, on occasion, heard Krell amps, but not under ideal conditions. However, it would be hard to imagine a Krell sounding worse than a QSC, to which I have had considerable exposure. Does anyone know if the QSC amp uses "blameless design"? IOW, does it use active current sources? Does the QSC have a regulated output supply? This feature has been a mainstay of Krell design. **Not quite. Krell amps use a stiff, regular (transformer/diodes/capacitors) power supply, with no active regulation. At least the ones I've seen anyway. -- Trevor Wilson www.rageaudio.com.au |
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#18
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the mckelviphibian stinks thusly
The moron asked:
What's the IM for each of these? What is the damping factor? What is the slew rate, not measured under small signal conditions, but, say, half way to the rails? What is the power supply capacity of each? __________________________________________________ ____-- Bob, thanks for once again showing you don't know ****. You really think the damping factor is an issue? You aren't aware of the fact that this is a meaningless spec? If you want the specs, you can go to their website and get them www.qscaudio.com Since they've been in business for 30 years and have their equipment in some of the most famous venues in the country, I have to assume their equipment is tough enough to do the job. The amps I gave specs for is a so called Class H design, and I have had experience with that design in the past and they are stable and kick out all the power they are called on to produce. ------------------------------------------------------------------------------------------------------------------------------ Bob embarrasses himself further: Contrary to what the mckelviphiban stinks, I am not a subjectivist. I do believe my ears can tell me alot, however, without the necessity of blind testing. -------------------------------------------------------------------------------------------------- Like Hell you're not a subjectivist, if you weren't you'd know better than to make stupid statements about not needing blind testing. Maybe you think you're some kind of half assed objectivist, but you don't have the diligence. DBT's for amps are essential if you really think you hear differences between amps that measure well. |
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#19
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the mckelviphibian stinks thusly
wrote in message ups.com... The moron asked: What's the IM for each of these? What is the damping factor? What is the slew rate, not measured under small signal conditions, but, say, half way to the rails? What is the power supply capacity of each? __________________________________________________ ____-- Bob, thanks for once again showing you don't know ****. You really think the damping factor is an issue? You aren't aware of the fact that this is a meaningless spec? **You idiot! Output impedance (nee: Damping factor) is VERY important. Audible frequency response flaws can be detected in many amplifiers, solely due to poor output impedance figures. If you want the specs, you can go to their website and get them www.qscaudio.com Since they've been in business for 30 years and have their equipment in some of the most famous venues in the country, I have to assume their equipment is tough enough to do the job. **No doubt. 'Tough', does not necessarily equate to 'good', however. 'Tough' is sometimes, well, just tough. An M1 Abrams tank is tough, but I'd rather drive a Porsche on a day to day basis. The amps I gave specs for is a so called Class H design, and I have had experience with that design in the past and they are stable and kick out all the power they are called on to produce. **Yep. So-called 'Class H' designs generally suck in decent audio systems. The rapid change in rail Voltages causes massive changes in output device characteristics. Those characteristics often cannot be countered through the use of Global NFB. Ever wonder why NAD dropped their variant of the system? Ever wondered why few decent amps use it? ------------------------------------------------------------------------------------------------------------------------------ Bob embarrasses himself further: Contrary to what the mckelviphiban stinks, I am not a subjectivist. I do believe my ears can tell me alot, however, without the necessity of blind testing. -------------------------------------------------------------------------------------------------- Like Hell you're not a subjectivist, if you weren't you'd know better than to make stupid statements about not needing blind testing. Maybe you think you're some kind of half assed objectivist, but you don't have the diligence. DBT's for amps are essential if you really think you hear differences between amps that measure well. **Perhaps, but you've yet to supply even a fraction of the numbers required. -- Trevor Wilson www.rageaudio.com.au |
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#20
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A Comparison
On 20 Oct 2005 15:00:13 -0700, "ScottW" wrote:
