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Old 23rd Mar 2019, 9:22 pm   #541
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Default Re: Audiophoolery?

I became aware of the effect of room acoustics on sound one evening in the 1970's when I had nodded off listening to the radio and was woken by the stereo test tones that used to be broadcast on Radio 4 after shut-down. As I moved myself to get up from the sofa to turn the radio off, I found that moving my head affected the loudness of the test tones. By suitably positioning my head I found I could completely null out the sound in either ear. I guess that you would need to clamp your head in a fixed position to ensure a proper comparison between systems, and even then, all the other items in the room wold need to be identically positioned too. I guess that, other than when comparing speakers, to eliminate room acoustics you would need to use a good set of headphones.
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Old 24th Mar 2019, 4:03 am   #542
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In the Victorian era, photographers had wooden clamps to stabilise people's heads so they didn't move and get blurred with the very long exposure times they had to use. The clamps were designed so they could not be seen from the front, so if re-introduced, they wouldn't intrude on the path for sound from speaker to ear.

Could this be the next big thing in audio listening? Piano finish, spiked feet, exotic woods, alloys and composites. There are possibilities. But you'd have to get the price up to an acceptable level.

David
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Old 24th Mar 2019, 8:20 am   #543
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A great shame the Leak name faded and hasn't yet been revived.

Mark
Leak (the brand name) was owned by Wharfedale. Back in the early 90's I was Technical Director of Wharfedale, and we re-introduced Leak products. This was a totally new line of high quality gear.

I'd recruited a young guy called Steve Sells (now Engineering Director of NAIM), and let him off the leash to design the best power amp he knew how, no holds barred. It was a stunning piece of work.

We also tied up with a guy who had designed a digital pre-amp (or more accurately control amp) - which was astonishingly radical in 1990.

Then I engaged a design company called Creactive, and their founder Hans Petersen did the appearance design.

We launched the line at what used to be the Heathrow Penta audio show, attended by the elderly widow of Harold Leak.

Then the recession bit, Wharfedale imploded, the board (actually an individual snot goblin, who I won't name) fired the CEO, then his PA, then the Ops Director, then me.

And those stunning Leak products never saw the light of day thereafter.

I have no idea who now owns the Leak brand name. But if it was part of Wharfedale when Stan Curtis sold the company to the Chinese, that is where it is, moribund again.

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Old 24th Mar 2019, 8:38 am   #544
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Craig, that's a bit of audio history I'd not heard of, fascinating stuff indeed, and a huge shame, what happened to the 'demo(?)' Leak equipment made under your wing? I believe the Leak name is now owned by Hinchley or Tamura? Something to do with transformers.

I have a bit of Leak equipment, Stereo 20, Point One Stereo plus matching Troughline II with a stereo decoder designed by a chap called Tim De Paravicini, all running a pair of B&W's.

This being my 'fleeting' trip down Hi-Fi lane in the late 90's, still sounding nice. How did they achieve such sonic possibilities back then, with carbon comp's, standard gauge wiring throughout, screw terminals and AC wiring within all the sources/amplifying stages?

On a different note, one thing I'd not heard of, 'Quantum Stickers'. Yep, 135 a go, https://www.audiocomav.co.uk/tuning-...-stickers.html not sure they'd survive on a set of EL84's.

Mark
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Old 24th Mar 2019, 9:01 am   #545
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Craig, that's a bit of audio history I'd not heard of, fascinating stuff indeed, and a huge shame, what happened to the 'demo(?)' Leak equipment made under your wing?

On a different note, one thing I'd not heard of, 'Quantum Stickers'. Yep, 135 a go, https://www.audiocomav.co.uk/tuning-...-stickers.html not sure they'd survive on a set of EL84's.

Mark
I have absolutely no idea. They were on a shelf in the electronics lab when I exited stage left. Probably got junked into a skip because there was no-one left who knew what they were.

They were heady days. I introduced ceramic domes for the tweeters. Sourced them from Idemitsu Petrochemical in Japan. The Young's modulus to density ratio were far higher than the traditional aluminium or titanium domes, which figure determines the first break up mode. Alumina pushed that to 55kHz. CVD diamond was my preferred material, but at that stage was far too expensive. Now it isn't and B&W have diamond dome tweeters, pushing the first break up mode to approaching 100kHz. The important thing is that those resonances are high Q, and when close to the audio band, the phase shift associated with the resonance means that the tweeter is no longer minimum phase, and shifting it out as far as practical makes that ideal condition more closely approached.

