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Old 23rd Jan 2020, 10:26 pm   #1221
Radio Wrangler
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Default Re: The Audiophoolery Thread.

I suppose it's very important to know which way round an interconnect or fuse was fitted when it was burned in professionally. Otherwise it would be easy (50% probability) to fit it in the reverse direction. This could explain uncertainty in people's experiences with advanced audio products.

It would be possible to engineer a centralised DeOxit distribution system. A reservoir and pump unit with a radial system of capillary pipes leading to every contact/conactor/switch in a system. By pressing a simple plunger, the system owner can deliver a shot of contact cleaner to all needy places at once, like one of those greasing systems on long-range lorries.

I'm a bit surprised they use DeOxit, though. Ordinary people use it, so it might not be high-end enough.

David
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Old 23rd Jan 2020, 10:40 pm   #1222
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Default Re: The Audiophoolery Thread.

Surely, as in the case of the topical use of many commonly-available drugs, the secret is knowing how much to apply and at what frequency. This is where the DeOxit Consultant would be called upon to prepare the prescription and determine the dose.
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Old 24th Jan 2020, 12:16 am   #1223
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Default Re: The Audiophoolery Thread.

I suppose if you look at it on a caveat emptor basis, many of the “audiophile” accessories that charlatans, flat-earthers and perhaps even the plain stupid offer are harmless. And they provide a good laugh for those of a more rational mindset.

However, I see that Russ Andrews (RA) has also dabbled in earthing and grounding, a subject that is best approached in strictly scientific and engineering-based way. See: https://www.russandrews.com/images/p...20Mk4links.pdf.

It starts off with :

“What is Earthing and Grounding? It is clearly crucial in any guide to improving your grounding that the basic practical difference is explained between earthing and grounding. The two are often confused and it helps to understand what each does.”

Not so, of course. Earthing and grounding are simply Trans-Atlantically different terms for exactly the same thing or group of things. I suspect that the intent was to differentiate between protective (safety) earthing/grounding on the one hand, and functional earthing/grounding on the other. But in this field, if you can’t get it right at the starting line, then “don’t pass go”, etc,

This misuse of the term is confirmed a bit later on:

“Earthing is for safety! Earthed equipment should always be connected to your earthed ring main.”

And:

“Grounding is the term we use to talk about connections to ground of the RFI signals picked up by the various exposed metal parts of your HiFi system. These connections are not safety related and are best connected with wires which you will need to fit to the casework,..”

Of course, functional earthing/grounding connections need to be carefully considered so that they never interfere with or compromise the protective earthing system. So they are safety related in that they must be designed to avoid creating any safety problems. A warning to this effect early on in the piece is surely a “no-brainer”, at least for a competently written paper. Blithely saying that functional earthing/grounding is not safety related is inappropriate.

I haven’t sifted through the various grounding (meaning functional earthing/grounding) connections that RA recommends, but I suspect that some are questionable in terms of their effects of protective earthing and in respect of the regulations, although the latter would vary by territory.

Returning to science and engineering rigour, this site: https://web.mit.edu/jhawk/tmp/p/EST0...ps_handout.pdf does I think provide a much better and professional analysis and synthesis in respect of the earthing/grounding of audio and audio-video systems, with emphasis on noise reduction. In comparison the RA paper looks like a “fail” on a topic where failing is not harmless.


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Old 24th Jan 2020, 12:30 am   #1224
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Default Re: The Audiophoolery Thread.

Please stop! I feel nauseated.

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Old 24th Jan 2020, 12:54 am   #1225
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Default Re: The Audiophoolery Thread.

I have a copy of Whitlock's paper stored already. Although it is generally excellent in its content (and references papers published at the Rane pro audio site).

He gets one thing wrong - the inductance of an isolated wire. This is something that dates back to 1908 "The self and mutual inductances of linear conductors" Edward B Rosa, Bulletin of the Bureau of Standards, V4No2.

Rosa derives the equations for the inductance of an isolated wire, which you can do from Biot-Savart (and that is the equation that everyone uses). But he also says that this cannot be demonstrated in practice because inductance is only defined when a circuit is closed. He then goes on to calculate the inductance of geometries in which there is a closed circuit.

In which case the inductance is defined by the circuit loop, and the inductance of an isolated wire has no meaning.

But the myth continues that you can have an isolated wire with inductance. Hence Whitlock's graph on page 4.