BS... Sander's right No, he's not. and only cheap ass amps whose max output voltage diminishes as a function of load need do this. What a moron. Essentially ALL audio power amps do that, since essentially NONE of them have regulated high-voltage rails. It's only a question of "how much" does the output voltage droop. You say Krell underrates their 8 ohm capability... You're wrong. Have you ever seen a review of a Krell when their power output is actually measured? Sheesh, the ignorance! I say QSC overrates theirs. What an idiot like you says means nothing. Which would you prefer.. an underrated amp or an overrated amp? We should not be surprised you'd ask such a stupid question. |
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#21
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A Comparison
"dizzy" wrote in message ... On 20 Oct 2005 15:00:13 -0700, "ScottW" wrote: BS... Sander's right No, he's not. and only cheap ass amps whose max output voltage diminishes as a function of load need do this. What a moron. Essentially ALL audio power amps do that, since essentially NONE of them have regulated high-voltage rails. It's only a question of "how much" does the output voltage droop. If the output droops the amp will have more than power problems. I think you mean DC supply droops... yet the KSA (the Krell I am most familiar with) has plenty of current reserve to prevent this. You say Krell underrates their 8 ohm capability... You're wrong. Have you ever seen a review of a Krell when their power output is actually measured? Sheesh, the ignorance! Provide a reference Arny... I mean Dizzy. I say QSC overrates theirs. What an idiot like you says means nothing. Which would you prefer.. an underrated amp or an overrated amp? We should not be surprised you'd ask such a stupid question. and you provide no answers... just noise. ScottW |
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#22
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the mckelviphibian stinks thusly
wrote in message ups.com... The moron asked: What's the IM for each of these? What is the damping factor? What is the slew rate, not measured under small signal conditions, but, say, half way to the rails? What is the power supply capacity of each? __________________________________________________ ____-- Bob, thanks for once again showing you don't know ****. You really think the damping factor is an issue? You aren't aware of the fact that this is a meaningless spec? Stinky Mikey, you are a coprophage. We don't want no part of what you're eating or stinking. |
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#23
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A Comparison
"ScottW" wrote in message news:XjY5f.3102$Ix3.2340@dukeread05... "dizzy" wrote in message ... On 20 Oct 2005 15:00:13 -0700, "ScottW" wrote: BS... Sander's right No, he's not. and only cheap ass amps whose max output voltage diminishes as a function of load need do this. What a moron. Essentially ALL audio power amps do that, since essentially NONE of them have regulated high-voltage rails. It's only a question of "how much" does the output voltage droop. There is also a subjective observation I can offer: A QSC amplifier sounds a lot like a Sunfire, or an (old) Bryston. There may be some who like that sound. I do not. To me, these particular amplifiers are abhorent. Of course, according to Arny, the above observation is invalid, must be ignored, because, IT CANNOT BE that anyone distinguishes between the sound quality of "properly operating amplifiers." Arny, you may as well take a **** shower, since you couldn't tell the difference between **** on your back and rain. |
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#24
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A Comparison
"dizzy" wrote in message
On 20 Oct 2005 15:00:13 -0700, "ScottW" wrote: BS... Sander's right No, he's not. and only cheap ass amps whose max output voltage diminishes as a function of load need do this. What a moron. You forgot the bull-headed part. Essentially ALL audio power amps do that, since essentially NONE of them have regulated high-voltage rails. It's only a question of "how much" does the output voltage droop. Exactly. You say Krell underrates their 8 ohm capability... You're wrong. Have you ever seen a review of a Krell when their power output is actually measured? Sheesh, the ignorance! You heard that old statement "Ignorance is Bliss"? Scotty should be very happy! I've been trying to educate Scotty about audio for years, and its like trying to teach a pig to sing. All I did is **** off the pig. I say QSC overrates theirs. What an idiot like you says means nothing. I think Scotty is a software guy. It seems like he saved up his sheckels and paid too much for some pretty good speakers, and now he thinks he's John Atkinson. Which would you prefer.. an underrated amp or an overrated amp? We should not be surprised you'd ask such a stupid question. Again agreed. What we want is amps that get the job done for a price we want to pay. Sometimes you have to spend a little money - that QSC PLX isn't exactly cheap. But the Krell is not about good audio, its about bragging rights for the new rich. |
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#25
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the mckelviphibian stinks thusly
"Robert Morein" wrote in message
