PSG Stereo Sound in A1-GT & Other Stereo Issues . . .

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By Dhampird

Hero (585)

Dhampird's picture

11-06-2011, 03:56

Hi very good, I have MMC SD Sinfox and MegaFlashROM SCC +, I installed a female jack audio conector in that cartridges to get stereo sound conected to Hi-Fi amplifier , at first time through that female jack stereo only I could get SCC sound and i couldn´t hear the PSG, in order to hear right the PSG through the female jack installed in the cartridges, i modified the internal PSG MSX sound signal using a pair of jumpers to select IN or OUT PSG, the default MSX PSG sound is always output signal that goes from cartridges to msx, with this change now i can get both types of sound (SCC and PSG) in the HB-F9S towards stereo out jack instaled, I guess there will be other methods to achieve this same, as an example i found a S1985 internal stereo modification but it seems that this mod eliminate sound in TV speakers, only could be use conected to amplifiers or external speakers:

www.museo8bits.com/mochalez/stereo_msx.htm

Now, let´s see the audio procedure I followed for the HB-F9S, (with this method sound on the monitor works perfectly):

img864.imageshack.us/img864/9787/clipboard02jm.jpg

This method works OK for Hb-F9s. The point is that I built same internal procedure with jumpers for a Turbo-R A1-GT but I could say that the sound I get is OK but with a slight background noise effect, (ears like a constant buzz, not too high; in Hb-F9s there is not any noise buzz effect) probably I didn´t find ideal spot where to pick up the signal from the PSG, I'm trying to locate a point where I will not get that background noise effect.

I would like know how do you get stereo audio in yours Turbo-R A1-GT, I guess through the RGB cable itself, installing 2 RCA, but I would like to know how exactly you built your audio methods to try compare quality audio output with some methods. Please let me know what methods you are using now in yours Turbo-R A1-GT.

Here i uploaded specific audio procedure HB-F9s diagram (working OK) and Turbo-R A1-GT diagram (...still in progress), maybe someone with more skills than me could help with ideas to try determine some other better points to get the PSG signal in the A1-GT without background noise effect ;( ). Any another stereo mod ideas for A1-GT are welcome ...

www.megaupload.com/?d=7CA8T5HL

Thanks a lot.

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By Gradius2

Hero (574)

Gradius2's picture

07-08-2011, 03:45

Hi,

That "background noise" sounds like interference. You can create a better cable against that by twisting a gnd cable with "live/positive" audio (not gnd) cable (not uncapped wires!).

Keep in mind turboR's are faster than regular MSXs, so high frequency tends to make background noise if the cables aren't thick enough or have no earth (to act like balanced).

Also, make them as short as possible, and against to PCB as possible, otherwise it can act as a radio antenna too.

By Gradius2

Hero (574)

Gradius2's picture

13-08-2011, 07:42

Let us know if you sorted out the problem.

I'm thinking to add stereo PSG on mine.

By Dhampird

Hero (585)

Dhampird's picture

13-08-2011, 21:35

Hi, Gradius2, thanks a lot for reply and sorry for delay in reply, like you said i had experiences with that "radio antenna" effect after the install, I could hear some radio antena voices for one moment. I´ll try to use thick cables, please try to explain better:
"twisting a gnd cable with "live/positive" audio (not gnd) cable", i think you mean twist a cable in each one already installed an conect that twisted cable to ¿"live/positive" audio? Tomorrow i think i could try to mod the install with Thick cables, if i get some results i´ll post here.

Thanks a lot for the tip.

By Gradius2

Hero (574)

Gradius2's picture

13-08-2011, 21:45

That is pretty hard to explain, let me buy a camera first (lol).

Btw, if you use thick cables, it could sort out the problem too.

By Dhampird

Hero (585)

Dhampird's picture

13-08-2011, 22:08

That is pretty hard to explain, let me buy a camera first (lol).

Btw, if you use thick cables, it could sort out the problem too.

Maybe you could draw a simple diagram with corel or another program to understand right that process.

By Gradius2

Hero (574)

Gradius2's picture

18-08-2011, 01:05

Is twisted wires, just like those you find inside a Cat5E (Ethernet) cable.

By Dhampird

Hero (585)

Dhampird's picture

24-08-2011, 02:54

Finally i tried installation with thick cables but same noise "background buzz sound effect" appear again, no radio antena effect now, about the "background buzz sound effect" i could say that the noise effect has been reduced a little or sound a little different ,but still is not fixed.