And oh dear - as I said earlier, any audio product that uses the term "quantum" is by definition complete and utter snake oil. Did you read the blurb on that page? You could use a simple sentence generator and put random pseudo-technical words in and write that sort of copy!

Craig

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Old 24th Mar 2019, 9:21 am   #546
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This thread has opened my eyes to a whole new world, one of which whereby I'm seemingly not alone being happy as a 'spectator'.

Some of the blurb, hyphenated, in some cases, x10 to the power indices etc, wowsers, who writes that up? Bluffing-splifora could describe the terminology.

Speaker technology has become a science, and come a long way as a result. Some of the materials used are truly breathtaking. Sadly, though not always, house in chipboard. I did see on the web today an audio isolation platform made from, & I kid not, 'audio-grade' MDF.

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Old 24th Mar 2019, 9:29 am   #547
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Some more quantum fairy dust

https://www.audiocomav.co.uk/quantum...-enhancer.html

There are pictures on the web of someone who took a Bybee quantum slipstream purifier to bits (you put these in series with for example your speaker cables). It turned out to be an 0.025 ohm wirewound resistor with a black coating.

Marketed by Bybee as reducing quantum noise (which they say is 1/f noise). Now there is absolutely nothing you can do to reduce 1/f noise. And even less an 0.025 ohm inductive wire wound resistor, which interestingly would have its own 1/f noise contribution.

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Old 24th Mar 2019, 9:56 am   #548
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Had been wondering about those little devices, looking suspiciously like power resistors in heatshrink.

On that very website, they sell aluminium 'stickers' which you apply to either the front, or rear, of your Hi-Fi separate, releasing a whole new world of sonics, apparently. Who'd of thought, just one sticker on the outside can make such a huge improvement.

I wonder, with a quantum sticker on each ear-lobe, and an aluminium sticker on the forehead, would everything and everyone sound like a decent stereo system? Add a foil shower cap to keep those dastardly cosmic rays out along with mains bourne RFI ... Oh the possibilities ... The central locking on your car, or neighbours lawnmower, would have never sounded so good.

Truly astonishing what's out there, pebbles to attach to your audio leads, as mentioned earlier in this post, stickers, keeping speaker leads off the floor, wooden boxes full of, well, who knows ...

One thing that did make a huge improvement to the sound of my Hi-Fi, since our cordless 'phone with mains charger used the same power outlet, cleaning the mains plug earth pin of 'earthed' equipment with an old duster & a spot of Brasso. Before, you could hear the 'phone being charged, with a high-pitch 'weet weet weet' noise, after the Brasso, the noise had gone.

Very old MK plugs they are, had badly tarnished brass contacts.

Mark
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Old 24th Mar 2019, 10:36 am   #549
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That is what I do too. Tarnish is bad. The only thing to make sure is that all traces of the brasso are gone. An alternative is green scouring pads to break up the tarnish, with a wipe over with IPA to get rid of the dust.

Of course the same thing happens inside the socket too, but a spot of contact cleaner on the now clean mains pins and then push it in and out a few times is all that is needed.

I've also found that older MK mains plugs (particularly the rubber ones) had silver plated fuse clips inside, which get thick black tarnish. I usually just dump those and put on a new plug.

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Old 24th Mar 2019, 11:03 am   #550
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Some more quantum fairy dust

https://www.audiocomav.co.uk/quantum...-enhancer.html

There are pictures on the web of someone who took a Bybee quantum slipstream purifier to bits (you put these in series with for example your speaker cables). It turned out to be an 0.025 ohm wirewound resistor with a black coating ...
I once fitted a few Bybee 'bullets' to a pre-amp for a customer (he had bought them second-hand for a lot less than the list price). Before I did I put a multimeter across them. The measurement said they were indistinguishable from a piece of wire, although I suppose they might have been 0.025 ohm. Bybee's literature didn't include much guidance about where to put them (now, now, it's a Sunday, stay polite ) so I think I fitted a couple in the input leads, one in the HT rail and the rest where they were clearly visible. Despite being a self-confessed believer in 'foo' even my customer couldn't hear any difference. So I took them out again and he moved them on.