What's the IM for each of these? The QSC amps are not slouchy - even in tests of high frequency IM. What is the damping factor? Way high, so high that a little speaker cable would be the determining factor. What is the slew rate, not measured under small signal conditions, but, say, half way to the rails? Irrelevant. What is the power supply capacity of each? I have here the service manual for a PLX 3402 including full schematics. I've seen Krells with their covers off. My recollection is that Krells have a traditional 60 Hz transformer, bridge rectifier, filter cap-based power supply. The QSC has a two-voltage (each for both plus and minus) switchmode power supply. IOW there are 4 main voltages for the output stage in addition to the seperate power supply voltages for the signal amps and logic. The output VCCs are +/- 117 and +/- 67 volts. Power FETs route the proper voltage to the output stage depending on what it takes to produce an undistorted signal. Does anyone know if the QSC amp uses "blameless design"? Nothing like it! It's a very characteristic design. For example, the output stage BJT transistors all have their collectors grounded - no insulators on the heat sinks. IOW, does it use active current sources? There's a ton more to the blameless design that just that. Does the QSC have a regulated output supply? For the op amps and logic. This feature has been a mainstay of Krell design. More Morein moronic nattering. Contrary to what the mckelviphiban stinks, I am not a subjectivist. I do believe my ears can tell me alot, however, without the necessity of blind testing. See Morein moronic nattering, above. :-( |
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#26
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A Comparison
Mikey wrote:
Maggie wrote: Ever heard of opportunity cost? I must admit I've not heard that phrase. Explain please. Yes, Mags, do explain the concept of "opportunity cost" and after that, please expound on "utility theory" and then wrap things up with "Schumpeterian profits." For an encore, dazzle us with an analogousness of "Gresham's Law" as applicable to rao. Cheers, GeoSynch |
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#27
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A Comparison
"Arny Krueger" said:
It's pretty well known in the industry that the Krell ratings sheet has been juggled by Krell. The 8 ohm power rating was backed off, to create the impression that it is an ideal amp and puts out twice the power into 4 ohms. If the Krell amp were rated more conventionally based on those tests that Sander's buddy Middius hates, there would be a different story. You're forgetting that the Krell also doubles current in 2 ohms. The 8 ohms power ratings must be way, way underrated then. The input impedance of the QSC amp is rather low, something to keep in mind when driving it directly from an opamp's output. Most conventional audio-grade opamps have absolutely no problem driving a 1K load to 5 volts rms, let alone just 2. Ditto for modern preamps, whether vacuum tube or SS. Then why does e.g. Sony advise to load their CD players with at least 50 kohms? Their output capacitors are at least 47 uF, so a low frequency rollof wouldn't be a problem (for the math challenged, the -3 dB frequency is then around 0.5 Hz). The input sensitivity should have nothing to do with the output load impedance, is this a typo, a mistake or does the amp use such a high amount of global feedback that the load has influence on the input? In the latter case, problems might arise with strongly reactive loads, and this may make for a different sounding amplifier. I also noticed the DF isn't specified. Shows that Sander can't see that the amps input sensitivity is scaled to its output ratings into various load impedances. ********. A good amp is a constant voltage source, regardless the load. That means the load should be of no consequence to the input level. If there is influence, it's a bad design. Simple as that. There are more issues to discuss, but that would require more information about both amps, and, preferably, the schematics. Looks like having Sander comment on power amps is like engaging the proverbial loose cannon. You think the specs Mike gave are enough to determine whether these amps will sound the same in a DBT, regardless the load? Don't make me laugh. Taking technical comments about SS amps at face value from a tube advocate like Sander is very risky. Taking technical comments about anything regarding audio on an Usenet forum is very risky, no matter who the source is. But given © that you seem to think of yourself as the "bearer of Light" on audio newsgroups, I don't expect you to adhere to this view. Party on, dude. -- "Audio as a serious hobby is going down the tubes." - Howard Ferstler, 25/4/2005 |
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#28
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A Comparison
"Sander deWaal" wrote in message
"Arny Krueger" said: It's pretty well known in the industry that the Krell ratings sheet has been juggled by Krell. The 8 ohm power rating was backed off, to create the impression that it is an ideal amp and puts out twice the power into 4 ohms. If the Krell amp were rated more conventionally based on those tests that Sander's buddy Middius hates, there would be a different story. You're forgetting that the Krell also doubles current in 2 ohms. The point is that what doubles is not the amps maximum current output but the amps spec. The 8 ohms power ratings must be way, way underrated then. Yup. If you derated the QSC in a similar fashion, it would still be more powerful by far. The input impedance of the QSC amp is rather low, something to keep in mind when driving it directly from an opamp's output. Most conventional audio-grade opamps