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transformer test

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#81
45 said:
I wouldn't be so sure about your conclusions. Distortion is not just harmonic and music is not just a sine wave or any other simple test signal.
Click to expand...

I made spectrum analysis, not just sinewave test on oscilloscope. There are no other proven methods to observe and measure distortions.

Additionally, I compared Spice simulation with ideal transformer to real world tests, they are surprisingly close.
 
#84
Replay to post 68

The things you wrote are out from reality.
I every case if you are looking for the quality and need to understand something you must have a good test setup.
In addition if you wrote something regarding tech facts is better that after the words some real test will come.

The use of C core at 0,1mm means that the efficency, respect to EI (standard quality, as normal we found) is better so the windings can be easier an the L at low frequency and parasitic at high are much better = bass response and low thd / wide band+low thd.
The graph I sent is exactly what I said.
I think that Hammond, in general, are a good products related to the price, but (as showed) some limitation.

Regarding the output tube stage of course it has an influence on final results but, at the same level of signal, you can see the difference because the load that the output tube stage sees is complex and the quality of OPT can influence the performance.
Normally I test the pp OPT with pentode configuration, it is less linear that triode conf. but I am sure that no FB are present on circuit.
For triode as 300B and 2A3 the problems, due to a low internal impedance, are les evident.

Regarding SE, at this link:
845 amplifier with Fiat transfomers
you can see some measurement that show the results after dozen of test made with C core ( at that time the lamination was 0,3mm)
You can see the shape of distortion, at max power, and it is not high but almost perfect as trend of harmonics.
The winding in this case is very simple.
The OPT weight about 6 kg; nucleus X51 double, dimensions wide 135mm x h. 120 x deep. 125; if we assign a power to this core (for 50 Hz, power trafo) it is 680w.

See you later! 🙂


Walter
 
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#85
waltube said:
Replay to post 68

The things you wrote are out from reality.
I every case if you are looking for the quality and need to understand something you must have a good test setup.
In addition if you wrote something regarding tech facts is better that after the words some real test will come.
Click to expand...

Sorry you put two graphs without any other information and basically concluded the EI core is bad and C core is good. I have put a link about transformers test where you can see that C-core and toroids are not better than EI. The EI transformer in that test is n.16. This is it, go to the bottom of the page to see the test results:
European Triode Festival - ETF2009 Shootout

I cannot upload anything of mines now because I am not at "home".
It is about correct design and application, not core type!

waltube said:
The use of C core at 0,1mm means that the efficency, respect to EI (standard quality, as normal we found) is better so the windings can be easier an the L at low frequency and parasitic at high are much better = bass response and low thd / wide band+low thd.
Click to expand...
This might be complicated, but not impossible, only in few cases like a 211 SE with more than 10K. Certainly not in most cases. It doesn't need to be complicated if you know how to do it and how to cope with parasitic effects, distortion etc.
Looks like you go for the easiest because have no clue about winding techniques....

waltube said:
The graph I sent is exactly what I said.
I think that Hammond, in general, are a good products related to the price, but (as showed) some limitation.
Click to expand...
Again your conlcusion is specific to your cases. It is not general!!

See here for example:
Output Transformers | Tubelab

Looks like the Hammond hasn't got any additional distortion at low frequency in comparison to 1KHz. Certainly not as bad as in your case. Explain this!!!

Efficiency has a precise meaning. If you want to be technical please use appropriate words. I can make an EI transformer as efficient as I want.
The advantage of C-core is the size. For a given performance C-Core is smaller but this might not be a true limit for DIY.

Bye
 
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#86
The test at the ETF is not the test as Tango do.
Look at the place they put the choke. Not the right position to do a frequency plot.

Do you have you other, better sources?

