The today’s (2008) audio (or low-frequency) amplifier world is nearly 100% “contaminated” by silicon solid-state components that ensure proper amplification for any signal from any source (CD, DVD, Vinyl, MP3, Radio, TV, etc.) to ones ears. A broad range of design supporting literature2 and other information sources and tools like eg. the internet or component producer’s applications help design engineers world-wide to come up with the right products at the right time on the right markets - hopefully. The percentage difference between 100% and nearly 100% is filled with gain making elements that are far away from silicon: vacuum valves and audio transformers. It’s an interesting fact that still many CD and/or DVD producing studios work with valve and transformer driven equipment like eg. the compressor types Teletronik LA-2A or UREI 1176LN or they bring into action valve driven microphones (eg. Neumann U47 or Rode Classic II) and mixers at the frontend of the recording chain. Not to forget all the valve powered measurement equipment (from eg. Bruel & Kj?r, Tektronics, etc.) still in use.