have absolutely no problem driving a 1K load to 5 volts rms, let alone just 2. Ditto for modern preamps, whether vacuum tube or SS. Then why does e.g. Sony advise to load their CD players with at least 50 kohms? They like to use small output coupling caps? Real men use the digital outputs of optical players, anyway. Their output capacitors are at least 47 uF, so a low frequency rollof wouldn't be a problem (for the math challenged, the -3 dB frequency is then around 0.5 Hz). I seem to recall that the output caps of my Sony CD player were 47 uF, for maybe the first year... ;-) The input sensitivity should have nothing to do with the output load impedance, is this a typo, a mistake or does the amp use such a high amount of global feedback that the load has influence on the input? In the latter case, problems might arise with strongly reactive loads, and this may make for a different sounding amplifier. I also noticed the DF isn't specified. Shows that Sander can't see that the amps input sensitivity is scaled to its output ratings into various load impedances. ********. Do the math. A good amp is a constant voltage source, regardless the load. Agreed, as is the QSC. That means the load should be of no consequence to the input level. If there is influence, it's a bad design. Simple as that. You're misinterpreting the spec. There are more issues to discuss, but that would require more information about both amps, and, preferably, the schematics. Looks like having Sander comment on power amps is like engaging the proverbial loose cannon. You think the specs Mike gave are enough to determine whether these amps will sound the same in a DBT, regardless the load? Nope, but I've measured enough QSC amps to know how the unspecified performance areas are. Don't make me laugh. Well Sander, I can't get you to even do simple math.... |
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#30
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A Comparison
There are far too many replys for me to read, so I'm probably repeating
what others have said. First, adding heatsinks or changing the fan will probably void the warranty, so it doesn't matter how good QSC's warranty is if you modify. Second, there are some important specs not mentioned below that will affect the audible performance. Things like TIM distortion and slew rate, overload recovery (maybe not so important with so much power), freedom from crossover effects. Frequency response isn't mentioned, but it's easy to acheive good frequency response in a power amp. In conclusion, even a staunch objectivist like me can't make a valid comparison given the specs below. TB wrote: Krell 350 Watt monoblocks @ $17,500.00 per pair 350 watts wpc @ 8 Ohms 700 wpc @4 Ohms 1400 wpc @ 2 Ohms Signal to noise = 118db 95 db @ 2.83 V THD = .05% 20 Hz - 20 kHz Input Impedance = 100 K Ohms Input Sensitivity = 2.6v RMS for max power Voltage gain = 26.4 db --------------------------------------------------------------------------------- QSC PLX 3402 Stereo amp $1200.00 700 wpc @ 8 Ohms 1100 wpc @ 4 ohms 1700 wpc @ 2 ohms Signal to noise 107 db THD = .03% 20 Hz - 20 kHz Input Impedance = 6 K ohms Input sensitivity = 1.9 Volts @ 8 ohms Voltage gain = 32 db I figure you get the QSC and either modify it by adding heat sinks or replacing the fans with very quiet ones, and still have saved around $15,000.00 and not be able to hear any difference. If you have a difference of opinion, please provide the technical reason why you disagree that would account for any differences in sound quality. Go ahead Robert, get technical, I'm sure I can find someone to translate if it gets to technical for what you think is my lack of brainpower. |
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#31
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A Comparison
"Sander deWaal" wrote in message ... " said: Krell 350 Watt monoblocks @ $17,500.00 per pair 350 watts wpc @ 8 Ohms 700 wpc @4 Ohms 1400 wpc @ 2 Ohms Signal to noise = 118db 95 db @ 2.83 V THD = .05% 20 Hz - 20 kHz Input Impedance = 100 K Ohms Input Sensitivity = 2.6v RMS for max power Voltage gain = 26.4 db --------------------------------------------------------------------------------- QSC PLX 3402 Stereo amp $1200.00 700 wpc @ 8 Ohms 1100 wpc @ 4 ohms 1700 wpc @ 2 ohms Signal to noise 107 db THD = .03% 20 Hz - 20 kHz Input Impedance = 6 K ohms Input sensitivity = 1.9 Volts @ 8 ohms Voltage gain = 32 db One of the things that I noticed immediately is the ability of the Krell to deliver twice the power (meaning current) in half the load, up to 2 ohms. I suspect that even in 1 ohm the figure would be close to the required 2800W, be it for a brief period of time. The QSC has only marginally more power into 2 ohms (not that those insanely high wattages have any meaningful use, you will note). Also, the current doesn't double with half the load. This means the Krell has a stiffer power supply, despite the lower average wattage. It is a true constant voltage source. You've jumped to a conclusion that's not borne out by the figures. The power output into a variety of load impedances is simply part of the spec. It does not mean that the power output of the Krell will double just by changing the load from 8 to 4 ohms. In other words, it has nothing to do with the "stiffness" of the power supply. What it DOES mean, on the other hand, is that the Krell is a 1400W amplifier designed for optimum performance into a load of 2 ohms or less. Since the output is voltage limited, it's an inefficient amplifier choice for an 8 ohm speaker. Norm Strong |
