Thursday, November 17, 2016

Silver Cables, and Zobels

Here's a company that sells interesting silver wire, teflon jackets.

According to subjectivists, silver wire may sound bright, etc.  (or everything else dull, if you're a silver favoring subjectivists).

The objective truth is that silver is better (though, most objectivists would say not so much as to be important).  Copper is worse because copper oxide is a very nasty conductor (a semi-conductor actually) and it forms readily wherever there is exposure to air.  And even if this is just a thin film, that thin film is specially important because of skin effect.  But there is further oxidation even below the film.

However I wouldn't jump to weird geometries.  Well shielded coax is hard to beat for rejection of interference in interconnects.  It is way better than loose twisted pairs, even if those twisted pairs are shielded.  Given high RF nowadays, and notably in my own house, I would not use anything but the most well shielded coax.  And all my equipment is high bandwidth, making ultrasonic interference rejection especially important.

Tinned copper, silver plated copper, gold plated copper or vacuum annealed copper (what Cardas does, for example) are three ways of addressing the oxidation problem in wires.  While audiophiles may think they love bare copper, bare copper should never be used, including in wire assemblies.

My own practice doesn't approach this yet, I used to think bare copper was the way to go.

Back to the geometry, speaker cable can be twisted pair.  Actually it turns out, that RF rejection and RF impedance are issues, just going for the least inductance might not be the correct answer.  I'm beginning to think it isn't the answer for my Aragon 8008BB.  I'm planning to switch back to zip from star cross, I think the extra inductance may be good for this amp (which has no zobel at the output).

I've been reading about that too...some say zobel is always necessary and you can't hear the choke, while John Curl, and Naim Audio, say you can hear the choke and they don't use one.  An interesting take may be that if you don't use the zobel on the output, you are achieving the same effect by overcompensating the amplifier, which is worse.  Iverson seems to have always used the zobel, and I think it becomes extra critical in high feedback amplifiers.

Anyway, Naim assumed they didn't need the zobel because they were assuming people were using zip wire, as they universally were in the 70's, or wire with sufficient inductance to provide the zobel effect.  Later, when specialty cables didn't, Naim stepped in to make their own "audiophile grade" medium impedance wire.

Here "zobel" is actually being applied to other named type networks, such as Thiele (sp?).  But it's the same idea.

Likewise MIT cables put their zobel networks at the load end, which is suitable for correcting the cable itself.  Perhaps the zobel should be built-in to the speaker itself, or something plugged into the speaker.

Some people say the MIT networks aren't just zobels, they are effectively tone controls.

It's not clear how much tone control you can actually do...and that is very amplifier dependent too.

A month ago the John Curl debating thread ("Blowtorch Preamp" topic) was discussing current mode amplifiers.  Mainly this was driven by Richard Marsh, whose been deep into the topic.  John Curl and others were quite interested.  Some objectophiles say it's a nonsense idea, not real electrical engineering.  Amps, volts, and impedances are real things, but "current mode" is just a marketing term.  Such as used by Krell (not mentioned in the Blowtorch room).  But seeing Marsh and other pretty serious guys considering it seriously, I think it's more than just a marketing term, it has some kind of effects, for example high bandwidth becomes not a problem generally.

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