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 Post subject: Modding older consoles for Digital S/PDIF audio?
PostPosted: Sat Jul 24, 2010 7:15 pm 
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So I'm on a campaign of killing the buzzing background noise inherent in my older consoles thanks to the mediocre shielding present in most of them and for the improved fidelity.

There are two on my mind at the moment are the Genesis and the Jaguar as there are barely any documented attempts (and none that I can find for the JAG) to mod either for Digital Audio.

The SNES, N64, Gamecube, Saturn, Dreamcast and PS1 all seem to have easy and heavily documented mods to make the process easy. But the Jag and Genny seem to have me flying by the seat of my pants.

ORIGINAL TOPIC:

I Really want to do my JAG as I want to hear Tempest 2K in real hi-fi. But now I'm in uncharted territory, I've never really tinkered inside of a Jag before so it's all new to me.

Anybody here experienced with the internals of the Jag & it's audio circuit willing to help me out with this one?

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 Post subject: Re: Is it possible to mod a Jaguar for digital S/PDIF audio?
PostPosted: Sat Jul 24, 2010 7:52 pm 
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Different console maybe a similar solution?
This repair unique to the notorious buzzing Vectrex, but may give some ideas.

Vectrex Buzz fix
http://www.playvectrex.com/vectech/quietvec/quiet_vectrex.pdf

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 Post subject: Re: Is it possible to mod a Jaguar for digital S/PDIF audio?
PostPosted: Sat Jul 24, 2010 8:21 pm 
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Nono, see the audio output on my Jaguar and all my other consoles is perfectly fine, I'm just basically sick of the "60hz hum" that's inevitable (turn up the volume on practically any integrated device/console without a massive/large filter capacitor like an AV reciever or hi-fi/video equipment and you'll hear it) when it's going through a 5.1 AV receiver and then into some decent speakers instead of the regular crapola TV speakers setup.

Basically it's not really an issue of the shielding or anything, but more of a "screw analog audio" thing. Digital S/PDIF via COAX or Optical will give me more fidelity, tighter bass and clearer highs and will be a noticeable improvement over what I've got now.

For example the Genesis is a prime culprit of this thanks to the general slacking on Sega's end to not use higher-end parts and therefore My genesis console has a constant low hum in the background. Note that this doesn't mean a loud and blatant hum such as the one present in the Vectrex, but more like the hum that would be typically caused by incorrectly connected cables and a lousy RF connection. Basically just the shitty analog circuitry inside of our older consoles. Even the SNES is at fault though to a lesser extent than the Genesis, but there's already an existing and well documented digital audio mod for it.

All of this having been said the Jaguar has a nice clean sound with no real trace of any humbars or ground loops I just want to use a digital COAX connection for increased fidelity and to deal with less wires.

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 Post subject: Re: Is it possible to mod a Jaguar for digital S/PDIF audio?
PostPosted: Sat Jul 24, 2010 9:08 pm 
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Oh okay, thought a shielding problem. Know what you mean, on analog audio.

My Vectrex's sound like a bee hive, keep justifying that its the character of the machine. In reality due to rareness, too precious for me to attempt that mod. I did incorporate a direct off switch to one of them, so my clumsy big fingers wouldn't have to mess with the volume rotate off switch. Made life easier when changing game carts. Also modded a couple old Apple II controllers as spares to supplement the single Vectrex controller,

Okay so a direct digital audio; where's Bacteria?


Attachments:
File comment: VECTREX MOD
opamp.JPG
opamp.JPG [ 69.43 KiB | Viewed 1920 times ]

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 Post subject: Re: Is it possible to mod a Jaguar for digital S/PDIF audio?
PostPosted: Sat Jul 24, 2010 11:19 pm 
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Flashes Bac Signal........

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Niode wrote:
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 Post subject: Re: Is it possible to mod a Jaguar for digital S/PDIF audio?
PostPosted: Sun Jul 25, 2010 9:38 am 
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Probably not the solution you're looking for but if you're going through a decent receiver why not try EQing out 60hz? Put a high-pass filter on there and you should be golden.

