Quietest FET selection for audio input stage

Parkera

Joined May 3, 2016
106
You have touched on a fascinating history; one which I continue to be amazed at as I learn more details. As I'm sure everyone knows, the first recordings were made acoustically, with a recording horn attached directly (or through a short rubber tube) to the recording head - basically a reproducer but with a stylus shaped to cut a groove rather than follow a groove. I tried making an acoustic cylinder recording on an 1897 Edison Home. A professional disc jockey with a loud voice could barely make a weak recording with his head literally in the horn. It took a 200 Watt stereo, turned almost all the way up, with the horn about 12" in front of the speaker to get a solid recording.

The broadcast industry favored carbon microphones because candlestick telephones were readily available as microphones and had a high output level. Later, the double button carbon mic was developed (shown in the 1930's Radio Broadcasting video) so it would have less distortion and less noise. Still a pretty limited frequency response, but adequate for AM broadcast purposes. The recording industry leaned toward the Western Electric condenser microphones with its wider frequency response. WE also invented the electrical recording process for all practical purposes in late 1925. Ribbon microphones were also used for early electric recordings.

Song writing, while still driven by sheet music, was for the most part limited to 3 minutes on a 10" record, or 4-1/2 minutes on a 12" record. Arrangements were often dictated by the capabilities of the recording equipment. For example, early recordings rarely used a full drum set because the equipment could not track loud impulse sounds. Eventually, this problem was, for the most part, overcome but the bass drum was still taboo in the recording studio, but was OK during a radio broadcast.

There are those who specialize in microphone history, early broadcast history and early recording history. Unfortunately, there are not enough hours in the day to learn all there is to know. PBS aired a series on making recordings 1920's style in 2017. This is an article describing the series. https://www.wired.com/2017/05/american-epic-return-of-the-lathe/.
 

Jeff Wagner

Joined May 2, 2019
1
Hello gang:

Designing a common source (Vdd 12VDC) amplifier to drive a tube input stage. I need to select a JFET (or mosfet?) that has very low noise. Data sheets don't really show NF's. I am looking at a J (174 or whatever) series or maybe a 2N3819, but I am open to other ideas aside from op amps or BJT's. Any suggestions?
Don't ignore the resistors you are using. Resistor noise is often overlooked and it's not insignificant. Vishay has agood low noise series as well as caddock. If you can afford it the vishay foil resistors sound a lot better than you would think possible.
 
Top