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#32
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A Comparison
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#33
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A Comparison
Arny Krueger wrote: "dizzy" wrote in message On 20 Oct 2005 15:00:13 -0700, "ScottW" wrote: BS... Sander's right No, he's not. and only cheap ass amps whose max output voltage diminishes as a function of load need do this. What a moron. You forgot the bull-headed part. Pot... kettle.... Arny... get some self awareness. Essentially ALL audio power amps do that, since essentially NONE of them have regulated high-voltage rails. It's only a question of "how much" does the output voltage droop. Exactly. You say Krell underrates their 8 ohm capability... You're wrong. Have you ever seen a review of a Krell when their power output is actually measured? Sheesh, the ignorance! You heard that old statement "Ignorance is Bliss"? Scotty should be very happy! Still no reference. Just talk. I've been trying to educate Scotty about audio for years, Funny... JJ taught me some things, Zelniker taught me some things, even Atkinson taught me some things. But you are a complete and total failure compared to these guys. You've taught me nothing. ScottW |
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#34
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A Comparison
wrote in message ... "Sander deWaal" wrote in message ... " said: Krell 350 Watt monoblocks @ $17,500.00 per pair 350 watts wpc @ 8 Ohms 700 wpc @4 Ohms 1400 wpc @ 2 Ohms Signal to noise = 118db 95 db @ 2.83 V THD = .05% 20 Hz - 20 kHz Input Impedance = 100 K Ohms Input Sensitivity = 2.6v RMS for max power Voltage gain = 26.4 db --------------------------------------------------------------------------------- QSC PLX 3402 Stereo amp $1200.00 700 wpc @ 8 Ohms 1100 wpc @ 4 ohms 1700 wpc @ 2 ohms Signal to noise 107 db THD = .03% 20 Hz - 20 kHz Input Impedance = 6 K ohms Input sensitivity = 1.9 Volts @ 8 ohms Voltage gain = 32 db One of the things that I noticed immediately is the ability of the Krell to deliver twice the power (meaning current) in half the load, up to 2 ohms. I suspect that even in 1 ohm the figure would be close to the required 2800W, be it for a brief period of time. The QSC has only marginally more power into 2 ohms (not that those insanely high wattages have any meaningful use, you will note). Also, the current doesn't double with half the load. This means the Krell has a stiffer power supply, despite the lower average wattage. It is a true constant voltage source. You've jumped to a conclusion that's not borne out by the figures. The power output into a variety of load impedances is simply part of the spec. It does not mean that the power output of the Krell will double just by changing the load from 8 to 4 ohms. In other words, it has nothing to do with the "stiffness" of the power supply. What it DOES mean, on the other hand, is that the Krell is a 1400W amplifier designed for optimum performance into a load of 2 ohms or less. Since the output is voltage limited, it's an inefficient amplifier choice for an 8 ohm speaker. **All well and good Norm, but when was the last time you measured a perfectly resistive loudspeaker load? -- Trevor Wilson www.rageaudio.com.au |
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A Comparison
"Robert Morein" wrote in message ... "ScottW" wrote in message news:XjY5f.3102$Ix3.2340@dukeread05... "dizzy" wrote in message ... On 20 Oct 2005 15:00:13 -0700, "ScottW" wrote: BS... Sander's right No, he's not. and only cheap ass amps whose max output voltage diminishes as a function of load need do this. What a moron. Essentially ALL audio power amps do that, since essentially NONE of them have regulated high-voltage rails. It's only a question of "how much" does the output voltage droop. There is also a subjective observation I can offer: A QSC amplifier sounds a lot like a Sunfire, or an (old) Bryston. There may be some who like that sound. I do not. To me, these particular amplifiers are abhorent. How many QSC amps have you listened to? Not all are the same. Of course, according to Arny, the above observation is invalid, must be ignored, because, IT CANNOT BE that anyone distinguishes between the sound quality of "properly operating amplifiers." No, it's just that no one has yet. |
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A Comparison
wrote in message oups.com... There are far too many replys for me to read, so I'm probably repeating what others have said. First, adding heatsinks or changing the fan will probably void the warranty, so it doesn't matter how good QSC's warranty is if you modify. I was not being serious. Second, there are some important specs not mentioned below that will affect the audible performance. Things like TIM distortion and slew rate, overload recovery (maybe not so important with so much power), freedom from crossover effects. Frequency response isn't mentioned, but it's easy to acheive good frequency response in a power amp. If you visit www.qscaudio.com and click on the produst links, you will find their amps are if anything over built. I was late and it was tired when I made the post. In conclusion, even a staunch objectivist like me can't make a valid comparison