PHILIPS REDUX - 3

'TOP-OF-THE-LINE' 40 WATTER

Again, here is another popular design with higher power output. Do note the protection circuits that have been incorporated; they worked very well indeed, as many would gladly attest. Quite a few of us had found that with an unregulated power supply and good components and a large, heavy heatsink, this design could take some beating! The circuit works very well without the protection circuit too, and for the experienced and careful constructor, the design has many merits even toay, I guess. If one doesn't want to 'brag' about the 'watts', this power amp could provide you with a solid foundation for your home-built system. Naturally quality of build and "setting up" the power amp are key factors in its sonic quality and reliability. For the younger brigade accustomed to "plug and play" with IC-based designs, setting up a quirky, high power amp would be something like a tight-rope walk, the art of which, once mastered, becomes easy and even enjoyable!

I am sure this foray into the past shall serve as the trigger for many new explorations, especially of a mature kind in search of true fidelity.

Happy DIY-ing !!

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PHILIPS REDUX - 2

15 W & 20 W  POWER  AMPLIFIERS

Back in those days, what separated the 'men' from the 'boys' was the output of their power amps; boys played about in the area below 10 Watts, and there was a 'grey' area between 10 and 20 Watts. The 'real' men occupied the upper echelons of 20 Watts and above. It was an expensive game when for umpteen reasons your power amp could 'teleport' itself into other worlds in a cloud of smoke, and to boot, take your precious speakers too along! And power transistors, especially matched pairs, were not exactly cheap and they surely did not grow on trees!

The 'flip side' of this power game was that in the melee, scant attention was often paid to the sonic merits of the designs. Considered from that angle, here are a couple of truly 'hi-Q' (a Philips trademark) power amps. If you have efficient speakers that do not need a connection to the nearest power house, these are wonderful options even today. I have found that the 15 W version is particularly suited to driving undemanding open-baffle speakers, and, be warned, the combination could sure sound addictive!

Perhaps what works the magic could in part be the circuit topology of these 'vintage' power amps.

Many of us could easily recall the mad race after fully complementary/fully symmetric designs. The designs looked particularly 'sexy' on paper with their picture-perfect symmetry and, of course, when well-designed, they did sound great too. But our obsession with such designs made us forget many of the golden nuggets from the past. Only recently have designers and enthusiasts like Wim de Haan and others done their bit to restore the quasi-complementary output stage as being 'sonically superior' to many other designs.

As a matter of fact the quasi-complementary design evolved out of manufacturing compulsions. It was easier in those days to fabricate high power N-P-N transistors. Fully complementary pairs were confined to the low power levels, and often used as drivers for the output devices. Now it is well documented by many designers in the field that there are subtle differences between the P-N-P / N-P-N transistors and as a result there are audible differences that mark the N-P-N pairs as being superior and "more musical" output devices. Whatever that might be, here is an opportunity for you to test that theory out with good quasi-complementary designs as these. Surely you will not be disappointed with the results!

A PHILIPS REDUX

In these days of sequels and re-makes, it should be no surprise to come upon another visit to the nostalgic past! Here is a collection of data from the yesteryears from the Philips stable. I have posted these in response to steady demand from a lot of fellow DIY-ers and hobbyists, not only in the senior league, but surprisingly from the younger set too. It seems that the youth brigade are none too happy about the "plug-in simplicity" of IC-based designs, especially when it comes to "getting your hands wet" with making a PCB, wiring it up, and finally, after a bit of tense trouble-shooting, arriving at the moment of sweet audition, which, I must say is its own reward.

I would like to stress the fact that the copyright on the material presented rests with M/s Philips and the data is only provided expressly for the benefit of hobbyists and for not-for-profit applications. Philips data sheets and application books are acknowledged fully as being the source of the material.

Philips was a 'household name' with music and hi-fi enthusiasts long before the field of hi-fi was 'hijacked' by the 'high-end' peopled by companies with exotic names. Revolutionary technologies like Motional Feedback Loudspeakers were introduced by Philips and I intend to touch this topic later from the angle of servicing/restoration of these epochal designs. Most of the designs of Philips were of truly high quality and often reflected the state-of-the-art, and were highly "user-friendly". Those who are sufficiently "long in the tooth" will recall many happy hours spent with Philips data sheets planning the next project. It is pleasantly surprising that many of these designs can more than hold a candle to the "cutting-edge" designs of today. Surely this is going to open the floodgates of nostalgia for many and I am sure many constructors, young and old, will once again experience those old thrills!

THE UNIVERSAL PRE-AMP

Here is that perennial 'hot' favourite, the 'universal' pre-amplifier. If somebody had been keeping count, this ought easily have got into the Guinness Book of Records for the sheer number of units constructed by hobbyists and DIYers. As for the many commercial designs that based themselves on this 'pilot design', again, there is no count. Those who begin to think that this is a 'dated design' should do well to remind themselves that circuitry very similar to this was inside the many pro and semi-pro equipment that served duty in the recording chains of yesteryears at least for a while. Carefully built on good quality glass-epoxy PCBs with selected components, they often rewarded the builder with absolutely enviable performance.

Welcome to the first step in this nostalgic trip!