Go for a 30VA Talema as this has higher inductance. Maybe a 15VA would work but this one could loose topend due to high capacitances(have one lying around but have not tried it yet). For the ECL82s to like the lowish inductance better you should triodestrap them!
You could also rework the SEPTOR for ECL82 with one pentode and one triodestrapped:
http://www.diyaudio.com/forums/showthread.php?postid=1631009#post1631009
It plays and measures great.
Or why not a SEPTOR with two trioded ECL82s in parallell with a MOSFET as the antitriode.
You could also rework the SEPTOR for ECL82 with one pentode and one triodestrapped:
http://www.diyaudio.com/forums/showthread.php?postid=1631009#post1631009
It plays and measures great.
Or why not a SEPTOR with two trioded ECL82s in parallell with a MOSFET as the antitriode.
Tyimo said:Yves!
Yes, I will. I am very curious.
I think those high inductance toroids are made with lower "B Total". Mine is set to 1.4. (the iron material is 1.7)
Maybe those are around 0.8T (?) What do you think as a Transformer Guru?
Tyimo
Can't tell ! !
It's the manufacturer choice.
It's easy to find the induction the manufacturer has choosen:
Add a temporary winding, says 10 turns, and measure the voltage on it with the primary powered at nominal voltage.
That done, you're able to compute (rule of 3) the turns number of the primary.
Then:
B = 2250 x U / N / F / A
where
-U is the applied voltage (eg 230V),
-N is the number of turns of the winding to wich this voltage is applied (eg the primary),
-F is the frequency (eg 50Hz) and A is the section of the iron core in cm².
-B is in Tesla.
And if you have acces to a Variac, plot the current in primary vs the applied voltage and you'll obtain a curve representing the permeability of the core vs B
It usually peaks around 0.8 T
Have fun
Yves.
Tyimo said:Yes, I did and I am surprised! I measured nothing! The current is under 2mA!
So, this method is not working for me.
This method works ! ! beleive me !
230 / .002 / 314 = 366 Hy
A normal value for a true OPT, far from impossible for a large PSU unit.
Measured a small 10W OPT today at 1mA . . . as expected
Yves.
Yves!
The vanderveen OPT has 485H, but there is a note: "maximum value, measured over secondary, transfered to primary" (?)
What does it mean?? Maybe something similar like your method?
The primer resistance is 155.4R mine has only 15R!
Tyimo
Hmmm... I wish you have true, but it looks to me too good to be true. I measured my 100VA toroid. Same size as the Vanderveen OPT has.
The vanderveen OPT has 485H, but there is a note: "maximum value, measured over secondary, transfered to primary" (?)
What does it mean?? Maybe something similar like your method?
The primer resistance is 155.4R mine has only 15R!
Tyimo
Cool !
This measure is valid at 50hz with 230V rms applied.
When I measure an OPT designed for, says 25Hz, 10 Wats and for a reflected impedance of 5K, the voltage will be 223 Volts, near of wich used, but the induction will double at 25 Hz because:
B = 2250 x U / N / F / A
That means that if the target was 1.4 Tesla, I effectively measure it at 0.7 Tesla where the permeability of the iron is much higher. (see plot below).
That said, I'm surprised too, a value around 70mA is more common for a 400VA EI style PSU transfo. (At least , it's what I accept for my own designs)
This would give:
230 / .07 / 314 = 10 Hys.
Please Tyimo, check again !
For exemple, loading the secondary must be reflected as a corresponding increase of current in the primary.
By the way, what could be the result obtained using other method, please indicate wich voltage level and wich frequency was applied to the "Device Under Test", so you know the resulting induction.
Here is a plot of M6X lams permeability vs induction:
And, yes, I admit I've only few experience with toroïds, you instilled some doubt in me.
Yves.
This measure is valid at 50hz with 230V rms applied.
When I measure an OPT designed for, says 25Hz, 10 Wats and for a reflected impedance of 5K, the voltage will be 223 Volts, near of wich used, but the induction will double at 25 Hz because:
B = 2250 x U / N / F / A
That means that if the target was 1.4 Tesla, I effectively measure it at 0.7 Tesla where the permeability of the iron is much higher. (see plot below).
