The early years
I had been exposed to DIY electronics in 1983-84, while I was at the BIT at Ranchi, thanks to a friend and fellow hostel inmate: Gautam Mani. He introduced me to Elektor Electronics (I have most of the issues from that period, starting with the second Indian issue). Gautam was a resident of Ranchi, and had learned electronics at school, I think. He was an electronics addict, always playing with chips, PCBs and flashing LEDs. He introduced me to Elektor, a new magazine at that time in India and totally in a different league compared to the indigenous "Electronics For You". (Both magazines are published even today.) Though I read a lot in Elektor and in Popular Electronics at the Institute library, I didn't touch a soldering iron. I just read, and day-dreamed. There were so many circuits of amps, Baxandall tone controls, and what not in these magazines that I began to dream of music consoles complex enough to put a 747 cockpit to shame. Anything with less than 200 LEDs appeared boring to my 17-year-old brain. In a few months, it was time to leave the institute and shift to another, a thousand miles away. I joined the IIT at Bombay; this was July 1984.
In 1986, I decided that it was time to try to actually build something. It all started with our gang in our hostel wing missing music. There was a large music system in the hostel lounge, but there was no music in our rooms. Our friend Ajay Shah in the next wing had a music system in his room: He had built amps using the TDA2020 chip, thought I didn't know it at that time, taking its feed from an El Cheapo "Unisef" brand Walkman (with an "S" instead of a "C"). We could hear Phil Collins' plaintive cry, "Take a look at me naaaaaoow..." from his room on many nights. We in our wing didn't have the money to build a stereo system, so we decided to pool in about a hundred rupees each and build a mono box. I was going to try to build an "ampli-speaker", using the TDA2020. (Gautam at BIT Ranchi had told me all about the TBA810, the 1010, and the 2020 three years back, though I'd never seen one till then.) The ampli-speaker would contain what I today call a "preamplifier", complete with tone controls. And in the process, I was also going to teach myself soldering.
I bought parts, an enclosure, a soldering iron, solder, and a TDA2020 kit, from Lamington Road, the electronics components bazaar of Bombay. Most of these things, other than the enclosure and speaker, came from Visha Electronics; I am their customer even today. The soldering iron had a wooden handle, and looked more like a housewife's belan (rolling pin) than the sleek plastic-handled Soldron-brand things with replaceable tips that I use today. For the preamp, I went with a circuit I read in a small, super-slim book called "741 Opamp Circuits" or some such title. It had a circuit diagram for a bass and treble control circuit. I used a prototyping PCB to assemble the preamp. When I put it together, it hummed cheerfully. Then the lab superintendent at the Hobbies Club at the IIT (I now forget his name, portly, mild-mannered South Indian gentleman who used to pronounce "circuit" as "sir-cute") admonished me for the poor quality construction, telling me that I should have first designed, etched, and made a proper PCB for my preamp. I was in no mood to redo the PCB, so prototyping PCB it remained. He also taught me about shielded cable. The problem with my circuit was that the tone and volume controls were hooked up to the PCB using unshielded cable. I replaced them with shielded cable, and the humming went away.
The opamp for the preamp was a 741. I don't remember now, but I think I'd used 7815/7915 chips for the opamp power supply, drawing current from the power amp's rails.
A preamp and power amp were not much use unless you could hear what it was generating. So I stuck the whole thing inside the speaker box. This box was made of particle board, probably 6mm or 8mm thick. It was not properly air-tight. It had a circular hole pre-cut for an "eight inch" driver. I bought perhaps the most famous speaker driver in the Indian after-market driver market: the Philips 8" dual-cone speaker. I fixed it in the box, and hooked the TDA2020 power amp to it. All the electronics, including the E+I power transformer and the bridge rectifier, went into this particle-board box. There were three holes in front through which I stuck out the sticks of the three pots, for the volume, bass and treble controls. Out of the back jutted out a long tail, which was essentially shielded two-core cable. At the end of this tail was a 3.5mm stereo mini-jack.
My friend John had a very high-tech Aiwa Walkman -- it had a metal body, auto-reverse, stereo recording facility and supported Dolby and metal tapes. John's father was a marine engineer with a shipping line and travelled to all sorts of places. He apparently loved John a lot, we had no idea why, and he had bought this Walkman as a gift for him. Once we saw it, the object of course became hostel-wing property, and we probably figured out more about it than he had. He didn't mind, and we really didn't ask him whether he did. When this ampli-speaker was done, we hooked up its 3.5mm jack to the headphone output of John's Walkman, and slurped up the music.
About five of us shared the cost of the project. I still remember that the total cost of all parts came to about Rs.480 or so. (At today's exchange rate, this would be about USD 10.00. At the exchange rates prevalent in 1986, my guess is that it would be about twice as many dollars.) The box, and John's Walkman, moved from room to room in our wing, and many a dark evening was spent listening to "The Wall" or America's "View from the Ground" or S&G in silence. The ampli-speaker made a really big difference to our collective happiness.
I am deliberately not going to analyse the sound of that box with my sensibility of today. That would be downright silly. However, I will list what I noted even at that time as problems. The first problem was that the box shook and vibrated. I didn't like that -- I had a music system at home, more than ten times as expensive as this one, whose speakers didn't vibrate like this. Secondly, the sound was not very smooth. The third problem is that the box was not very silent even with zero signal ... there was always a sort of light hiss, though there was no hum. But we were happy.
I was in my second year of my BTech (Bachelor of Technology) programme when I made this box. It did sterling service in our hostel wing till the end of our BTech days (1988) and lay in a corner of one of our rooms as we finished our courses and left the hostel one by one. And I never touched a soldering iron after that, till 2002 or so. But the confidence I have today in attempting my DIY projects is all because of that box I built in 1986, without the Internet and online forums, in my hostel room as a teenager.
Even today, I would say that this route offers a great way for a non-technical music lover to start on the road to DIY audio. Instead of the TDA2020, today you would probably start with a Gainclone.