The great T-Amp shootout. - Page 7 - Home Theater Forum and Systems -

View Poll Results: Which amp would you like to see ? I am ordering 2.
Trends TA-10.1 @ $150 7 30.43%
Pop Pulse T40i @ $225 9 39.13%
Trends TA-10.1 Mini Mod @ $175 1 4.35%
Trends TA-10.1 Value Mod @ $235 6 26.09%
Voters: 23. You may not vote on this poll

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post #61 of 97 Old 05-13-08, 01:13 PM Thread Starter
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As is pretty easy to understand from reading the responses here, deciding how to construct a blind test is not a simple task.

I know some people got irritated with me for some comments I made about T-amps - and amps in general - earlier in some threads here, including this one.

Since the late 70's, 30 years ago, I have taken and/or set up 100's of blind tests. It does require a lot of preparation, and also thought, to do one properly.

So ... perhaps everyone will indulge me while I lay out what I think the hypothesis of this test should be, and how to set about proving - or disproving it.

The hypothesis: When operating within their rated output specifications, Some amps sound better than others. Many listeners claim to hear an immediate difference when switching from one amp to another.

The test: We will take a small panel of listeners and no more than 4 amps. These amps will be level matched to within 0.1 dB using a 1000 Hz sinewave. The panel of listeners will get to listen to each amplifier for a period of 2 minutes each, and will then vote on the sound quality of each amp.

This will be repeated, with the amps being played in a random order each time, for a total of 10 rounds of 4 x 2 minutes.

Speakers will be a pair of high quality bookshelf speakers of reasonable efficiency.

Sound pressure levels will be set to make sure none of the amps clips during the 10 rounds.

If the listener cannot hear a difference, he has 2 choices, guess - and hope he doesn't get "caught", which will be unlikely, given the odds over a preiod of this many trials.

Or - he will vote each amp the same.

If the listener DOES hear a difference, it will be consistent over the 10 trial periods.

Ok guys - that is my take on this. Please, feel free to chime in ... :thumbsup:
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post #62 of 97 Old 05-13-08, 01:15 PM
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How should the Gizmo be tested?

A test that is just 2 chanel, with easy to drive speakers and volumes intentionally held below the smallest amps clipping might seem to be a good choice. BUT, such a test ignores the Gizmo's sub out feature. It ignores the Gizmos 4 ohm capability. It ignores the Gizmo's 25 watts or the benefits of offloading bass duties to a powered sub.

Hmmm, how about we test a couple of pickup trucks by driving them off road. Since most of the test trucks are two wheel drive, we will leave the 4wd truck or trucks in their 2h mode to keep things fair. Sounds silly doesn't it? But then again, if you always drive on paved roads doesn't it sound silly to be testing the trucks offroad to give the 4wd versions an advantage?

In the end, I think the limited load 2 chanel "test" probably will be the least controversial and maybe we can get an idea if within their limits all of the amps sound generally if not completely the same.

You could then increase the load or SPL until you can hear the differences and maybe define those points. I think a 2.1 comparison with the amps that can be used with a sub, either with a sub out or the subs high level inputs would be even more usefull to many people, and if some of the amps can not be used with subs in either manner, it should be noted in the results since that could be a huge factor to a potential buyer. That is now 4 tests. Within their limits, pushed to the limits in 2.0 and within the limits and pushed to the limits 2.1.
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post #63 of 97 Old 05-13-08, 01:28 PM
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craigsub wrote: View Post
The hypothesis: When operating within their rated output specifications, Some amps sound better than others. Many listeners claim to hear an immediate difference when switching from one amp to another.
I think the better and easier way to test this is to ask people to listen to a pair of amps and vote same or different. If the theory is they sound "different" directly test that.

Pick just two amps for each run and either play AA AB BA or BB. You could then track how many times people think they hear a difference when there is none or can not hear one when there is.

To make the ordering random I would have the switcher flip two coins to set the amps for each trial. Heads is A tails is B, the nickle is the first amp played, the quarter the second.

Given the low wattage of these amps I would select fairly efficient speakers and quality recordings but with limited dynamic range (peaks) so the average volume levels are relatively high to make it easy for a group setting to hear.
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post #64 of 97 Old 05-13-08, 01:30 PM
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mfine, again, i dont know if you are referring to me, but did not state better in my post, so i am unsure...

Craig i think that is a more than acceptable test...

mfine, this test does ignore the sub out etc... BUT it does compare to the sound quality up to the limitations of the smallest amp. To me this is the point of THIS particular test. is there a significant difference in sound quality at the specified spl level of all the amps, and (presumably tested at lower spl's as well). You can have a disclaimer that this does not test anything in excess of this spl level...

regarding the 4wd analogy, i think it is fair to test it in 2wd, as long as you state you are testing its 2wd capabilities over it's 4wd. You are outlining the limitations of the actual test.

