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In Reply to: Re: There are 3 kinds of passive preamps (at least) posted by Steve Eddy on February 23, 2003 at 12:40:54:
hey steve,(SE) There's a fairly well known psychoacoustic phenomenon whereby if the brain is fed the harmonics of a bass tone..
yes, and i would say this is the case, but the guy did it by measurement, and just looked for the best sine wave.... increasing the current made the above sine wave look better! (using a non gapped PP design SE)
(SE)Increasing the DC current would increase low frequency distortion far more dramatically than high frequency distortion
thats the book answer, but increasing current made the above sinewave look like one again... first guess was the lowerd source Z from the increased current caused this, but when he substituted a tube with a lower Rp and less DC offset things got worse!?!
(SE) That doesn't make any sense. An air gap is used to linearize a transformer in the presence of DC, but here you're saying it's the DC that linearizes the transformer.
I know that... thats the conventional thinking, but more and more i think it is dead wrong for audio where sound, and not money is the key desing factor... take money out of the equasion for all the historical work in magnetics, and i suspect the rules would change.
(se)All I can say is that I've never seen an instance where any amount of DC current has improved the linearity of a transformer except in the case of an offsetting current I mentioned above.
i can think of many unique situations where this would be the case, it all stems from the concept of a linear inductance vs. higher nonlinear inductance, and what roles they play in the whole mix, unfortunately... there is no stereophile measurement for such an example, since inductance is such an archaic design elelment.
oddly enough, if high perm (read high inductance) is your only goal, i have seen certain nickels (4-79 permalloy) for example that have very high initial perms, and the addition of a magnetic field actually increases the perm... granted the added field is in the milli-oersted range... but whats not to say that a microvolt or two of DC offset might not accomplish that??? my point is this addition of DC is a unique situation where things become very nonlinear, but a similar alloy of moly permalloy is ruler flat for the small offset of H (which is what DC does)
the big problem is each alloy is specifically designed for a unique use, and info for other uses is not documented, this is not because it is not able to be pressed into other uses, just because there is no way in hell anyone would pay enough for it...i wonder what those guys would say to $5000 interconnects :-)
btw... do you have hosting??? i'll send you some images that are relavant, several of which still confuse the hell out of me with what they say, since i have zero formal education i actually could be missing something obvious, which is why i try to have these conversations.
and to add this final disclaimer... everywhere i look and dig for this info is based solely on what i have heard with my own experiences... i really don't care what is supposed to happen, i just really take note when what supposed to happen, and what really happens doesn't line up... when this is based on listening, its an anecdote, and i search for more anecdotes.... but when a measurement or two show up... i really wonder if there is something there.
dave
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- Re: There are 3 kinds of passive preamps (at least) - dave slagle 19:26:47 02/23/03 (0)
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