For this reason the THD vs Frequency at different level with and without FB is relevant as test
It tells a lot of thing
First OT alone then with entire output stage
In the low end mainly the tube needs to give more current due the fall of inductance and for this reason the distortion increase
It tells a lot of thing
First OT alone then with entire output stage
In the low end mainly the tube needs to give more current due the fall of inductance and for this reason the distortion increase
By insertion loss we usually mean copper loss. If we also include core losses then it is impossible to give a number because these losses are flux and frequency dependent.
The insertion loss at any frequency can be measured.
Terminate the secondary with a non-inductive resistor equal to the rating of the secondary tap.
Drive the primary at the frequency of your choice.
Measure the voltage across the primary, and the current into the primary, and measure the phase angle.
Calculate the power factor, the Volt x Amps, and the Real power.
Measure the volts across the secondary load resistor; calculate the real power into the load resistor; since the resistor is purely resistive, the power and VA are exactly the same (phase is 0 degrees).
Calculate the insertion loss at your frequency of choice: % loss, dB loss, etc.
(You have measured the Real Power into the primary, and the real power into the secondary load resistor,
so you can calculate the insertion loss).
That loss accounts for Primary DCR, Secondary DCR, Leakage Inductance, Distributed Capacitance, Insulation Dissipation Factor, Core Loss, etc.
It does not get any better than that.
Right?
Terminate the secondary with a non-inductive resistor equal to the rating of the secondary tap.
Drive the primary at the frequency of your choice.
Measure the voltage across the primary, and the current into the primary, and measure the phase angle.
Calculate the power factor, the Volt x Amps, and the Real power.
Measure the volts across the secondary load resistor; calculate the real power into the load resistor; since the resistor is purely resistive, the power and VA are exactly the same (phase is 0 degrees).
Calculate the insertion loss at your frequency of choice: % loss, dB loss, etc.
(You have measured the Real Power into the primary, and the real power into the secondary load resistor,
so you can calculate the insertion loss).
That loss accounts for Primary DCR, Secondary DCR, Leakage Inductance, Distributed Capacitance, Insulation Dissipation Factor, Core Loss, etc.
It does not get any better than that.
Right?
.
You can do those measurements, it isn’t that difficult. Keep us informed, is it it useful or just a waste of time….
This is indeed possible, but even more graphs (and not a number):frequency/insertionloss and that for different output levels. But, we seldom see those graphs (I never did).
You can do those measurements, it isn’t that difficult. Keep us informed, is it it useful or just a waste of time….
file:///C:/Users/Presentator/Downloads/Radiotron_Designers_Handbook_4th_Edition.pdf
chapter 5.3 the audiotransformers p211 has an very interesting figure 5.13B
I see it as an indication for what is happening, I doubt if the figure is really reliable but it's a start
chapter 5.3 the audiotransformers p211 has an very interesting figure 5.13B
I see it as an indication for what is happening, I doubt if the figure is really reliable but it's a start
I know this document.
And it is possible to see that THD on graph. 17 will increase with level (with different core material ). The 30 dBu max is the max level in output of AP
0dBu is 0,77 volt, at +20 dBu the THD is 50 times greater (in some case)
Even the Zs is much lower than Rp of a tube.
In graph. 19 the THD is increasing with Zs but from one iron material to another there is a ratio 12 and more ( around), if you look at 800-1k of Zs, p.e.
And this is the reason to understand with the test of the OT alone can work at different level
Where do you see 50 times? The 84% nickel doesn’t go to +20dBu, the others have lower distortion.
The figures tell exactly what i had in mind.
Jensen doesn’t make output transformer for tube amplifiers. Those are all small signal transformers.
What we can also learn is that the contribution of the core for thd is very little. The core material dos much more. For me the transformer design has the biggest impact on the performance.
Oh! my error for 84%
the value is 250 times; look at around 0dB to around +18 dB; from 0,004 to 1%
for 49% we are at 50 times ( my right value) from 0dB at 0,02% to around 1% at 21-22 dB
the 84 nichel probably goes to +20dB with a lot of thd. The diagram is truncated.
For M6 we are not so good in relation.
For the other it is evident the incresing of thd with level, even you can't see it
And it is not important the type of trafo ( of course some attention can be always made)
In terms of low-excitation domain distortion, high-nickel and nanocrystalline magnetic materials are one of the finest. Second in my tests came amorphous 2605SA1. These were test of low-excitation region permeability as low as 0.005T. Unfortunately my notes remained in the company I worked for.
What I did discover back then was that airgapping the core and biasing it with DC via CCS would not do much to increase permeability for micro excitation signals (M5 core material tested).
What I did discover back then was that airgapping the core and biasing it with DC via CCS would not do much to increase permeability for micro excitation signals (M5 core material tested).
Still no walter, you see it wrong, a lot lower then 50. Doesn’t matter nobody cares.
No Walter you wrote “49% we are at 50 times ( my right value) from 0dB at 0,02% to around 1% at 21-22 dB”
And again 84% nickel saturates before +20dB so that would, if it ever reaches +20dB has much more distortion.
You are two times wrong! At least! Because all the numbers about 84% are also wrong, you are not able to read those figures correctly.