exxos's Atari, Amiga & retro forum

exxos wrote: 02 Jan 2023 22:25 I don't know anything about the MSX unfortunately. Is there not any schematics for such a FPGA system ? maybe just needs a stupid pull-up on the pin or something ? I have no idea what the FPGA is trying to output. I know pretty much diddly squat about FPGA stuff as well.

Well that makes two of us. Essentially is a 3.3V Square wave that goes through the circuit shown below. "Other Input" is a PSG just like an ST. So this should be pretty familiar. Its just going to be a case of getting the right values for the bias i guess.

terriblefire wrote: 02 Jan 2023 22:32 Well that makes two of us. Essentially is a 3.3V Square wave that goes through the circuit shown below. "Other Input" is a PSG just like an ST. So this should be pretty familiar. Its just going to be a case of getting the right values for the bias i guess.

The values on the H4 audio amp were not that far off from the original ST circuit. It is only really a buffer / mixer. But that 100nF could be upsetting your results.

But that screenshot you posted earlier I really would just use that as it should work and be all set up fine anyway.

No sound at all? Have you tried SCC games like Nemesis 2 or 3?
Also try using the Megaflash /P1 parameter to clone psg to the cart.

@terriblefire So that's simulation is the circuit you have actually built ? Because those series 100nf will not be large enough I think.. Probably need 1uF - 10uF really. Ceramic is best.

This is my original simulation circuit..


Ignore R5 & C3 on that.


For your circuit, this would / should be a "get you running" type of design.


Also your "other input" should really be floating are not connected to GND.

The 100nF cap that you've changed to 10uF is part of the carts delta sigma DAC setup. Sorry i realize that wasnt very clear before.

So i think i've sorted it ... created a new mixer circuit and tested it today



and



I think i'll drop the Yamaha gain by 20% as its just clipping. Thats the TFMSX problems that i know of all solved.

Great to hear more progress has been made.

Hoopy!

Woohoo!!! That's awesome!