tube CD player (was Re: sizes (was Re: vacuum tube computer))

<> The part I haven't figured out is the photodetector. Even those early L <> players used a phototransistor for the detector. < <Would a selenium cell be fast enough? A CdS photresistor probably wouldn' <be, I think. Silicon photodiode predated the transistor. You would need that or a photo tube to be remotely fastenough as the selenium or CdS is far to slow. In the early 50s when the tube was king germanium and silicon diodes were reality and very common in computer and other uses. The problem is the LASER postdates transistors! The optical light source would have to be a collminated point source. Memory is easy, delay lines really big ones! BACK OT... A vacuum tube computer using germanium diodes and tubes in under 400 of them would eb hard even with a 12bit word. It takes a minimum of 1/2 a duo triode to make an inverter and a FF needs at least one dual triode tube and a few diodes for steering. AND and OR gates using diodes are trivial but a 1 bit full adder would eat several tubes and lots of diodes. a full function ALU like '181 using tubes would easily eat about 50-100 of them for 4bits though some logic economies could gotten by using pulse coupled logic. Register and ALU are the primary consumers of transistors/ICs/Tubes with gating of signals being a next level user. Allison