Where Have All The Tubes Gone?
Posted By: Aaron Partridge

A few years ago my brother gave me a fine pair of audio speakers and I have recently been looking for a decent amp to drive them.  I want something well built, but not too expensive.  I am not a big electronics consumer and do not even have a TV, but since I am an analog engineer I am particular about amp quality.  That has sent me looking at and listening to amps in audiophile shops.  Most of the amps at these stores are solid state systems, but a few are vacuum tube designs. The tube amps don’t perform very well, they distort the signals, but some people like “the tube sound”.  I don’t.

That got me thinking about tubes.  When I was a kid there were tubes everywhere.  They didn’t actually work very well, they burned out all the time, they had low gain, they came in only one polarity, they were hot enough to singe my fingers, and the voltages on them could shock me!  I didn’t like tubes, transistors were much better.

Nowadays tubes are used in just a few narrow applications.  High power microwave sources and RF amps still use tubes, and some audiophiles like they way their distortion sounds.  That is about it.  Application by application tubes have given way to smaller, higher performance, more efficient, and more reliable silicon transistors.That is what is happening to quartz crystals.  Silicon is replacing them – application by application crystal oscillators are giving way to silicon oscillators.

Two years ago SiTime introduced the first commercial MEMS-based silicon timing solutions.  These support processor and general clocking applications and offer programmability, short lead times, and fantastic reliability.  Eighteen months ago we introduced low jitter oscillators for serial datacom applications.  Ten months ago we introduced high-frequency oscillators (up to 800 MHz!) for very low jitter differential applications. We also have spread spectrum and voltage controlled oscillators, and we are now releasing multi-frequency clock generators and low power oscillators to full production.  Our new SiT8003 takes less power than the vast majority of crystal oscillators, and supports battery operated and handheld applications.

So we have general purpose, low jitter, high frequency, spread spectrum oscillator, voltage controlled, multi-output, and low power oscillators.  And one by one quartz applications are moving to silicon.  Eventually, quartz oscillators will be relegated to a few narrow applications.  Perhaps some audiophiles will like how they sound.


Feb 11, 2022

Jan 11, 2022