Hi.
We established a forum: http://1bit.i-demo.pl/
At the moment it's mainly about ZX Spectrum.
But if any of You would be interested in sharing ways of generating music on ZX81 via Z80 and ULA, through the MIX port, then You're welcomed to join us. It could be actually very interesting.
Also some clues about ZX81 modifications to make the MIC port louder.
Well, it's just an info, anyway.
Y
Well, it would be really nice. Why - actually generating sound on ZX81 via Z80+ULA isn't very well-known subject. Actually it's more like mysterious. Probably mostly because the MIC port is silent so it didn't become popular.
However it is also a kind of popularizing the ZX81 among other people so I though - if anybody has experience in this area, would be cool to make our knowledge wider. Including some hardware modifications, amplifiers on-board etc.
I remember in 1982 a friend of mine and me went to a school in venlo Netherlands where a small computer fair was takin place. We were "president" and "Vice President" of the ZX user club publishing our ZX-Journal in those times.
We showed zx80 and zx81. Often there was no or very little interest in Sinclair computers so we were bored a little.
I wrote a little mc code making music notes via mic output according to key pressed 1 to 0.
I set up my tape recorder in record mode (without tape) and added a speaker to the ear output.
This way we could present "music" on the silent ZX81.
I remember there was still little interrest, but any time my friend played the English national anthem there were crowds coming over to see what was happening.
Kind regards
Paul
In theory, there is no difference between theory and practice. But, in practice, there is.
yerzmyey wrote:Hi.
We established a forum: http://1bit.i-demo.pl/
At the moment it's mainly about ZX Spectrum.
But if any of You would be interested in sharing ways of generating music on ZX81 via Z80 and ULA, through the MIX port, then You're welcomed to join us. It could be actually very interesting.
Also some clues about ZX81 modifications to make the MIC port louder.
Well, it's just an info, anyway.
Y
To make the mic port output a bit stronger a simple op-amp pre-amplifier like the type found here is the way to go...
Then feed the output into a power amp. You could also use the stereo one also listed here and feed the mic output to both input channels for dual mono.
You can also knock up the same thing on a bit of vero board I've done lots of them over the years for guitar/mic preamps and with fewer components than the ones shown here .
I would add though they need regulated or battery supplies as unregulated supplies bring with them a lot of buzz/hum.
Probably mostly because the MIC port is silent so it didn't become popular. 