Dubbing 78s to CD

Your article on the Magnetic Cartridge Preamplifier in the August 2006 issue is interesting, as I have experimented in transferring audio from records to CD. I have a good quality turntable but it has only 33 and 45 RPM speeds. For 78 RPM records, I have played the records at 33 RPM with a 78 RPM pickup cartridge, and used the editing software to subsequently correct the pitch. I built a preamplifier based on the Universal Stereo Preamplifier (SILICON CHIP, April 1994) which uses the same compensation circuit as your new preamp for the RIAA LP specifications.

I included switched alternative compensation for a couple of 78 RPM equalisation curves. The time constants were also adjusted for the pitch ratio of 77 to 33 RPM. I had assumed that the editing software would modify only the pitch. The system worked but the results were not as positive as expected. Perhaps my calculations of the time constants were at fault.

I would be interested if you could investigate the question of the equalisation where there is a pitch change and perhaps offer a design review of your preamplifier to allow for others who are unable to play 78 records at correct speed.

Ross Kirkham,

via email.

Comment: changing the playback speed from 78 to 33 RPM really is not the best way to go about it. Not only will the pitch change but the equalisation time constants all have to be shifted down in frequency to compensate (this aspect is covered briefly in the next article, in September). However, because all the signal frequencies are shifted down by more than 2:1, the output of the cartridge will be reduced substantially and the signal-to-noise ratio (ie, signal-to-surface noise) is likely to be degraded as a result.

More breakout boxes needed

I think SILICON CHIP articles need some basic explanations boxes. For example, the August 2006 article about the Ultrasonic Eavesdropper was discussed in the context of a radio receiver without ever actually explaining how the radio receiver worked – it was assumed knowledge.

The same thing happened in the September 2006 issue on LP records. If anyone under the age of 35 has the faintest idea of how LP records work I’d be amazed! For example, why, specifically, are levels higher for higher frequencies with a magnetic cartridge? I assume that this is like an AC generator where amplitude increases with frequency of rotation but that is just my assumption.

These articles and many others would work so much better for a wider variety of people if some basic explanations were included. There’s very much an air of "of course you all know how this works" which I think must exclude the content from many.

The same applies for nearly every constructional project that uses standardised circuit ideas (Schmitt triggers, etc). If the explanations are in breakout boxes, the experts don’t need to read them. Lots and lots of back-to-basics breakouts would be hugely advantageous, with zero detraction for those who already know it all.

Julian Edgar,

via email.

Comment: you are right. Most articles on electronics do assume a certain level of background knowledge. The same assumption occurs in any specialist publication, no matter what the subject.

To be fair though, the basic heterodyne principle used in the Ultrasonic Eavesdropper was clearly described and supported by a diagram (Fig.1 on page 73).

Magnetic cartridges are velocity-sensitive devices. A typical moving magnet cartridge has an output of 1mV/cm/sec which relates to the velocity of the groove modulation.

50th birthday of TV in Australia The 50th anniversary of the introduction of TV to Australia brings back many memories. In 1956, I was 10 years old. People had their eyes glued to television sets displayed in shop windows and had earnest discussions on how close to the TV to sit, the best lighting arrangements for the TV room, and the best sort of antenna. I was delighted that SILICON CHIP has issued a DVD of all the issues of "Radio and Hobbies". In 1957, it published articles which raised the exciting possibility of making your own TV. My father was a radio ham and an electronics enthusiast and because of him I had developed a fascination for electronics. It took about a year but in due course I built my own 5-inch TV, using a 5BP1 tube (and later a 6-inch VCR97). Sockets for the VCR97 were very rare and I soldered the wires directly onto the pins (actually flat sliding contacts, if I remember correctly). As a 12-year old I was of course rather proud of myself but the most irritating questions were "Did you make all the resistors and condensers yourself?" and "Why is the picture green?" Just for fun, I also connected up a 1-inch cathode ray tube (1CP1) and got a picture the size of a postage stamp. A couple of years later I dismantled the 5-inch set and built a 17-inch version which the family used for many years. It was not that unusual for people to build their own TV in those years and several of my friends did likewise. Later on, the ham radio bug hit. In 1961, I listened to the first satellite carrying an amateur radio transmitter on the two metre band. It was called OSCAR (Orbital Satellite Carrying Amateur Radio). My father calculated its distance and velocity from the Doppler shift as it passed overhead with its Morse message "HI". Inspired and taught by him, I sat and passed the Theory and Regulations exams for the ham radio license at the age of 15 but you had to be 16 to get the licence. Imagine my surprise and delight when I woke up on July 21, 1962 to find my licence among my birthday presents! My father had been able to persuade the authorities to issue my licence on the strict understanding that he would not give it to me until I turned 16. I doubt that this would be allowed nowadays. The Moon landing was on July 21, 1969, my 23rd birthday. I was a medical student and we were in the middle of a Pathology class. The laboratory at Monash Medical School had closed circuit TV monitors connected to the demonstrator’s microscope but on that day we interrupted the practical session to watch Neil Armstrong set foot on the Moon in real time, and utter his immortal words. The Americans celebrate the occasion on July 20 but Australia is (was) a day ahead. Television in Australia is 50 years old. I celebrated my 60th birthday this year with an article in "The Australian" (written with my friend Bruce Leyland) on the decryption of the Dedication to Shakespeare’s Sonnets, confirming Brenda James’ assertion that it contains hidden messages that reveal the true author to be Sir Henry Neville. Decryption did not involve any electronics but my personal computer was a great help in typesetting the graphics. I have to admit that the world is not yet convinced. But to quote Eliza Doolittle from the 1950s hit musical My Fair Lady, "Just you wait, Henry Higgins, just you wait". Professor Jim Goding, VK3DM, Department of Physiology, Monash University, Clayton, Vic. Comment: many of us contemporaries can remember the moon-walk in 1969. The editor was in the laboratory at "Electronics Australia" at the time and we all stopped work to watch the momentous event on a 21-inch TV set designed and constructed by Jim Rowe. It is strange that there are now conspiracy theories propounded on the internet that the USA never went to the Moon! Such is the irrational hatred for the USA in some quarters. Weird!

