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Intriguing measures on tube amp
Intriguing measures on tube amp
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Old 15th April 2018, 02:28 PM   #1
jama is offline jama  Spain
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Default Intriguing measures on tube amp

Hello guys. I am new here (tube thread) and I would like ask one question. I own one elekit amp with 300b tube. I like a lot how sound with my full range drivers. With complex music is superb. Instruments separation really is spectacular. Cons: little output power, but my room is small, so with this 4 watts (more or less) is enough for my tastes.
Well, I have some very nice measure instruments (some borrowed) to measure amps, and I have done it with this tube amp. Before tubes I built a lot of solid state amps (some with vfets) from Pass thread. There, measures are important, our obsessions were perform a lot of measures, try reach the same performances that Nelson with his amplifiers..
But now, with tube amps I found that measures are something not very important. Before this elekit amp I built one nice tubelab with very old opt by curiosity. Measures in this little amp were really bad. But a friend from forum told me that I must hear it before dismount it.. What shock!!... Sound incredible. Why???
So, later I purchased the elekit tu8600, and later a lot of tube rolling I found my tube set for this amp (12au7 rca clear top, e83cc tesla and EML or ELROG 300b). Spectacular, superb,...
Well, now I perform the measures of harmonic pattern. What surprise!!
The harmonic pattern is, by far, a lot worse than solid state. But the sound a lot better. Look the images, and the total amount distortion at 1W rms and 8 ohm : 1.3%.
Can somebody tell me why this harmonic pattern is so good to my ears???
Measures are something useful or fireworks???
I do not believe in magic, but if objetive measures are no telling us how good is an amp, what is???
I asked this question in elekit thread but nobody reply me, so I am here...
Thanks in advance..
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Old 15th April 2018, 02:29 PM   #2
jama is offline jama  Spain
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Default More pictures

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Old 15th April 2018, 02:30 PM   #3
jama is offline jama  Spain
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Old 15th April 2018, 02:48 PM   #4
smoking-amp is offline smoking-amp  United States
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The 1st thing I notice there are the smoothly tapering off harmonic sequences.
So obviously not a linear response, but rather a smoothly "curved" response (FFT of a low-power law distortion). Apparently the ear is still happy with this. Maybe you have straightened out the cone support tension curve of the speaker?

Last edited by smoking-amp; 15th April 2018 at 02:51 PM.
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Old 15th April 2018, 02:52 PM   #5
jama is offline jama  Spain
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So, then is possible this pattern is a manipulate response?.
This pattern is not tube regular response?
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Old 15th April 2018, 03:03 PM   #6
smoking-amp is offline smoking-amp  United States
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Tube amps do generally end up with smooth tapering harmonic sequences if designed "well". But then "well" could just be what sounds good to the designer using his speakers. A rather circular design rule.

Have you tried reversing the wire connections to the speaker(s)? But then, maybe speakers have the same (symmetrical odd harmonic at least) suspension distortions, so that would not make much difference. (except for the even order distortions, which seem to sound OK at low % anyway)

Last edited by smoking-amp; 15th April 2018 at 03:12 PM.
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Old 15th April 2018, 03:35 PM   #7
RajkoM is offline RajkoM  Bosnia and Herzegovina
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It's hard to beat a good SET amp in combination with full-range drivers. That's known for a long time.
Try some 2-way or 3-way speakers with complex passive xover. If you still like sound with 300B amp, its matter of taste then.
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Old 15th April 2018, 03:37 PM   #8
audiowize is offline audiowize  United States
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Measurements are still very useful for tube amps, even SET amps. You'll generally want to look at how low you can go at full power for 5% and 10% THD.

You can put some feedback around the amp and listen to it without most of the THD. You would likely find that the feedback isn't helpful to your ears, but very helpful to your FFT.
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Old 15th April 2018, 03:55 PM   #9
traderbam is offline traderbam  Europe
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Quote:
Originally Posted by jama View Post
Can somebody tell me why this harmonic pattern is so good to my ears???
Is there a false premise in this question?
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Old 15th April 2018, 04:19 PM   #10
jama is offline jama  Spain
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Default Why?

Why?. I do not understand why this harmonic pattern sound so good when I have seen a lot better harmonics pattern in a others amps, and the final sound is worse, for my taste.
For example, I own an original J2 from Nelson. I have measure the same. Look image. This is the original J2 (best amplifier of 2017, Stereophile). For me, sound is not as good as tube amp. All music is more transparent, more details and instruments separation with elekit. J2 is an incredible amp (is my second amp), but I feel 'more' hearing with 300b.. And this is the problem, why?. Measures are better with J2, harmonics are a lot lower in value...
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