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 Post subject: Re: Is it possible to mod a Jaguar for digital S/PDIF audio?
PostPosted: Sun Jul 25, 2010 12:14 pm 
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Yeah, not really what I'm looking to do. I honestly just want to nix as much analog audio as I can in general on my setup and replace it with digital wherever possible.

Basically just looking to consolidate my hookups.

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My Consoles:
Genesis - Nomad - SegaCD - GameGear - Sega Saturn - Dreamcast - NES - SNES - N64 - Gamecube - Wii - Playstation - PSone & LCD - PS2 - PS3 - Xbox - 3DS

Niode wrote:
Send him a dodgy cheque. Make it out to Scammy McScammerson.


Check out my sale thread below, NeoGeo MVS carts & Arcade gear wanted!:
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 Post subject: Re: Is it possible to mod a Jaguar for digital S/PDIF audio?
PostPosted: Sun Jul 25, 2010 6:08 pm 
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Mod_Man_Extreme wrote:
Flashes Bac Signal........

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:lol: :mrgreen:

What I know of the Jaguar is it's easy to A/V mod as I did it a couple of years ago, A/V mod means no need for the RF box or shielding, which might help.

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 Post subject: Re: Is it possible to mod a Jaguar for digital S/PDIF audio?
PostPosted: Sun Jul 25, 2010 9:17 pm 
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Actually, I had our resident Mythbuster, Hobie make me an S-Video cable with stereo RCA's. I'm just wondering if some form of internal mod to strip the digital audio signal right off of the Jag's audio chip and output it to my reciever ala the Gamecube, SNES N64, PS1, Saturn and Dreamcast mods that do the same.

EDIT!: I'm just trying for coax audio, so what I plan on trying for if possible is to use the existing RF box/jack on the back of the JAG. De-solder it from the board, proceed to pry it open, rip out the RF stuff and wire the coax output to it. That way I'll have coax and everything on the back will look as if it wasn't modified.

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My Consoles:
Genesis - Nomad - SegaCD - GameGear - Sega Saturn - Dreamcast - NES - SNES - N64 - Gamecube - Wii - Playstation - PSone & LCD - PS2 - PS3 - Xbox - 3DS

Niode wrote:
Send him a dodgy cheque. Make it out to Scammy McScammerson.


Check out my sale thread below, NeoGeo MVS carts & Arcade gear wanted!:
viewtopic.php?f=22&t=11366


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 Post subject: Re: Modding older consoles for Digital S/PDIF audio?
PostPosted: Tue Jul 27, 2010 3:02 am 
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BUMPY!

In addition to my curiosity about possibly modding the JAG for S/PDIF I'm now researching to mod my Genny for Digital audio as well as the Jaguar.

Our very own Brendan Raymond has created what is (to my knowledge) the first digital audio mod for the Genesis. But from what I've read about the mod since is that because the YM2612 inside the Genny contains an internal DAC the sound is taken directly from the chip's analog output circuit and converted to digital on the spot by an ADC.

So, I'm thinking of possibly replacing the internal YM2612 with it's Non-Internal-DAC equivalent, the YM2608; then take the sound off of it from there and wire it straight to a coax/optical jack with a lot less hassle. Basically I'm looking to get a 100% digital transfer and avoid having to take and convert any of the Genny's YM2612 Analog circuitry if possible.

Is there any way this would be possible? From what I know the YM2612 in the Genny and YM2608 itself use an identical instruction set so that would make the transition easy once I trace the circuit and wire it correctly. Of course that would mean loosing all analog audio from the Genny unless I used some form of DAC but I doubt I'd miss it. Though I probably would put in some form of DAC just for BC with non-digital stereo systems.

Wiki's on the corresponding chips:

http://en.wikipedia.org/wiki/Yamaha_YM2608

http://en.wikipedia.org/wiki/Yamaha_YM2612

_________________
My Consoles:
Genesis - Nomad - SegaCD - GameGear - Sega Saturn - Dreamcast - NES - SNES - N64 - Gamecube - Wii - Playstation - PSone & LCD - PS2 - PS3 - Xbox - 3DS

Niode wrote:
Send him a dodgy cheque. Make it out to Scammy McScammerson.


Check out my sale thread below, NeoGeo MVS carts & Arcade gear wanted!:
viewtopic.php?f=22&t=11366


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