That said, I'm surprised too, a value around 70mA is more common for a 400VA EI style PSU transfo. (At least , it's what I accept for my own designs)
This would give:
230 / .07 / 314 = 10 Hys.
Please Tyimo, check again !
For exemple, loading the secondary must be reflected as a corresponding increase of current in the primary.
By the way, what could be the result obtained using other method, please indicate wich voltage level and wich frequency was applied to the "Device Under Test", so you know the resulting induction.
Here is a plot of M6X lams permeability vs induction:
And, yes, I admit I've only few experience with toroïds, you instilled some doubt in me.
Yves.
Hi Shoog,
It will. German studio supplier Klein+Hummel also had an "end user" range of tubed HiFi amps and f.e in their VS55 ECL82PP design, they use a 22M resistor to bias up the grid of the cathodyne stage using grid leak current. The VS55 schematic is available somewhere on the 'net.
Regards,
Tom
Shoog said:
It will. German studio supplier Klein+Hummel also had an "end user" range of tubed HiFi amps and f.e in their VS55 ECL82PP design, they use a 22M resistor to bias up the grid of the cathodyne stage using grid leak current. The VS55 schematic is available somewhere on the 'net.
Regards,
Tom
Hi Tyimo,
Any load you want . . . as far as it has a know value allowing to predict what should be the primary current !
Obviusly, the same than in the secondary divided by the voltage ratio, more some losses . . . less than 10%.
In fact, just a way to validate the test jig
Never be doubtfull enough !
Yves.
Any load you want . . . as far as it has a know value allowing to predict what should be the primary current !
Obviusly, the same than in the secondary divided by the voltage ratio, more some losses . . . less than 10%.
In fact, just a way to validate the test jig
Never be doubtfull enough !
Yves.
Hi Yves!
I think our discussion getting to be Off topic, but without a good OPT we cann't kill the baby Huey....
Well, this reflected impedance and primary inductance theme always confused me.
I know that the primary inductance (which has a direct effect on the low frequency response of the transformer) is the most important for the tube load and operating.
The -3dB low frequency cutoff point can be determined by the following formula:
f = 2*Pi*L or even better with the f = Z/(2*Pi*L)
where Z is the primary source impedance ( the reflected impedance in parallel with the source impedance presented by the tube's plate) and L is the primary inductance.
For the reflected impedance I use the following:
Impedance ratio is the square of the turns ratio, which is also the square of the voltage ratio, as shown in the following equation:
Zp/Zs = (Np/Ns)2 = (Vp/Vs)2
With this I can calculate and find the sufficient Toroid OPT, (115+115Vac: 6.3Vac for 8K:6K but it works only from the reflected impedance view. The primary inductance (measured with inductance meter) is still too low!
I think your measuring theory is related only to the reflected impedance. (I realy wish that you have true and it would work as you say. )
I know, if I want better low frequency response from the transformer, I have to increase the primary inductance, which means a larger core and/or more turns on the primary.
I would need minimum, on 20Hz (-3dB) 65H. It would give me ca. 8Kohm reaktance.
So, my question is: what is the important the reflected impedance or the primary inductance?
Tyimo
I think our discussion getting to be Off topic, but without a good OPT we cann't kill the baby Huey....
Well, this reflected impedance and primary inductance theme always confused me.
I know that the primary inductance (which has a direct effect on the low frequency response of the transformer) is the most important for the tube load and operating.
The -3dB low frequency cutoff point can be determined by the following formula:
f = 2*Pi*L or even better with the f = Z/(2*Pi*L)
where Z is the primary source impedance ( the reflected impedance in parallel with the source impedance presented by the tube's plate) and L is the primary inductance.
For the reflected impedance I use the following:
Impedance ratio is the square of the turns ratio, which is also the square of the voltage ratio, as shown in the following equation:
Zp/Zs = (Np/Ns)2 = (Vp/Vs)2
With this I can calculate and find the sufficient Toroid OPT, (115+115Vac: 6.3Vac for 8K:6K but it works only from the reflected impedance view. The primary inductance (measured with inductance meter) is still too low!
I think your measuring theory is related only to the reflected impedance. (I realy wish that you have true and it would work as you say.
)I know, if I want better low frequency response from the transformer, I have to increase the primary inductance, which means a larger core and/or more turns on the primary.
