The National Valve Museum: Amazing Vacuum Tube Resource

Found Here: The National Vacuum Tube Museum

Wiki:

A vacuum tube consists of electrodes in a vacuum in an insulating heat-resistant envelope which is usually tubular. Many tubes have glass envelopes, though some types such as power tubes may have ceramic or metal envelopes. The electrodes are attached to leads which pass through the envelope via an airtight seal. On most tubes, the leads are designed to plug into a tube socket for easy replacement.

The simplest vacuum tubes resemble incandescent light bulbs in that they have a filament sealed in an evacuated glass envelope. When hot, the filament releases electrons into the vacuum: a process called thermionic emission. The resulting negatively charged cloud of electrons is called a space charge. These electrons will be drawn to a metal plate inside the envelope, if the plate (also called the anode) is positively charged relative to the filament (or cathode). The result is a flow of electrons from filament to plate. This cannot work in the reverse direction because the plate is not heated and does not emit electrons. This very simple example described can thus be seen to operate as a diode: a device that conducts current only in one direction. The vacuum tube diode conducts conventional current from plate (anode) to the filament (cathode); this is the opposite direction to the actual flow of electrons (called electron current).

Vacuum tubes require a large temperature difference between the hot cathode and the cold anode. Because of this, vacuum tubes are inherently power-inefficient; enclosing the tube within a heat-retaining envelope of insulation would allow the entire tube to reach the same temperature, resulting in electron emission from the anode that would counter the normal one-way current. Because the tube requires a vacuum to operate, convection cooling of the anode is not generally possible unless the anode forms a part of the vacuum envelope (in which case the cooling is by conduction through the anode material and then convection outside the vacuum envelope). Thus anode cooling occurs in most tubes through black-body radiation and conduction of heat to the outer glass envelope via the anode mounting frame. Cold cathode tubes do not rely on thermionic emission at the cathode and usually have some form of gas discharge as the operating principle; such tubes are used for lighting (neon lamps) or as voltage regulators.

Sometimes another electrode, called a control grid, is added between the cathode and the anode. The vacuum tube is then known as a “triode.” A triode is a voltage-controlled device, in that a voltage that is applied as an input to the grid can be used to modulate the rate of electron flow between anode and cathode. The relationship between this input voltage and the output current is determined by a transconductance function. Control grid current is practically negligible in most circuits. The solid-state device most closely analogous to the vacuum tube is the JFET, although the vacuum tube typically operates at far higher voltage (and power) levels than the JFET.

FRITZING: A Software Website In The Spirit of Processing and Arduino

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ABOUT FRITZING
Fritzing is an open-source initiative to support designers, artists, researchers and hobbyists to work creatively with interactive electronics. We are creating a software and website in the spirit of Processing and Arduino, developing a tool that allows users to document their prototypes, share them with others, teach electronics in a classroom, and to create a pcb layout for professional manufacturing.

Soundmagic Spectral For MAC OS X: Freeware Suite of 23 Audio Unit Plug-Ins

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Reference

SoundMagic Spectral is a FREEWARE suite of 23 Audio Unit plug-ins that implement real-time spectral processing of sound. This groundbreaking set of effects give you unprecedented control and creativity in the processing of audio, whether from static audio files or live audio streams. SoundMagic Spectral builds on the work of the OS 9 software known as SoundMagic DSP, and takes it to even more exotic sonic realms.

The Cool Sound of Tubes-IEEE Technical

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” Although solid-state technology overwhelmingly dominates today’s world of electronics, vacuum tubes are holding out in two small but vibrant areas. They do so for entirely different reasons. Microwave technology relies on tubes for their power-handling capability at high frequencies [“Tubes: still vital after all these years,” Robert S. Symons, IEEE Spectrum, April, 1998]. The other area–the creation and reproduction of music–is a more complicated and controversial story.Reference

Tone Generator-Create Audio Test Tones, Sweeps or Noise Waveforms

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Wiki:

A signal generator, also known variously as function generator, pitch generator, arbitrary waveform generator, digital pattern generator or frequency generator is an electronic device that generates repeating or non-repeating electronic signals (in either the analog or digital domains). They are generally used in designing, testing, troubleshooting, and repairing electronic or electroacoustic devices; though they often have artistic uses as well.

There are many different types of signal generators, with different purposes and applications (and at varying levels of expense); in general, no device is suitable for all possible applications.

Traditionally, signal generators have been embedded hardware units, but since the age of multimedia-PCs, flexible, programmable software tone generators have also been available.