Amplimo SE toroid :http://www.amplimo.nl/images/downloads/ds vdv/vdv3035.pdf

Amplimo PP toroid
http://www.amplimo.nl/images/downloads/ds vdv/vdv3070.pdf

btw the other link, with Hammond and Edcore, show bad frequency response (resonance)

45 said:
Sorry you put two graphs without any other information and basically concluded the EI core is bad and C core is good. I have put a link about transformers test where you can see that C-core and toroids are not better than EI. The EI transformer in that test is n.16. This is it, go to the bottom of the page to see the test results:
European Triode Festival - ETF2009 Shootout

I cannot upload anything of mines now because I am not at "home".
It is about correct design and application, not core type!


This might be complicated, but not impossible, only in few cases like a 211 SE with more than 10K. Certainly not in most cases. It doesn't need to be complicated if you know how to do it and how to cope with parasitic effects, distortion etc.
Looks like you go for the easiest because have no clue about winding techniques....


Again your conlcusion is specific to your cases. It is not general!!

See here for example:
Output Transformers | Tubelab

Looks like the Hammond hasn't got any additional distortion at low frequency in comparison to 1KHz. Certainly not as bad as in your case. Explain this!!!

Efficiency has a precise meaning. If you want to be technical please use appropriate words. I can make an EI transformer as efficient as I want.
The advantage of C-core is the size. For a given performance C-Core is smaller but this might not be a true limit for DIY.

Bye
Click to expand...
 
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#87
esltransformer said:
The test at the ETF is not the test as Tango do.
Look at the place they put the choke. Not the right position to do a frequency plot.

Do you have you other, better sources?

Amplimo SE toroid :http://www.amplimo.nl/images/downloads/ds vdv/vdv3035.pdf

Amplimo PP toroid
http://www.amplimo.nl/images/downloads/ds vdv/vdv3070.pdf

btw the other link, with Hammond and Edcore, show bad frequency response (resonance)
Click to expand...

It was about distortion at low frequency not frequency response. And speaking of Tango's...the XE20 isn't that better than U808 in terms of frequency response! Can you make a HiB C-core transformer much better than that on large scale and at same price? If yes why don't you do it?
Do you have a technical argument? Have you seen what happens to Hi-B C-cores at 1.88T? I don't think so....
 
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#88
See the link in post no 1 for the frequency plots and you can see that you are wrong.
Read LinuksGuru answers too.



45 said:
It was about distortion at low frequency not frequency response. And speaking of Tango's...the XE20 isn't that better than U808 in terms of frequency response! Can you make a HiB C-core transformer much better than that on large scale and at same price? If yes why don't you do it?
Do you have a technical argument? Have you seen what happens to Hi-B C-cores at 1.88T? I don't think so....
Click to expand...
 
#89
 
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#90
esltransformer said:
See the link in post no 1 for the frequency plots and you can see that you are wrong.
Read LinuksGuru answers too.
Click to expand...

You are right, you are wrong....again!! You seem to be short of knowledge to discuss this subject. Looks like you just wind transformers in a more or less random way based on superficial knowlwdge taken from here and there.

Sorry you are a bit confused! I can't see any distortion measurement as function of frequency and power with a reference to the actual B. I can only see a measurement at low signal level.
If it goes beyond 100KHz this doesn't make it necessarily better than one that stops at 50KHz. Can you hear the difference?


A Hi-B C core as a GOSS toroid will be rather linear up to 1.7T. After that the kink of hysteresis will be quite harder and harder and distortion will go sky high very quickly.
If you use 1.7T as max B for specifying RMS power at 30Hz, for example, then if you build an amplifier of that RMS power it could not go any higher than that. Peak power will also be your RMS power pretty much like most SS amps and so you won't take one of the adavantages of vacuum tubes. It's just a way of defining things in a practical way rather than bare numbers.


In the end LinuksGuru did the same mistake he was criticising in the first place. If the distiortion of the amplifier increases substancially a low frequency it doesn't mean that the transformer has no role in it just because its self distiortion might be one order of magnitude lower. It does not depend on how much B you use only and although it is inevitable at some point it can be minimized at expense of size, regardless of the core type one uses. But one has to decide what he wants first....otherwise it is just complete cobblers!
 
