Chair : Menno van der Veen , Ir. Comparing the characteristics between these tubes, the grid current at lower plate voltage and positive grid bias condition is modeled successfully with novel perveance parameters for the first time, though it was known that the perveance depends on both grid and plate bias. It is shown that the modulation factor of the space charge for the MT triodes is different from the other classic tubes.
The model is implemented in LTspice to result in a good replication for a variation of three-order magnitude of grid current and cathode current. We compared the static noise floor exhibited by single and various parallel MEMS microphone configurations and a conventional and commonly used electret capsule, as well as the directivity patterns of selected configurations.
The results suggest that while current types are exhibiting an already acceptable static noise floor, a direct parallel circuit of MEMS microphones allows further reductions of the noise floor close to the theoretical value of 3 dB SPL per doubling of number of microphones while maintaining omnidirectionality below 5 kHz. However, designers must deal with supply rail, and radio frequency interference, as well as the need to switch power devices at high frequencies.
Because of these, and other problems, not everyone wishes to use switching based technologies for their amplifiers. Unfortunately, linear amplifiers are significantly more inefficient than switching amplifiers, under sine wave testing. However real audio signals spend much more time at low amplitudes than a sine wave. The paper develops optimum switch points for both single and multiple switching points, with respect to the expected amplitude distribution of the audio.
Both applications require high interactivity, which typically demands an algorithmic codec delay between 15 ms and 35 ms. Audio quality aspects are discussed and compared against other codecs with a delay below 10 ms.
