Power cords should have listening tests

I must ask on what basis you dismiss the possible usefulness of after-market power cords for hifi, in the Publisher’s Letter for the May 2004 issue. If you accept the scientific paradigm that testing a hypothesis is the only way to disprove it, then please tell me about your listening tests of these cables. If your objection is theoretical only, then say so.

Please note that I am not defending their amazing prices, only requesting a scientific approach that would seem to demand that disproving a claim about better sound would require assessment of the sound (not merely of resistance, capacitance, inductance etc).

David Collins, via email.

Comment: these power cords are only about two metres in length and connect between your power point on the wall and your amplifier (or whatever). So no matter how wondrous the power cord is, the power still has to come via your existing mains wiring, the power point (GPO wall socket) and the internal mains wiring in your amplifier. So the whole exercise is utterly pointless.

If normal supplied power cords were notably poor in construction, with very high wire resistance, poorly made contacts and terminations, etc, a superior cord might have some effect. But standard power cords supplied with brand-name equipment are always quite adequate, in our experience.

Secondly, even if the entire mains power distribution to your amplifier could somehow be improved, eg, cleaner waveform, absolute line voltage regulation. etc, it would still make no difference to the sound quality of your amplifier or any other part of your system. This is because amplifiers are designed to largely reject or be impervious to any disturbances in the power supply rails.

If the power cord incorporated comprehensive filtering to remove all mains hash, switching tones, etc, it might be worthwhile, although typically, mains-radiated hash, switching clicks and control tones do not come into an amplifier via the power supply but are picked up by the input leads or speaker leads. In any case, these exotic power cords make no such claims. In fact, any claims they make are extremely vague and not quantifiable.

All of which IS theory, backed up by lots of practical experience. If anyone believes that there is some slight chance that a hugely expensive short power cord with an exotic name can give an audible improvement, then they are severely deluded.

ESR meter works well

Well done SILICON CHIP for the ESR Meter Mk2 described in the March and April editions this year. The unit basically paid for itself soon after I finished constructing the kit. The first day I used the thing, it made easy work of troubleshooting three different switchmode power supplies that were destined for the junk heap.

It’s child’s play to operate and the Dick Smith Electronics kit produces a professional looking piece of test equipment.

Jason Cox, Brisbane, Qld.

Microwave heating separates core halves

I was interested in your article on a "Dirt Cheap, High Current Power Supply" in the October 2003 issue. I had previously been interested in an article on the same subject in the November 1998 issue of Radio and Communications magazine. Both articles detail how to convert a PC power supply to a 13.8V high current supply.

Both articles mention rewinding the main transformer in the supply. Your article details how to separate the two halves of the ferrite core by immersing the transformer in paint stripper. I followed the instructions but the transformer ferrite sections were glued together with some agent that was resistant to paint stripper.

I had tried on a number of occasions over a couple of years to separate the two halves by various means and been frustrated in every case by fracturing the ferrite core. Finally I decided that maybe heating the core in a microwave oven might solve the problem. I placed the transformer in the oven, along with a cup of water to absorb some of the energy – just in case funny things happened. I decided on a period of 60 seconds at full power in a 900 watt microwave oven.

It worked like magic – the core of the transformer was very hot and the two halves came apart easily. The downside of this success was a nasty smell in the oven. I haven’t tried again but I suspect I could reduce the "cook" time and thereby reduce the odour and still have the result I needed.

So, if you want to dismantle a switchmode power supply transformer easily, you can use the microwave oven. But don’t do it before cooking a meal and make sure you don’t burn your fingers on the hot ferrite!

Keith Farmer, via email.

Complete listing of Autotrax commands

Since I haven’t used a CAD package for designing PC boards before I thought I would follow through the 3-part tutorial series by Peter Smith published in the February to April 2004 issues.

While these articles did give a good deal of information I felt they fell short of giving sufficient detail for beginners. Many of the command sequences required to perform a particular function were shortened so much that they could not be followed and the desired function was unable to be performed without more searching and reading via the web.

One thing that was missing was a complete listing of all the commands available in Autotrax 1.61, which I could not locate in any of the references given. The closest command listing available applied to Easytrax 2.06 which, being an earlier incarnation, is not the same. I finally located an excellent reference specific to Autotrax 1.61 at www.lupinesystems.com/easytrax/

In fact, the home page at www.lupinesystems.com/ is an ex-cellent site for anyone wanting to start off making PC boards.

Despite my criticism of the lack of detail in these articles, and I do understand that a proper treatment would take up far more space than could be given, I applaud SILICON CHIP for running them. They encouraged me to do something I had intended to do for many years.

Ross Herbert, Carine, WA.

Comment: thanks for your comments. You’ve answered your own criticism though – we could not justify all the space that would be required to do what you request.

Slur on real estate agents unjustified

As a person who works in the real estate industry I was deeply offended by your Publisher’s Letter in the May 2004 issue. To label all real estate agents as dishonest people is ridiculous. We are a highly regulated industry that is regularly audited; there are very few shysters/hucksters to be found in my industry.

I wish I could say the same for the so-called tradesmen we deal with on a daily basis, including members of trades that would regularly read this magazine.

