From mboxrd@z Thu Jan 1 00:00:00 1970 From: cube1@charter.net (Jay Jaeger) Date: Tue, 09 Dec 2008 20:41:49 -0600 Subject: [pups] PDP-11 / vacuum tube interface In-Reply-To: <5904d5730812091737g501a4b4ai98ac0862b13107be@mail.gmail.co m> References: <2f30dc950812091600t2028222dw3f855b2271a12593@mail.gmail.com> <2f30dc950812091600t2028222dw3f855b2271a12593@mail.gmail.com> Message-ID: <4.3.2.7.2.20081209203649.01d65d08@cirithi> Back in the 1970's Paul Pierce used a D/A converter on a PDP-11 at the UW Computer Systems Lab to generate music much like early PC sound cards did -- by combining harmonics in various ratios. Although he happened to have used RT-11, there is no reason why it could not be done under Unix. (The UW Computer Systems Lab also had a Votrax). So, sure, you could, with an A/D and D/A converter do something like that. I am not sure that the various emulators have done emulation for A/D or D/A, but in principle, it ought to be possible. AC coupling (via a capacitor) of the input or output would remove any concerns about the relatively high DC voltages. Besides, input signals ordinarily come into the grids of vacuum tube circuits by way of a transformer. Ditto for outputs from tube circuits. Jay Jaeger At 05:37 PM 12/9/2008 -0800, Carl Lowenstein wrote: >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 >_______________________________________________ >PUPS mailing list >PUPS at minnie.tuhs.org >https://minnie.tuhs.org/mailman/listinfo/pups --- Jay R. Jaeger The Computer Collection cube1 at charter.net