Plugpacks are undesirable

I have noticed that the majority of smaller SILICON CHIP projects which are powered from 240VAC mains, invariably rely on the ubiquitous "plugpack".

I can well understand why a plugpack AC or DC supply might be preferred for a particular design but there are many projects where this solution may not be the most appropriate. For small low-powered projects which will fit in small plastic or metal "jiffy" boxes, an internal transformer may unjustifiably increase the physical size and weight but many projects would be better off by using one.

Plugpacks introduce two points of unreliability, one due to the weight of the plugpack itself and the other due to the poor design of the coaxial plug and socket arrangement at the appliance end. They are usually fitted with quite flimsy figure-8 flex which can be easily damaged due to rough handling and in some cases the plug and/or socket, or even the PC board on which the jack is mounted, can be damaged.

Plugpacks also tend to place a fairly heavy physical strain on GPOs and it is not uncommon for them to fall out of the GPO due to their bulk, or get knocked out unintentionally. I know of cases where items of business communications equipment have failed due to office staff accidentally knocking a plugpack so that it stops operations. A maintenance engineer gets a service call to come and fix the system and that makes for an expensive and embarrassing fix.

Some business offices I have visited try all sorts of tricks to overcome the problem such as tying the plugpacks down to multi-outlet power boards using adhesive tape or Nylon cable ties. Where several plugpacks are required to power different pieces of co-located equipment, it is often impossible to fit them side-by-side in adjacent GPOs due to their bulk.

These items are generally inexpensive, particularly the simple AC type, but the regulated and switchmode types get progressively more expensive depending on output capability and voltage. However, I think that SILICON CHIP, in the interests of both good engineering practice and reliability, should raise its sights and incorporate internal power transformers in their projects where possible.

Back in the days prior to the appearance of plugpacks, electronics magazines such as EA, AEM and ETI (among others) had no option but to use an internal transformer and there were no real disadvantages or hazards encountered. Except in rare situations, I don’t think things have changed much in that regard.

There are many small transformers, both chassis-mount and PC-mount, which are readily available from Altronics, DSE, Jaycar, RS Components and Farnell. Although 3VA is the smallest size available at Altronics, it is not difficult to obtain 1.15VA types from RS and Farnell with which you can build a linear regulated DC supply measuring 70 x 40 x 30mm complete with a screw terminal input connector.

One particular SILICON CHIP project which I was interested in building was the 4-Channel A/V Selector, published in April 2006. Here we have an enclosure with acres of board space inside going to waste and the thing is being powered from a damned plugpack. Surely it would be more practical and would promote good engineering design practice to utilise a fully integrated internal power supply. There are a number of other SILICON CHIP projects which could also be provided as examples.

I anticipate that one of the reasons offered as justification for their use will be that of electrical safety, particularly where inexperienced constructors are involved. To that I would answer that when we were learning the trade as kids we had to be aware of the hazards involved with 240VAC. An occasional "nip" from a project we were working on didn’t kill us then and it served to make us even more careful. Of course, in today’s litigious society, magazines such as SILICON CHIP have to be more careful.

Ross Herbert,

Carine, WA.

Comment: we agree with all your objections to plugpacks. Many of them are cheap and nasty, have high magnetising current and excessive magnetic leakage and are a loose fit in the 3-pin sockets. You have also put your finger on the main reasons we use them: cheap, convenient and no mains wiring in the project – a big factor in their acceptability for school projects.

