Practical Electronics 500 Watt Amplifier

[Aub]

Hi all,

Was in WH Smiths today and saw that in PE there's a project to build 500 watt ( into 4 ohms ) amp. Just thought I'd let folks know

Aub

[Bazz4CQJ]

Well, my NAD cannot last for ever... think I need me a copy of that .

B

[Aub]

Remember, you'll need two for stereo

Aub

[paulsherwin]

Somebody must have a big lounge (and deaf neighbours).

[Aub]

Yes Paul From my quick scan, I think it uses five or six complimentary pairs of bi-polar transistors in the output stages, with fan cooling when required.

Cheers

Aub

[Craig Sawyers]

Feed that into a pair of horn loaded speakers and go deaf really quick ;-)

Craig

[stevehertz]

I didn't think that any of the old hobby electronics mags still existed. Which ones still do out of interest?

[Chris55000]

I'm not sure about overseas Continental publications, but as far as I'm aware, there's only "Practical Electronics" and "Elektor" (not in print in the shops but you can order "Print and Digital" on their website) left in the UK and "Silicon Chip" in Australia, from which P.E. projects are from – all the others are long gone!

Chris Williams

[Cruisin Marine]

Originally Posted by Chris55000

I'm not sure about overseas Continental publications, but as far as I'm aware, there's only "Practical Electronics" and "Elektor" (not in print in the shops but you can order "Print and Digital" on their website) left in the UK and "Silicon Chip" in Australia, from which P.E. projects are from – all the others are long gone!

Chris Williams

That is such a shame, a mag article in real print is one of the best ways to learn a new discipline.

[Philips210]

Practical Wireless is also still available from WH Smith.

Back in the early 1980s you were almost spoilt for choice. On Smith's shelves there was, PE, PW, EE, R&EC, Television, Elektor, ETI, Hobby Electronics, WW/EW and later on others such as Maplin magazine. It is indeed a great shame there isn't such a selection of magazines any more.

I still regularly buy PE but must admit to not building any of their projects for many years. I occasionally purchase PW as well.
I have a large collection of the above magazines but the great convenience of the WRH website makes it easy for searching for an article/project. There's still no substitute to having a paper copy in front of you and I still enjoy thumbing through old mags.

Regards,
Symon

[stevehertz]

'Blame' computers for one. Fringe electronics hobbyists were drawn towards playing with computers rather than making a fourth generation plant moisture detection warning unit (not surprising). I witnessed this first hand in my place of work (Thorn EMI Electronics) where the later apprentices were putting together computers and buying computer peripherals and learning programming (what's that for?!) whereas a few years previously myself and other apprentices built the Texan amplifier, simple radios and electronic car ignition systems. Plus, as I previously infer, electronics mags were running out of ideas for build projects and not only that, the days of making something from a strip of veroboard, a few transistors, resistors and capacitors had largely gone, a lot of the new projects required expensive, 'hard to find' ICs and a somewhat complex PCB. Making electronic things had moved from a relatively simple, inexpensive hobby making things to use around the house, to a more complicated process involving a greater commitment in terms of both time and money to make more esoteric things for niche applications that the average hobbyist had no interest in or use for.

[Craig Sawyers]

There was a series in PW in the early 70's called Take 20. This was a longish running series for projects having fewer than 20 components and costing less than 20 shillings (the series started pre-decimalization, so a pound) to build.

But back to grunty amps. I use active speakers - the open baffle Linkwitz LX521.4. These have five drivers per side. Two woofers, lower mid, upper mid and tweeters.

After the active crossover, I have 150W into each woofer, and 80W into each of the other drivers. So 540W into each speaker.

Needless to say, at normal listening levels, the heatsinks (I massively overrated them!) get barely tepid. It is only when running into dummy loads at full whack that the sinks get fairly hot.

Craig

[David G4EBT]

Originally Posted by Chris55000

I'm not sure about overseas Continental publications, but as far as I'm aware, there's only "Practical Electronics" and "Elektor" (not in print in the shops but you can order "Print and Digital" on their website) left in the UK and "Silicon Chip" in Australia, from which P.E. projects are from – all the others are long gone!

Chris Williams

That's true, and a glance at any of those magazines will show that the days of conventional home construction as we once knew it are largely behind us. Most articles will be more akin to computing, with projects using Arduino and Raspberry P1. Those that aren't - the 500-Watt Class D Amplifier for example will use ready made modules. Silicon Chip states:

"Use two inexpensive Modules to make this 500-Watt Class-D Amplifier".

