Sound with the pdp1

[Matthias Barthel]

I want to create sound with my ESP32-powered PDP1. And I want to make the sound as close to the original as possible.

the original pdp1 uses the 4 flipflops from the Programflag-leds to generate the sound.

pf1+pf2 is one audiochannel, pf3+pf4 is the other audiochannel - is this right ?

my first intention was to build a r-2r ladder with a ampflifer as io-device, but the goal is to play the original files from the pdp1.

is the theory with the 4 flipflops right ?

best matthias

[Bill E]

This has already been done in both the regular release and improved in the mods release.

There were no flip-fops, the signals were taken directly from the program flag drivers, passed thru 4 R-C filters, and pf 1&2 combined via 2 resistors for one channel, 3&4 for the other.

The regular relaase just sent the square wave to SDL which handles driving the USB audio adapter.

The mod release added 4 digital filters to reproduce the original R-C filters, and each is tunable.

I confirmed this by getting the schematic, actually a simple sketch, from the CHM from Peter Samson directly. He did the original PDP-1 implementation.

Bill

https://github.com/wjenh/pidp1-mods.git

[Matthias Barthel]

Ok thanks Bill,

The programflag drivers generates the sound via a r-c filters. The program for the music, sets and clears the flags and this makes the music.

Best matthias 

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