Testing say the geo vs ferrari, which drives better from 0-40mph, is quite significant. There is quite a diff between the two, even though you limit it to the capabilities of the geo, it still provides significant data, ie. city driving. One has better handling at this speed, the ferrari is difficult to drive at this speed due to having to keep the revs in the upper band. etc...
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post #65 of 97 Old 05-13-08, 01:34 PM
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I think Craig outlines a perfectly valid blind test but to me the results won't matter much at all because I don't listen that way. I like the direction Bill seems to be leaning. Give the amps a test drive in various conditions.

Nearfield computer-desk kind of set up seems very appropriate, with moderate volume, as would a larger room to simulate someone using in bedroom or maybe as primary two channel, where you'd certainly want to push the SPL.

I'd probably want to swap two different speakers into the test, something relatively efficient (88+dB) and something below 85dB, that is maybe considered harder to drive relative to impedance curve.

I'd like a few types of music to be evaluated - classical/orchestral, jazz w/female vocal, and some hard rock cover it for me. Maybe more or different genres are more approprioate?

The feedback I'd want is more commentary and less "amp A beats amp B". Try to explain what you hear in each scenario. Tell me what stood out, both good and bad. If a specific difference was significant then tell me, but don't try to force yourself to hear differences that are negligible.

I'm not asking or suggesting that this work be done. It would be very time consuming, although I imagine a lot more fun than a double blind. If something like it was put together, however, I think it would give potential customers a lot more info than is easily put together today. And they'd be able to logically pick a product for their intended use. Knowing that Gizmo and Trends can't be easily discerned by four guys listening to a bunch of two minutes samples won't help me know what to buy or why to buy it.
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post #66 of 97 Old 05-13-08, 01:43 PM
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ddoonie wrote: View Post
mfine, again, i dont know if you are referring to me, but did not state better in my post, so i am unsure...
If you do not want to test which one is best, then I am not refering to you am I? But, much if what I said was meant as food for thought for everyone.

My biggest fear is that if a test is conducted, the results will be used by potential buyers for whom the test is completely irrelevant. The next fear is the crowd of forum trolls it will attract. Picture a splash of blood and the nasty people from "I am Legend". That movie had the most realistic depiction of Grandarf and company yet to come out of Hollywood and they will be all over whatever we do.
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post #67 of 97 Old 05-13-08, 01:44 PM
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But it would help me with my choice. Lets say that i wanted to buy the trends ta-10, which has a max output of 15w (or whatever it is) at $150, this test shows that at the max output of the trends amp, the gizmo has no discernible difference in sound quality, has an additional 10w, a subout, and is 129.

So to me this test made my decision easy. I got all the trends had to offer with additional power, an optional sub out, and at a cheaper price...

ps. thanks for the clarification mfine, didnt really warrant the attitude, but whatever...
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post #68 of 97 Old 05-13-08, 01:48 PM
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Isn't the blind aspect necessary? If I want/expect the Gizmo etc. to sound "better", then I might subconsciously have a bias towards it.

I don't see the big to-do about a test. Put the amps on some measureable and equal playing field, and turn your back to them while someone else does the switching. And why would anyone criticize the results? If they think there was something left out, they can do their own comparison.
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post #69 of 97 Old 05-13-08, 01:56 PM
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ddoonie wrote: View Post
So to me this test made my decision easy. I got all the trends had to offer with additional power, an optional sub out, and at a cheaper price...
Ahh, but it is not that easy since none of the amps come with power meters. If in your normal listening you will have peaks that push past the rated limits, how each one handles the peaks could be the most important feature and it is not tested.

Lets say you will often get peaks that require 30-35 watts. Perhaps the Gizmo clips hard at 25 watts and makes harsh and painful noises. The trends may softly clip the peaks, reducing their levels but not adding any harsh distortion. Or maybe one of them behaves like a tube amp and adds even order harmonics that sound somewhat warm and pleasant (in some peoples opinions). Is the Gizmo still the better deal?
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post #70 of 97 Old 05-13-08, 02:15 PM
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I know one test will not satisfy everyone's questions, but acts as an indicator. In this situation it is still a better deal, as i sit .5m from my 87db (sensitivity) speakers rarely exceeding 90dbspl.

I understand what you are saying, but you can do that for ANY test that could ever be conducted. You can find a limitation with any test. The only way to bypass these limitations is with an unlimited budget, unlimited time for testing etc...

I am in no way saying these tests will lead to the ultimate amp rating guide. But to me it gives me information i find relevant, and is much more beneficial to lack of info. I dont think any of the test participants will be going public saying gizmo is better than this amp blah blah, i think they will let the test results speak for themselves, allowing you to derive your own opinion on the tests. I know to take tests with a grain of salt, such as statistics. Statistics are taken with goals in mind, BUT they can provide helpful information as long as you review the testing parameters.
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