'Inexpensive' is a subjective term of course.

Silicon Chip Magazine can be bought as a hard copy for $195AU (£105GBP) post free.
As a digital download (hence no postal delays), it's $95AU (£52 GBP).

https://www.siliconchip.com.au

As Chris says, for some years now, PE (Re-named from EPE) has sourced articles from Silicon Chip in Oz. They're invariably complex designs, using components that for the most part, would need to be sourced from Oz, most likely from Jaycar, and for something such as the amplifier, which I guess will be quite expensive, with the added complication of import duty, and a collection fee by the courier/Royal Mail.

https://www.jaycar.com.au

I'm not sure what's going on with PE. On the few occasions I see it in Smiths, it still looks like a nicely produced magazine, albeit rarely with anything I'd want to build, but it's website seems poorly maintained and well out of date. EG:

Quote:

"Sourcing Practical Electronics during the Covid-19 lockdown: We are still publishing PE every month! If you are having trouble buying the latest issue then you can buy it here for EXACTLY the same price and we will post it to your address, p&p included. (UK only)".

End quote.

https://www.electronpublishing.com

(All legal restrictions on lockdown including social distancing ended in England on 21 July 2021).

Furthermore, if I click on the 'Latest Issue' link, it lists the whole of 2022 - not the 'latest issue' appears:

https://www.electronpublishing.com/p...2-back-issues/

Elektor Mag has for some years been by subscription only. Eight issues a year, 92 Euro (£81GBP) post free. Digital download 72 Euro (63GBP):

https://www.elektor.com

It always was a tad esoteric - ('bat detectors, poltergeist detectors, voice changers' etc), never more so than now, and as with Silicon Chip, (and hence P.E.), Arduino, Raspberry-Pi, PICs etc.

As to PW, whatever you do, don't search on google 'PW Magazine' or it will quickly become apparent that PW (as in 'Practical Wireless') aren't into Search Engine Optimisation. The first few links will take you here:

https://pw-magazine.com/home

Oh dear!

This is where you'll find PW (as we know it):

https://www.radioenthusiast.co.uk/st...ical-wireless/

Ironic that at the start of the index to this month's PW mag, it touches of the topic which is the thrust of this thread:

Quote:

What's in this Issue?

Keylines:

'Don looks back at amateur radio magazines that have come and gone in the UK'.

End quote.

There's a review of the 'Gypsy' portable antenna:

https://www.amazon.co.uk/WINDCAMP-5-.../dp/B074CW8GXH

Two lengths of wire and a 50 Ohm balun.

As simple as a dipole can get.

£140.

Time was when there would have been an article on how to make such an antenna and balun.

I despair. Antennas are about the simplest thing that radio amateurs can make.

How can a magazine which has 'practical' in its title print 'advertorial' for commercial products, when not so many years ago it would be showing how to make one? In all the years that I was active on air, all my antennas but one (a multiband vertical) were homebrew and worked just fine. Trapped dipoles with baluns, a rotary 'mini-beam' Inverted V etc.

If amateur radio has minimal practical, experimental or construction content, and only involves buying things with moulded on plugs and plugging them together, in reality, over the last thirty years or so, it's morphed into 'posh CB'. If others derive enjoyment from it as some clearly they do, I don't have a problem with that, but it's just not for me.

I'm not deriding any of these magazines - times change, electronics has evolved and we can't create a future by living in the past. I think it's more about my generation, which has now all but fizzled out, being trapped in a time-warp , having grown up in more austere times when our mindset was formed by mottos such as 'make do an mend', 'waste not - want not', 'penny wise, pound foolish', cut you suit according to your cloth', ‘neither a borrower nor a lender be’.

Others may have a different perspective, which is fine by me - I'm in a rut as deep as a grave, and have more than enough practical projects involving metalwork, woodwork, and electronics to keep me occupied in my own little world.

[DrStrangelove]

I stopped buying PW when it changed hands and Tony Nailer's stuff was done away with at what seemed like a whim of the new establishment. His articles were all I bought it for.

The subscription to Wireless World lapsed sometime around 2007 when I wondered why I was paying money for something little better than one of the old professional freemags. It had suffered from a new editor who had previously edited one or other of the IEE mags.

Similarly the sub to EPE (as it was then) demised with the advent of the Silicon Chip articles.

I forget quite why the sub to Elektor went the same way.

Probably terminal ennui with the state of electronics and electronics education, working, at the time, in Higher Education.

