Sega Genesis 1 Stereo Mod

[mrsmiley381]

I know you guys here seem to prefer discussing video mods, but I'm having some problems regarding Genesis 1 stereo output through the headphone jack. Specifically, no matter where the volume slider is, Shining Force sounds like what could best be described as "complete and total ass." I'm thinking I have a faulty headphone jack.

The following subjective listening tests were done:
Genesis 1 Mono via AV Connection: Sounds bad due to mono audio. Distortion minimal in comparison.
Genesis 1 Stereo via standard headphone jack to TV: Heavy distortion.
Genesis 1 Stereo via headphone jack to red/white audio cable connector from Radio Shack: Heavy distortion, maybe worse than above test.
Genesis 1 Stereo via headphone jack to Sega CD headphone jack: Complete and utter ear rape.

So, I'm seeing a few options here.
1) Drill holes and add a stereo mod to the back of the system.
2) Figure out what pins on the expansion slot connector can be used to send audio to the Sega CD a la Sega Genesis 2 expansion slot.

I'd really like to try method 2 in order to simplify the clusterfuck of wires hanging out the front of the system. I would need a little help on this, as Ii can't find a pinout of the Genesis 2 expansion slot, only the Genesis 1 expansion slot. I would also need to know from where to pull the stereo audio, as I'm not sure if the audio sent over expansion slot in the Genesis 2 is amplified or not. If anyone can compare a Genesis 1 and 2 quickly or even find a pinout list, I'd appreciate it. Google hasn't found the answer to my two questions thus far, but perhaps you good folks can.

[shmuppyLove]

Are these of any use?

[mrsmiley381]

Unfortunately, they're not. Sega made a bit of a flaw in the audio department on both revisions of the Genesis. The Genesis 1, as shown by the diagram, only outputs mono audio from its AV jack. The Genesis 2, however, will do stereo just fine. The problem is then that the Genesis 1, aside from the latest revision, has the real YM2612 chip on board for the "authentic" audio, whereas the Genesis 2 has a different version of the chip and a pretty bad audio circuit overall. What I'm trying to find is data on the expansion port of the Genesis 2 compared to the Genesis 1. The following link gives the full data on the Genesis 1, but not on the Genesis 2.

http://www.gamesx.com/cartouts/gennyport.htm

He does mention audio on A29 and B29, but that may not be where the Genesis 2 actually sends its audio to the Sega CD. I think my stereo volume control circuit is so mangled that it only adds interference when using a mixer cable to send audio to the Sega CD. Generally, running audio from a Genesis 2 to the Sega CD makes it sound better as apparently the Sega CD has a nice audio circuit. That's why I hypothesize that pulling raw Genesis 1 audio and running it to the Sega CD should eliminate my problems.

[BPzeBanshee]

I'm not familiar with this kind of hardware, but maybe Eke-Eke the guy who develops Genesis Plus GX for the Wii might know about it.

You can find his details at genplus-gx.googlecode.com, he's stated he's happy to answer any questions about how the Genesis/Megadrive works so if anyone's got the know-how it'd be him.

[Fudoh]

I have done a stereo mod for my MD1 a few months back. A line-level stereo signal is available on the mainboard. You just need an additional IC amp (LM358 which costs about $1). Very easy to do. I can provide instructions if you want to try it. Sound quality is the best you can get from a MD1.

You can put the stereo audio signal on the Din8 output. The output provides composite and sync on two different pins and you only need one of these two, so you can kill one and use the Pin for right audio.

[mrsmiley381]

I have done a stereo mod for my MD1 a few months back. A line-level stereo signal is available on the mainboard. You just need an additional IC amp (LM358 which costs about $1). Very easy to do. I can provide instructions if you want to try it. Sound quality is the best you can get from a MD1.

You can put the stereo audio signal on the Din8 output. The output provides composite and sync on two different pins and you only need one of these two, so you can kill one and use the Pin for right audio.

