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


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

first we have to agree music is not sinusodal, then i have to ask so what if we are unipolar or AC... in the case of the pulse core, after a singlke pulse without the -Bdc applied, the core would remain at the +Br, but when the -Bdc is added the core then returns to the bias point rather than the Br. would this be any different if AC were used instread of a pulse?

(se)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.

but if we assume the loop momentarily ends up at a -Br point during a musical passsage, the bias point will demagnetize and remagnetize the core to the Bdc point. the question becomes what happens if the signal ends on a +Br point, then i am not clear and what oyu say may be correct.

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

there are a lot of "ifs" and assumptions in that statement. i don;t know if i woukld call it a fact (unless you assume) that Bmax=Bsat then i'll agree, but when Bmax is a fraction of Bsat wouldnt; be suprised to see the most linear part of the loop being somewhere other than (0,0) as an origin.

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

yes, and whats more linear than air?

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

but above the knee of the loop the core is quite linear (your perm is very low, but thats a different issue)

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

it will be perfectly linear without the core, i think thats the point :-) your perm will be 1, but thats a different issue.

sure it may be picking an nit, but i think its an important nit to understand. adding a magnetic core is adding nonlinearity, much of the time the increase in perm more that offsets any nonlinearity introduced by the core hence we see lots of iron cored (or nickel :-) outputs and very few air cored ones.

dave

dave

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