given the specs below. wrote: Krell 350 Watt monoblocks @ $17,500.00 per pair 350 watts wpc @ 8 Ohms 700 wpc @4 Ohms 1400 wpc @ 2 Ohms Signal to noise = 118db 95 db @ 2.83 V THD = .05% 20 Hz - 20 kHz Input Impedance = 100 K Ohms Input Sensitivity = 2.6v RMS for max power Voltage gain = 26.4 db --------------------------------------------------------------------------------- QSC PLX 3402 Stereo amp $1200.00 700 wpc @ 8 Ohms 1100 wpc @ 4 ohms 1700 wpc @ 2 ohms Signal to noise 107 db THD = .03% 20 Hz - 20 kHz Input Impedance = 6 K ohms Input sensitivity = 1.9 Volts @ 8 ohms Voltage gain = 32 db I figure you get the QSC and either modify it by adding heat sinks or replacing the fans with very quiet ones, and still have saved around $15,000.00 and not be able to hear any difference. If you have a difference of opinion, please provide the technical reason why you disagree that would account for any differences in sound quality. Go ahead Robert, get technical, I'm sure I can find someone to translate if it gets to technical for what you think is my lack of brainpower. |
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#37
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A Comparison
"ScottW" wrote in message oups.com... wrote: "Sander deWaal" wrote in message ... " said: Krell 350 Watt monoblocks @ $17,500.00 per pair 350 watts wpc @ 8 Ohms 700 wpc @4 Ohms 1400 wpc @ 2 Ohms Signal to noise = 118db 95 db @ 2.83 V THD = .05% 20 Hz - 20 kHz Input Impedance = 100 K Ohms Input Sensitivity = 2.6v RMS for max power Voltage gain = 26.4 db --------------------------------------------------------------------------------- QSC PLX 3402 Stereo amp $1200.00 700 wpc @ 8 Ohms 1100 wpc @ 4 ohms 1700 wpc @ 2 ohms Signal to noise 107 db THD = .03% 20 Hz - 20 kHz Input Impedance = 6 K ohms Input sensitivity = 1.9 Volts @ 8 ohms Voltage gain = 32 db One of the things that I noticed immediately is the ability of the Krell to deliver twice the power (meaning current) in half the load, up to 2 ohms. I suspect that even in 1 ohm the figure would be close to the required 2800W, be it for a brief period of time. The QSC has only marginally more power into 2 ohms (not that those insanely high wattages have any meaningful use, you will note). Also, the current doesn't double with half the load. This means the Krell has a stiffer power supply, despite the lower average wattage. It is a true constant voltage source. You've jumped to a conclusion that's not borne out by the figures. The power output into a variety of load impedances is simply part of the spec. It does not mean that the power output of the Krell will double just by changing the load from 8 to 4 ohms. BS. Power output is either current limited or voltage limited. Obviously into an 8 ohm load the amp is voltage limited. The QSC is also voltage limited into 8 ohms but becomes current limited into 4 ohms. IF the QSC is driven to max output into 8 ohms with 1.9 V rms input it will suddenly find itself current clipping if that load is increased to 4 ohms. The max input is now only 1.7 V rms. Since the gain is the same the useful dynamic range of the amp is reduced. In other words, it has nothing to do with the "stiffness" of the power supply. I guess we differ on the meaning of "stiffness". In my opinion... the power (current and voltage) capability of an amp is very dependent on its power supply. What it DOES mean, on the other hand, is that the Krell is a 1400W amplifier designed for optimum performance into a load of 2 ohms or less. Since the output is voltage limited, it's an inefficient amplifier choice for an 8 ohm speaker. Excess current capacity may bother you, I like it. It makes the amp more versatile and acceptable for use with virtually any speaker. The QSC suffers degraded dynamic range with load and the specs also show it suffer increased THD into 4 ohm loads as well. ScottW Here's the whole list. 8 ohms 20 Hz-20 kHz 0.03% THD 200W 300W 425W 550W 700W 4 ohms 20 Hz-20 kHz 0.05% THD 325W 500W 700W 900W 1100W 2 ohms 1 kHz 1% THD 600W 800W 1200W 1500W 1700W BRIDGE MONO MODE 16 ohms 20 Hz-20 kHz 0.1% THD 400W 600W 850W 1100W 1400W 8 ohms 20 Hz-20 kHz 0.1% THD 700W 1100W 1500W 2000W 2200W 4 ohms 1 kHz 1% THD 1200W 1600W 2400W 3000W 3400W Signal to Noise (20 Hz-20 kHz) -106 dB -107 dB -108 dB -107 dB -107 dB Input Sensitivity @ 8 ohms 1.0Vrms 1.2Vrms 1.5Vrms 1.7Vrms 1.9Vrms Input Sensitivity @ 4 ohms 0.9Vrms 1.1Vrms 1.3Vrms 1.5Vrms 1.7Vrms Voltage Gain 40x (32 dB) 40x (32 dB) 40x (32 dB) 40x (32 dB) 40x (32 dB) Output Circuitry AB AB 2-Step Class H 2-Step Class H 2-Step Class H Power Requirements (1/8 Power Pink Noise @ 4 Ohm) 6A 10A 8A 10A 12A ALL MODELS Distortion (SMPTE-IM) Less than 0.01% Distortion (Typical) 20 Hz-20 kHz: 10 dB below rated power 1.0 kHz and below: full rated power Less than 0.01% THD Less than 0.01% THD Frequency Response 20 Hz-20 kHz, +/- 0.2 dB / 8 Hz-50 kHz, +0, -3 dB Damping Factor Greater than 500 Input Impedance 6 k ohms unbalanced, 12 k ohms balanced Input Clipping 10 Vrms (+22 dB) Cooling Variable-speed fan, rear-to-front air flow Connectors, each channel Input: 3-pin XLR & 1/4" TRS balanced Output: Neutrik Speakon(TM) and touch-proof binding posts Amplifier Protection Full short circuit, open circuit, thermal, ultrasonic, and RF protection Stable into reactive or mismatched loads Load Protection On/off muting, DC-fault power supply shutdown Dimensions 19" (48.3 cm) rack mounting, 3.5" (8.9 cm) tall (2 rack spaces) 13.25" (33.7 cm) deep (from front mounting rails) Gain 40x (32 dB) Weight 21 lb (9.5 kg) net, 27 lb (12.3 kg) shipping |