That's an interesting way to handle it. In that case, however, it sounds like I'd be sacrificing functionality in the video department. If I drop sync I won't be able to get proper RGB out in the event that I decided to get a proper converter, but if I nuke composite I won't be able to take the Genesis somewhere else unless they can handle my RGB output somehow. However, the info on the amp may prove invaluable if I figure out how to send the audio over the expansion bay. I will, however, e-mail Eke-Eke and see what he knows.

This morning, despite a headache and sleep deprivation, I managed to fiddle around with my setup. As it turns out, my TV was set to surround sound, which was causing a lot of audio to be too quiet and drop sound effects in Sonic CD. Disabling it didn't seem to help Shining Force, but at least I confirmed it wasn't that causing a problem. Additionally, bass and treble settings seemed to do very little. I'm going to double check that the cartridge is clean when I get home as that's the only other factor I can imagine at this point. Considering that Shining Force sounds like shredded aluminum and Sonic CD sounds somewhat normal, it wouldn't surprise me if a dirty cart would be the culprit. Regardless, I will still try to get a decent stereo mod out of this.

[Fudoh]

That's an interesting way to handle it. In that case, however, it sounds like I'd be sacrificing functionality in the video department. If I drop sync I won't be able to get proper RGB out in the event that I decided to get a proper converter, but if I nuke composite I won't be able to take the Genesis somewhere else unless they can handle my RGB output somehow.

If you really want best RGB and composite, just add a switch to have them both on a single pin. You could also drop the 5V voltage instead. It's just needed for automatic switching on Euro Scart TVs, not to get RGB in general. Using the usual AV output is by far the easiest solution with this little internal mod.

[robneal81]

I have done a stereo mod for my MD1 a few months back. A line-level stereo signal is available on the mainboard. You just need an additional IC amp (LM358 which costs about $1). Very easy to do. I can provide instructions if you want to try it. Sound quality is the best you can get from a MD1.

Fudoh, I'm sorry to rehash a year-old discussion, but I was very curious about your IC idea.

I had been getting stereo from the front headphone jack, but as others noted, it can be very distorted at times. I decided to mod my Genesis and pull line out directly from the audio chip. So far, it's outputting perfect: loud and clear.

Do you think I'll get a better audio signal if I add the IC?

For reference, here's pics of my mod (pic 1 is the top of the chip, pic 2 is the bottom):

[Fudoh]

This Sony chip isn't the sound chip. It's part of the headphone amp, isn't it ? Never done that of heard that. I mean, just compare it to the Mono signal you get from the AV port. If it's the same quality, stick with it.

What I did was grabbing the audio before it runs into the LM358 (which you can find under the big metal thingie in the back). That's the line amp for the AV output. You can split the signal before it's combined into a Mono one, let the left channel run through the old LM358 and run the right channel through another, additional LM358.

[robneal81]

Oh, I didn't realize the Sony chip was the headphone amp. I just double checked something:

I turned on a game with the audio hooked up via my mod and slid the headphone volume slider around. The volume did not change. At the very least, that means I'm not simply getting the headphone output from the board.

It sounds great, so I'll keep it. The next time you need to stereo-mod a Genesis, give it a try. At the very least, it's a simple mod, so if you don't get the same good results I did, you'll only have wasted a few minutes.

[Fudoh]

It's a solid approach. I believe to remember that the front output has more noise though, so at least check it back with the standard AV output.

[system11]

If you're getting distortion it's because the amplified audio from the jack is too high for the input device. Simple - turn the slider down, it's supposed to be about 7 when using it as an output. I've got no problems with noise or distortion at all, mine runs out of the jack, and into the jack of the mega-cd underneath it. The scart lead connects to the phono plugs on the MCD. Bingo, stereo from CD and console.

[robneal81]

If you're getting distortion it's because the amplified audio from the jack is too high for the input device. Simple - turn the slider down, it's supposed to be about 7 when using it as an output. I've got no problems with noise or distortion at all, mine runs out of the jack, and into the jack of the mega-cd underneath it. The scart lead connects to the phono plugs on the MCD. Bingo, stereo from CD and console.

I'm sorry, but that was not at all the case with me. I was getting distortion, regardless of slider position. Many things could cause it, from a dirty headphone jack to damaged components.