Ian Boyd-Jones, Thirroul, NSW.

Comment: Talk about unintended consequences! We apologise.

Jug elements as dummy loads

I think the use of jug elements in the article "Amplifier Testing Without High-Cost Gear" is absolutely brilliant. I’d never thought of that before.

Heating elements from ovens can also be used, as long as the element(s) are matched to the load impedance of the equipment, and that the elements are guarded to prevent accidental contact. Jug and oven elements can also be used for testing high-powered RF amplifiers.

Bryce Cherry, via email.

Comment: glad you liked the concept but we would not use unshielded jug elements for testing high-powered RF amplifiers. They would radiate a lot of signal.

Surface-mount ICs are agony

I am puzzled that the designer of the Component Video to RGB Converter would put kit builders through the agony of working with surface-mount ICs if the required performance could be achieved easily with normal components.

He says proudly that the MAX4451 "has a -3dB bandwidth of 210MHz . . ." etc but why do you need this for signal with a maximum bandwidth of 5MHz and an adding circuit with unity gain? Surely there are stacks of conventional ICs which would do this job quite adequately?

John Neate, via email.

Comment: it is true that off-air video signals only have a modest bandwidth (5MHz) but if you want the best picture from DVDs, digital STBs, etc, 100MHz or better is desirable since it gives zero phase shift over the pass-band.

Video projects not user-friendly

SILICON CHIP’s range of video projects are innovative, compact, no mains wiring for safety, no connecting cables/wiring needed internally (usually) and easy to construct. But user-friendly? No!

In an effort to keep costs down, safety high and better repeatability, has SILICON CHIP and particularly Jim Rowe, lost sight of the fact that they are messy to use (because of the need to hide them, due to cables connected to front and rear).

As for the Component Video to RGB converter (May 2004), it performs faultlessly. However, it has to be kept out of sight like many other recent video projects and then you have to hide a big plugpack (which takes up two power board spaces) behind your entertainment unit, along with other plugpacks which are live at all times. There is often no provision for an On/Off switch on the unit itself either.

How many readers like the idea of a number of hidden plugpacks which are on all the time, hiding behind furniture and plugged into a couple of power distribution boards sitting (probably) on carpet.

The PC board may be small due to the use of modern components but a bigger case with an on/off switch, internal power supply and ALL sockets at the rear, could sit unobtrusively on top of the DVD player or other item. In many cases the front panel would only need an on/off switch and a LED. That’s what I intend to do with the Component to RGB Converter.

Alex Kethel, via email.

Comment: we don’t like the idea of multiple (hidden) plugpacks either but we tend to adopt them because they are: (1) cheap and safe (they meet Australian safety and EMC standards); (2) enable a much smaller and cheaper case; (3) remove hum fields from the immediate circuit (can be critical for video and audio devices); and (4) can be built by school students (under school supervision) because there are no mains voltages.

Hot glue not good as high-voltage insulation

On page 86 of the May 2004 issue, a reader asks about substituting hot-glue for silicone sealant to insulate metal nuts on a mains-carrying PC board. I am not familiar with the original circuit but I assume that a degree of insulation was deemed necessary for safety purposes. If so, then hot-glue may prove totally unsuitable.

I am a professional electrical engineer and have been involved in one capacity or another with electronics for about 40 years. It has been my experience that hot-glue (what I would refer to as "hot melt" glue) loses its adhesive properties after about a year - maybe a few years at best. After this, if it is mechanically retained by the way that the glue has set relative to mechanical fixtures then it will "loosen its grip" but stay in position.

However, if it is not mechanically restrained, it will drop off. When the glue is the critical means of mechanical retention it invariably fails. I have seen many devices, where hot-melt glue was used to anchor wiring or components, in which the "anchored" object is now floating free. Sometimes this leads to equipment failure and sometimes just to interesting noises when the equipment is moved.

If this insulation is necessary for safety purposes at any time after construction, then hot melt glue should not be used. Silicone sealant does not act in this manner. It retains tenacious adhesive properties over its lifetime (which can be in excess of 20 years).

Russell McMahon, via email.

On fraudulent power cords

I’ve just read your May 2004 editorial on high-priced power cords and thoroughly enjoyed your comments. As the Good Book says (Ecclesiastes) "...there is nothing new under the sun" and this kind of garbage has gone on in the audio world for ages.

I’d be giving away my vintage if I was to relate the waffle that hifi salesmen used when expressing "power". That an amplifier could consume, say 120 watts and blast your ears with 500 "watts" per channel – well, why spoil a good spiel with the facts?

Anyway, I’m off to rewind my power transformers in an anti-clockwise direction, to compensate for the Earth’s magnetic field and spin in the southern hemisphere.

Frederick Finkelstein,via email.

Brass screws give low distortion

Further to your "spot on" Publisher’s Letter in the May 2004 issue, my attention has just been drawn to the latest Jaycar Engineering Catalog. On page 14, we read about their Studio 350 kit: "Our kit includes the special 5/32-inch non-plated brass screws that guarantee the lowest possible distortion. Beware of cheap plated steel screws in inferior kits!".

