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Thunder Force IV (1992)

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It's time to reveal a new Mega Amp variant! Introducing the System C-2 Mega Amp, a modification of the Sega System C-2 arcade board's audio mixing circuit prior to its power amplifier modified for proper use on the Genesis. This is a more complicated Mega Amp requiring a total of 6 op-amps instead of 4. Schematic is below and will be added to the first post once I clean it up a bit:

https://imageshack.com/i/f5x3cjp

This is essentially what the Genesis' audio circuit would be like were it based directly off the Sega System C-2 arcade board. Filtered FM synthesis at 3.39KHz, virtually unfiltered everything else at 15.92KHz. This gives Genesis games a different sound than you would normally expect with all audio sources filtered at the same cutoff frequency.

A preview of the System C-2 Mega Amp can be downloaded here.

http://www.mediafire.com/download/m6i0hjhitg7hc69/Mega+Amp+Sample+Set+9+preview.zip

For now, this is only available for the discrete YM3438 and ASIC YM3438, but will be adapted to the GOAC YM3438 and YM2612 later on.

THE MEGA AMP

What is it?
So what exactly is the Mega Amp? It is a universal audio amp designed to work in every Genesis ever made with minimal alterations. Put this in any Genesis and you will experience either the sound of a VA0 MegaDrive Model 1 or the full spectrum of the Genesis' sound hardware.

How did this come to be?
If you remember back in 2012, I posted a replacement audio circuit made specifically for the VA2 and VA2.3 Genesis Model 2s, of which only one console exists with this circuit and it's Mexico (no, it's not a Mexican Sega-16 member who has it). I then started working on a universal audio amp for use on GOACs, but now, it has become something bigger. After having been approached by Villahed94 to make something bigger than any of my previous two circuits and with his assistance, the Mega Amp was born. Working off those old circuits, which have become early Mega Amp prototypes, we now have the most complete replacement audio circuit for the Genesis.
Two different circuit types are available, which are named "Filtered" and "Unfiltered." Same circuit, different low-pass filter. The filtered circuit uses a 3.68KHz low-pass filter to give that sound the Genesis Model 1 is known for while the unfiltered circuit uses a 21.16KHz cutoff frequency to get the full spectrum of the Genesis' audio hardware.
The schematics of each circuit are below. Click on the thumbnails to view the schematics at full size.

YM2612 Filtered:

http://imageshack.us/photo/my-images/22/7kx5.png/

YM2612 Unfiltered:

http://imageshack.us/photo/my-images/15/wexu.png/

ASIC YM3438 Filtered (also works on the discrete YM3438):

http://imageshack.us/photo/my-images/854/g4a3.png/

ASIC YM3438 Unfiltered (also works on the discrete YM3438):
http://imageshack.us/photo/my-images/838/rpbv.png/

GOAC YM3438 Filtered (for Sega GOACs and GOAC-based Geniclones):

http://imageshack.us/photo/my-images/21/dabi.png/

GOAC YM3438 Unfiltered (for Sega GOACs and GOAC-based Geniclones):

http://imageshack.us/photo/my-images/854/3zi2.png/

GOAC YM3438 Filtered (for x-in-1 clones with GOACs):

http://imageshack.us/photo/my-images/191/uapb.png/

GOAC YM3438 Unfiltered (for x-in-1 clones with GOACs):

http://imageshack.us/photo/my-images/22/vzv9.png/

If you would like to build a Mega Amp but don't have access to a TL074, any quad op-amp or two dual op-amps with at least 3MHz bandwidth will work. The only exception to this is the LF347 which, while having 4MHz bandwidth, outputs horribly mangled audio when used with a 32X. As such, it is HIGHLY suggested to not use this chip. The recommended setup is a single TL074 or two TL072s.

So, here's a general summary of the Mega Amp:
-Simple design based around a single TL074 quad op-amp
-Filtered circuits deliver the same sound as a VA0 to VA2 Genesis Model 1 minus distortion
-Unfiltered circuits deliver the full spectrum of the Genesis' audio output
-Audio levels louder than any previous mod, on-par with later Genesis Model 2s
-Headphone support with the optional transistor buffers
-Stereo and Mono audio outs for a complete replacement circuit

More info at: http://www.sega-16.com/forum/showthread.php?26568-Introducing-the-Mega-Amp-The-universal-Genesis-audio-circuit

Music from: Thunder Force IV.

Created by: Ace & Co-Creator Villahed94

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