[antron]

I wonder if it was just dust in the slider pot. Like a jitter with an old Atati paddle.

[robneal81]

I wonder if it was just dust in the slider pot. Like a jitter with an old Atati paddle.

Probably. Either way, it works PERFECT now that I modded, so I'm leaving it this way.

[lettuce]

did you wire the headphone amp to the AV socket on the read of the console, did you rewire your scart lead for stereo sound then? Can you post some more detailed pics?

[robneal81]

did you wire the headphone amp to the AV socket on the read of the console, did you rewire your scart lead for stereo sound then? Can you post some more detailed pics?

Actually, I just used an RGB SCART cable that had the lead to pull stereo from the headphone jack...but instead of plugging that into the headphone jack, I plugged it into the audio out I soldered:



I get all my RGB SCART cables from an eBay seller, Retro Console Accessories. Her cables have all been flawless:

http://myworld.ebay.com/retro_console_accessories

I can post more pics if you'd like, but there's not much more to it. Just buy one of these (make sure it's long enough):

Then cut the red and white ends off, solder the cables to the points I posted above and dangle the cord out the back of your Genesis. I used the RF hole, since there's enough room for the cable to pass through. I'm sure you could make nice looking audio-out ports on the back of your Genesis, but I'd rather not cut mine.

[robneal81]

I apologize if this is a really dumb question, but does the 32x produce any audio, or is it just a pass-through?

I'm asking, because after hearing the audio difference, I'm getting a Sega CD (combined with my modded model 1 Genesis) to replace my CDX. When I hook up the Sega CD, I'll put a cable from my audio mod to the Sega CD input. Should I wire the audio-out of the Sega CD into the 32x (I'd make a custom cable), or can I just take the audio out directly from the Sega CD and skip the 32x altogether?

Once again, I apologize if this is a stupid question...I've just never really used a 32x and when I did, it was easily wired into my CDX.

[lettuce]

did you wire the headphone amp to the AV socket on the read of the console, did you rewire your scart lead for stereo sound then? Can you post some more detailed pics?

Actually, I just used an RGB SCART cable that had the lead to pull stereo from the headphone jack...but instead of plugging that into the headphone jack, I plugged it into the audio out I soldered:



I get all my RGB SCART cables from an eBay seller, Retro Console Accessories. Her cables have all been flawless:

http://myworld.ebay.com/retro_console_accessories

I can post more pics if you'd like, but there's not much more to it. Just buy one of these (make sure it's long enough):

Then cut the red and white ends off, solder the cables to the points I posted above and dangle the cord out the back of your Genesis. I used the RF hole, since there's enough room for the cable to pass through. I'm sure you could make nice looking audio-out ports on the back of your Genesis, but I'd rather not cut mine.

So in your opinion the sound its better with this mod then from out the headphone jack at the front??

[Fudoh]

Regarding the Sega/Mega CD: if you do the mod the way I've done it, you'll get full stereo from both the MD and MCD from the AV port in the back. No need for additional external wiring or mixing.

[robneal81]

So in your opinion the sound its better with this mod then from out the headphone jack at the front??

I guess it depends. If your headphone jack is outputting clear sound, then it may be the same. Since my headphone out was distorted, the mod sounded better for me.

[robneal81]

Regarding the Sega/Mega CD: if you do the mod the way I've done it, you'll get full stereo from both the MD and MCD from the AV port in the back. No need for additional external wiring or mixing.

I'm sorry, I haven't used an original Sega CD since it came out when I was a kid and for the past year I've owned a CDX, so this is a bit confusing. I thought the only way to get the audio from Sega CD games was to use the audio-out ports on the back of the Sega CD itself:



Will the Sega CD pass it's audio through the Genesis, or do you have to use the connections in the back of the CD unit? Also, how does the 32x fit into all of this? Does it produce any audio, or just pass it through?

Hopefully, I'll be able to pick up a Sega CD today, so I can test this myself.