After that i tried twistes cables (cat6), i reinstaled all audio mod again. To understand this install ok i´ll try to explain it, using cat6 cable for example i get a 2 pair cables like "green-white green" (typical ethernet cable), the "green cable" goes to one signal in mobo ,and the "white-green cable" (that is twisted around the "green cable") was conected to GND, i made this for all signals in mobo, this way all signals are protected with GND. Result is same "background buzz sound effect", the GND "protection" didnt work.

I noticed that the jumper minipcb board that i made (to select Audio IN or OUT, like i told above post) responds to some kind of interference if i touch part of the jumpers when msx is working, this is normal, but to avoid problems i reinstalled again the mod, this time i completely removed the mini pcb jumpers, after that i used only a directly cable avoiding jumper settings, i get same effect "background buzz".

The issue is that it seems the instalation is ok, i mean that the point from i get PSG from mobo seems ok and all installation process, maybe could be another way to do this to work without that buzz background sound effect, "Gradius2" if you want to build this mod to your A1-GT please tell me, i´ll send to you all process with pictures for if you know another way to try the mod, if you want let me know you mail to talk about it. Like i said the mod works, the "background buzz sound effect" only it is very annoying when you hear no sound in games, for example if you press F1 in a konami game you could ear the interference sound very well in background, this audio IN&OUT procedure is similar in HB-F9s and results are perfect, no background noise effect can ear with HB-F9s.

What do you think? Will be neccesary add any extra circuit that could filter that noise? Maybe will be another better point in mobo to get PSG signal without interferences?

Thanks.

By Gradius2

Hero (574)

Gradius2's picture

26-08-2011, 02:55

Well, isn't good to use ethernet cables for that, since they are optimized for digital signals only (not analogue).

Looks like the internal amp on turboR isn't good or too old (bad capacitors perhaps?) hence the noise you're getting.

I would try to use that mod @ www.museo8bits.com, I run my GT @ 1080p after all, so I would just put two RCA outputs to use it with an external AMP or even a mixer (PSG+FM+SCC). B-)

About GT, how do I get the PCM sound from it (which IC which PIN)? I know about PSG, FM, and SCC, but not PCM.

By Dhampird

Hero (585)

Dhampird's picture

26-08-2011, 18:57

Hello, thanks for reply, about:

Well, isn't good to use ethernet cables for that, since they are optimized for digital signals only (not analogue).

Ok, but i get same results using different type of cables, also tell that use cable more thick not make any difference in this case, using ethernet type cables have same effect.

Looks like the internal amp on turboR isn't good or too old (bad capacitors perhaps?) hence the noise you're getting.

It´s strange because when i conect Turbo-R to any monitor with RGB and with speakers, the sounds can ear perfectly without any interference, the interference only appears after make the audio procedure mod.

I would try to use that mod @ www.museo8bits.com, I run my GT @ 1080p after all, so I would just put two RCA outputs to use it with an external AMP or even a mixer (PSG+FM+SCC).

Please, let me know diagrams of that mod because i tried to search in that link but i dindt find anything. Let me now mod diagrams you´re talking about. Thanks.

About GT, how do I get the PCM sound from it (which IC which PIN)? I know about PSG, FM, and SCC, but not PCM.

I´m not pretty sure what point is neccesary to get PCM. Maybe someone knows about it. Let me know if you know another PSG methods and also how get FM in A1-GT. Thanks.

Well, i´ll attach here how i installed to get audio psg procedure IN&OUT in A1-GT, with mobo pictures, this audio mod allows PSG pass through cartidge and you could get PSG sound if you install a internal jack in cartidge, if anyone knows more about it please post some solutions, because i couldnt get solve background noise after make the mod. All A1-GT audio internal mods or Turbo-R audio mods are welcome! B-)

Here are the diagrams:

www.megaupload.com/?d=7HQ26W3G

I hope somebody knows any solution.
Thanks a lot.

By Gradius2

Hero (574)

Gradius2's picture

26-08-2011, 21:29

Hi,

If so, then there are no more doubts. The amp (or pre-amp) inside them just sucks, so far the only way I see is to getting the audio output directly from IC (PSG), FM, etc.

About PCM I'll need to check out the service manual, but if someone else already knows, please post it here.

I don't know if PCM is on same PSG IC (newer S1985) will need to check.

I'll look the diagrams, but looks like getting the signal directly from IC is the only choice.

Fernando

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