Home Theater Shack 2015 High-End Amplifier Evaluation Event Reporting and Discussion Thread - Page 7 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #61 of 250 Old 03-16-15, 06:19 PM
 
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Re: Home Theater Shack 2015 High-End Amplifier Evaluation Event Reporting and Discussion Thread

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I'm steadily growing on this bolded part. Power power power... more power... cleaner output. I'm beginning to wonder if 125w all channels driven if that really should be like 400w each channel that the Emotiva XPR-5 can deliver.

I can literally sell my Krell and buy a new Emotiva XPR-5 for the same price. Hmm....
ore power is only needed if you can't get to the levels you want cleanly with your current amp. With my current setup I actually went down on power as I do not need it to hit reference levels.

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post #62 of 250 Old 03-16-15, 06:26 PM
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Re: Home Theater Shack 2015 High-End Amplifier Evaluation Event Reporting and Discussion Thread

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Sonnie said himself he has clipped the amp. Me... I've ran these SVS ultras to 105db playing pink floyd with the X4000 in direct mode and the volume set to +8db and never heard of any strain at all.
I clipped my X5200 with the Ultras. Perhaps I was listening at louder levels than 105dB... not sure. I plugged my Behringer EP2500 in the loop and there were no issues... problem solved. I wanted a better looking amp and got a really really good deal on a Parasound HALO A31, so I purchased it.


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Not arguing that one or the views is absolute and carved in stone. But I thought the following quote from Lonnie Vaughn, Chief Technical Officer at EMOTIVA, offers a decidedly non snake-oil explanation for why amps sound different:

"Amplifiers do sound different for a number of reasons. Paul cites a good one, the square wave response. On a personal note, I believe the power supply plays a big part in the way an amp sounds. I get that the power supply accounts for the biggest part of an amplifiers cost. But so many companies take it down to the bare minimum required to meet the specs that there is no headroom in the system at all and the amp itself just sounds flat as a board. In these cases, all the designer had to do was put in a few dollars more in storage and it would have made it a completely different unit." (Taken from an article on this webpage)
I agree they will sound different if pushed really hard with certain speakers... in that one will clip, one will not. That is my experience... although someone else may hear something different for a different reason.


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The Denon tested has a normal non toriodal type transformer and that ended up falling last by the posts that was made?.... is that still true?
Not sure where you got that... the Denon was well received. We did not attempt to push it to the limits. I don't think any of us have ever doubted that you can overdrive an amp and that you need to make sure you have sufficient power to drive your speakers, therefore this event was not setup to test that aspect.



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I'm steadily growing on this bolded part. Power power power... more power... cleaner output. I'm beginning to wonder if 125w all channels driven if that really should be like 400w each channel that the Emotiva XPR-5 can deliver.

I can literally sell my Krell and buy a new Emotiva XPR-5 for the same price. Hmm....
"Sharp ears" Dennis liked two of the amps more than any others... wasn't all that impressed with the Emotiva "in comparison"... however, when he left he was highly considering purchasing an XPA-3 for his system and perhaps later considering one of his favorites. I think this echoes how subtle the differences were... in that even one of the amps that he did not favor "in comparison" as much as the others is still an amp he would have no issues owning and can still make very nice sound for his "sharp ears".
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post #63 of 250 Old 03-16-15, 06:44 PM
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Re: Home Theater Shack 2015 High-End Amplifier Evaluation Event Reporting and Discussion Thread

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Hey guys, a few things I'd like to add.

1. Yes, my results could be chalked up to chance.
2. 5 out of 7 is statistically significant and should not be ignored.
3. I admitted to fatigue at toward the end if the testing.
4. I did not start to miss until the end of the testing. My last few pairing evaluations took considerably more time due to this fatigue.
5. There is only so much time in the day and the group dedicated DAYS to this test, so we did the best we could with the time we had.
6. I feel that I could repeat this test and expect a similar outcome.
7. Each person used different, non standard methods to evaluate the pairings. This was probably the biggest deviation from control in the entire evaluation effort. I am not certain that a standardized method would be useful as we all hear differently and like different music.
8. Our sighted evaluations had better soundstage and imaging properties than the blinded, due to the bulky (but necessary) shrouding used to hide the amplifiers from view.
9. Audible differences in amplifiers are generally very small.
10. I have a favorite amplifier and will reveal that favorite after Leonard has crunched the numbers and posted the results.
Whether 5 of 7 is statistically significant depends on how you define it. By most research standards it would not be, as the probability of getting 5 of 7 if the probability of each choice is .5 would be about 84%. That means that there is a 16% probability of it being by chance. Most would consider 6 of 7 statistically significant, where the probability of it happening by chance is down around 5%.

I did not find that the imaging suffered in the blind tests. My big issue with the blind testing was time and confusion about trying to recall what X sounded like.

You have to consider our overall results, however, for 28 trials, to reach a 95% certainty we would need to be right 18 times. I think we could easily do that with more time and not restricting X for such a limited listening time and fewer amps.




