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Re: PP Iron for SE - repost of a 1996 rec.audio.tubes by "Paul"....

there is a practice for the use of pulse cores to apply a negative Bdc to just before saturation to allow for nearly 2X the available flux for the pulse. suddenly the huge remanence of the square loop cores is an asset, since deltamax (49% square loop nickel) which normally saturates at 14KG can now be used in pulses at 27KG. this suggests to me that it isn;t a simple shift of the axis.

But here you're talking about a pulse, which is unipolar. We're dealing with AC waveforms.

i think you misunderstood, we know that the Bdc acts as a magnetizing force, so if the Bdc can magnetize, it must also be able to demagnetize depending on its relationship to the current state of the core.

But in a cored transformer, the demagnetizing force is the energy stored in the magnetic field. It's the collapse of the field, returning energy back to the system which demagnetizes the core.

With a DC offset, while you produce a field, the energy stored, the energy which is responsible for dematetizing, doesn't get returned to the system until the offset is removed.

So I fail to see how the DC offset can act as a demagnetizing force.

it depends completely on the AC flux at hand, i suspect kondo realized that the very small AC flux provided by the MC stepup wouldn't come anywhere near close to saturating a core, so actually the most linear area might actually be one that resides somewhat up the loop.

That notion is easily dispelled by the fact that as you increase DC offset the transformer becomes more and more nonlinear.

i think thorsten said in a cryptic way above that actually at saturation you will have ideal linearity... and i agreed... think about that.

No, that's not what he said.

He said that as you increase saturation you get closer and closer to an air core transformer.

That's NOT the same as saying you will have ideal linearity. Indeed, as you get closer and closer to saturation, distortion increases.

Take one of your transformers and remove the core and tell me how linear it is compared to with the core. :)

se






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