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#38
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A Comparison
"ScottW" wrote in message
oups.com You've jumped to a conclusion that's not borne out by the figures. The power output into a variety of load impedances is simply part of the spec. It does not mean that the power output of the Krell will double just by changing the load from 8 to 4 ohms. BS. Power output is either current limited or voltage limited. You're one young naive puppy, Scotty. When you're talking spec sheet power output, the operative limit is in the mind of the guy writing the spec sheed. Obviously into an 8 ohm load the amp is voltage limited. If you put them on the bench, you'll no doubt find that they are spec sheet limited. *every* power amp I've ever tested in the past 10 years beat its specs on the test bench. The QSC is also voltage limited into 8 ohms but becomes current limited into 4 ohms. If you're talking about what happens on the test bench then yes, that could be said. OTOH, if you want to be pedantic, the power amp is voltage limited in both cases. It's just that with the lower load impedance, the voltage limit is lower because the power supply puts out less voltage when more current is drawn from it. The amp is still clipping because the output stage is attempting to exceed an internal voltage limit. IOW, the output transistors are saturating because their VCE is too low. This is actually a real-world distinction because power amps typically have some kind of current limiting. With 4 and 8 ohm loads its exceedingly rare for the current limiting to come into play. The chances that the QSC's current limiters are being activated in a standard bench test at rated power with a 4 ohm resistive load is approximately zero. Its only slightly more probable that current limiting is being activated with a 2 ohm load. IF the QSC is driven to max output into 8 ohms with 1.9 V rms input it will suddenly find itself current clipping if that load is increased to 4 ohms. Exactly. Thus, the input voltage required to drive the amp to a lower rated output voltage is lower. Get it now? The max input is now only 1.7 V rms. Since the gain is the same the useful dynamic range of the amp is reduced. Depends on how you talk about dynamic range. The usual convention is to rate the dynamic range of a power amp based on power output into the stated load. Since the amp can put out more undistorted power into the lower load impeance, most people would say it has more dynamic range. In other words, it has nothing to do with the "stiffness" of the power supply. I guess we differ on the meaning of "stiffness". In my opinion... the power (current and voltage) capability of an amp is very dependent on its power supply. Not always. Since you mentioned current limiting, we've got to remember that current limiting circuits operate pretty much independent of the power supply. What it DOES mean, on the other hand, is that the Krell is a 1400W amplifier designed for optimum performance into a load of 2 ohms or less. More correctly, its designed for acceptable performance into a load of 2 ohms or less. Since the output is voltage limited, it's an inefficient amplifier choice for an 8 ohm speaker. Compared to what? All good amps are generally voltage limited. Excess current capacity may bother you, I like it. It makes the amp more versatile and acceptable for use with virtually any speaker. The QSC is rated to put out more current into low impedance loads than the Krell because, because of its higher power rating - 1700 watts versus 1400 watts. I suspect that on the bench the same ordering continues. The QSC suffers degraded dynamic range with load and the specs also show it suffer increased THD into 4 ohm loads as well. Actually there's no evidence to base this conclusion on. Any comparison of the two spec sheets is a comparison of the fantasies or marketing guys. You'd have to measure them yourself to know whats *really* happening. |
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#39
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A Comparison
"Trevor Wilson" wrote in
message wrote in message ... "Sander deWaal" wrote in message ... " said: Krell 350 Watt monoblocks @ $17,500.00 per pair 350 watts wpc @ 8 Ohms 700 wpc @4 Ohms 1400 wpc @ 2 Ohms Signal to noise = 118db 95 db @ 2.83 V THD = .05% 20 Hz - 20 kHz Input Impedance = 100 K Ohms Input Sensitivity = 2.6v RMS for max power Voltage gain = 26.4 db --------------------------------------------------------------------------------- QSC PLX 3402 Stereo amp $1200.00 700 wpc @ 8 Ohms 1100 wpc @ 4 ohms 1700 wpc @ 2 ohms Signal to noise 107 db THD = .03% 20 Hz - 20 kHz Input Impedance = 6 K ohms Input sensitivity = 1.9 Volts @ 8 ohms Voltage gain = 32 db One of the things that I noticed immediately is the ability of the Krell to deliver twice the power (meaning current) in half the load, up to 2 ohms. I suspect that even in 1 ohm the figure would be close to the required 2800W, be it for a brief period of time. The QSC has only marginally more power into 2 ohms (not that those insanely high wattages have any meaningful use, you will note). Also, the current doesn't double with half the load. This means the Krell has a stiffer power supply, despite the lower average wattage. It is a true constant voltage source. You've jumped to a conclusion that's not borne out by the figures. The power output into a variety of load impedances is simply part of the spec. It does not mean that the power output of the Krell will double just by changing the load from 8 to 4 ohms. In other words, it has nothing to do with the "stiffness" of the power supply. What it DOES mean, on the other hand, is that the Krell is a 1400W amplifier designed for optimum performance into a load of 2 ohms or less. Since the output is voltage limited, it's an inefficient amplifier choice for an 8 ohm speaker. **All well and good Norm, but when was the last time you measured a perfectly resistive loudspeaker load? Maybe he's measured a ribbon tweeter lately. |