I would need minimum, on 20Hz (-3dB) 65H. It would give me ca. 8Kohm reaktance.
So, my question is: what is the important the reflected impedance or the primary inductance?
Tyimo
Here is the Vanderveen/Amplimo/Plitron OPTS data:
Type and Application : VDV8020PP = PAT4000: 2 x EL84.
Primary Impedance : Raa = 8 [kOhm]
Secondary Impedance : Rls= 5 [Ohm]
Turns Ratio Np/Ns : Ratio = 40 [ ]
Ultra Linear Tapping at : tap = 33.3 [%]
-.1 dB Frequency Range [Hz to kHz] (3): flf= 8.261 fhf= 51.826
-1 dB Frequency Range [Hz to kHz] (3): fl1 = 3.524 fh1 = 89.045
-3 dB Requency Range [Hz to kHz] (3): fl3 = 1.793 fh3 = 131.564
Nominal Power (1) : Pn = 20 [W]
- 3 dB Power Bandwidth starting at : fu = 28.5 [Hz]
Total primary Inductance (2) : Lp = 485 [H]
Primary Leakage Inductance : lsp = 8 [mH]
Effective Primary Capacitance : cip = 0.25 [nF]
Total Primary DC Resistance : Rip = 155.4 [Ohm]
Total Secondary DC Resistance : Ris= 0.161 [Ohm]
Tubes Plate Resistance per section : ri = 8 [kOhm]
Insertion Loss : Iloss = 0.219 [dB]
As you can see it has:
- high Primary DC Resistance Rip = 155.4 [Ohm] what means it has more turns on the primary than mine (15R) and also means it has lower Btotal, it isn't it?
- Turns Ratio Np/Ns : Ratio = 40 [ ] what is the same like I get with my calculation.
- Total primary Inductance (2) : Lp = 485 [H], what is very high (mine is just 4.5H) and "measured over secondary, transfered to primary" so it means it is related with the reflected impedance, it isn"t it??
Tyimo
Type and Application : VDV8020PP = PAT4000: 2 x EL84.
Primary Impedance : Raa = 8 [kOhm]
Secondary Impedance : Rls= 5 [Ohm]
Turns Ratio Np/Ns : Ratio = 40 [ ]
Ultra Linear Tapping at : tap = 33.3 [%]
-.1 dB Frequency Range [Hz to kHz] (3): flf= 8.261 fhf= 51.826
-1 dB Frequency Range [Hz to kHz] (3): fl1 = 3.524 fh1 = 89.045
-3 dB Requency Range [Hz to kHz] (3): fl3 = 1.793 fh3 = 131.564
Nominal Power (1) : Pn = 20 [W]
- 3 dB Power Bandwidth starting at : fu = 28.5 [Hz]
Total primary Inductance (2) : Lp = 485 [H]
Primary Leakage Inductance : lsp = 8 [mH]
Effective Primary Capacitance : cip = 0.25 [nF]
Total Primary DC Resistance : Rip = 155.4 [Ohm]
Total Secondary DC Resistance : Ris= 0.161 [Ohm]
Tubes Plate Resistance per section : ri = 8 [kOhm]
Insertion Loss : Iloss = 0.219 [dB]
As you can see it has:
- high Primary DC Resistance Rip = 155.4 [Ohm] what means it has more turns on the primary than mine (15R) and also means it has lower Btotal, it isn't it?
- Turns Ratio Np/Ns : Ratio = 40 [ ] what is the same like I get with my calculation.
- Total primary Inductance (2) : Lp = 485 [H], what is very high (mine is just 4.5H) and "measured over secondary, transfered to primary" so it means it is related with the reflected impedance, it isn"t it??
Tyimo
Tyimo said:
You're right all along, and you answered yourself to the question !
The primary inductance defines a reactance wich must be equal to the reflected impedance at the frequency where you accept -3dB gain.
The reflected impedance having previously be choosen using plate curves to achieve proper load for the tube(s), ie best power transfer to the LSPs.
Note that the method suggested to measure primary inductance is nothing else that measuring the primary reactance at 50 Hz then converting it in inductance ( because 314 in the formula IS 2 * pi * 50) !
Yves.
Primary DC resistance is fonction, not only of the turns number, but of its section too
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