Cheers,

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Old 24th Mar 2019, 11:49 am   #551
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Noise from a decent quality metal or metal film resistor is almost entirely thermal. They suffer very little 'excess noise' unlike carbon and ruthenium oxide or tantalum nitride thick-film parts.

This noise isn't 1/f shaped, it is flat out to microwave frequencies subject to stray L and C. The statistical distribution of voltage is Gaussian. The power density level is k.T Watts per Hertz where k is the Maxwell-Boltzmann constant, and T is the absolute temperature in Kelvins. 1/f shaped noise is usually an indication of an active device somewhere at work.

Craig has his background in Wharfedale and can be very illuminating on the hifi industry and where various bodies are buried. I was the originator of the HP/Agilent/Keysight noise figure analyser and the matching smart noise sources, which are used to measure noise contributions right down to the amount which a good resistor gives at only a handful of Kelvin above absolute zero. It takes a bit of work to get down there and to cover frequencies up to 26GHz with extenders to go above. Between the pair of us, I think we can see through all the shenanigans. Add in Jeremy, G-J and Martin etc. and the hypesters probably avoid this group like the plague. Ohms law does rule here, and a few other honest to goodness physical laws.

When I see the word "Quantum" in audio context, I just have a sad chortle. As said above, it's a sure indicator of snake oil and silly prices ahead.

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Old 24th Mar 2019, 12:44 pm   #552
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As I intimated on the "PX4 Valve Wanted" thread earlier, the sort of thing that turns up re the uninitiated in the Audio world is neither exclusive or at all new! Of course Snake oil is an old product but if people think there is a difference then arguably there is-as for 40% of the people in severe discomfort, during a recent Placebo Trial, who reported they were pain free! [Doctors have always known this!] The description of a "quantum purifier" [post 127] is very reminiscent of a miracle aerial device from the thirties enclosed in a 3" cardboard tube emblazoned with a red and black dynamic Logo. It was designed to produce fantastic [literally] reception results, eliminating the need for a long wire, by simply connecting it between the aerial and earth sockets. Forum members may have seen these. The actual contents were a capacitor and a resistor encapsulated in black pitch! More recently we discussed a miracle Digital set top TV aerial on here that was claimed to pick up Cable Subscription Channels [for free] well.

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Old 24th Mar 2019, 2:39 pm   #553
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No doubt the stickers are a development of the adhesive checkered tape that boy racers used to stick along the sides of their Ford Anglias in the 1960's to make them go faster!

I clean tarnished brass plug pins using a rotary wire brush.
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Old 24th Mar 2019, 3:52 pm   #554
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As I intimated on the "PX4 Valve Wanted" thread earlier, the sort of thing that turns up re the uninitiated in the Audio world is neither exclusive or at all new! Of course Snake oil is an old product but if people think there is a difference then arguably there is-as for 40% of the people in severe discomfort, during a recent Placebo Trial, who reported they were pain free! [Doctors have always known this!] The description of a "quantum purifier" [post 127] is very reminiscent of a miracle aerial device from the thirties enclosed in a 3" cardboard tube emblazoned with a red and black dynamic Logo. It was designed to produce fantastic [literally] reception results, eliminating the need for a long wire, by simply connecting it between the aerial and earth sockets. Forum members may have seen these. The actual contents were a capacitor and a resistor encapsulated in black pitch! More recently we discussed a miracle Digital set top TV aerial on here that was claimed to pick up Cable Subscription Channels [for free] well.

Dave W
Ironically that device probably often worked quite well as it was an old dodge to connect the aerial socket of a wireless to 'earth'. The reason being that many household earths were't very good ones, and were as good at picking up wireless signals as they were at shunting any interference etc down to earth. I tried the method myself many years ago in an old house that I lived in at the time and lo and behold it brought in stations loud and clear! But yes, if the earth is 'good' then in theory at least, it shouldn't work. I suppose they did business on the basis that many houses had poor earths!
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Old 24th Mar 2019, 4:10 pm   #555
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Oh right, well that would be handy for the manufacturer I suppose Steve. As with the Placebo responders, there would always be some people saying "Well that aerial thingy worked for me" blurring both the science and when it didn't!

