Archivo por meses: enero 2011

El sintetizador más simple, controlado con un sensor lineal

simplest_synth
Después de bastante tiempo, una nueva entrega del proyecto 50 maneras de tocar Una Plata d’Enciam. Esta vez quiero enseñaros los principios más básicos de la síntesis de audio. Es un proyecto muy sencillo, básic y barato, con grandes posibilidades de éxito incluso para los novatos en electrónica.

Recuerdo de las épocas de la universidad cuando estudiaba los circuitos RC, las ecuaciones diferenciales asociadas, y cómo la curva de carga y descarga de un condensador es una función exponencial. En este circuito conseguimos cargar y descargar el condensador de forma cíclica, gracias a dos transistores que se abren cuando el condensador está cargado, y se cierran cuando el condensador se descarga. Escogiendo los valores de resistencia y condensador adecuados la frecuencia de resonancia está dentro del espectro audible, que podemos escuchar con un pequeño altavoz. Con una resistencia variable podemos conseguir variar la frecuencia, consiguiendo un pequeño theremin o tanerino.

I aquí va el video mostrando cómo se construye este pequeño sintetizador, y cómo se puede tocar una canción como Una Plata d’Enciam.

Más información en la wiki

Tannerin: slide theremin synth

tannerinThis is a tannerin, not a real theremin. It is played with a slide (similar to a ribbon sensor), and the most known performance with this synth is Good Vibrations by the Beach Boys (Pet Sound album, 1966). Brian Wilson plays the instrument adviced by Paul Tanner, who was at the time using the instrument, build by Tom Polk.

The Tannerin is an electronic instrument that produces a pure sine wave, variable over three or four octaves. It is played by sliding a knob along the length of the instrument, on some models starting and stopping the tone with a contact switch located on the pitch knob and operated by one’s forefinger. You can see the video how Brian Wilson plays the tannerin:

Grabando un disco antiguo de Louis Armstrong

Canon EOS 550D and Terratec DMX6 FireChristman has gone, and I have a new camera that I want to use as a full HD video recorder.

Last week I recorded an 1961 Louis Armstrong recording from LP to mp3, using my new Canon EOS 550D as videorecorder, and my new (but 8 years old) Terratec DMX6 Fire 24/96 audio interface as audio recorder. And everything using open source tools (linux OS, Ardour DAW, ffmpeg video processing). The album is called Sincerely. Louis Armstrong, and the song is called If, and I bought this old single years ago in a Barcelona flee market. Google thanks, I found information about the single:

http://michaelminn.net/armstrong/index.php?section6#19550118b
Decca 29421: Sincerely (Louis Armstrong With Sonny Burke’s Orchestra – 1955)

Armstrong, Louis (Trumpet, Vocal)
Burke, Sonny (Conductor)
Candoli, Pete (Trumpet)
Young, Trummy (Trombone)
Bigard, Barney (Clarinet)
Ruffell, Donald (Saxophone)
Gentry, Chuck (Saxophone)
Koch, Jos Cook (Saxophone)
Kyle, Billy (Piano, Celeste)
Shaw, Arvell (Bass)
Deems, Barrett (Drums)

The resulting video is not realiiy full HD, just HD (1280×720) because the video combines the camera recording and a screencast, and the combination of screen and nvidia graphics card limits the overall resolution.

The resulting wav and mp3 files have fine quality. The recording levels are OK, without saturation, and the only noise you can listen is the noise expected from an old LP recording, just the noise that some people like to listen in this sort of ancient recordings.

So this video is a test of the capabilities of my Canon EOS 550D as a video camera, and my Terratec PCI audio interface as a linux compatible device.