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ive been tracing and looking at what seems to be lack of datasheets, and have not found any decent resources. help is GREATLY appriciated.
im suppose looking at the A1034 chip right?
any help is appriciated =]
also, im rocking a sega genesis VA3 if thats any help.
Thanks
Last edited by Alley Beach (Apr 17, 2012 6:25 am)
No you hook up an RCA or whatever from the existing video/audio output, which is line level. Theres heaps of documentation out there.
http://www.gamesx.com/avpinouts/genesisav.htm
One tutorial video:
You probably want TmEE's crystal clear audio mod. However, the image with the schematic seems to have vanished from the face of the planet. It used to be here:
http://www.hot.ee/tmeeco/STUFF/GSSCHEM.JPG
This one still works and contains a messy schematic of the audio hardware.
No you hook up an RCA or whatever from the existing video/audio output, which is line level.
That works only for mono, you have to get stereo from somewhere else.
This one still works and contains a messy schematic of the audio hardware. http://www.hot.ee/tmeeco/MDSNDMOD.JPG
Further to nitro's post:
http://arcade.ym2149.com/megadrive/mdsndmodv3.jpg
http://arcade.ym2149.com/megadrive/mysmd2.jpg
But that's for Gen/MD2. Here is a good one I've just found, but haven't tried.
http://freezerdev.blogspot.com.au/2012/ … dding.html
Stereo Audio
1. By tapping the CXA1034P directly you bypass the headphone amp and should get a cleaner signal. But is this output too low for the TV, does it need additional amplification? Answer: Surprisingly the audio output directly from the CXA1034P was perfect line-out levels. I did not need any amplification before passing onto the TV.
2. Does the headphone slider effect the audio output levels in anyway? Answer: The headphone slider does not affect the audio levels in anyway. So tapping the CXA1034P directly is a great way to get clean stereo audio.
Bypassing the amps might remove some of the early motherboard features, like bass response. i'd test it before making it permanent.
The output as it is on my VA3, straight from the headphones plug, is not noisy/.
nitro2k01 wrote:This one still works and contains a messy schematic of the audio hardware. http://www.hot.ee/tmeeco/MDSNDMOD.JPG
Further to nitro's post:
http://arcade.ym2149.com/megadrive/mdsndmodv3.jpg
http://arcade.ym2149.com/megadrive/mysmd2.jpgBut that's for Gen/MD2. Here is a good one I've just found, but haven't tried.
http://freezerdev.blogspot.com.au/2012/ … dding.html
that blog used those pinouts, but I tried out those pins and got nothing. I tried the post and pre signals and nothing worked 
the regular Jack worked fine though. Has anybody found a decent pinout on the amp ic?
I got two consoles (one Genesis VA3 and one japanese MD VA6) with a friend, both already moded by him. The Genesis has stereo RCA outputs straight from the headphones, and the MD has line level outputs, bypassing the amps. I thought the sound quality on both are pretty much the same, but the MD volume is incredibly lower than the Genesis. I'm asking him to make the headphones plug mod in the MD as well.
Ive been looking for an opportunity to bring this up. I did a bunch of research into this, trying to get line level stereo out on megadrive model 1. I have a ton of photos and saved docs so I'll come back later and post them.
I could be wrong on any of these points as this is just a hobby for me so please correct me if I am.
Everything i read online was people either tapping the amp for the headphone jack or the CXA chip, both of which I found less than satisfying.. the headphone amp for obvious reasons and the CXA chip because, from what i saw in the schematic i found and from looking at the board, the separate channels get merged before an op amp, then passed through the CXA as a buffer, then sent out the back. So not true "stereo" line level out..
What i did was copy the capacitor / resistor values from the op amp configuration and picked up the un amped, un merged signals before the amp, brought them to my own board with another op amp, amplified them seperately (dual amp), then sent them out the back. This keeps the headphone jack working uninterrupted, you don't need a cable hanging off the front of your genesis to get stereo audio, and to my knowledge this is the "cleanest" signal possible...
I tried making a track with TFM music maker that panned hard left to hard right, then used the dead fish rom maker to get it on my everdrive, only to realize my CRT only has 1 speaker...
is this something I should bring further?
Genesis Model 1 schematics:
http://i.imgur.com/jcTCW.png
http://i.imgur.com/1Vptj.gif
http://i.imgur.com/pmxh1.gif
If you look in the top right of the first image you see the CXA chip with only one audio out. Directly below that is the LM358, listed as 1/2, because only half is used to amplify the audio. You can clearly see right before the LM358 that the audio signals get merged into one signal. The other half is used to amplify some other signal from basically the other side of the board, I got lost following the trace many times, if this chip isn't intact the system wont boot up.
Would this also work on the Nomad? I've noticed the audio from the video/audio combo jack is pretty noisy