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Old 24th Mar 2019, 4:35 pm   #556
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Noise from a decent quality metal or metal film resistor is almost entirely thermal. They suffer very little 'excess noise' unlike carbon and ruthenium oxide or tantalum nitride thick-film parts.

This noise isn't 1/f shaped, it is flat out to microwave frequencies subject to stray L and C. The statistical distribution of voltage is Gaussian. The power density level is k.T Watts per Hertz where k is the Maxwell-Boltzmann constant, and T is the absolute temperature in Kelvins. 1/f shaped noise is usually an indication of an active device somewhere at work.
David
LIGO, who know a bit about noise sources, have published a survey of 1/f noise levels in a wide selection of resistors from named manufacturers. They are plotted by resistance value and voltage level.

https://dcc.ligo.org/public/0002/T09...rent_noise.pdf

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Old 24th Mar 2019, 6:09 pm   #557
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That's rather a good paper on excess noise created by a DC bias current, essentially fluctuations in the resistance of a resistor. Their figure 6 compares a large number of makes and types of surface mount resistors. As can be seen, the best ones give very little excess noise even down at 1Hz, while the worst on their plot are 50dB worse.

As a rough guide, the difference between good parts and bad ones is 20dB at 1kHz.

The Johnson noise is the thermal floor where a resistor carrying no current acts as a generator, converting heat into random electrical noise, and is dead flat. The other curves show fluctuations in the resistance modulating the voltage across it. This noise output is powered by the DC bias current the resistor is subjected to.

Note that this plot is limited to surface mount parts and 100 Ohm values. Carbon comps would show up as very bad.

NIST (boulder colorado) and NPL (London) maintain noise reference resistors at carefully controlled temperatures. These items are chosen for negligible excess noise at RF and are used as primary standards for calibrating solid-state noise sources for use as transfer standards for noise measurements. The fun part of these standards is calculating corrections of the noise contributions of cable losses across the thermal gradient.

Figure 6 of the paper above, shows you just which types you want to avoid in low noise audio applications and in the tuning lines of frequency synthesisers which can be fiercely sensitive.

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Old 24th Mar 2019, 11:03 pm   #558
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When we were designing a PLL frequency synthesizer in the early 1970's, we had problems with loop stability. My colleague traced it to the thermally-generated noise in the resistors of the R-C loop filter, where at one point, the signal was so small that the thermal noise was affecting it. Fitting low noise resistors provided a complete cure.
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Old 24th Mar 2019, 11:31 pm   #559
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Yes, that's a common situation. Careful VCO design doesn't use a high value resistor buffering the RF on the varactor from the tuning line. Inductors are used. Phase detectors with higher current outputs into lower Z time constant networks are another ploy.

With the high MHz/V needed in some oscillators, switched capacitor pretuning is another ploy.

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Old 25th Mar 2019, 11:22 am   #560
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Now there is absolutely nothing you can do to reduce 1/f noise. And even less an 0.025 ohm inductive wire wound resistor, which interestingly would have its own 1/f noise contribution.
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Noise from a decent quality metal or metal film resistor is almost entirely thermal...
This noise isn't 1/f shaped, it is flat... 1/f shaped noise is usually an indication of an active device somewhere at work.
LIGO, who know a bit about noise sources, have published a survey of 1/f noise levels in a wide selection of resistors from named manufacturers. They are plotted by resistance value and voltage level.

https://dcc.ligo.org/public/0002/T09...rent_noise.pdf

Craig
Thanks both! I was originally thinking exactly the same as RW. But the paper on noise measurements from Craig certainly shows that lots of resistors have an excess noise, and it's 1/f shaped. Definitely reading material for later!

Only thing which worries me, now that solid scientific principles are being discussed, that it might be OT for an audiophoolery thread and the mods step in and close it!

However, bringing back on-topic, as Johnson noise increases with temperature, might there be a market for a cooled amplifier system for minimum noise? I'm thinking, entry-level version, a refrigerated preamplifier maybe operating at -50C. Mid-end system, LN2-cooled pre-amplifier and low-level resistors of the power amplifier at -196C. Top-end system, helium-cooled pre-amplifier resistors, RIAA equalisation network, pick-up cartridge (by piping LHe along pickup arm), LN2-cooled power amplifier, speaker cables and crossover network. If the whole listening room is cooled in the process, that will minimise background noise due to random air molecule motion too!
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