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March 2011 issue

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March 2011 issue
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World Mail    March 2011 issue        

 

Write to us!    E-mail –>     This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Letters are published first in the magazine, then here in our web archive. We cannot guarantee to answer all mail, but we do manage most!

 

Or  comment in the Comment section at the bottom of each page.

 

Your experts are -

DP David Price, editor; NK Noel Keywood, publisher; PR Paul Rigby, reviewer; TB Tony Bolton, reviewer; RT Rafael Todes, reviewer (Allegri String Quartet); AS Adam Smith, reviewer; DC Dave Cawley, Sound Hi-Fi, World Design, etc.

 


prof

Professor Richard Feynman had problems with electricity, so perhaps we can be forgiven for not knowing too!

(picture courtesy of Apple Computer)


CABLE SOUND

I’ve been an occasional reader of hi-fi mags over the years and witnessed the ongoing wrangles regarding the effects of cables on sound quality. I may have missed some of the arguments on both sides, but having recently read The Super Cables Cookbook, by Allen Wright of Vacuum State Electronics, I was prompted to revise my understanding of how electrical energy moves from source to load. I have discovered that the electrical theory I learnt at school and college (City and Guilds) had left me with a misunderstanding of what electricity is or is not.


Rather than try to explain here myself, I include some links that provide some basic electrical theory which I believe demonstrates that, indeed cables will inevitably affect sound quality in some way.


The notion that the electrical energy conveyed to the load is carried not in the conductor, but in its surrounding dielectric was a revelation to me. I thought all this was in the realms of r.f. theory not relevant to audio frequency or d.c.


I suspect my misunderstanding is not uncommon given the explanations of electrical theory at sub-degree level and would perhaps explain why many people have difficulty accepting the notion of cable sound. I wonder if an article produced by yourselves revising this electrical theory, in the context of hi-fi, would help shed light on this murky area for those of us not so well versed?

Regards,

Matt Rowland

 

 

http://www.vacuumstate.com

http://www.physics.princeton.edu/~mcdonald/examples/EM/galili_ajp_73_141_05.pdf

http://amasci.com/miscon/eleca.html#electron

http://amasci.com/miscon/ener1.html

 

Hi Matt. Thanks for the references. As they are publicly available I will take the liberty of quoting one part, with acknowledgements and thanks to William Beatty, Research Engineer, University of Washington, and the Science Hobbyist website.

 

"During an electric current, the wires become surrounded with magnetic field. This field IS the electrical energy. Also, whenever a pair of wires is connected to a battery or generator, the two wires become oppositely charged, and they become surrounded with an invisible electrostatic field. This field IS the electrical energy. Magnetic and electric fields exist in the empty space surrounding your lamp cord, and these fields contain the “wattage”, they contain the flow of electrical energy that powers the light bulb."

 

Don't we tend to forget that the power in our homes, all the light and heat, reaches us through nothing, or what the Victorians called "the ether". That's because it has been through numerous power transformers where the current flowed through space, not wire. How wire directs current without carrying energy seems contradictory – for it gets hot doesn't it? Where and how the energy is transmitted is beyond my knowledge; I am not a physicist, and nor is my name James Clerk Maxwell I regret to say! We are taught it exists in the electric and magnetic field that weakens with distance from the conductor, but just how do you conceive of power, hundreds or thousands of amps, being transmitted through a vacuum?  Sceptics will still ask: "where is the evidence of influence upon the signal, irrespective of transmission mechanism?" of course. But realising that energy exists in the fields, and the fields are the electricity, makes cable influence seem all the more likely. In effect the power travels through the insulation and space surrounding the cable.