Now I have a great respect for Whitlock. He is Technical Guru at Jensen transformers, and was the inventor of the InGenius balanced receiver chips sold by THAT http://www.thatcorp.com/Balanced_Line_Receivers.shtml . These are optimised for staggeringly good CMRR, admittedly at the cost of lower SNR. He is also a Fellow of the AES. Smart guy.
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Old 24th Jan 2020, 7:04 am   #1226
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Default Re: The Audiophoolery Thread.

A straight, isolated wire does have inductance. If it has a finite radius, its surface area gives it capacitance as well. Both are distributed properties, so many Henries and Farads per unit length. Together, they give the wire a characteristic impedance.

Measurement with an inductance meter involves completing a loop around the wire, changing circumstances. Similarly if you want to use a capacitance meter, where do you put the other probe?

If I had a sphere in space, it would have various potential differences with respect to all other objects in the universe. Absolute potential is a curious concept. If I dumped x dozen extra electrons onto it, it would become a bit more negative with respect to all of those other objects. Whatever its original absolute potential was, it's just shifted. If we know the amount of shift from adding a known amount of charge, then we can calculate its capacitance.

Its capacitance with respect to what?

Its capacitance with respect to everything!

Isolated items do have inductance and capacitance and resonances and characteristic impedances etc. There may be reasons that mess up attempts to measure them by direct connection to lumped-element instruments, but the resonant frequencies and characteristic impedances they create fit with calculated L and C distributed values.

In more mundane electronics with lumped components, you can't use a length of straight wire as an inductor without completing the circuit, which affects things.

David
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Old 24th Jan 2020, 6:46 pm   #1227
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Default Re: The Audiophoolery Thread.

Quote:
The word "will" is actually not used a lot
I am sure I saw it, your explanation must mean it is in a "harmless" place.
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After a long battle I succeeded in getting the ruling overturned by carrying out a day of tests at an EMC lab.
Proper paid for engineering job I gather from a previous post, all in a days work. I must admit to buying some "dedicated" 'speaker cable from Maplin once, it was super flexible and clear, this meant I could pin it (drawing pins) under some shelves very easily. It did make a difference to the sound because 'er indoors didn't comment on it being visible (bliss!).
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Old 24th Jan 2020, 8:34 pm   #1228
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Default Re: The Audiophoolery Thread.

Quote:
Originally Posted by merlinmaxwell View Post
I must admit to buying some "dedicated" 'speaker cable from Maplin once, it was super flexible and clear, this meant I could pin it (drawing pins) under some shelves very easily. It did make a difference to the sound because 'er indoors didn't comment on it being visible (bliss!).
Perhaps high end audio manufacturers should pay more attention to this sort of thing. After all domestic serenity is so important. However it's possible that once audiophoolery reaches a certain level the afflicted individuals end up living on their own anyway.

Alan
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Old 24th Jan 2020, 8:51 pm   #1229
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Default Re: The Audiophoolery Thread.

The high-end ethos, though, is to make things stand out. To scream out to the world just what you've bought and how expensive they are. Besides they have to be run along the floor on little stands made of sapient pearwood and holy water so that more people notice them by tripping over them.

They'd drop MM into a world of grief.

David
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Old 24th Jan 2020, 9:09 pm   #1230
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Default Re: The Audiophoolery Thread.

It's a genuine illness, not dissimilar to OCD. An unending, untiring devotion to finding perfection in a subject to a degree that to most of us is way above what is necessary to gain fruitful levels of enjoyment and fulfilment. So the constant search for perfection (real or imagined) becomes the enjoyment factor, not the end goal as it is for most people, the joy of listening to clear, recorded, beautiful music.
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Old 24th Jan 2020, 9:54 pm   #1231
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Default Re: The Audiophoolery Thread.

I'm a bit surprised they use DeOxit, though. Ordinary people use it, so it might not be high-end enough. Ha Ha DeOxit for peasant use only we might get it cheaper now .
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Old 25th Jan 2020, 12:11 am   #1232
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Default Re: The Audiophoolery Thread.

Quote:
But in this field, if you can’t get it right at the starting line, then “don’t pass go”, etc,
Russ seems to have redefined the laws of physics. He isn't passing go, but still manages to collect the 200 quid!
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Old 25th Jan 2020, 1:42 am   #1233
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Default Re: The Audiophoolery Thread.

We've had this conversation before about Russ Andrews, and the continuing quest to characterise the man and the company as a load of charlatans that are not worth a crock. And it exercises many threads on many forums.

Of course since there is a no-quibble 60 day return 100% refund policy, I'm surprised that no-one here has bought an RA product and tried it out. We can all theorise because we all all smart engineers. But hey - try something out and see.