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post #64 of 250 Old 03-16-15, 06:47 PM
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Re: Home Theater Shack 2015 High-End Amplifier Evaluation Event Reporting and Discussion Thread

One thing for sure... this was a major undertaking trying to accomplish all that you group has done.

Major Kuddos!

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post #65 of 250 Old 03-16-15, 06:48 PM
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Re: Home Theater Shack 2015 High-End Amplifier Evaluation Event Reporting and Discussion Thread

I think it is curious that even though we felt that we could hear differences in some comparisons, everyone came away convinced that the differences were so small, if real, that we would all opt for the cheapest amp that had the power we need.

I will be publishing the comments on individual amp impressions in the context of the comparisons made soon.




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post #66 of 250 Old 03-16-15, 06:50 PM
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Re: Home Theater Shack 2015 High-End Amplifier Evaluation Event Reporting and Discussion Thread

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One thing for sure... this was a major undertaking trying to accomplish all that you group has done.

Major Kuddos!
Indeed. It was a large investment in time and money, the latter more for Sonnie and the guys who travelled farther. The experience of working with this group is well worth it, however. We always have enormous fun and learn something, even if it is exhausting.




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post #67 of 250 Old 03-16-15, 07:03 PM
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Re: Home Theater Shack 2015 High-End Amplifier Evaluation Event Reporting and Discussion Thread

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Sonnie wrote: View Post
I clipped my X5200 with the Ultras. Perhaps I was listening at louder levels than 105dB... not sure. I plugged my Behringer EP2500 in the loop and there were no issues... problem solved. I wanted a better looking amp and got a really really good deal on a Parasound HALO A31, so I purchased it.

Nice amp! The X5200 is rated around 120w to 5 channel driven so for you to tell me you were clipping tells me the power requirements of the Ultras I got from you. I may end up looking for something with more power behind it as a "just in case" scenario


Not sure where you got that... the Denon was well received. We did not attempt to push it to the limits. I don't think any of us have ever doubted that you can overdrive an amp and that you need to make sure you have sufficient power to drive your speakers, therefore this event was not setup to test that aspect.

Understood I was speaking out of the side of my head.

Notes in red.

You guys really build some suspense making us wait for the end results lol

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post #68 of 250 Old 03-16-15, 07:05 PM
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Re: Home Theater Shack 2015 High-End Amplifier Evaluation Event Reporting and Discussion Thread

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Indeed. It was a large investment in time and money, the latter more for Sonnie and the guys who travelled farther. The experience of working with this group is well worth it, however. We always have enormous fun and learn something, even if it is exhausting.
Next time send an invite to me as the official photographer (my main passion)


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post #69 of 250 Old 03-16-15, 07:07 PM
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Re: Home Theater Shack 2015 High-End Amplifier Evaluation Event Reporting and Discussion Thread

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Each person used different, non standard methods to evaluate the pairings. This was probably the biggest deviation from control in the entire evaluation effort. I am not certain that a standardized method would be useful as we all hear differently and like different music.
Absolutely... each person needs their own set of evaluation music and methods of comparing.

What I do think we need to add next time is having more repetitive ABX comparisons between the same two amps, which Leonard suggested. This will eliminate any suggestion of chance... and about the only way to verify that it is not chance. There is no doubt there needs to be multiple blind rounds to eliminate chance, but we just didn't have time. We know subjectively you guys heard differences... so no real reason to do that next time. Next time it can all be blind.

I think our next gathering, if we can make it happen, we'll have 3-4 speaker reviews and only 2 amps for repetitive ABX'ing. Frank also said the popping noise during switching was not normal and I am sending it back to him for repair/replacement. That way next time someone can swap amps with the lights off and the listener can determine if amps were switched. Makes it more interesting.

I know we may not be able to get you back over here... if you are working, but maybe we can find someone who feels like they are seasoned in hearing differences to attend and and let them take a swing at it. We might throw in one set of cable comparisons too.

It may also be good to have those not testing to go outside the room while others test. During the blind testing you guys only spent 15-20 minutes on each amp comparison and that was spread out over the course of the day/night. So hearing the other music while others were listening apparently played a role in fatigue. Otherwise, I wouldn't think a couple of hours of listening over a 12 hour day should be that fatiguing.
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post #70 of 250 Old 03-16-15, 11:56 PM
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I like the idea of repeatability, and agree that leaving the room can help offset fatigue.

My first few evaluations went quickly, I was done in just a few minutes. Sitting and listening to others do their evals was fatiguing, and toward the end of the day, my evals were 3 to 4 times longer and my notes reflect my uncertainty at this point.

I feel confident that I could have picked up at least one more correct answer if I had not felt so weary toward the end. Those last few were VERY difficult.

"I left in love, in laughter, and in truth and wherever truth, love and laughter abide, I am there in spirit." - Bill Hicks
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