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#40
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A Comparison
Arny Krueger wrote: "ScottW" wrote in message oups.com You've jumped to a conclusion that's not borne out by the figures. The power output into a variety of load impedances is simply part of the spec. It does not mean that the power output of the Krell will double just by changing the load from 8 to 4 ohms. BS. Power output is either current limited or voltage limited. You're one young naive puppy, Scotty. When you're talking spec sheet power output, the operative limit is in the mind of the guy writing the spec sheed. Obviously into an 8 ohm load the amp is voltage limited. If you put them on the bench, you'll no doubt find that they are spec sheet limited. *every* power amp I've ever tested in the past 10 years beat its specs on the test bench. Its called margin. The QSC is also voltage limited into 8 ohms but becomes current limited into 4 ohms. If you're talking about what happens on the test bench then yes, that could be said. OTOH, if you want to be pedantic, the power amp is voltage limited in both cases. It's just that with the lower load impedance, the voltage limit is lower because the power supply puts out less voltage when more current is drawn from it. BS... this doesn't happen until you have exceeded its current capacity. The amp is still clipping because the output stage is attempting to exceed an internal voltage limit. IOW, the output transistors are saturating because their VCE is too low. This is actually a real-world distinction because power amps typically have some kind of current limiting. With 4 and 8 ohm loads its exceedingly rare for the current limiting to come into play. The chances that the QSC's current limiters are being activated in a standard bench test at rated power with a 4 ohm resistive load is approximately zero. Then you have no valid explanation for the reduced sensitivity or less than double 8 ohm load power output. You just keep spinning yourself into a hole. Its only slightly more probable that current limiting is being activated with a 2 ohm load. IF the QSC is driven to max output into 8 ohms with 1.9 V rms input it will suddenly find itself current clipping if that load is increased to 4 ohms. Exactly. Thus, the input voltage required to drive the amp to a lower rated output voltage is lower. Get it now? Yeah.. I got it. and effective dynamic range is also reduced as the noise floor is probably relatively fixed. The max input is now only 1.7 V rms. Since the gain is the same the useful dynamic range of the amp is reduced. Depends on how you talk about dynamic range. The usual convention is to rate the dynamic range of a power amp based on power output into the stated load. Since the amp can put out more undistorted power into the lower load impeance, most people would say it has more dynamic range. You measuring noise floor in power? I don't think so. In other words, it has nothing to do with the "stiffness" of the power supply. I guess we differ on the meaning of "stiffness". In my opinion... the power (current and voltage) capability of an amp is very dependent on its power supply. Not always. Since you mentioned current limiting, we've got to remember that current limiting circuits operate pretty much independent of the power supply. So much for the drooping bandwagon you jumped on. What it DOES mean, on the other hand, is that the Krell is a 1400W amplifier designed for optimum performance into a load of 2 ohms or less. More correctly, its designed for acceptable performance into a load of 2 ohms or less. Since the output is voltage limited, it's an inefficient amplifier choice for an 8 ohm speaker. Compared to what? All good amps are generally voltage limited. Lost track of who you're responding to again I see. Excess current capacity may bother you, I like it. It makes the amp more versatile and acceptable for use with virtually any speaker. The QSC is rated to put out more current into low impedance loads than the Krell because, because of its higher power rating - 1700 watts versus 1400 watts. I suspect that on the bench the same ordering continues. The QSC suffers degraded dynamic range with load and the specs also show it suffer increased THD into 4 ohm loads as well. Actually there's no evidence to base this conclusion on. Any comparison of the two spec sheets is a comparison of the fantasies or marketing guys. You'd have to measure them yourself to know whats *really* happening. and you'd have a sample of 1. I'm sure QSC isn't report increased THD into 4 ohm loads because they think it sounds cool. ScottW |
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