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In Reply to: Re: PP Iron for SE - repost of a 1996 rec.audio.tubes by "Paul".... posted by Steve Eddy on February 20, 2004 at 10:00:42:
how do you figure that???dave
Follow Ups:
how do you figure that???I guess I could ask you the same thing. :)
Both the x and y axes in your plot are logarithmic. That being the case, as far as I'm aware, a linear function will produce a straight line. And looking at the plot, Hdc = 0 is the closest approximation to a straight line and would therefore be the most linear.
Here, I overlaid some straight lines on the plot to make it more obvious.
se
to be fair i chose around 12KG which is a fair bit less than Bmax.what next... you can only use a 3KG signal for it to be linear.... if i only had a 3KG max flux on the core i would use nickel :-) and then of course gap it to get the linearity rather than use a dc offset.
dave
OK so the increase in perm is linear, but who cares?to me a linear perm would be a straight horizontal line.
dave
OK so the increase in perm is linear, but who cares?Who cares? I thought you did. You were the one talking about linearity, no?
to me a linear perm would be a straight horizontal line.
A linear permeability would be a straight line. Period. Doesn't matter if it's horizontal or not. And while the plot with the highest Hdc is the more horizontal of the bunch, it's not the straightest of the bunch and therefore is not as linear.
Hdc = 0 is the most linear.
se
you are completely missing my point.when we (at least me) refer to linear perm, it is in reference to it being the same value wrt AC excitation any derivation from that is a nonlinearity. fabricate two inductors based on the curves one at h=0 the other at H=10.
now use these inductors to form a simple LR divider. which one will more closely follow what an ideal (linear) inductance will give?
to me what i consider linear perm is the same as linear inductance, a situaiton where the value does not change with applied voltage or frequency...
dave
dave
you are completely missing my point.Ok...
when we (at least me) refer to linear perm, it is in reference to it being the same value wrt AC excitation any derivation from that is a nonlinearity.
Then I'd say you're using the wrong terms to describe what you mean.
Seems that instead of linear you mean static and instead of nonlinear you mean dynamic.
And with respect to the graph you posted, Hdc = 0 is less static but more linear while Hdc = 10 is more static but less linear.
In any case, what's your point? What's the "problem" you're trying to address here? Or more to the point, exactly what effect on the signal are you trying to minimize?
se
OK its a mixup in terms.so when people refer to linear inductance, they really mean static inductance?
and when compared to the static (ideal horizontal line) which is more linear? not to mention it seems to (incorrectly) be the trend in audio to look only at the big numbers, so if we look at the "linearity" and i mean "linearity" from 0-15KG which is more linear?
as for the point, i was suggesting one possible reason why a core with a DC offset might sound better.... and the suggestion is because the inductance is more "static" :-) my whole motivation for this is based on several empeircal reports of improved behavior from a DC offset, and i just don;t buy the easy answer "you like distortion"
dave
so when people refer to linear inductance, they really mean static inductance?No, they mean an inductor which has linear behavior.
and when compared to the static (ideal horizontal line) which is more linear?
Again, the more linear is that which most closely approximates a straight line.
If you have a perfectly straight horizontal line and a perfectly straight line at say 45 degrees, they're both equally linear.
If you have a perfectly straight line at 45 degrees and a less than perfectly straight line more horizontally, the line at 45 degrees will be the more linear.
And again, going back to your graph, Hdc = 0 is the more linear than Hdc = 10.
as for the point, i was suggesting one possible reason why a core with a DC offset might sound better....
Ok. And I'm simply saying that DC offset on the core increases nonlinearity and subsequently distortion.
...and the suggestion is because the inductance is more "static" :-) my whole motivation for this is based on several empeircal reports of improved behavior from a DC offset...
Ok. But I haven't seen any evidence that the "improved behavior" is any sort of objective technical improvement. It's been well-established for perhaps a century now that DC on a transformer's primary or secondary increases signal distortion.
...and i just don;t buy the easy answer "you like distortion"
Why? That might well be the answer. If you're going to reject that possibility out of hand, then you're obviously more concerned with confirming some preconcieved belief than getting at the truth.
That being the case, I think I'll just go back to enjoying listening to music with a bit of DC bias on my transformers and not really care why it sounds better to me.
Have a great weekend!
se
(se)Ok. But I haven't seen any evidence that the "improved behavior" is any sort of objective technical improvement. It's been well-established for perhaps a century now that DC on a transformer's primary or secondary increases signal distortion.well established by whom? what has been established is the reduced perm, hence the reduced inductance for a given source increases distortion if you don;t account for the reduction in perm.
(se)Why? That might well be the answer. If you're going to reject that possibility out of hand, then you're obviously more concerned with confirming some preconcieved belief than getting at the truth.
no, it just makes no sense to me.... having too little inductance causing distortion makes sense, and that could explain a pleasing distortion, but discussion of linear perm is much more "pure" and untainted from the numbers that limit an arguement.
i really don't care, like you i enjoy what i like and feel no need to make excuses, and won;t apaologize for what i like, but that doesn;t stop me from trying to figure out why.
(se)That being the case, I think I'll just go back to enjoying listening to music with a bit of DC bias on my transformers and not really care why it sounds better to me.
its this percise belief that made me want to have the discussion with you in the first place.... thanks.
dave
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