@polpo I'm going to actually disconnect the AY output from the preamp and everything else on the board and feed it directly to my PC line out. It looks like the various capacitors actually f*ck up the signal.
The MB4C does not have capacitors and the audio output is crystal clear.
Also it seems the AY already outputs a line level audio signal, no need for a preamp or anything else.
This is a design for standalone speakers like the original one of the A2.
@fenarinarsa
yes the capacitors make some sort of low pass filter that kills the bass. I've had zx spectrum people complain at me that the mockingboard I'm using ruins their music
@deater78 I don't really get what happens.
I captured a normal bass line directly from the AY output, only connected to the ground through a resistor. And it's still broken.
It shouldn't happen... maybe I need to really remove all capacitors from that board.
At this point, this old MB design is useless anyway.
It was worse with some AY chips than others, almost suspected either counterfeit chips or else damanged pulls somehow. Never managed to track down what was going n.
@deater78 so you solved it by making the code faster? Strange because I think we’re already really fast and we never got issues with it. Will have a second look.
@fenarinarsa
I don't think I ever solved the problem.
I did modify my code so it actually met the deadlines set in the AY-3-8910 datasheet (really hard to do with a 6522 running at 1MHz) but I don't know if that helped
eventually I just tried AY chips until I found a set that wasn't as bad at the others
I wonder if the AY chips you get off ebay are rebadged YM chips or something else, seems unlikely they'd bother to counterfeit them though
@deater78 I guess the only thing I have left to try is to replicate another computer output design and see what happens (like the ZX spectrum or CPC)
it's only a few resistors but I need to actually cut traces on the MB to do this. Oh well.
@fenarinarsa I think all the recent reproduction mockingboards have AYs from the same source, as they all have similar chip markings. I was hoping to eventually source an "original" mockingboard from back in the day to see if an older chip would be better.
I also was trying to get some of the people who decap chips as a hobby to do some AY ones but apparently it's not interesting enough
@polpo If that works, yeah it would be convenient to make a new board with the minimum required. Which means half the board can be dumped, just keeping the VIAs and AYs
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