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Old 24th March 2012, 12:24 PM   #91
Merlinb is offline Merlinb  United Kingdom
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Quote:
Originally Posted by Wavebourn View Post
The problem is, I have MS in Electronics Engineering, and learnt physics of semiconductor devices in details... It disagrees with your statement.
Ah, I only have a BEng in Electronic Engineering (including device physics) and an MSc in an unrelated subject.

On the other hand, even an exponential law has no 'sharp corners' in it, AFAIK...

Last edited by Merlinb; 24th March 2012 at 12:30 PM.
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Old 24th March 2012, 12:32 PM   #92
SY is offline SY  United States
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Quote:
Originally Posted by tinitus View Post
SY, I suppose you suggest other than ecc types

according to this spec sheet. the ecc82/12AU7 have the lowest distortion of the commonly used ecc types, and seems pretty much independant of the voltage, as well as the gain...
Of the ECC types, the 12AU7 has the poorest linearity. See Morgan Jones's measurements in "Valve Amplifiers." The 3rd and 5th harmonic distortion were an order of magnitude worse than a 6SN7. Comparing my measurements, the ECC81 is similar to 6SN7 (not quite as good, but higher gain) and ECC83 is better yet (much higher gain and must be buffered).
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Old 24th March 2012, 12:38 PM   #93
popilin is offline popilin  Argentina
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Hi DualTriode
Thanks for your feedback.
The equation for the output impedance of the SRPP from The Valve Wizard is for cathode resistor bypassed, for unbypassed cathode resistor, the correct is

Zout = [Ra + Rk (u+1)]/2

It gives almost 54K for the SRPP.
Just get up and I'm asleep, sorry if I say anything more stupid than normal.
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Johann
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Old 24th March 2012, 12:46 PM   #94
popilin is offline popilin  Argentina
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Hi SY
How lucky that I see you around here.
Wavebourn told me you were the one to help.
Could you give me a trick to remove the magnet wire enamel?
I'm going crazy with an OPT, and I can't with 0.2mm wire because the enamel is polyester imide resin.
And tested with aspirin, acetone, thinner, and up brake fluid !!!
Fire tends to ruin the wire, please, help me.
Best regards
Johann
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Old 24th March 2012, 12:47 PM   #95
SY is offline SY  United States
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Solvent won't do it- the enamel is a thermoset. You're stuck with abrasion or scraping. Sorry.
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Old 24th March 2012, 01:09 PM   #96
popilin is offline popilin  Argentina
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Quote:
Originally Posted by Wavebourn View Post
I was 53 then, on avatar.
Hi Wavebourn
As I said, you have more than kept secrets of aspirin...
What do you suggest that I leave?
Tobacco, alcohol, women...

I congratulate you also for your paper Tubes 201 - How Vacuum Tubes Really Work.
I had seen a few times, very deep, the best I found on the web.
But, why John Harper?
Best regards
Johann

Last edited by popilin; 24th March 2012 at 01:19 PM.
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Old 24th March 2012, 01:17 PM   #97
popilin is offline popilin  Argentina
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Quote:
Originally Posted by SY View Post
Solvent won't do it- the enamel is a thermoset. You're stuck with abrasion or scraping. Sorry.
Hi Sy
Thanks for your feedback.
I'm looking for a psychiatrist. How difficult it is to make an output transformer,
10 primary, 8 secondary and lots of wire to be soldered.
Best regards
Johann
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Old 24th March 2012, 02:20 PM   #98
popilin is offline popilin  Argentina
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Hi Wavebourn
Forgive me if I offended you, was not my intention, but the first time I feel among friends in the forum, and ask things that are not my incumbent.
Best regards
Johann
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Old 24th March 2012, 05:32 PM   #99
popilin is offline popilin  Argentina
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Hi all
What about this?
Now Zout is in the order of 1K
Best regards
Johann
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Old 24th March 2012, 06:00 PM   #100
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Quote:
Originally Posted by Merlinb View Post
Ah, I only have a BEng in Electronic Engineering (including device physics) and an MSc in an unrelated subject.

On the other hand, even an exponential law has no 'sharp corners' in it, AFAIK...
Ohh, I probably forgot to mention that I graduated as well high school where learnt Algebra. Sorry. And AFAIK different curves can be described by functions of different orders. When you take smaller part of a curve you get more smooth transfer function than when you take it's longer part, and it looks more linear: higher weight of the 1'st order member than of higher order members. It works for both, function of power 2/3 ad for exponential function, but exponential curve is described by function that is sum of members of infinitely high orders. It is sharper by nature already.

Now, straightening the curve described by low order function by multiplicaion (negative feedback) you increase it's order. That means, making it more linear you make it bent sharper.

However, feedback applied to the amplifier described by exponential function does not do any harm to it: you can't increase it's order. That's why transistor amps always benefit from feedback in terms of non-linear distortions. But when you apply feedback to tube amp you increase order of it's transfer function, i.e. make it sharper.

Now let's go back to perception and think, which changes of waveshapes we got used to hear in nature and don't hear as distortions, and which of tem will be audible as something that our perception can't recognize as natural changes of sounds?

The keyword is amplify power. Amplifying power you can add distortions that are not heard as distortions, they are filtered out by our own perception. It sounds louder, but still clean. Now trying to minimize this distortions you add some other distortions that perception does not filter out, and hears as something odd. I is what happens when going for lower TD we remove distortions that don't sound as distortions, but add distorions that sound as distortions.

Do you hear e now?
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