I have asked this question before in the past. Don't even remember if it was on the forums or on a mailinglist... but, as I didn't get an answer back than, and as I have to make myself a new cable soon (old one is breaking down ...

I have connected my turboR, moonsound and MSX-Audio to a mixed, allowing me to listen to all MSX sounds on my stereo. I connected the turboR by wiring the GND and Audio pins on the RGB DIN-output to a cinch plug. However, the audio quality of this cable is quite poor. You can actually 'hear' the image the turboR is displaying, as if the cable was badly grounded. The more white the image is, the more noise you can hear.

I thought I read about this problem in an old magazine, which explained this problem could be solved by adding an extra resistor (or something like that). Does anybody know what is the best method to reduce unwanted noise? Or would I be better off to get my GND from somewhere else (like the MSX-Audio)??

The display noise, and also terrible noise from the diskdrive, is added on the motherboard...
Tho I'm not an expert, I think there's little you can do about it aside from soldering a seperate sound output with some wires on the motherboard.

If you have an ST there's not much you can do about it like Guyver said. If it's a GT it shouldn't have too much noise and it's probably caused by grounding differences. I think you can indeed solve it by using a resistor and a capacitor, or just a capacitor. Since I don't know too much about electronics I can't really help you with this.

I do however remember a friend of mine solving this problem with a cap. I am not sure, but *I think* he used a 47uF cap. I really don't remeber tho. You can try it by connecting it between the positive and the negative wires while taking polarity into account. Nothing bad should happen if I remembered the value incorrecty... Don't worry about that... Good luck...

I do have a GT, so that's a good start. I'm also quite sure that I'm not going to solder a separate sound output. However, trying a capacitor is worth a shot. Does anyone here know if 47uF does the trick, for sure?

Lemme know if it works, coz my GT is damn noisy ^^;

Quote:

Does anyone here know if 47uF does the trick, for sure?

It really doesn't matter much... Like I said, you're not gonna do any damage... Just give it a go and see if it works. You can also try some other values. Do mind the polarity tho, most caps have them. If you connect it the other way around it won't work.

Norally a cap will explode with a really cool smoke effect if you hook it up wrong, but ofcourse the output voltage/current is way to low for that in this case. If you're ever bored on a droopy sunday I guess you can have some phun with a car battery and some caps tho

Just in case... Don't go hookup a 2000uF cap to your MSX either Anything bigger (in size) than a cigarette filter you'll wanna avoid... So no 'taking the cap out of my dad's old camera flash' please. The cap goes between the GND wire and the AUDIO wire. Like if you were connecting a light bulb. It does not go in series like a resistor does.

It seems to be a common "problem" on turboRs. My A1GT is also quite noisy and, as you said, depending on the image/colour displayed you can hear/distinguish different "shrill" sounds.

Curiously this never happaned when using my old Sony HB-501P with a RF lead...

Sonic you're refering to elec.capacitators which do have polarity indeed.
But uh, doesn't the turbo R have a 3.1/4 jack insert for ouput device? I use that one and it's signal to noise ratio isn't that bad at all. Indeed using the RGB cable provides extra noise on the audio signal path.. you should have a clear signal running from the standard output jack (or atleast on ST models)

On a GT there is no seperate audio output.

that's a big bummer...

I took the easy way out. I made a new audio cable, connecting the GND of the MSX-Audio to the GND, instead of the GND on the DIN. Sounds a LOT better now

I took a look at the pin layout that is in www.msxnet.org:

http://faq.msxnet.org/connector.html#rgbscart

You can see:

"1 audio ground 4 (and 5, 9, 13, 14, 18 to be sure)"

My cable has the audio ground only connected to 4 in the SCART connector. Will a connection to 5,9,13,14 and 18 cause some effect?

No, because at the GND at the turboR is all that matters. Apparently it's badly grounded. However I think if you cnonnect any other ground than the one coming from the turboR, you'll be fine.

to prevend groundloops you might also want to disconnect any other grounding paths between turboR/extra_devices and other Grounded equipment (your Stereo set for example)