Is it really that easy to improve the sound?

Neville Cohen, Randwick, NSW.

Comment: in this case, it really is that easy. We specified brass rather than nickel-plated screws for the Studio 350 and Ultra-LD amplifiers because there is a distinct distortion reduction. This is noted on page 25 of the February 2004 article and covered in more detail in the December 2001 article on the ULtra-LD amplifier (see page 63). Dissimilar metal joints in the power signal path can cause distortion.

Smart flash trigger responds to infrared

The article for the Smart Slave Flash Trigger in the July 2003 issue states: "Actually these both have an inbuilt IR (infrared) filter but they still have more than adequate response to visible light to do the job here". This description is wrong.

The BP104 has an IR filter but the filter is there to stop visible light and let the IR light through to the sensor. The specifications sheet for the device shows the spectral response of the device peaks at 950nm.

The IR sensor in this project IS detecting the IR output of the flash gun (not the visible light). And that is good because electronic flash tubes put out more IR (heat) than visible light. Put your hand in front of a flash gun and feel the heat pulse when it is fired.

Dirk Stoffels, Canberra, ACT.

Comment: you are right. It turns out that the spectrum output of a typical flash tube also peaks in the infrared. Either way, it does not matter whether the detector responds to visible or infrared light – it works!

Component video to RGB converter

Has someone made a boo-boo with regard to the Component Video Converter? Shouldn’t the name be "composite video converter"?

I guess that you will blame the auto-correction feature in somebody’s spelling checker. Over the years, I have seen some real mess-ups where a minor spelling error has caused the spelling checker to substitute a different word which completely changes the meaning of a sentence.

Harry Pfeifer, Warragul South, Vic.

Comment: "Component Video" is correct. In this case, the Luminance signal is equivalent to composite video (ie, B&W video). On the other hand, our reference to the project on the front cover as a "Video Standards Converter" was not correct.

Technicians need better communication skills

I almost agree with your comments in the Publisher’s Letter in the April 2004 issue, about the status technical people hold with the general public. It is not too good, as you say, and quite undermining for self-esteem.

However, putting some more "Tickets on ourselves" as you express, I think won’t help. That will only make our appearance more nerdy. We must overcome a shortcoming within ourselves, as technical people, of not being too good at communicating.

Isn’t our world becoming more "touchy feely" and we, by becoming the techos, have gone the other way and shied away from all that. We find more satisfaction in the lab or the back room, away from view.

Joe Public seeks primary advice all too often from the shop counter person, who might have no more technical qualification than some company indoctrination. The real knowledge is elsewhere.

We are in competition with the rest of society for our place. It must be earned. Knowing what we know is great for us but won’t raise our status. So our training must include people skills, just as much as basic electronic principles, etc.

Hugh Paton, Tallangatta, Vic.

More details on ultra-bright LEDs

It was good to see the article in the April 2004 issue about the new breed of ultra-bright LEDs. There certainly are some interesting devices available now. However, just thought I might add some information on a couple of things mentioned in the article.

Lumens per watt figures are a good way to compare LEDs to other light sources, and while most LEDs do come in around 35 lumens per watt or less, some actually perform quite a bit better. Many LED manufacturers bin their LEDs according to colour, voltage drop and light output and some of the top bins can exceed 50 lumens per watt; the red-orange 1W Luxeons are in this class. The Luxeon 5W white devices, although they have a very short life, are also binned, with the top-level bins coming close to 50 lumens per watt.

I have a converted Maglite torch that has a 5W Luxeon LED from one of the better bins, and its output really is impressive compared to an equivalent halogen. It would be close to a 20W halogen in total light output, although admittedly, with fresh batteries (three CR2032 3V lithiums) it pulls around 8 watts from the cells! It is by far the brightest torch I have ever owned.

In regards to halogen replacements that use LEDs, we have evaluated quite a few of these, and none really come close to a 50W halogen, as you would expect - the light output of the best LED halogen replacement bulbs is usually less than 100 lumens, compared to 1000 or more for a 50W halogen. The halogen fittings themselves limit the amount of power a LED-based bulb can use. The maximum seems to be 4W or less – any more than that and you simply cannot remove the heat generated fast enough and the LEDs overheat, reducing their light output and their life-span considerably.

As far as future improvements are concerned, according to a recent US Dept of Energy study, if $100 million was spent on LED development in the next 15 years or so, we should expect to see LEDs in the 180 lumen per watt class, with prices falling to around US$2.50 per kilolumen. This would be a stunning improvement, and even a figure half this good would spell the end of just about every other form of lighting in general use. Some more information on this and LEDs in general is available in our latest issue of ReNew magazine.

Lastly, you didn’t mention multi-chip LEDs, such as those available from www.ledsales.com.au and other suppliers like Roithner Laser, who have multi-chip, ceramic-based arrays up to 20W and 500 or so lumens! These devices generally use standard chips (20 or 25mA-rated) connected in parallel or series-parallel arrays to provide more light than a standard LED. In fact, the Luxeon 5W devices are actually four 1.2W chips connected in a series-parallel configuration.

Lance Turner, ReNew magazine.