KeithL
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Posts: 10,261
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Post by KeithL on Aug 11, 2016 9:32:34 GMT -5
But, since every speaker is different, WHICH real load would you like to use? (And, yes, that Power Cube thingy was interesting, and probably got you closer to a speaker than a simple resistor, but that was still a relatively SIMPLY approximation - and not nearly as complex as many real speakers are anyway.) I have always been an advocate of 'real world load'. Without regard to the manufacturers need to advertise a power / distortion number, the REAL test continues to be into a REAL reactive load. 2 amps can measure identically into a resistor and be worlds apart when asked to drive a reactive load. Poor performance into a real speaker load CAN ACCOUNT for differences in audible performance, even though they may 'measure' the same into a resistor. That's the solution to 'Garbulky's Conundrum'. This system, linked, integrates nicely with the AP gear and provides a very good characterization of amp performance into real world loads. www.ap.com/technical-library/measuring-power-amplifiers-with-reactive-loads/ |
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KeithL
Administrator
Posts: 10,261
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Post by KeithL on Aug 11, 2016 9:38:18 GMT -5
So, exactly how can you tell the mileage of an elephant... and what do you measure it in "mpp"? (miles per pound of leaves)  (sorry, I just couldn't resist) The sixth elephant is the fact WE ALL hear thing differently..... He already said "your mileage may vary" so I think five is probably more realistic. |
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Post by vcautokid on Aug 11, 2016 9:48:59 GMT -5
Here is a novel idea. Smiles per hour. How does your amplifier or your whole system get along there? There is something to measure. Frankly, I close my eyes, lights out, and listen too my system. I don't much care to look at where the music is coming from, as to just focus on listening to the performance instead. If I want to watch something, there is always TV. Just saying. This measurement thing is way out of control. It is nice to know MPG,MPH,Watts whatever, and C02 emissions, but at the end of the day, what are the intangibles that are really meaningful as to why, and how your system brings you joy? Looks meh. I could have a round big coffee can of amplifier if it is musical. I could care less about the looks. It is the substance of that performance that is important. Doesn't listening to your music give you enough to do in your system anyway at the end?
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Post by leonski on Aug 11, 2016 11:24:48 GMT -5
But, since every speaker is different, WHICH real load would you like to use? (And, yes, that Power Cube thingy was interesting, and probably got you closer to a speaker than a simple resistor, but that was still a relatively SIMPLY approximation - and not nearly as complex as many real speakers are anyway.) I have always been an advocate of 'real world load'. Without regard to the manufacturers need to advertise a power / distortion number, the REAL test continues to be into a REAL reactive load. 2 amps can measure identically into a resistor and be worlds apart when asked to drive a reactive load. Poor performance into a real speaker load CAN ACCOUNT for differences in audible performance, even though they may 'measure' the same into a resistor. That's the solution to 'Garbulky's Conundrum'. This system, linked, integrates nicely with the AP gear and provides a very good characterization of amp performance into real world loads. www.ap.com/technical-library/measuring-power-amplifiers-with-reactive-loads/Just like ANY standard, you pick one and go with it. Industry Standards are more complicated and than you get Political. The amp power would state 'Measured per standard ABC, a simulated speaker load.' I'll go with Stereophile on this one. It is a documented AND characterized (measures known) kind of load. Nothing wrong with the Power Cube, either. Using a power resistor is FINE for a first pass, but if you want to KNOW how an amp performs? You'll need to stress it somewhat more aggressively and in tune with what it will see 'in the field'. About the most benign speaker load I can think of are (generally) the Magnepan line. Though they ARE of much lower than average sensitivity. This is ONE idea for such a load. Among a dozen or more. www.stereophile.com/reference/60/#B6KbZdpjOT4tRTjx.97 |
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Lonnie
Emo Staff
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Pay no attention to the man behind the curtain
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Post by Lonnie on Aug 11, 2016 15:21:25 GMT -5
While I think an active load test is a good thing, I am not sold on how important it is for a class A/B amp. Class D makes since. Their frequency response will vary greatly as the recombinant filter interacts with the load. But an active load on a class A/B will simply show you if the amp is current limited or has very poor damping or inadequate power supply. If the power supply is solid and designed accordingly to support the amp stage and if the amp stage has enough output devices to have good damping, then the results are very predictable. In the case of our amplifiers an active load will not reveal anything out of the ordinary because these are two of the major things I focus on in the design.
Just my .02
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Post by garbulky on Aug 11, 2016 15:27:54 GMT -5
While I think an active load test is a good thing, I am not sold on how important it is for a class A/B amp. Class D makes since. Their frequency response will vary greatly as the recombinant filter interacts with the load. But an active load on a class A/B will simply show you if the amp is current limited or has very poor damping or inadequate power supply. If the power supply is solid and designed accordingly to support the amp stage and if the amp stage has enough output devices to have good damping, then the results are very predictable. In the case of our amplifiers an active load will not reveal anything out of the ordinary because these are two of the major things I focus on in the design. Just my .02 I think that's your winning formula - power supply and amp stage. Even the weakest of the emo amps have all not sounded strained on my speakers. Most other amps I've tried sound strained even at low volumes especially cheap class D units. |
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Post by yves on Aug 11, 2016 16:32:35 GMT -5
So, exactly how can you tell the mileage of an elephant... and what do you measure it in "mpp"? (miles per pound of leaves) (sorry, I just couldn't resist) He already said "your mileage may vary" so I think five is probably more realistic. No, he said *your* mileage may vary. By contrast, the elephants are just *standing* in the room so their mileage doesn't vary.  |
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Post by leonski on Sept 5, 2016 2:24:07 GMT -5
Yes, elephant mileage varies EVEN for Standing elephants. You'd know this if you ever had to CLEAN UP after one.
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Post by Jim on Nov 22, 2016 22:06:03 GMT -5
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I have always been an advocate of 'real world load'. Without regard to the manufacturers need to advertise a power / distortion number, the REAL test continues to be into a REAL reactive load. 2 amps can measure identically into a resistor and be worlds apart when asked to drive a reactive load. Poor performance into a real speaker load CAN ACCOUNT for differences in audible performance, even though they may 'measure' the same into a resistor. 