More equalisation networks needed for preamp I refer to the Magnetic Cartridge preamplifier in the August 2006 issue and to the article on dubbing LPs to CDs in the September 2006 issue. Firstly, both articles are excellent for their respective purposes. A lot of research has gone into the preamp’s EQ designs for the numerous recording standards used in earlier days. In the second article, quite an amount of the text is devoted to the issue of EQ selection for various records. The principle thread, as embodied in the text, is the need to be able to select the right EQ for each and every record one wishes to play and record. Unfortunately, there are more EQ curves than selectable links – there are five microgroove, five coarse groove, three flat and one tape. The problem for all users of the preamp is the practical difficulty in being able to meet such ongoing needs; ie, the difficulty in easily changing between any of these EQ response curves, apart from the three hard-wired EQs – and even those need the cover to be removed on each occasion. Could the circuit be revised to incorporate all 11 EQ positions? This could be switched by a rotary switch, pushbuttons, relay, etc at a moment’s notice. The gain in functionality and utility would be immense. For those who wish to simply continue to play the original recordings (ie, without a desire to record them digitally for future use), such a box would be a normal part of their playback chain and so could be given prominence and not placed "out of the way". Perhaps this could be a 1U rack box? This would have room for LED/pushbutton pairs for selection of all equalisation. Graeme Dennes, via email. Comment: it certainly would be possible to have a preamp with switched feedback networks for all possible equalisations but it would be quite messy in the wiring. We don’t think it would be worth the trouble to design a special PC board to do this. It would probably be better to have the extra networks on a piece of Veroboard with all the wires brought up to a 2-pole 11-position switch – if you can get such a device. Also, the switch should have make-before-break contacts otherwise there will be enormous thumps from the preamp if you switch equalisation while it is powered up.

Compressed natural gas is the right way to go

Let me say how strongly I agree with the September 2006 Publisher’s Letter regarding CNG for our vehicles. It is a perfect fit for Australia.

Your readers might like to know that if there are any doubts on the availability of the technology, all they have to do is visit New Delhi. All commercial passenger vehicles there (three-wheelers up to buses) now run on CNG by law. The impetus was pollution control – particulate pollution in the city dropped 80%, by the way. The technology exists.

Unfortunately, there are two vested interests that will try to stall such progress here: oil companies and our government. When the same idea was suggested in Texas in the 1990s (oil was $18/barrel then!) it was slowly crushed by the oil companies.

Imagine this very plausible scenario if you already have natural gas piped to your home for cooking/heating: A compressor is installed in your garage. Every night, you drive in, connect the compressor, and go inside. Next morning your car has a full tank of CNG. Big oil will not like this as they are excluded from the retail sales. Big government will not like this, as they would loose huge fuel excise taxes. Government will either have to slap on an excise on "home" gas or make us have two meters for each house so they can charge different prices for the (same) gas going into the car and the gas heating the kettle.

Rob Clark,

via email.

DVD regions: a farce?

As an inveterate internet shopper I have long been frustrated by the excellent DVDs available overseas which are not available here and which cost much less than the local product. And I found the division of the world into DVD "regions" both frustrating and silly. I know it’s supposed to prevent piracy but it always seemed like overkill.

A friend who is involved in the business suggested to me that if I wanted to buy DVDs designated for regions other than our Region 4, I should go right ahead and that I would find they would play on most Australian-marketed DVD players. In particular, he said, they would play on the cheaper DVD players available from chain stores, which he said, did not contain the circuitry needed to discern between regions. It turns out he is right.

I bought a couple of Region 1 (USA) DVDs on the internet and also bought a DSE G1928 ($50) player and a Base DV 350 (from Target: $58). Both were embossed with a "4" on the machine and both played the Region 1 DVDs and, later, DVDs from other regions, without any trouble. Then, leafing through the manual of my much more expensive Philips MX 5500D player and surround sound system, I noticed a loose page, containing a code, which, entered into the player, it said, would allow it to "play DVDs from other regions." It’s been cheerfully playing DVDs from all regions, ever since.

I have also tried five other DVD players belonging to friends and family and only one very early model has refused to play "foreign" DVDs. So what was all the fuss about? Who’s kidding whom? And why go stamping "4" on players that readily play all regions?

Have the DVD manufacturers seen the folly of this arbitrary carve-up of the world or did the player manufacturers quietly give up on them?

John Tingle,

Port Macquarie, NSW.

Comment on TV history

I congratulate Kevin Poulter on his interesting series on the history of TV in Australia. This history would not be complete however, without some understanding of how TV programs were relayed around Australia.

From the early 1960s onwards, the Post-Master General’s (PMG) Department constructed a vast network of broadband (analog) microwave links between major population centres around the country. By the mid 1960s all major cities, with the exception of those in the NT and possibly WA, were connected via this network. This was the means by which all of the TV networks, commercial and ABC, relayed their programs around the country. Satellite relays within Australia only appeared as an alternative during the late 1980s.

Each radio "bearer" could typically carry either one TV program or 1200 telephone channels and required a repeater every 30-40km. There were typically 12 such bearers between capital cities. The PMG also built a co-axial cable network but this was rarely used for television.

Contrary to the author’s comments, the ABC regional TV service was relayed live from ABC studios in each state capital to regional transmitters via the PMG’s microwave network. Almost all program content was relayed live with very little originating from regional studios. It was this network which made the ABC regional TV service possible.

It is interesting to note that in those days the Government was willing to provide important tele-communications infrastructure when it was needed regardless of the cost, whereas today it seems, corporations only consider the "bottom line" when deciding to upgrade the backbone telecom network. The public interest, it appears, is not their first priority.

Malcolm Walker,

via email.