I'll also repeat what I said earlier - The company is 12 hard working people in Kendal in the Lake District. Would you be the person to put them out of work because you don't agree with what they do?

Well no of course you wouldn't.

But I'd be interested in a link to the Russ Andrews page that uses the word "will", as Merlinmaxwell thinks is there somewhere.
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Old 25th Jan 2020, 9:13 am   #1234
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Default Re: The Audiophoolery Thread.

I once met the chap and found him sincere. I think he really believes what he says. He is free to do so. I am free to choose what I do and don't believe in.

The try-something-out-and-see argument doesn't work on me. If it did, I'd already have been bankrupted by all the medicinal remedies, car mpg boosting magnets and such stuff. I have to exercise some selectivity over just what I do try. I have to believe it has a chance of delivering what it promises, and that belief hinges on there either being a reasonable physical mechanism, or on careful testing by neutral parties, with care taken to avoid results due to expectations.

The stuff on RFI effects of fancy cables IS reasonable. Things can be done to cables to reduce their effectiveness at collecting environmental radio noise/signals, and routing them into amplifiers etc. However, this is also an indication of how poorly designed plenty of electronics is. It would be better to add a few components to amplifiers and do some decent as-used EMC susceptibility testing. Ferrite cores on cables a la mode for computer monitor cables are cheap and helpful. The silly high prices aren't justifiable as there are cheaper ways. Maybe the prices are a result of very low turnover?

I wonder if RA remembers me? I'm the (then) young man who when told in his shop "You won't get anything better sounding for any less" replied "A wheelbarrow full of concert tickets?"

David
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Old 25th Jan 2020, 11:03 am   #1235
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Default Re: The Audiophoolery Thread.

The RA products that I use are:

SD mains cables. I designed them, and I know from measurement that they work in effectively attenuating differential and common mode RFI up to 1GHz by 20-40dB as compared with a regular "kettle" type lead.

I agree entirely with David that effective broadband RF should be done by design in product, but that is rarely done in domestic audio products. The instrumentation industry goes to great lengths by using multiply shielded mains transformers to reduce primary/secondary capacitance, (in the extreme, using boxed-shielded transformers to reduce capacitance to 0.01pF), but audio. transformers are usually entirely unshielded.

I've recently measured a 120VA 15/15V secondary Block transformer on my HP4275 bridge. Up to 200kHz the primary/secondary is essentially capacitive at 490pF. The phase angle then shifts to increasingly inductive until at 10MHz (the limit of my bridge) it has become inductive with 3.4uH. However it is easy to find papers that show that as the frequency goes up, the impedance goes through a series of LC resonances. So how good is an unshielded transformer at suppressing (in this measurement common-mode) interference? Well not so good. Even a single shield, correctly grounded, reduces winding/winding capacitance to around 5pF - but no-one seems to do this simple thing in the audio world.

Speaker cables. That is essentially for practicality. I use Linkwitz LX521 open baffle speakers. I therefore have 5 channels of power amps on L and 5 on R. Because of the risk of wiring up the bass channel to a tweeter with predictable results, I use Neutrik Speakon connectors - one 8-way and one 2-way, so once the cable connections are made correctly there is no possibility of miswiring the speakers. Of course, the wiring is bundled in expanding sleeving, and preventing crosstalk between drive units is difficult to optimise. However the braided Kimber speaker cable has almost immeasurably low external voltage and magnetic field (by measurement). So I use bundles of braided cables to ensure low drive unit crosstalk.

All other line level connections, of which they are many, are balanced. I use professional grade star-quad balanced cable from Canford at about £1.50 per metre, and Neutrik EMC series XLR's. All colour coded to reduce the possibility of miswiring from the crossover to the power amps.

Craig

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Old 25th Jan 2020, 11:48 am   #1236
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Default Re: The Audiophoolery Thread.

Screens in mains transformers are good over part of the spectrum, but above that the inductance of their ground connection forms a common element in the capacitive input loop and the capacitive output loop.... and then you have resonances as well.

Broadband RFI filtering is an impossible task. The frequencies you want to pass are well-defined and easy, but those you want to stop are limitless.

Repelling low frequency boarders requires large inductors and large capacitors, tending to infinite as the frequency tends towards DC. This isn't so bad. Transformer isolation is fine down here and a screen extends the range usefully Regulated power supplies take out the very low frequency that Ls and Cs can't touch. Once you get higher in frequency and want to repel RF, then transformers with screens run out of steam. Mains filter modules are the usual weapon. Ferrite beads come into their own.