#91
esltransformer said:
Extra information (because i am to lazy to write it myself and others did already before....)
Modern High-end Valve Amplifiers: Based on Toroidal Output Transformers - Menno van der Veen - Google Boeken

And some old stuff
http://www.classicaudio.ru/articles/Output_Transformer_a57.pdf
http://www.classicaudio.ru/articles/ot_distortion_p2_a57.pdf
Click to expand...

I woundn't say you are lazy otherwise you would even respond. I would rather say you don't have the knowledge to tell things in your own words! Do you think I have never see those links before?
 
#92
Maybe seen but did you read it? Or understand it?

What do you think what happens it you use a air gap?
I published here a SE transformer and that dos have such thing as an air gap.
You can read it in the articles i linked.



45 said:
I woundn't say you are lazy otherwise you would even respond. I would rather say you don't have the knowledge to tell things in your own words! Do you think I have never see those links before?
Click to expand...
 
#93
esltransformer said:
Maybe seen but did you read it? Or understand it?
Click to expand...
What does it mean the fact that a transformer has an influence on tube distiortion even if its self distiortion is much lower?



esltransformer said:
What do you think what happens it you use a air gap?
I published here a SE transformer and that dos have such thing as an air gap.
You can read it in the articles i linked.
Click to expand...

esltrasnformer it is better if you stop plyaing the professor. If you really understood the subject you would already know I had already answered all your questions. But as your understanding of the subject is poor you keep going round in circles and don't realize the extent of some answers. I will NEVER give you more details that those because I really don't like the idea that people like you make money without being professional!! If you can do it the better for you if can't I don't care.
 
#94
45 said:
You are right, you are wrong....again!! You seem to be short of knowledge to discuss this subject. Looks like you just wind transformers in a more or less random way based on superficial knowlwdge taken from here and there.
Click to expand...

It is easy to criticize the work of others, if you have a better method of design, or better equations, please post them, as I do with mine. 🙂

45 said:
I do.
I am not sure about your numbers. Even without considering that pretty small loss, what is the Bmax (AC + DC) you get for 30W at 18Hz with 120 mA DC current and 30H minimum (i.e. with 10 Gauss AC)? Although the C core has an advantage respect to E+I in terms of size for the same specs the difference is not like between night and day.
The biggest core I consider acceptable is the EI 150/70 (i.e. 50x70 core size) and this would not be enough! 50x75 would be the minimum to achieve 30W at 18Hz with 120 mA DC current at my usual Bmax = 7500 G. So I would need to accept higher B at that frequency for 30W (and thus more distortion because in less linear area). A 50x70 core alone weights about 8.5Kg!!! For a reasonably sized transformer those numbers are impossible. Specifying max power at 30Hz is more than enough for SE OT, provided that will work not so close to saturation (7500 Gauss total induction limit for E+I and a bit higher for C cores). Together with an inductance that gives a ratio between reactance at 30Hz (i.e. 2*pi*f*L) and equivalent resistance (i.e. the plate resistance in parallel to the nominal primary load) equal to 8 it will already guarantee low distortion at least down to 30Hz. Of course the higher the better but practicality cannot be ignored at some point..... what's the point of having a huge transformer to get those numbers down to 20Hz rather than 30?
Click to expand...

I don't know amplifier details, but the OP claims

Zp=3500 Ω Zs=8 Ω ip=120 mA fo=18 Hz W=30 W

Supposing a more common lamination like EI155 (EI114 for eu), and your suggested Bmax=1.3T, using Eq.(41)

Np≈3836

Using

W=Ep^2/Zp

For 30 W

Ep≈324 VRMS

Using Eq.(22)

Np≈4316

Then we can increase current up to ip=135 mA, easy with current density of 3 A/mm^2, and not so big transformer. 😉
 

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#95
45 said:
It is easy to write down numbers without an idea of what will happen in real operative conditions! The inductance as function of B? The distortion? The power loss? Frequency response? Sorry...too many turns and sky high current density. Your design would be really poor for hifi standards!
Click to expand...

