The only reason why I chose 400hz was because I use a biamped open baffle (the bass driver is run in an aperiodic box for efficiency sake with TL type response) where the narrow width dictates the high crossover point to get flat response. For most normal situations something below 100hz would be ideal.
Shoog
Shoog
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ampere turns, since turns are fixed, when more current is drawn, this leads to saturation...
also more applied voltage that leads to more current...
what made you say that?, i hate people parading calculations and derivations of formulas that others have done before....
there is only one transformer formula, but there is the imperial and metric units of measure...it has been done before by the early engineers, why do i need to repeat them....?
i just use them to make my needs...
i am more of a practical ways, charts and tables and graphs if they can help is always better and helpful...
there is only one transformer formula, but there is the imperial and metric units of measure...it has been done before by the early engineers, why do i need to repeat them....?
i just use them to make my needs...
i am more of a practical ways, charts and tables and graphs if they can help is always better and helpful...
Against your belief, there are equations not derived yet.
What about people people parading amplifiers that others have done before?
There is not only one equation for transformers, and some of them are wrong.
If you do not want to say which of them you use, it is fine, this forum is a free place.
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i do not need anything from you, that is for sure, but i am eager to see your finished traffos and amps if any....this is diy forum and here people build things not blah blah blah.......
The AC magnetic field in a transformer is given by
Bac(max) = (Uac x 10⁸) / (√2 π fo S Np)
It has nothing to do with current, but with voltage.
If a power transformer is used, maintaining Bac(max) constant, being fo' the new lowest frequency, the useful plate to plate RMS voltage will be at most
Vp-p(max) = (fo'/fo) Uac
Let's suppose a 230V/50Hz mains (best case scenario) for fo'=30Hz
Vp-p(max) = 138 V RMS
This was already said by GoatGuy on post#6, and that's why some folks use high current valves.
It is a bit disappointing, I must continue winding my own transformers. 🙄
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I wonder how much tolerance is designed in for mains fluctuation; perhaps a 230V winding doesn't cause core saturation until 250V input?
I very much agree with Shoog that unless you've tried you cannot know how successful these mains toroids can be with the right tubes. If you've got efficient speakers and a few horizontal deflection tubes, it's an easy and inexpensive experiment.
btw, has anyone tried 6S33S with mains toroids? The enforced current sinks would stop these temperamental tubes from running away.
I very much agree with Shoog that unless you've tried you cannot know how successful these mains toroids can be with the right tubes. If you've got efficient speakers and a few horizontal deflection tubes, it's an easy and inexpensive experiment.
btw, has anyone tried 6S33S with mains toroids? The enforced current sinks would stop these temperamental tubes from running away.
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I do not think so, manufacturers are greedy, and they mostly works on the saturation knee, even so, for 250V
Vp-p(max) = 150 V RMS @ 30 Hz
For primary load Zp-p=2K, it yields about 11W, mere 1.7W more.
I like to design my transformers for fo=15Hz, but if some folks are happy with 30Hz, it is just fine.
Agree, but here toroidal PTs are very expensive, so winding an E I OPT with M4 GOSS is cheaper, and I can choose the right amp with prefered valves.
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The long E laminations used for constant voltage xfmrs (CVT) are rarely used these days. One vendor sent me a 50 lb box for free years back. Probably are long gone now. These lams allow two standard bobbins on the center leg, so are perfect for making ultra low leakage, balanced (split bobbin P-P) OTs. Almost as good performance as audio wound toroids.
There are still SOLA CVTs on Ebay if you can find one cheap. After knocking out the small shunt lams, you are left with a 115V winding and a 600V winding (no CT) already placed on the long E lam core. Not ideal to have them separately wound, but should be usable for an OT.
There are still SOLA CVTs on Ebay if you can find one cheap. After knocking out the small shunt lams, you are left with a 115V winding and a 600V winding (no CT) already placed on the long E lam core. Not ideal to have them separately wound, but should be usable for an OT.
But increased voltage implies increased current through a given load...
Since you know a lot more math than I do. What is the max 20Hz freq through a 25VA 120+120:6+6 coil at a voltage of 300V B+? In otherwords, can you give me the math to explain why this set up give only 2.5V out sine at 20Hz but 1000Hz is good to 15W? Sorry if this seems "noob" but I am definitely a "shadetree" builder.
I would also say that if the max allowable voltage (in the UK) is now 250V, why wouldn't manufacturers design for worst case? Like why design a coil for 230V is it might saturate under normal conditions?
Roughly, the magnetic field B depends on voltage and the magnetic field H depends on current.
With no load B reaches its maximum, with load, primary voltage is slightly reduced due to primary DC resistance, and hence B is slightly reduced too. The current creates H however both fluxes, primary and secondary, cancel each other.
I am just a TV repairman, but following above analysis
Vp-p(max) = (20/50) 240V = 96V
Turns ratio remains the same
Np/Ns = 240/12 = 20
Then on the secondary you have (neglecting losses)
96V/20 = 4.8V
If you apply a huge AC voltage at 20 Hz, the core will saturates and losses will be huge too, difficult to make a proper calculation.
At higher frequencies, the core is going to leave the scene (Bac goes as 1/f) and the windings are dominant.
I have not a clue, I do not live in the UK.
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Thank you for your explanation. So it would seem that low frequency response is limited which backs up what Shoog and others have said regarding low voltage, high current tubes.
Sorry but what are B and H respectively?
Sorry but what are B and H respectively?
You are welcome. Yes, the low frequency response is limited, unfortunately.
Some people call B something like "induction magnetic field" and H something like "intensity of magnetic field", I simply say B and H 😀
Typical post for a US member thinking the world stops beyond US borders....
See http://www.waasner.de/fileadmin/Assets/PDFs/Katalog_Waasner_12_2015.pdf#page=7