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Intriguing measures on tube amp
Intriguing measures on tube amp
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Old 15th April 2018, 09:57 PM   #21
6A3sUMMER is offline 6A3sUMMER  United States
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1. Try building a good push pull tube amplifier. Generally it will have very little 2nd harmonic distortion.
Do a listen and compare it to the solid state amp.
Now think about that one.

2. Both the single ended tube amps and the push pull tube amps tend to have a lower damping factor than the solid state amps.
The resultant frequency response of the loudspeaker is different for the tube amps versus solid state amps.
Now think about that one.

3. Many loudspeaker crossover resonances are affected by the driving impedance (lower damping factor equals higher driving impedance).
The effect of a low damping factor amp driving a loudspeaker resonant crossover is to lower the Q of the resonance.
Now think about that one.

4. Then there is the woofer resonance frequency impedance, or with a ported enclosure the 2 resonant frequency impedances.
Below critical woofer damping, there can be a different sound.
Now think about that one.

One point is to remember that this is a case of a system, with positive and/or negative synergies, or both. It is not a case of just the isolated parts of the system.

Last edited by 6A3sUMMER; 15th April 2018 at 10:07 PM.
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Old 16th April 2018, 12:06 PM   #22
DF96 is offline DF96  England
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Quote:
Originally Posted by jama
what must be our criterion to select our audio chain?
It is a matter of choice. Some people want accurate reproduction of the original sound, while others want a sound which they find pleasing. Some people want one but think they want the other. People who want accurate reproduction may differ on which imperfections they find annoying and which they can tolerate.
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Old 16th April 2018, 12:55 PM   #23
petertub is offline petertub  Sweden
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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.
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Old 16th April 2018, 02:56 PM   #24
jama is offline jama  Spain
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Hi all. Later read the article aimed by dady (thanks, friend), and thinking about all ideas from all of you (thanks a lot), I think:

Facts:

1. My tube amp with 300b sound more detailed and accurate than my other reference amp: original J2 from Fistwatt.
2. My tube amp has a clearly 'worse' harmonic distortion pattern than J2.
3. I have heard both amps with my full range driver (94 db) mounted in open baffle and using active filter, B5, from Firstwatt, one push-pull amp as lows amp and two woofers as reinforcement bass. Room is the same (small, around 10m2) so, with 3 or 4 watts rms is enough for a enough sound level.
4. I do not use any passive crossover.
5. Music I am hearing is camara, vocal and big orchestra.
6. I am using the same measure equipment: Rodhe & Schwarz UPL (but anymore because I must return it this month). But I have get one old HP3580A that measure reasonably well. I have 'calibrate' it using the UPL and harmonics and its values are the same. This will be my harmonics analyzer from now.
7. I have read the article of 'Do your ears deceive you'. of Dr. Tom Farrimond (1980).

Next actions:

1. Later read the article above, I know exactly that I do not have the technical resources and knowledge to perform a depth study of this question.
2. I assume that all results I get, will be absolutely subjetive and without any generality (my ears, room, speaker, amps, dac and sources).
3. My reference will be my subjetive criterion of live sound as a lot of live concerts I went.
4. Repeat hearing of any amp along some days and different 'state of mind'.
5. Build one push-pull with SS (already done) and other of tube type (with EL84 because I have some very old OPTs), get one digital amp with a nice TPA3116D2 chip from Texas, use one old AB amp that I own too.
6. Get all harmonics pattern of these amps.
7. Using the experience building SE with vfets, build one to choose differents harmonics patterns (changing gate voltage and PS supply is possible).
8. AND THE MOST IMPORTANT: enjoy hearing music and performing this little test...

What can I expect from all this?:

1. Try find a very slight response to my doubt (looking now how complex is the subject).
2. Choose the amp like more to my taste.
3. Get its harmonics pattern
4. ENJOY doing this...

I have decide the way to follow.
Thanks a lot to all of you for the ideas and advices.

Best
Juan Antonio
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Old 16th April 2018, 03:02 PM   #25
RajkoM is offline RajkoM  Bosnia and Herzegovina
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8. AND THE MOST IMPORTANT: enjoy hearing music and performing this little test..


+1
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Old 16th April 2018, 03:05 PM   #26
merlin el mago is offline merlin el mago
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Quote:
Originally Posted by dady View Post
There are some questions not answered with normal rules of thinking, there are more elements in play that we can not precise yet. have your read the article Do your ears deceive you_.pdf - Google Drive
Buenísimo / very very good.
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Old 16th April 2018, 03:05 PM   #27
kevinkr is offline kevinkr  United States
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Intriguing measures on tube amp
Quote:
Originally Posted by jama View Post
So, then is possible this pattern is a manipulate response?.
This pattern is not tube regular response?
This is very typical behavior in SE amplifier designs, but I will say that even for SE 1.3% at 1W is not stellar performance. It's quite possible to achieve THD numbers below 0.5% at 1W with a 300B SE without global feedback.

The Elekit TU-8600 is nonetheless a pretty good sounding little amp in my very limited exposure to it.
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Old 16th April 2018, 03:24 PM   #28
jama is offline jama  Spain
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Hi Kevinkr. In my future plans are build a better 300b amp, sure. But this amp has been my introduction in tube word.. I need time for focus and rest from build amp without stopping without enjoying the music.
Elekit has one problem for me. My drivers is 16 ohm, and of 7 or 8 watts of max output power at 8 ohm I only get half, but I am lucky because my room is small and drivers are of 94 db.
So, for now is ok, but in the future, God will say..
Best
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Old 16th April 2018, 04:49 PM   #29
popilin is offline popilin  Argentina
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Quote:
Originally Posted by jama View Post
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???
I think that the main reason was explained brilliantly by my good friend dady

Quote:
Originally Posted by dady View Post
There are some questions not answered with normal rules of thinking, there are more elements in play that we can not precise yet. have your read the article Do your ears deceive you_.pdf - Google Drive
At page 5 on the pdf, was quoted Békésy, he was not a foolish at all

Georg von Bekesy - Wikipedia

Another reason, and this is just my opinion, is that valve amplifiers are slower than SS, I mean if on the primary of OPT you have, lets say 100V/μs, on the secondary you will have 4V/μs @ 1W, on the other hand, speakers are electromechanical devices, hence they are slower too and match much better with valve amps than SS amps.

As for GNF, you cannot correct in the present (output) an event of the past (input), because time travel to the past is physically impossible, Hawking himself did say that if it were possible, the present were full of tourist from the future, which is far more convincing than to quote Boltzmann.
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Old 16th April 2018, 05:47 PM   #30
dady is offline dady  Balearic Islands
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Send a message via MSN to dady Intriguing measures on tube amp
I actually understand the epiphany in measure an VT amplifier, watching the saw tooth wave with a sinusoidal one in it, and then, complete disappointed with it, you put AER speakers and feed the monster waves devourer with Otorino Respighi's Pines and fountain of Rome. Then you start to read again Aristotle or presocratic philosophers cause you not understand how the science could explain the contradiction of your findings with your feelings.
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Last edited by dady; 16th April 2018 at 05:49 PM.
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