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Intriguing measures on tube amp
Intriguing measures on tube amp
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Old 16th April 2018, 09:03 PM   #41
dady is offline dady  Argentina
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Quote:
Originally Posted by petertub View Post
It is two different things to build :
- an amp that reproduces music as it is recorded
and
- and amp that is sweet to the ears

It all boils down to what the goal of the amp.
HEHE but now, how you know which of all the reproductions are as it recorded"?
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Old 16th April 2018, 09:04 PM   #42
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Quote:
Originally Posted by DF96 View Post
Item 1 is an opinion. Items 2 to 7 are facts.
Or not...
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Old 16th April 2018, 09:27 PM   #43
dady is offline dady  Argentina
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Right now, I can not became overwhelmed with the capacity of people, technician, profane, experts to find conclusions in nowhere, far from any question and showing like masters their findings about nothing to add, simply criticizing the readings of the common men. But now I don't want to add any to them saying that, in the matter you asking Mr Jama, I can say, humble more than ever... We are biologic machines, in this kind of devices, the result of the mathematical operations always are approximate, music is a subjective expression, volatile and always is impossible to find a numerical response.
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Old 16th April 2018, 09:53 PM   #44
audiowize is offline audiowize  United States
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Quote:
Originally Posted by popilin View Post
As for GNF, you cannot correct in the present (output) an event of the past (input),
So opamps don't work...
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Old 16th April 2018, 10:08 PM   #45
popilin is offline popilin  Argentina
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Quote:
Originally Posted by audiowize View Post
So opamps don't work...
Op Amps sucks, even to make a decent PSU...
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Old 17th April 2018, 10:59 AM   #46
6A3sUMMER is offline 6A3sUMMER  United States
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dady,

You Said:
Is possible to guess that the distortion of the amp cancel the response of the speaker ?

Answer:
Speakers have 2nd harmonic distortion. Single Ended amps have 2nd harmonic distortion.
You can either increase or partially cancel the 2nd harmonic distortion, by connecting the speaker up one way or the other (the + and - leads to match the amp + and - out;
and then with the + and - leads opposite to the amp out).

One experiment used a double pole double throw switch from the SE amp out to the speaker.
Just one channel and one speaker was used, and a 100Hz tone from a low distortion oscillator.
One person switched the switch, and the other person listened. Then the two people
swapped who had the switch, and who listened.
The Timbre of the sound did change depending on the switch position.
This is similar to the cancellation of the 2nd harmonic distortion of a push pull amp.

No attempt was made to say which switch position was preferred, the experiment was just to prove that there was an easily discernible difference.
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Old 17th April 2018, 01:22 PM   #47
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I did this last afternoon with my J2 and my full range speakers. Some change inside...
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Old 17th April 2018, 01:23 PM   #48
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Thanks SixAthree summer....!
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Last edited by dady; 17th April 2018 at 01:29 PM.
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Old 17th April 2018, 02:36 PM   #49
gabdx is offline gabdx  Canada
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I find the 3rd 4th and 5th very low, and there are no other higher distortion.

High 2nd distortion is ok relative to a push-pull amp which cancels (in tests especially!) the 2nd harmonics. 2nd are mostly harmless, the wave form is simply asymmetric in the horizontal plane.

A good pair of speakers have -30 to -35 db of distortion below music level at 2 meters at 95db. This makes the whole amplifier distortion a quasi-non issue. We only use thd to try to improve amplifiers and make sure we are not making a design worse.

The only negative aspect of this amplifier is that if paired with a low sensitivity speaker the sound will soft clip which will blur musical impacts and details of low signals making the sound soft and homogenous/euphoric.

As 6A3sUMMER pointed out, this is a very basic performing 300B amplifier, still with great audio and THD in my opinion.

I have a set of amplifiers from 2 watt to 100 watts, the low wattage sounds lovely, but as the power increases the resolution of the speaker increases too. Be happy with your amplifier and keep it.
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Old 17th April 2018, 02:42 PM   #50
gabdx is offline gabdx  Canada
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Quote:
Originally Posted by jama View Post
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...
This response is produced with less linear components as you can see the ramp of high order harmonics. This is also a feedback design it would appear which has not a good control of the high harmonics vs your tube amplifier.

This type of amplifier has a loud sound with less realism. feedback introduce 3rd harmonics which are not measurable and mask low level signals. When the amplifier is near clipping I suspect the ramp of high harmonics will raise dramatically with a very harsh sound and more musical blurring.
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