Holmes
Experienced Member
So I am working on adding sound to my PET 2001N.
I have combed the internet sources, and found several designs based on using the CB2 pin. I got one from the "PET cookbook", and it used a variable resistor with a transistor and speaker and a 5V power source. I tried this design, but only got some wimpy sound from my speaker, which I was able to modify with some POKEs. Maybe I could try hooking up a piezo speaker to this setup and see if it gets any louder.
Some designs need an amplifier (the design from the first screen of space invaders) but I wanted to avoid any complicated circuits or too much additional equipment. I have not seen any plans for a piezo speaker, which I believe is that the PET 4000/8000's had.
I am interested in adding a mod for the piezo sound. I looked at the online schematics for the 8000's, and it seems on that they hook the CB2 pin up to pin PA7 on the 6520 chip through a NAND gate, and then through a 10 ohm resistor, to the piezo. I don't understand the connection to the 6520, or the need for the NAND gate.
It seems strange to me that no-one would do this mod, since it's what Commodore did on its later machines.
Has anyone successfully wired a piezo speaker mod to an early PET?
Any other thoughts or ideas?
I have combed the internet sources, and found several designs based on using the CB2 pin. I got one from the "PET cookbook", and it used a variable resistor with a transistor and speaker and a 5V power source. I tried this design, but only got some wimpy sound from my speaker, which I was able to modify with some POKEs. Maybe I could try hooking up a piezo speaker to this setup and see if it gets any louder.
Some designs need an amplifier (the design from the first screen of space invaders) but I wanted to avoid any complicated circuits or too much additional equipment. I have not seen any plans for a piezo speaker, which I believe is that the PET 4000/8000's had.
I am interested in adding a mod for the piezo sound. I looked at the online schematics for the 8000's, and it seems on that they hook the CB2 pin up to pin PA7 on the 6520 chip through a NAND gate, and then through a 10 ohm resistor, to the piezo. I don't understand the connection to the 6520, or the need for the NAND gate.
It seems strange to me that no-one would do this mod, since it's what Commodore did on its later machines.
Has anyone successfully wired a piezo speaker mod to an early PET?
Any other thoughts or ideas?