Back to Paul's Posts

Early amplifiers

— By Paul McGowan —
I mentioned in yesterday's post that the early transistor amps invading the hi fi and consumer electronics scene were dreadful sounding. But why? The tale is long and complicated, filled with many twists and turns and the complete story is not within the scope or space of these short daily posts. But I can shed some light onto the subject, light that will help us understand what happened and some of the evolutionary process manufacturers went through from both sides of the aisle. And by the 'aisle' I do mean the same definition as the common usage of strong political sides being taken. In Washington those sides of the aisle can get pretty polarized, sometimes downright nasty. This is because the differences of opinion of those in congress can be very much opposite of each other. And such is the case with the two sides of the aisle in audio reproduction: those that listen as the final test and those that measure. But I jump ahead of my story. In the beginning of transistor amplifiers it was common practice to simply replace the vacuum tube with a transistor and leave everything else the same. What you wound up with didn't have the frailties and requirements of a vacuum tube (heater power, microphonics, warm up, relatively short lifespan, heat), but also lacked the sound of the tube; a sound that had been honed over many years of work and listening. The reason this was done was simple, the engineers who implemented the new fangled transistors were schooled in tubes; they knew no better. It's instructive to remind ourselves that the pioneers of solid state electronics at Bell Labs were trying hard to replace the vacuum tube as well as the mechanical relay that made up the massive phone system in our nation (and those around the world). Imagine how expensive, how difficult it must have been to handle all phone switching and amplification with the likes of vacuum tubes and mechanical relays. It took armies of technicians to replace tubes and relays that routinely failed and these antiquated devices limited the performance of the system as well. To send telephone calls over long distances you needed many repeater stations along the way, each powered by tubes and relays, devices ill suited to the task. The pressure was on to replace the glowing fire bottles that plagued Ma Bell, and a team of physicists headed by one hell of a crazy man, William Shockley, led the way to developing the transistor that would forever change not only the phone system but everything else in our lives; and not by just a little bit. So it was not by accident that the engineers of the day, including those of audio companies, did little more than replace vacuum tubes with transistors and call it new. But with any new technology, you need to branch out and take advantage of what that device has to offer, something these early engineers did not do. I can remember gasping at these circuits in horror. Here's a picture of one such approach. Early amplifier The little curly symbol separating transistor Q1 from Q2 and Q3 shows a transformer between them. And the output of Q2 and Q3 also has an audio transformer to couple to the next stage. This circuit is guaranteed to sound awful. I do not need to prototype it to know. It's just bad design. But that's what we had in the beginning. Tomorrow we'll move forward as a new crop of engineers learned to take advantage of the transistor's unique characteristics that make it superior to a vacuum tube in some applications. As an aside, reader David Blank sent me an interesting tidbit of info worth sharing. Turns out one of the first Pacific Stereo stores (if not the first) was in Palo Alto, in the same building as Shockley Labs, one of the three men credited with inventing the transistor.

0 comments

Leave a comment

0 Comments

Your avatar
Rate this article:

Loading comments...

🗑️ Delete Comment

Enter moderator password to delete this comment: