TFMSX Sound Circuit

[terriblefire]

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.

Screenshot 2023-01-02 at 22.29.44.png (636.04 KiB) Viewed 1938 times

[exxos]

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.

[Gooeyblob]

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.

[exxos]

@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..

Capture.PNG (11.69 KiB) Viewed 1929 times

Ignore R5 & C3 on that.


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

Capture.PNG (273.57 KiB) Viewed 1918 times

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

[terriblefire]

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.

[terriblefire]

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.

[PhilC]

Great to hear more progress has been made.

[stephen_usher]

Hoopy!

[GadgetUK164]

Woohoo!!! That's awesome!