[JN] magik ???
toobman57 at gmail.com
Mon Feb 1 15:41:19 CST 2021
Well, I've long thought that the key point in the old Peerless Pinstripe
trannys was not to "add a little Permalloy" to the silicon iron, similar to
bypassing a medium quality cap with a small high-quality cap, but to
provide a *crossover* from one material to the other, with the Permalloy
handling the tiny *changes* in the signal. The trick is to have the
permalloy begin to saturate just as the silicon-iron is beginning to
overcome its hysteresis, i.e., as the Si-Fe's mu is beginning to rise,
which is the "crossover." To do this (1) the two permeabilities much match
-- i.e., the permalloy's air-core must reduce its mu (permeability) to that
of the Si-Fe (which may also have an air-core), (2) the ratio of the
Permalloy's mass to the Si-Fe's mass must be such that the Permalloy
saturates just as the Si-Fe kicks in (overwise you get a boost in the
overall mu), and (3) the *shape* of the Permalloy saturation curve and the
Si-Fe's initial mu curve must be compatible, i.e., they must combine to
form a reasonably good crossover (I *think* a 1st-order crossover).
In other words, the Supermagic boxes may use two core materials that meet
the above 3 requirements, although really, you should add a 4th
requirement, namely, the core materials must have zero magnetostriction
(zero core expansion/contraction with the signal, causing it to vibrate).
The trick is to find various combinations of materials that are compatible,
and then sort by price and theoretical quality. One that I've long been
interested in, especially for output trannys, is a Sendust main core
combined with a permalloy. Sendust is *very* similar to permalloy, being
only very slightly inferior, has quite a few variants, and is *much* less
expensive! It is brittle, but when combined with its zero magnetostriction,
that makes it very stable. Another potentially very good main core is
Vitroperm, which has an incredibly linear B-H curve, which I *think* means
that the low-freq pole remains constant. I'm not sure whether that's
actually all that great of an advantage, but it might be. However, it's
initial mu could definitely be helped by crossing over to one of the
permalloys. Unlike Sendust, however, it is *very* expensive.
Or, maybe they just used a powdered molypermalloy core, which might be the
best core of all, although I've never heard of it actually being used in
audio (mainly radio), so I'm not sure.
On Mon, Feb 1, 2021 at 8:14 AM Marc Wauters via Sound <sound at soundlist.org>
> Anyone want to take a stab on just what is in those cans. If it really
> does anything I have to ask just why transformer would do it. I'd generally
> be rather skeptical that noiseless gain of 6 dB at line level can do much
> of anything to improve sound. Their claims are quite ambitious. They even
> claim it improves (or have in the past) the sound from MM cartridges when
> placed between it and the phono input. Seems the impedances there might be
> an issue.
> Thing is that similar claims and reports were given on the Expressive
> Technology SUT 1 ( I think that was the model name) moving coil step up,
> that improved the sound beyond any other step up available, but of course
> in that position it's hard to compare.
> Tell me this is just something like a Jensen J11 wired as an autoformer
> for 6 dB gain and I'll go buy a bunch!!!
> Sound mailing list
> Sound at soundlist.org
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