The problem with "know-how". - Page 8 - diyAudio
 The problem with "know-how".
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 26th June 2013, 11:42 PM #71 diyAudio Member   Join Date: Nov 2006 Location: Indiana Blog Entries: 1 Fourier representations of music, and superposition? (so sinusoidal analysis is applicable?) Last edited by gootee; 26th June 2013 at 11:45 PM.
 27th June 2013, 09:25 AM #72 diyAudio Member   Join Date: May 2007 I might respond to post 70 if I could understand it. I don't recall saying anything about "rectangular signals" from a generator, or distortion figures with lots of 0's after the decimal point. Perhaps the OP has the same trouble understanding me as I have understanding him? If we have yet another Fourier denier then it is not worth responding. I get bored talking to YAFDs on here.
diyAudio Member

Join Date: May 2007
Quote:
 Originally Posted by nigel pearson In a strange way SE tube amps are symmetrical
A very strange way indeed: using the word 'symmetrical' in a sense which doesn't involve symmetry.

diyAudio Member

Join Date: Mar 2007
Location: Oxfordshire
Quote:
 Originally Posted by DF96 A very strange way indeed: using the word 'symmetrical' in a sense which doesn't involve symmetry.
I agree and I know what I mean . There is a very small place where the signal seems reasonably symmetrical . A triangle wave is good to see it . Maybe it is what Sergey is saying ? As I said I do not have the maths for it . Bad hi fi is 2 D . Especially so on Quad ESL 63's . You see , what you hear from them has to happen in the chain . They are not the ones doing it . They can be so poor if wrongly feed .

It is binary. The trick is to get the amp to do it with typical valves . I got it in the end to do it with KT 88 and EL 34 to the point where it was almost identical . The big surprise was retesting the valves . The KT 88's were very different make to make . It might not be exactly symmetry . It is the sweet spot where the magic happens . It almost impossible to find . First thing is stop reading . It causes the correct answer to be lost . As Feynman says " First you have to define the problem " . If you use too many standard ideas what you will do is reinvent the wheel .

BTW the BH curve of the transformer comes into it . Far too long to discuss and I would need PHD help . Take it as the defect is in fact a nice thing . Like DC bias . Hate what it does to the bass . I said it before you had to . If there is a PHD in listening my daughter has it . She is Aspergers and was tested as an experiment in Oxford ( hearing of people like her ) . She has drastically better hearing than most . I supplied some of the test gear years ago . They use Hamsters rather than Mice because Hamsters are most like us in hearing . I source verified KEF T27's to do the work . The tests have to go above 40 kHz to be thought valid .

Last edited by nigel pearson; 27th June 2013 at 10:46 AM.

diyAudio Member

Join Date: May 2007
Quote:
 It is the sweet spot where the magic happens . It almost impossible to find . First thing is stop reading . It causes the correct answer to be lost .
Not too hot, not too cold, but just the right amount of 2nd for audio warmth. As this depends on the valve details and bias it is not surprising that it is different for each sample. I now understand what you mean by 'symmetrical': you mean just the right amount (for your ears) of asymmetry. Opposite meaning from that used by the rest of English speakers, but hey!

Stopping reading is more likely to cause the correct question to be lost.

 27th June 2013, 05:26 PM #77 diyAudio Member   Join Date: Mar 2007 Location: Oxfordshire I was rather sad that my friend John intends to build a Mullard circuit with the bits I gave him . He beamed and said he always wanted to . John has test gear probably above Audio Precision in ability to measure ? It won't be as easy to uses for audio work as that's not it's prime function . My guess is he can look at the sub - 140 dB range . He builds installments for measuring minute magnetic field variation . Hey Ho . His face said it all . That's what he wants to do . I will suggest injecting some 100 kHz to see if we can make the linearity improve . It is a push pull . Then take it out as in class D . It might work . Reading too many books = Mullard . The statement " a poor thing but mine own " that I hold to be important .
 27th June 2013, 06:34 PM #78 diyAudio Member   Join Date: Mar 2007 Location: Oxfordshire DF 96 . Asymmetry almost symmetrical . Is all done by cheating I know . I did find the tripple cheat a bit special . That is both pre-distortion and loop feedabck + UL . With my transfomer 9.5 dB loop seemed splendid . 16.5 db was about the limit . The point that seems most important is to get the valve centered with respect to bias . Then if two valves there are so many variations , more than that I dread to think . I did use transistor current sources and sinks until the end just to know how good it can be . I probably lost >6db of distortion reduction by not using them . My friend probably would have not listened to them if I had included them . One thing I did find is running one valve about 80% above normal voltage was splendid . I read in it's notes the limiting voltage and used it . Reading carefully it was not clear it would be OK so I went to a more standard 320 V . Shame because it worked well . At home I would use it as it never gave trouble .
 28th June 2013, 03:42 AM #79 diyAudio Member   Join Date: Jan 2012 Location: Moskow All this is very good and it is close for me. But truth search always leads to revising of customary concepts. With a support on the already known. Last edited by Sergey A; 28th June 2013 at 04:00 AM. Reason: Summ
 28th June 2013, 09:17 AM #80 diyAudio Member   Join Date: Mar 2007 Location: Oxfordshire The crazy example of this was Galileo . I think the Church of Rome held Aristotle to be part of the Bible ? That saves about 10 hours of typing . The C of R believed that the heavens were perfect and Earth was corrupt because Aristotle said it . The Moon was less perfect because the " bad " Earth was corroding the Moon . Seems reasonably correct to me so far . When Galileo showed that the Moon had mountains like Earth he was in trouble . It made all the C of R was saying a lie to many . So sad for he who they represented to cause that . Take he as a philosopher if you prefer . Galileo took the invention of two children which he improved . Venice had the best glass makers in the world . That gave him an advantage . His big crime was he was arrogant and disliked . I never met him so I am only saying what is remembered by others , the children in Holland ( ? ) also . The point is a very simple idea can change everything . Also bringing in the respected scientists or philosophers sometimes takes us away from the truth . I love philosophy , I seldom regard it as the truth . I think Descartes said " I think , therefore I am " , to which I say " if I don't think , therefore I would not be " . The truth usually is simple . When complexity arrives usually it is wrong . Chaos maths is useful as it defines things we can not easily know and why it happened . We can always design so as not to have the problem . When in an aircraft I am sure of that . Our Prime Minister announced an upgrading of the power of our Weather prediction computer . Give me strength . How many billion pounds for one extra day ? I can tell him for £1 000 000 what he ( we ) need to know for eternity . Compared with Northern Spain it will be rubbish . That area is said to have an ideal climate . It might continue to have it regardless if I am right . Buy your house 100 metres above sea level and have room to grow things . Have big dogs that are " usually " friendly and be happy .

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