Lsc
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Post by Lsc on Apr 22, 2013 18:52:39 GMT -5
Don't jump on the poor guy for a legitimate question.... I wonder what is their definition of constant power output? Till the capacitors run out? Anyway, I'm not very worried about it. I have no doubt it actually tests out as the AP specs say it does and pumps out those watts. Its not Emotiva's definition...there is a standard called RMS power. en.wikipedia.org/wiki/Audio_power#Continuous_powerAnd yes, there is no need to worry about it.  |
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Post by TUGA Audiophile on Apr 22, 2013 19:12:46 GMT -5
Looked at XPA-1L specs and they just don't seem right. 500 watts @ 4 ohm (0.1% THD) 450 VA heavy duty toroidal transformer How is this actually possible? Another thing that bothers me is 35 watts in cllass A. This would produce so much heat that with no active ventilation you could make toasts on the amp.. The description says it just gets slightly warmer. Just look this one... www.mosconi-system.it/product/a-class/ |
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Post by garbulky on Apr 22, 2013 19:22:44 GMT -5
So, I guess the main question is how does an amp get to a continous output of so many watts if the power supply is less than the amount of watts it can produce ( i also assume power supplies are not 100% efficient). It's a serious question that I would like to know. For instance class D can produce crazy power from tiny circuitry. But for this instance so as not to confuse me let's talk about class AB amps with torroidal transformers. Is it to do with capacitance? How does for ex 450 VA relate to 500 watts output at 4 ohms - which the amp actually does.
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Lsc
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Post by Lsc on Apr 22, 2013 22:31:09 GMT -5
When you find out, please let us know. Thanks. |
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Post by Gary Cook on Apr 22, 2013 22:54:39 GMT -5
So, I guess the main question is how does an amp get to a continous output of so many watts if the power supply is less than the amount of watts it can produce ( i also assume power supplies are not 100% efficient). It's a serious question that I would like to know. For instance class D can produce crazy power from tiny circuitry. But for this instance so as not to confuse me let's talk about class AB amps with torroidal transformers. Is it to do with capacitance? How does for ex 450 VA relate to 500 watts output at 4 ohms - which the amp actually does. My view, I'm not an electronics engineer, is that continuous power is not the same as contiguous power. Example a sine wave at 50 hz  Cheers Gary |
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Post by garbulky on Apr 23, 2013 5:17:06 GMT -5
Thanks for the response. You mean power waves that continously changes like 50hz vs 120hz?
How does it make the results on the ap test (that it does - no argument there) with the sine wave at watts higher than 450 at standard ratings? I know it does do it but how? Is it something to do with the 4 ohm output vs 8 ohm output or output is at a different voltage from house power causing an increase?
Something else I was wondering, what does 450VA mean (does 450 VA mean 450 watts)? How do you correlate that to how many watts an amplifier can put out?
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Post by doc1963 on Apr 23, 2013 6:42:50 GMT -5
No, volts and watts are completely different. A tranfrormer is a "magnifier" of the supplied line voltage. Capatance, in relation, would be storage.
Using a basic "voltage to watts" conversion calculator (which can be found online) a 450 VA supply is capable of producing 54,000 watts on a 120 volt circuit.
Once you figure in a resistive load, there's no doubt (as Dan said) that this transformer is more than capable of hitting the ratings of the amp.
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Post by garbulky on Apr 23, 2013 7:15:11 GMT -5
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Lonnie
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Post by Lonnie on Apr 23, 2013 7:47:24 GMT -5
Gentleman, You are way over thinking this. The amp stages are powered by the capacitor bank and the transformer and rectifiers are used to recharge the capacitors. When you add in the crest factor that is inherent in the transformer there is more than ample VA to keep the capacitors charged well beyond the required duty cycles as set forth by the IEEE to not just meet but exceed the RMS output standards. If we had little to no secondary capacitance, then yes, we would have to have a massive transformer to keep the rails nice and stiff, but my approach has always been to use lots of secondary capacitance. The reason for this is a capacitor can supply dynamic energy on a whole order of magnitude faster than a transformer. A transformer takes a long time to come up to speed when power is required whereas a capacitor can dump energy at extremely high rates and this is one of the reasons our amps have such good dynamic power. Hope this helps. Lonnie |
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Post by garbulky on Apr 23, 2013 8:37:43 GMT -5
Thanks Lonnie. That helps answer my question. From what I gather is it acheives the continous power by capacitors and the power supply can keep the capacitors charged enough to supply the power before the capacitors fully run out therefore extending the continous power by a good bit. Is that pretty much the gist?
