From mboxrd@z Thu Jan 1 00:00:00 1970 From: carl.lowenstein@gmail.com (Carl Lowenstein) Date: Tue, 9 Dec 2008 17:37:31 -0800 Subject: [pups] PDP-11 / vacuum tube interface In-Reply-To: <2f30dc950812091600t2028222dw3f855b2271a12593@mail.gmail.com> References: <2f30dc950812091600t2028222dw3f855b2271a12593@mail.gmail.com> Message-ID: <5904d5730812091737g501a4b4ai98ac0862b13107be@mail.gmail.com> On Tue, Dec 9, 2008 at 4:00 PM, Ross Tucker wrote: > Dear all, > (This has got to be the strangest cross-post I've ever done.) > > I have just taken a bet from a friend to challenge my geekiness. I was > telling him about my love of Vintage Technology and he proposed that I > combine two hitherto separate hobbies and see what happens. The > topics: the DEC PDP-11 minicomputer (vintage: 1970s) and vacuum-tube > ham radios (vintage: 1960s). I do sincerely apologize for > cross-posting, but I am rather younger than either of these > technologies (vintage: 1984) and this seems like a monumental > challenge. > > My question for y'all: how could I possibly design+build a project > that uses both of these technologies? My thought is to port some radio > receiver Digital Signal Processing (DSP) application into PDP-11 > assembler, compile and run it via emulator on my PC, then use it with > the vacuum-tube regenerative receiver that I built a few years ago... > Does anybody know if PDP-11 UNIXes even had the capability for a > "sound card"? Well, you could look at "Votrax" on Wikipedia. Allegedly, the first words spoken by a Unix system at Bell Labs, using its Votrax synthesizer, were "file not found". Things that are now known as "sound cards" were called A:D and D:A converters back in those days. And there were a fair variety of them available for both Unibus and Qbus systems. > Or, to get ambitious, I would LOVE to design some > interface circuitry between PDP-11 digital circuitry and vacuum-tube > electronics... The challenges are legion: the tube side of the circuit > operates around 350V DC levels with radio-frequency (RF) signals at 7 > MHz (almost the clock rate of some PDP-11s!) and I don't have the DEC > Handbooks, but I'm pretty sure that even those ancient pre-TTL > circuits operate below 350V! The vacuum-tube circuits may be running from 350 VDC but somewhere there are low-level inputs from which everything is amplified. Think microphone. carl -- carl lowenstein marine physical lab u.c. san diego clowenstein at ucsd.edu