Don't get me wrong, folks. I do not personally dislike solid state technology. My first experience with transistors dates to about 1967. I was five years old and had a four transistor Zenith radio that used two AA batteries, one for the RF section and one for the audio section. The transistors were actually in sockets! When the radio seemed to die out, I would change around the transistors. When that did not work, I changed the batteries around and that would cause it to work. It seems that RF circuit did not need as much current as the audio circuit did. They generally do not due to class B or C operation. More on that on the tech page. The audio circuit was a class A transformer coupled circuit. That plus the likelihood that at least the RF circuit used germanium transistors made for one heck of an efficient radio. And at 1.5 volts, the audio circuit was likely germanium as well. More on that on the tech page also, for those who do not know.
However, my real curiosity came when I lost my old Magnavox tube heaven. I was 20 at the time (1982) and my father replaced it with a solid state system. Man, talk about a change! It was like going from a live performance to a pocket transistor radio! It was ok sounding, but (playing the same LP's I had listened to through the Magnavox tube system) the mid range was peaky, the imaging was gone, the bass sounded way too smooth. I mean that it was there but with no texture that made one know that there was a bass playing it. It was more like a single sine wave than the complex tone it really was. Upper bass sounded like it came from a guitar or violin. The overall sound stage was blended, not distinct. Looking at the schematic revealed absolutely no rhyme or reason as to why. It looked like any number of well designed amplifiers, even by today's standards. The power supply was definitely well made. So why?
I was going to a technical college at the time and started experimenting with a little used in audio component called the field effect transistor (FET). It is basically a silicon based component that uses a field of electrical charge to control current flow through a channel of silicon (sound familiar? Later). Being a fan of RF and any wave phenomena for that matter, I undertook the experiments of RF design. I built a simple RF amplified crystal radio, just to see how this device worked. Before then I had always experimented with bipolar transistors. Using bipolars in RF I needed to use a long antenna and a ground connection in order to receive anything. I also noticed that the higher frequencies came in better than the lower ones did. Using the FET however, I needed to make the following circuit low in impedance. The next stage's input resistor needed to be the same as the previous stages output resistor. The circuit would oscillate fiercely if I did not do this. This never happened to me with bipolars. Then when oscillation was removed, a wild thing happened. I did not need an antenna or ground! The circuit was picking up all of the AM radio stations I could hear in N.Y.C. BUT, the lower frequencies came in better than the higher ones did!
The overall sensitivity was explained to me by a fellow classmate who was a middle age gentleman who was there for new technology education. He said that the input impedance was very high like that of a tube, so it matched the tuning circuits impedance at resonance. Like that of a tube!!!
I then tried a crazy experiment. I made a two transistor (FET) buffer (one per channel) to stick between the cartridge of my turntable and the amplifier. My mouth dropped as I heard the beginnings of what would be my prize circuit design. Separation went beyond the walls. Bass became distinct and full. Instruments became independent. That old tube sound came back, from transistors!
Well, now I had to find out why. I went on a rampage search to find out 1) why transistors sound different from tubes, and 2) why this lowly, seldom used (even today!) FET made the transistor amp sound like a tube one 3) is harmonic distortion the be all and end all of the differences between the two technologies?
There are a few
conclusions I came to before embarking on a real multi-discipline approach
to discovering and concluding why the two technologies sound different
as a supplement to Russell Hamm's work. I will discuss them on these pages
along with some tech, experiments and schematics.
Transistor History and