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Lonnie
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Post by Lonnie on Apr 23, 2013 10:15:30 GMT -5
Thanks Lonnie. That helps answer my question. From what I gather is it acheives the continous power by capacitors and the power supply can keep the capacitors charged enough to supply the power before the capacitors fully run out therefore extending the continous power by a good bit. Is that pretty much the gist? Pretty much. Lonnie |
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Post by geebo on Apr 23, 2013 10:26:07 GMT -5
So is continuous in this instance a finite amount of time or does it mean continuous for how ever long you want to test it?
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Post by geebo on Apr 23, 2013 10:29:22 GMT -5
No, volts and watts are completely different. A tranfrormer is a "magnifier" of the supplied line voltage. Capatance, in relation, would be storage. Using a basic "voltage to watts" conversion calculator (which can be found online) a 450 VA supply is capable of producing 54,000 watts on a 120 volt circuit. Once you figure in a resistive load, there's no doubt (as Dan said) that this transformer is more than capable of hitting the ratings of the amp. You might want to recheck that. VA is VoltAmperes and is closely related to Watts which is V*A. There is no way that transformer is capable of putting out 450 amps at 120V to get 54,000 watts. |
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Lonnie
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Post by Lonnie on Apr 23, 2013 10:42:37 GMT -5
So is continuous in this instance a finite amount of time or does it mean continuous for how ever long you want to test it? Finite. The required duty cycle for audio gear is roughly 20%. If this were a motor control or something like that, then the duty cycle would be much higher, but audio is just not that way. Even with a test sine wave, each output device is only working 50% of the time. When actually playing music it will normally drop well below 20%. Lonnie |
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Deleted
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Post by Deleted on Apr 23, 2013 10:46:15 GMT -5
CFS EMOTIVA (5 XPA-1) provided a link to Gladen power amps...
While I find these to be interesting designs, and it is very nice that they are rated into a 2 ohm load, one spec I found disturbing was their SN ratio of only 77 dba at 1 watt into 4 ohms. My XPA-5, which is certainly not Emo's top-of-the line amp, has a SN ratio of > 97 db at 1 watt - Emo does not specify the impedance at which this was measured.
Additionally, Gladen rates the the power of their amps at < 1% THD, Emo does so at 0.1% - one tenth of Gladen's. Honestly, it probably does not make much difference sonically, but it would be interesting to see what the Emo amp could do at 1% THD. I suspect that its power rating would jump quite dramatically.
And 20 db is a HUGE difference in Signal to Noise. An amp that offers only 77 db of SN is really not up to par, IMHO.
Long story, short - Emo produces one whale of a good amp for a very low price...
-RW-
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KeithL
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Post by KeithL on Apr 23, 2013 11:12:23 GMT -5
To calculate watts WITH DC you simply multiply volts x amps (so, for DC, VA = watts). With AC power, there is another thing called "power factor". With AC power, if you have a reactive load (an inductor or a capacitor), there may be a phase difference between the voltage and the current, which affects the math considerably. If the voltage and current aren't "happening" at the precise same time, then they don't multiply directly together. The extreme example is to connect a (non-polar) capacitor directly across an AC line. It will have voltage across it, it will draw current, but will dissipate no watts at all (if it is a perfect capacitor) - because the voltage and current are out of phase - and so when you multiply them together, taking phase into account, the result is zero. [So, for example, a capacitor could draw 200 VA, but 0 watts.] A transformer is a partly inductive load (the details depend on what it is connected to), so the voltage and current may be slightly out of phase. Let's say it's connected to 125 VAC and it's drawing 4 amps of current. That would be 500 VA. But, if the two are slightly out of phase (we say that the transformer is a reactive load), that 500 VA may only work out to 450 watts. Transformers are usually rated in VA because the two important ratings are the voltage they expect to run at and the maximum current they can deliver. In an application like an audio amplifier power transformer, this will be similar to the amount of watts they can deliver (the watts will be slightly lower). Of course, since speakers are largely reactive, they are ALSO subject to power factor - but, to include that in the calculations, would mean that the amplifier output would have to be calculated differently for each speaker you might connect it to - and nobody is going to bother with that.... which is why we just "assume" that a speaker is a resistor for purposes of measuring things. Devices like fluorescent lamps and motors may be very reactive - and so their VA may be quite different than their watts (large motors and other very commercial large appliances are usually "adjusted" so that their watts and VA are close to each other - this is called "power factor correction" - which, for reasons far outside this discussion, is preferable to the power company.) |
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Post by KeithL on Apr 23, 2013 11:24:17 GMT -5
Thanks, and.... I'm a bit confused here.... I Googled Gladen, and it looks like what they make are very high end CAR amplifiers. Because car amps (even with voltage up-converters) run at relatively low rail voltages, big ones are usually designed to run into very low loads (because that's the easiest way to get LOTS of power from low power supply rails), and the speakers intended to go with them are also usually very low impedance versions. It also means you're working with high-current low-voltage wiring for everything, which also goes better in cars for all sorts of reasons. At a guess, you will also probably find that their distortion doesn't drop as rapidly as you reduce the output level - which is another consequence of many designs that run off relatively low supply rails. For something to deliver a S/N of 77 dB while running off a car electrical system is actually quite impressive engineering, but it IS NOT "home hi-fi". Because of the environment, car gear really isn't expected to deliver the same level of performance as home gear. You probably won't hear their noise floor, or the 1% distortion, over the engine noise in your car (if you can hear anything ever again after cranking it up to those sorts of power levels in a car). You're really comparing apples to artichokes to compare them to Emotiva gear CFS EMOTIVA (5 XPA-1) provided a link to Gladen power amps... While I find these to be interesting designs, and it is very nice that they are rated into a 2 ohm load, one spec I found disturbing was their SN ratio of only 77 dba at 1 watt into 4 ohms. My XPA-5, which is certainly not Emo's top-of-the line amp, has a SN ratio of > 97 db at 1 watt - Emo does not specify the impedance at which this was measured. Additionally, Gladen rates the the power of their amps at < 1% THD, Emo does so at 0.1% - one tenth of Gladen's. Honestly, it probably does not make mush difference sonically, but it would be interesting to see what the Emo amp could do at 1% THD. I suspect that its power rating would jump quite dramatically. And 20 db is a HUGE difference in Signal to Noise. An amp that offers only 77 db of SN is really not up to par, IMHO. Long story, short - Emo produces one whale of a good amp for a very low price... -RW- |
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Post by TUGA Audiophile on Apr 23, 2013 14:20:21 GMT -5
CFS EMOTIVA (5 XPA-1) provided a link to Gladen power amps... While I find these to be interesting designs, and it is very nice that they are rated into a 2 ohm load, one spec I found disturbing was their SN ratio of only 77 dba at 1 watt into 4 ohms. My XPA-5, which is certainly not Emo's top-of-the line amp, has a SN ratio of > 97 db at 1 watt - Emo does not specify the impedance at which this was measured. Additionally, Gladen rates the the power of their amps at < 1% THD, Emo does so at 0.1% - one tenth of Gladen's. Honestly, it probably does not make much difference sonically, but it would be interesting to see what the Emo amp could do at 1% THD. I suspect that its power rating would jump quite dramatically. And 20 db is a HUGE difference in Signal to Noise. An amp that offers only 77 db of SN is really not up to par, IMHO. Long story, short - Emo produces one whale of a good amp for a very low price... -RW- Projects are different, but it serves to justify the power of the power supply ... Let the engineers work and thank's quality/price ratio ... My NAD T973 and C270 cost me $4.500,00. Now with $5.000,00 I can upgrade into a dream system with 5 MONOBLOCK'S XPA-1 EMOTIVA!!!  - You know what we are talking about?  Thank's to all. |
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Post by TUGA Audiophile on Apr 23, 2013 14:27:14 GMT -5
I forgot - Already bought 2 XPA-1 just are missing + 3 ...  ;D  |
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Post by ludi on Apr 23, 2013 16:30:14 GMT -5
Keith and Lonnie, both thanks for the explanations about amplification, watts, VA, and related stuff. It feels like I'm back at the university  |
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;D 