 

I would love to "shed light on this murky area" but, to be frank, I haven't a clue! The references you so usefully provide underline that this subject is for physicists, not hi-fi journos. Something metaphysically deep lies in the notion of transmitting energy (i.e. doing work) via an invisible force though the nothingness of a vacuum, if you ask me. I'll stick to Tiddlywinks. NK

 

All this underlines to me that existing measurement practices are inadequate to describe the sonic performance of cables, and that just because we can't 'measure' cables in a particularly useful way, doesn't mean cables don't have their own sonic characteristics. My ears tell me that cables can sound quite obviously different, and yet I can't claim to understand why. I suppose a degree of humility is needed here; we don't need to understand something completely to use it and enjoy it; my cat doesn't understand how my house's central heating works but he's still chosen the room where the boiler is as his bedroom! DP

 

INFORMED OPINION

I am writing to express my disappointment at your choice of Letter of the Month in the February issue. In his letter on cables Mr Villanueva refers to the vast amount of pseudo-science on the topic. In fact there is a vast amount of proper science on the subject which he clearly has not bothered to investigate, unforgiveable when so much information is only a mouse click away. I would suggest that he logs on to Wikipedia and types ‘twisted pair’ in the search box. The links in the article will lead to a wealth of information on the subject. Such an approach might also benefit Mr Howgego, whose letter on mains leads and interconnects you published in the January issue. Although in his case it was fairly obvious that he had never actually listened to any of the products that he was denouncing. And I thought inductive reasoning had gone out of fashion after The Enlightenment!

Euan Grant

 

Hi Euan. I think you are being a little unkind to Jezza. He is right that there is a lot of pseudo-science on all this and the standard lumped parameter electrical model hardly provides enlightenment about what is happening in a cable.

 

The history of the twisted pair is an interesting way of looking at the problem and seems to have become the way to deal with modern high speed data transmission in digital data links, including HDMI cable that relies of three high data rate/bandwidth twisted pairs, carrying Red, Green and Blue digital video, with audio interleaved. Thanks for your reference.

 

On the flow of electrical current Feynman wrote: ‘‘this theory is obviously nuts, somehow energy flows from the battery to infinity and then back into the load, is really strange.’’ Feynman, however, did not persist and left the problem for others to find a reasonable explanation, says Galilia and Goihbarg in a paper quoted by Matt. They go on to explain what is happening when current flows in a wire, something I hope you find interesting. They say this knowledge has only been available since the 1960s and Professor Richard Feynman didn't attempt to tackle the problem of deriving a plausible explanation, so perhaps we can all be forgiven for 'not knowing'. NK

 

HEADPHONE AMPS

As a regular reader of your illustrious magazine, which I enjoy greatly, I cannot recall any recent reviews of headphone amps. I am sure headphones play an integral part of many systems and I believe are as important as phono amps, being the last line in the audio chain.

 

My query is about matching ‘phones and amps. I don’t have a particularly good hi-fi set up but as I have been fortunate enough to acquire AKG 702 headphones your advice would be appreciated.

 

My current amps are Pioneer A400 and Sansui 555A, but I don’t think they do justice to the 'phones. On browsing the internet they seem to have really good reviews, but one thing that bothers me is that they seem hard to drive. I had Sennheisers, £30, in the seventies which I played through the speaker outputs of a cheap amp and they sounded great. Could I do this with the AKGs?

James Gillen

Bishopton


vcans

 

Musical Fidelity's V-CANS headphone amplifier "offers a crisp and clean rendition" says David Price.

 

Hi James. Yes, you can drive headphones from an amplifier's loudspeaker outputs, without destroying them, and this is what usually happens inside an amplifier; the headphone socket is connected to the loudspeaker outputs, often with a muting mechanism that cuts out the loudspeakers. Headphone impedance varies from 40 Ohms up to 500 Ohms or so, we have found in tests. Alternatively, buy a headphone amplifier; they usually have a simple, low power silicon chip amp inside. NK

 

Hi James – we've reviewed a range of headphone amps over the years; the most recent being the Fidelity Audio HPA100 in the February 2011 issue, which we really liked at £350; it has a strong, punchy sound that makes the best of phones such as the Sennheiser HD650. Musical Fidelity's V-CANS at less than half the price offers a more crisp and clean rendition, but there's less inner detail and finesse; it's really great value though. DP



 

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