YM2413 - HAAG - noisy

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By Pencioner

Scribe (1376)

Pencioner's picture

13-02-2021, 19:58

Nope. Instead i followed the way of adding external output to my cartridges if they have none, and buying an audio mixer... So i can mix whatever i want the way i want, avoiding internal mixers of MSX computers

By sdsnatcher73

Paragon (1737)

sdsnatcher73's picture

13-02-2021, 20:24

Pac wrote:

Panasonic FS-A1WX schematics. In addition the Panasoft FM-PAC schematics if helps.

The original FM-PAC also sounds very clean!

By Daemos

Paragon (1940)

Daemos's picture

13-02-2021, 20:41

Scope images show white noise combined with 50hz sinal hum and 100hz filter residue. Is this from the PSU?? check and compare. Remember that noise does not equal hum. There is noise, high frequency pollution and hum and they all have different sources and sound very distinct.

If the PSU is your trouble maker then use some extra capacitors and if all fails use a capacitor multiplier and remember: voltage regulators are very bad AC suppressors and could make matters even worse introducing high frequency pollution.

High frequency pollution is extremely hard to suppress and silver mica caps are your best bet combined with some inductance. White noise can easily be killed using low pass filters and hum doesn't like lc filters and capacitpr multipliers.

How does it sound? The ear can really help defining the source of your audio polution.

Then audio mixers using opamps are great but prone to white noise. Thats a standard problem with opamps. There are low noise opamps but usualy sound sharp because of extra 3th harmonics (if you can hear the differences)

MSX computers all have "interesting" audio mixers. Overly complex and sometimes even downright badly designed (see nms8250).

Ohw and then there are groundloops. If you have those you are on your own Wink

By dublevay

Supporter (13)

dublevay's picture

16-02-2021, 00:45

Thanks for the responses. I will study the schematics supplied some more - particularly the FM-PAC.

I like the idea of the capacitor multiplier. I currently have 2x 1000uF where the power enters the board, and another 2x 1000uF in close proximity to the YM2413. I've also got the Horowitz and Hill open on my desk, and am going to have a good review of LC filters again - given that the MSX machines seem to make so much use of inductors.

By st1mpy

Paladin (744)

st1mpy's picture

25-02-2021, 00:51

I've got a ym2413 setup on a breadboard and connected to a fpga msx (de1). initially I had an oscillator just feeding into XIN. It was acting strange, and it was affecting the de1's internal fm sound (it was randomly skipping notes), and it is not because of using the same port (the external is write only). I replaced the oscillator with a crystal and capacitors, and this problem is gone. Interesting as it was mentioned in this thread earlier.

Now it is just noisy, but hopefully its because its on a breadboard... I'll solder these to a protoboard and see...

By sdsnatcher73

Paragon (1737)

sdsnatcher73's picture

25-02-2021, 06:46

I don’t think the noise will magically go away when mounted on a PCB. If you look at an FM-PAC you will see how elaborate the circuit is that they had to design to, amongst other, fight the noisy OPLL. They had to use caps that sink through the PCB to keep the cartridge thin. Nowadays this can probably be achieved with smaller components and e.g. an FM-PAQ lite from EBsoft is not noisy at all, so it is possible in a smaller design.

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