If you could measure at 50 Hz it would certainly meet specs. LCR meters are meant for measuring chokes because these work at 100-120 Hz (i.e. rectified supply voltage) depending on the country. The LCR is also good for air core chokes as there is no core loss. No one cares about audio transformers too much as these represent a fraction near zero in the global market....you have to look for some expensive professional gear.
Pieter Treurniet's reply:
"45, I read that curve a bit different: at 20 Hz impedance is 10k6, that is effective inductance of 84 H; at 50 Hz impedance is 16k, that is effective inductance of 51 H; at 100 Hz impedance is 20k, that is effective inductance of 32 H. Nowhere near 130 H; maybe you need some (new) glasses?"
Verstuurd van mijn GT-N7000 met Tapatalk
Ha, ha, ha I don't need glasses. First that graph is not very representative as you get close to 100 Hz because you a have a resistor limiting the impedance. It can be somewhat useful only below 50Hz. Then maybe you should study some magnetism! Do you know how permeability works? It is only 1V applied. Have you ever heard about initial permeability? For that type of core with very small gap an increase of a factor of 2-3 is normal.
As a manufacturer you should know that there is quite a difference between minimum inductance and inductance. Minimum inductance is based on very small applied voltage and thus on initial permeability. I don't know any manufacturer which gives minimum inductance without specifying it. It would be like selling gold for brass!!
Rather than discrediting the others using your servant why don't you come here to discuss your transformers and show how good they are?
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Is is not even good enough at 50Hz because the reactance is too similar to the resistive load. In fact I put a real measurement of an OPT where it can be clearly seen that with open secondary it does have quite higher impedance at low frequency when the secondary is unloaded. Regardless of this reflected impedance drops inevitably even when the secondary load is such that the reflected primary impedance should be 3-4 times lower!
This is it again: 8K/6R PP transformer. Such transformer is rated for 270H minimum inductance (with 4V applied voltage) and 560H maximum inductance. Frequency is not specified.
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Actually the frequency for which inductance is specified can be derived from the curve with unloaded secondary. It is 50Hz!
In fact the impedance with unloaded secondary at 50 Hz is about 85 Kohm which means that L=85000/2pi50=270H that matches precisely the specs (i.e 270 H for 4V input).
If I did the wrong math as Mr Pieter did, not accounting for the resistive load, I would get a lower value for sure even at 1Hz....
In fact the impedance with unloaded secondary at 50 Hz is about 85 Kohm which means that L=85000/2pi50=270H that matches precisely the specs (i.e 270 H for 4V input).
If I did the wrong math as Mr Pieter did, not accounting for the resistive load, I would get a lower value for sure even at 1Hz....
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If you measure the Hashimoto with 1V rather than 5V you won't be anywhere near 70H. I can bet on that. I think you need to measure inductances properly before saying that specs are not true. The inductance of a push-pull transformer is inevitably more affected by the input voltage because there is no (or very little in practice) gap. Does your LCR meter apply 5 Vrms signal? Mine doesn't...and on top of that you have to account for core losses as it measures at 120Hz.
If you load the LL1635/5 mA with a 20K resistor and you get almost 11K at 20Hz with just 1V applied it should be actually more than 130H. I would say something in the region of 170-180 H! At 50 Hz you will get 130 H at worst applying few more volts just like the Hashimoto.
1V rms applied to the IT in an amplifier like the one we are talking about here (i.e. a 6N7 driving the 45) means about 1 MILLIwatt output power and doesn't create any problem even if 130H is not the minimum inductance at 50 Hz with 1V input. 5V driving the 45 mean about 30 mW output power!
I gave for granted all this basic knowledge but it looks like this is not the case.
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Hi!
Not true. The PP has a gap too to allow tolerance in the driving pair of tubes. It is actually good for 4-5mA DC
Thomas
Not true. The PP has a gap too to allow tolerance in the driving pair of tubes. It is actually good for 4-5mA DC
Thomas
In general your observation is correct: you need to have the DC through to get a precise results. I was just thinking about the LL1635/5 mA which has been the object of discussion in the last posts. In that case, as there is a gap for 5 mA DC the permeability will be lower in comparison to PP. If you don't have DC superimposed you will get substantially different result only when there will be quite some AC induction (i.e. some volts). Those measurements were made with 1V only so the result will be not very different if you superimpose the DC, if the transformer is made so that the initial permeability is still almost constant as function of the static field (which should be the case for the Lundahl up to 5 mA).
Bas Horneman;342499145: said:
No. I just said that from that graph one can see that the transformer impedance is 16K at 20 Hz because I made a quick evaluation, didn't just take the value from the graph. The transformer impedance is not the impedance when loaded by a resistor. I wrongly assumed you knew this instead you don't even know how to measure or evaluate the inductance in the correct way! So I had to tell you how to evaluate/measure the inductance in the following posts!! Your calculation of inductance is simply wrong, you should study and understand how a transformer really works before concluding that your competitors are cheating....
The permeability story is REALITY: the inductance does depend on the applied voltage.
There is no law that imposes a protocol and I think that if you ask Lundahl they will tell you. I think the info Lundahl publish is enough for the average user. They do give practical suggestions to make it work in the best way.
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801A instead of a 45
Hi to all smart and honorable men,
Since I intend to use that amp later as a driver for a 211, Thomas suggested to change the 45 for a 801/801A because it will give more headroom.
Of course I'm tempted because it's an opportunity to try a new tube.
However, the voltage range of 801 is large, do you have suggestions for HV?
Thanks,
Pierre
Hi to all smart and honorable men,
Since I intend to use that amp later as a driver for a 211, Thomas suggested to change the 45 for a 801/801A because it will give more headroom.
Of course I'm tempted because it's an opportunity to try a new tube.
However, the voltage range of 801 is large, do you have suggestions for HV?
Thanks,
Pierre
Sorry for this mistake, i read this in the post from Pieters servant in post 16.
btw you can calculate the difference between dc permeability for a ungapped core or gapped core.
µ*=1/((1/µ)+(Lg/Lfe))
Lg= length airgap
Lfe=mean iron path length
Pieter Treurniet's reply:
Ah, since we have found our master maybe you can tell us a bit more how you "quickly evaluate"?
Pieter Treurniet's reply:
then why did you come up with that Pimm graph, as it apparently gives no information on non loaded transformers below 100 Hz?
Pieter Treurniet's reply:
Yes, voltage and frequency for a given core.
Pieter Treurniet's reply:
Mmm, I hope my customers are still able to enjoy their amplifiers...
I ask you to stop insinuating that I accuse my competitors of cheating; all I did was bringing into discussion an inductance specification from a manufacturer with whom I have a (mutual) friendly and respectful relationship.
Once more it has become clear to me that on a forum like this it is almost impossible to be a DIY interested member and manufacturer at the same time, and I fully understand colleagues who decide to stay away from whatever forum.
This was one of the reasons to close my account here, and the experience of this "discussion" confirms it to be the right decision.
For me the discussion is closed, and contributing to this forum has definitely ended.
I wish you all luck and pleasure with whatever project.
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