I agree, but with that particular arrangement, see Eq.(40), magnetic hysteresis curve become thinner and more linear, and then reduces loss.
As a physicist you would already know it. 😉

Inductance was chosen to obtain a 18 Hz roll off, 30 H as you correctly suggested.
Too many turns? Probably, but if clever interleaved, you could obtain a very good FR.
Is 3 A/mm^2 a sky high current density? Probably, but with 0.25 mm wire, losses are pretty low.
BTW, what current density do you use, or Tango, or your favorite transformer?

The purpose of my few scribbles is to illustrate the point that the OP numbers are totally possible, I can't to design a Hi-Fi OPT in just ten minutes, and if I could it, it would be a commercial secret. 😀
 
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#97
john_ellis said:
I think your Bmax of 1.3T is too high for a core carrying D.C. The excursion at low frequencies will distort. As a rule I use half which would be 0.65T.

John
Click to expand...

Me too, 1.3 T is a lot, so I took 0.65 T for Bmax(AC) and 0.65 T for Bmax(DC) for calculations, if you look Eq.(40) in attachment, is difficult to make my own notation consistent with other posters notation.
 
#98
popilin said:
I agree, but with that particular arrangement, see Eq.(40), magnetic hysteresis curve become thinner and more linear, and then reduces loss.
As a physicist you would already know it. 😉
Click to expand...
Yes I know as I know there is copper loss as well! Have you calculated it? And transformer insertion loss is usually referred to 1KHz.

popilin said:
Inductance was chosen to obtain a 18 Hz roll off, 30 H as you correctly suggested.
Too many turns? Probably, but if clever interleaved, you could obtain a very good FR.
Is 3 A/mm^2 a sky high current density? Probably, but with 0.25 mm wire, losses are pretty low.
BTW, what current density do you use, or Tango, or your favorite transformer?
Click to expand...
Probably? This is funny.
I didn't want to be unkind with you but I don't think you can put over 4000 turns into that core using 0.25 wire size. Even if you use the lower insulation type (0.285 mm) you wont be left with any useful space for the secondary once you also add in the insulation between primaries and secondaries!

popilin said:
The purpose of my few scribbles is to illustrate the point that the OP numbers are totally possible, I can't to design a Hi-Fi OPT in just ten minutes, and if I would it, it would be a commercial secret. 😀
Click to expand...
Try to do it and you will see by yourself if that is possible even not considering HiFi requirements! Once you know it doesn't take ages...
 
#100
Here there is the first proto of toridal with mumetal
http://www.multitask.it/thd vs freq/20140213_172136.jpg

Is a push-pull; the firsts test aren't very good but something interesting.
This is a thd vs freq at 1 w no FB
http://www.multitask.it/thd vs freq/1w_thdfreq_noFB.jpg
we have to understand what happen mainly at low freq.; but the test was good from 100Hz to 10 kHz

This is a freq.answer at 4 vout on 8 ohm load no FB:
http://www.multitask.it/thd vs freq/4vout_8ohm_NoFB.jpg
the results is good but also we have to investigate the curve at high freq. .
We try to use a different winding; now it os very simple.

Regarding the techical aspect it is very important to consider , it help (with reference on formulas) to give you a starting point.
But I am not a factory that can buy tons of iron (good or bad isn't importnat) and make a trafo; I have to discover step by step some sources then I hope to get some sample or just a few kilos of stuff.
In this way the only method to find a results is to spend time to make protos (with my friends) and put on table to test.
At the of the story the adventure is less complicated than we think at the beginning; the main thing is to have a good test test ( I repeat this concept again).

See you later!

Walter
 
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