Originally Posted by One of my HNC lecturers

I can't teach the current degree students (late 1990s) the stuff I used to teach the HNC students back in the 1970s

And as for the IET replacement for the old IEE "Electronics & Power" I don't see that any more since it went "green" and online. Saves me the trouble of throwing them in the recycling.

[Malcolm T]

Another good read and for projects was short wave magazine .
The simplest dipole is a length of twin speaker wire split at one end and knotted in the center to form the top section for the frequency in operation, the rest of it is the twin feeder section .

[Chrispy57]

DrStrangelove -
Quote:
Originally Posted by One of my HNC lecturers
I can't teach the current degree students (late 1990s) the stuff I used to teach the HNC students back in the 1970s

An intriguing quote, but what does it actually mean? I can think of two very different interpretations, but would be very interested to learn more about the underlying message, as a late 1970s HNC Student and a 1990s Degree student.

Cheers
Chris

[DrStrangelove]

Originally Posted by Chrispy57

DrStrangelove -
Quote:
Originally Posted by One of my HNC lecturers
I can't teach the current degree students (late 1990s) the stuff I used to teach the HNC students back in the 1970s

An intriguing quote, but what does it actually mean? I can think of two very different interpretations, but would be very interested to learn more about the underlying message, as a late 1970s HNC Student and a 1990s Degree student.

Cheers
Chris

What I took it to mean & from some personal observation, he was saying that the stuff he taught in the 70s was rather more complex than the stuff he taught in the 90s.

Then again, having done the CEI Part II course following on from HNC I can readily believe that.

[Chrispy57]

Thanks for that clarification, that makes a lot of sense to me too. I learned so much from my HNC and Endorsement courses at the local Technical College in the 70s and always felt that it was the best electronics education that I had, over a career that later included a B. Eng. Degree in the 90s and an M.Sc. Degree in the early 2000s. CEI Part 11 was offered there too at one time, but circumstances intervened for a few years and then it was gone.
Cheers
Chris

[Radio Wrangler]

From the point of view of interviewing graduates for R&D jobs there has been a noticeable change over the period, and these were people pre-selected by a personnel department looking for 2:1 or above honours graduates. There were exceptions, of course, but these were people with an active interest in the subject who would have educated themselves anyway, anywhere. I assume that the broadening of the subject matter into computers and their ilk diluted studies into heavyweight analogue stuff and the maths behind it.

When I was an undergrad student things like control theory, filters and antennae scared the living bejasus out of students and propelled the uptake of modules on software and computers. I looked at this and realised there was a market opportunity that wasn't being filled. It turned out that the lecturers in these areas were so thankful for anyone taking their subjects. Lab facilities for these areas were not being fought over, you got a better choice of projects and they wrote nice, welcoming exam questions! Once I got into it, it wasn't even difficult.

Around the same time, a schoolfriend was doing an HND. I was surprised to find that he was getting more work than I was for a degree, and that he was having to work a lot harder at it. I remain mystified. A normal degree took three years, a thick sandwich one took four years, but the colour TV course at Huddersfield tech was six years from start to finish.

What I later learned was that fresh degree graduates then took a year or few to learn what was needed to come up to speed for a design job. Those on the TV course should have had enough experience through the course and industry to be gainfully effective by the end.

So, I don't see any justification for people getting precious about qualifications. There is a lot of overlap and pieces of paper don't guarantee capability. Universities teach people how to analyse. Employers pay people to synthesise and to solve problems and to invent new things. There is a gap between the two. It needs someone with a personal interest to have the drive to bridge it.

Friends in the educational business bemoan the capability levels they see coming out of the secondary schools. The grades on paper have been ramping up, but what the students can do has been, on average, reducing. Again, those with interest and drive buck the trend, but then they always did.

David

[DrStrangelove]

I can safely say that CEI Part II was the most difficult set of exams I ever took.

Of the twenty or so of us in the cohort two passed, me being one, and another geek being the other.

I still remember the shock of the first exam: field & circuit theory: it was completely different to all the past papers.

Fortunately I'd been revising stuff since before Xmas & managed to do enough to pass the damn thing.

One chap was so upset by it that we never saw him again.

It was set up so you could take all 6 exams full time (as in 30 hours a week in class/lab) or 3 exams one year & 3 exams the next but with a higher pass mark.

I had a look at the exam papers a couple of years ago: did I really know all that stuff?

An externally set degree level exam was no joke since there wasn't time to cover the whole syllabus.

To make it easier we did Operational Research and Production Systems as two of the exams since control theory etc. was known to make strong men weep.

The Electronic exam, on the other hand, was comparatively easy.