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Thread: M1 Double Mega: Reaching the Finish Line:

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    The legendary gargoyle Road Rasher Firebrandx's Avatar
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    Genesis M1 Double Mega: Reaching the Finish Line:

    It's been a long while since I started R&D on the M1 Double Mega, but finally I was able to brainstorm a much more compact and streamlined mod for toggling between 3438 and 2612 output. The board takes up MUCH less room, and is considerably easier on the budget to produce. Here are pics of the new prototype testing with my Mini Mega mod (which also is getting a new proto in from OSH Park here in a couple days):



    And here's the board without the YM2612 and YM3438 installed:



    Of course we need ear feast test recordings:

    96kHz:

    Thunder Force II - Knights of Legend

    Thunder Force II - Death's Face

    Thunder Force III - The Grubby Dark Blue

    48kHz

    Castlevania Bloodlines - Sinking Old Sanctuary

    Sonic the Hedgehog - Labyrinth Stage

    As soon as I get in the Rev 5 Mini Mega boards, I will do an install video and post both board back up for pre-order on my web site.

    Cheers!

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    The legendary gargoyle Road Rasher Firebrandx's Avatar
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    Got in the prototypes and realized I might be able to get even cleaner results by testing various decoupling capacitor combinations. Discovered ultimately the simple 1uF ceramic capacitor by itself does the best job of high-pitched noise floor reduction. I've designed what should be the final prototype and public release board:





    I've ordered a small run to get started on pre-orders once all the parts arrive. Very excited to finally get this project polished off!

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    WCPO Agent CrossBow's Avatar
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    Quote Originally Posted by Firebrandx View Post
    Got in the prototypes and realized I might be able to get even cleaner results by testing various decoupling capacitor combinations. Discovered ultimately the simple 1uF ceramic capacitor by itself does the best job of high-pitched noise floor reduction. I've designed what should be the final prototype and public release board:





    I've ordered a small run to get started on pre-orders once all the parts arrive. Very excited to finally get this project polished off!
    Looking excellent! I still have one of your earlier proto boards on hand should it be needed for a future project in addition to one of your earlier M1 Mini Mega amp boards also. Might have to grab one or two to replace the earlier version in my primary va2 and another to have on hand.

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    The legendary gargoyle Road Rasher Firebrandx's Avatar
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    I've also updated my Mini Mega boards one final time to rearrange the output pads. I found Vcc was a little too close to other pads, and I took the opportunity to included centralized ground pads for doing twisted pair runs on the left and right channel outputs to RCA jacks:



    Vcc and Ground should be tied directly to the 2nd voltage regulator for best results. Having direct line access to power means no shared ground dumping with video circuits like you would on a TBP board.

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    Road Rasher ironnick23's Avatar
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    The 2612 with the heat sink !!! Good thing, otherwise you might set the whole place on fire!

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    Hedgehog-in-Training Hedgehog-in-Training
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    Any chance on adding pads for A27 and B27 to your Mini Mega board? Or does your design even support it?

    One reason why I built a Mega Amp Pro 2 for my MD1 using The Real Phoenix's PCB design instead of purchasing your board, was due to the fact that I was able to add the Mega CD pass-through to the mega drive 1 using the original schematic of the Mega Amp 2.
    I'm using this on a Model 1 Mega Drive with a Model 2 Sega CD, and the pass-through is working great (I am still looking at developing a mod for the model 1 CD).

    Either way, I look forward to see how the final product will develop, and I am especially interested in the M1 Double Mega. Great work so far!

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    WCPO Agent CrossBow's Avatar
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    Quote Originally Posted by ironnick23 View Post
    The 2612 with the heat sink !!! Good thing, otherwise you might set the whole place on fire!
    Yeah I don't think we understood just how hot the 2612 got until Firebrand started this project. I know that I had previously been using the piggyback method for this and had I known how hot the 2612 got back then, I wouldn't have. I've not personally experienced any sound issues in regards to the 2612 due to heat but it was still quite a surprise to find out all the same. I've got a heatsink on mine as well as most of the other large ICs in my va2 model 1.

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    The legendary gargoyle Road Rasher Firebrandx's Avatar
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    Quote Originally Posted by ironnick23 View Post
    The 2612 with the heat sink !!! Good thing, otherwise you might set the whole place on fire!
    It's to ensure longevity, not worry about house fires. You may not realize it, but the 2612 uses older HMOS tech, and gets pretty damn hot under load. The 3438 uses CMOS and hardly gets warm.

    Anyway, I've since installed the finalized Mini Mega with rear RCA jacks as my recording station for testing chips:





    Some recordings from this station:

    Sword of Vermillion - Statts

    Phelios - Watch Dog in Hell

    Thunder Force II - Knights of Legend

    The final Double Mega boards are still in fabrication, but should be done any day now. I'll be selling the first batch to Patreon supporters, and then will use the money to order a larger batch after that.
    Last edited by Firebrandx; 02-19-2020 at 05:08 AM.

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