In the late 70's/early 80's Germany started implementing new rules on RF emissions/susceptibility that were a bit fiercer than anything seen before. I was given the task of going through a number of existing HP products and bringing them up to the new standard so we didn't lose sales in an important market. I had to develop cost-effective techniques for fixing problems which also could be done without major redesign.

After the learning curve was climbed, I found it wasn't hard. If such measures were implemented at the design phase, they weren't terribly onerous or expensive. Done later, they certainly cost more.

What is missing in the audio industry seem to be people experienced in these areas, and people who view taking these precautions as simply good housekeeping.

The Agilent Noise Figure Analyser covers 10MHz up to 26GHz in basic form, with extenders to higher frequencies. It can measure the noise contributions of transistors, amplifiers, receivers etc. It measures noise figures of cryogenic amplifiers which use serious cooling to reduce their noise. It can resolve noise down to the quantum mechanical floor at a few dozen Kelvins. This is very sensitive... there isn't much more sensitive that anything can go. There are TWO switch mode power supplies inside its cabinet, and a microprocessor system. It doesn't just have to repel outside noises, it makes enough inside. I originated this box and led the hardware design. What I'd learned fixing existing products 15 years earlier came in rather useful.

Twisted pairs routed together, if the twists have the same pitch can couple quite strongly. Offset one half a pitch then the coupling nulls. Want to add a third pair? then you're in trouble. No offset works, you need a different pitch.... but then you get eventually forced into very long and very short pitches as you add more pairs. There is another way! Look up 'Walsh Functions' used to swap over telephone line pairs to avoid crosstalk.

I'm not a fan of woven speaker cables. They work for RFI avoidance, but they add stray C and that C is good to rather high frequencies. Some domestic audio amps aren't stable into such loads. Driving capacitive loads is a field in itself. The classic case was Naim amplifiers destroying themselves into capacitive cables. Someone thought trying to make cables with 8 Ohm characteristic impedance would be nice and fancy weaving was needed to get the C/length up high enough. Those amplifiers didn't have the traditional 'Zobel' network on their outputs. I think the designer didn't like them or maybe wasn't RFy enough to know what they did.

All this said, the pricer seen on some cult cables are ridiculous, and when pseudoscience gets wheeled out to justify things, it's risible.

Wisible? Always look on the bright side of life.... Fare thee well, Terry Jones.

David
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Old 25th Jan 2020, 12:32 pm   #1237
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Default Re: The Audiophoolery Thread.

Your posts are always insightful and on point, David. I've just dowloaded a 1975 book on Walsh Functions and their Applications, which I will definitely digest.

I agree that woven cables on the output of power amplifiers are not a universal panacea. Some historical Naim amplifiers actually need Naim cable to ensure they did not self destruct. They work find with Self Blameless amps (which I use), with the output networks doing their job just fine. There is another UK manufacturer whose name escapes me for the moment who deliberately omit SOA protection and output networks, and that needs two widely spaced wires to prevent self destruct.

And I agree, when daft price cables need pseudoscience and semi-religious belief as their selling point, that loses the plot big time.

Craig
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Old 25th Jan 2020, 12:38 pm   #1238
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Default Re: The Audiophoolery Thread.

Got it - DNM. Dennis Morecroft's little company.

http://www.dnm.co.uk/
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Old 25th Jan 2020, 2:27 pm   #1239
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Default Re: The Audiophoolery Thread.

It boggles my mind to think that a well-known OEM would market power amps that are so close to the stability threshold that some types of (admittedly audiophool) cable would take them over the edge.

The same OEM makes a power amp with an RRP of £150K. And they don't publish its THD+N spec. Publishing such mundane data is beneath them!

We ought to find someone with one of these amps and pay them a visit with some dummy loads and an AP analyser. We can publish the figure for them!
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Old 25th Jan 2020, 2:33 pm   #1240
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Default Re: The Audiophoolery Thread.

The Zobel thingy isn't safe operating area protection, it's to isolate the amplifier from directly seeing load capacitance.

Capacitive load on a feedback amplifier creates an added pole in the loop response set by the open loop output impedance of the amplifier and the capacitive load. Because of where the feedback is picked off the output, this added pole is within the loop when the loop is closed.

The frequency of the capacitance load pole depends on the load capacitance, so high capacitance brings its frequency down and it takes out the phase margin of the loop design and the whole amplifier bursts into ultrasonic/RF oscillation, followed by smoke and pyrotechnics.

I've seen some circuits where the feedback got taken off AFTER the Zobel... which rather neatly spoils the point of it. Oh, well. So much audio stuff gets designed on witch-doctory principles. Maths gets left right out of it.

David
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