I have been thinking about this. If wired such that the DC magnetic field cancels, you have no storage of magnetic field energy to use for doubling the output efficiency when demanded by modulation of the current.
Indeed no need of air gap for the choke.
If you use matched masfets LU and secondaries of a toroid transformator you could even delete the capacitors as there will be only a few mV across the output teinals (source of mosfets)
But balanced cancels second harmonic? Not good for thd spectra
If you use matched masfets LU and secondaries of a toroid transformator you could even delete the capacitors as there will be only a few mV across the output teinals (source of mosfets)
But balanced cancels second harmonic? Not good for thd spectra
Small air gap to accept small unbalance if the magnetic field cancelation can be obtained using an EI transformer. There is a small gap between the E and I laminate.
Guys,
Can we focus on the developments of the LuFo amp in this thread?
For other discussions maybe better to open a new thread.
Can we focus on the developments of the LuFo amp in this thread?
For other discussions maybe better to open a new thread.
Absolutely agree. I am all for open discussions but significant variations on the original design are best served by new threads.
Best,
Anand.
Agree; it's just that X came up with the idea for a bridged (push pull) LuFo (post #100), and I do have some experience with this (Zeus) so felt free to do some suggestions...
It would interesting to find a MOT with center tapped primary and center tapped secondary.
If you use a center tap choke the DC fields will cancel because of the phase of windings... Then no need for a gaped choke. An EI transformer wit center tap will do the same...
Think again. The two DC bias currents create two a positive and a negative magnetic field, which are superimposed to each other. They are both there, and can be used to what you call 'double the output efficiency'.
You could unwind/remove the secondaries and wind a new second primary with 14ga magnet wire (not easy) and then connect the center tap. I don’t think there is any practical reason for a low cost uW oven MOT to have a center tapped primary.
But let’s keep future discussions of the balanced output LuFo in another thread.
But let’s keep future discussions of the balanced output LuFo in another thread.
Today I received qty 2 of MD-803 MOTs. Inductance at 20 Hz 69.8mH and 71.4 mH using a WT2 to measure. DCR ~ 0.52 ohms.
They are visibly aged and battered but test ok. $35 / ea delivered. When the Mouser crimp connectors arrive, I can connect the LU PCB and start some measurements.
They are visibly aged and battered but test ok. $35 / ea delivered. When the Mouser crimp connectors arrive, I can connect the LU PCB and start some measurements.
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X,
Max RMS voltage prior to the onset of clipping you have stated is about 17V RMS or 48Vp. I don’t know what distortion level we are talking here but I am sure it’s 1% or more. That being said, for the gain stage, what voltage swing would you recommend the stage does cleanly?100Vpp minimum?
Best,
Anand.
Max RMS voltage prior to the onset of clipping you have stated is about 17V RMS or 48Vp. I don’t know what distortion level we are talking here but I am sure it’s 1% or more. That being said, for the gain stage, what voltage swing would you recommend the stage does cleanly?100Vpp minimum?
Best,
Anand.
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Nice! Those are good inductance and DCR values. Not bad for $70/pair. Yes, they often look like they were drop kicked across a concrete floor. 🙂
Is WT2 a woofer tester?
Measuring inductance with no 3A DC current applied has no value at all!
In case of core saturation the inductance will drop, and you will not have the necessary reactive load for the mosfet.
Setting up an amp and monitoring a 20 Hz signal for core saturation at full power seems to be the only way to check if these MOT's are up to their task.
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