[Fudoh]

I'm sorry, I haven't used an original Sega CD since it came out when I was a kid and for the past year I've owned a CDX, so this is a bit confusing. I thought the only way to get the audio from Sega CD games was to use the audio-out ports on the back of the Sega CD itself:

no, the only way to get STEREO was to use the external connection. The SegaCD passes stereo through the internal connection into the MD, but due to the Mono-design of the MD's internal amp this wasn't the best way. Iirc the SegaCD's audio is NOT mixed into the front headphone port.

[robneal81]

I'm sorry, I haven't used an original Sega CD since it came out when I was a kid and for the past year I've owned a CDX, so this is a bit confusing. I thought the only way to get the audio from Sega CD games was to use the audio-out ports on the back of the Sega CD itself:

no, the only way to get STEREO was to use the external connection. The SegaCD passes stereo through the internal connection into the MD, but due to the Mono-design of the MD's internal amp this wasn't the best way. Iirc the SegaCD's audio is NOT mixed into the front headphone port.

Ohhh, I think I finally understand: The Sega CD passes stereo audio into the Genesis' main audio chip and your mod pulls sound directly from there, so if I modded my Genesis that way, I wouldn't need any external audio cables.

If I keep my mod and want stereo sound, I'd have to use the external cables in and out of the Sega CD.

Also, I found some info about the 32x's audio:

"One little-known aspect of the 32X was its vastly improved audio subsystem, known as Q-Sound and developed by QSound Labs. While this theoretically gave the system audio capabilities that outstripped even the Super NES, the sound chipset proved to be poorly documented and exceptionally difficult to program for. As a result, most games ignored the Q-Sound system and used the Mega Drive's on-board sound chip, thus leaving the 32X's audio capabilities largely untapped."

So I guess that means if I play a 32x game that uses the Q-Sound chip, I'd definitely need to pass the audio through the 32x.

[lettuce]

I have done a stereo mod for my MD1 a few months back. A line-level stereo signal is available on the mainboard. You just need an additional IC amp (LM358 which costs about $1). Very easy to do. I can provide instructions if you want to try it. Sound quality is the best you can get from a MD1.

You can put the stereo audio signal on the Din8 output. The output provides composite and sync on two different pins and you only need one of these two, so you can kill one and use the Pin for right audio.

Fudoh do you have a guide to this mod?, as all I can find is guides that take the audio from the headphone jack amp.

[Fudoh]

http://shmups.system11.org/viewtopic.ph ... 64#p638564

[Akira]

I had been getting stereo from the front headphone jack, but as others noted, it can be very distorted at times. I decided to mod my Genesis and pull line out directly from the audio chip. So far, it's outputting perfect: loud and clear.

Sory to necrobump this thread, but I wanted to thank you.
This is exactly what I was looking for. I knew you could replace the MD amp but I didn't want to do so. I assumed bypassing whatever goes to the slider would be good enough for me.

I just did this to a PAL MD1 and it works great. Yes, the mono output from the AV port is louder, but this gives non distorted, perfect stereo output on my machine without the fuss of adding the extra amp. All I have to do is lift the volume on the TV set a bit more. No big deal.
I added two RCA plugs on the back for this. No need to mess with the AV port. Done like this, the headphone port also works, in case you need this at all.

Anyway, thanks again!

[ApolloBoy]

I had been getting stereo from the front headphone jack, but as others noted, it can be very distorted at times. I decided to mod my Genesis and pull line out directly from the audio chip. So far, it's outputting perfect: loud and clear.

I suppose I should add that an amp is totally unnecessary on very early revisions of the model 1 Genesis/MD (VA0-VA2), if you tap the audio from the preamp chip as shown, you'll get perfect line level audio. Apparently the audio is slightly overdriven on these early revisions, so getting stereo audio this way is far better than getting it from the headphone jack.

[Einzelherz]

Is it possible/smart to feed this direct audio stream back through the headphone jack? I ask because I'm using an RGB cable that pulls from it and it'd make things simpler than adding another jack.

[ApolloBoy]

Is it possible/smart to feed this direct audio stream back through the headphone jack?

Only if you cut the traces going to it of course.