Sega Genesis Audio Quality - The Problem - Sega-16 Forums

evildragon · 11-09-2006, 08:35 PM

I have been tinkering around, and have found out why later models of the Genesis have crappier audio than the original that does NOT have the License screen.

Joe Redifer, I know you are going to love to know why it happens..

On the original model, on the circuit, the crystal they used has a very powerful output.. This crystal powers both the CPU and YM2612.. For the CPU, it sets the speed.. For the YM2612, it sets the DAC (not the 6th channel DAC, I am talking about the FM DACs), so it can produce a steady audio wave. On this original Genesis model, it was fine, because as stated, the crystal used was powerful, and produced a VERY clean clock.

On later models of the Genesis, while they used the same crystal, it was a cheaper model. It produced a slightly noisier clock. To the CPU, this is fine, to the YM2612, this was a disaster, it made the DAC clock itself down, to be able to produce anything. This limits it's highest frequency sound it can do.

Why does this happen? Because Mr. Moto 68k sucks up a LOT of the clock. This is why people that have put in a 68k10, report the audio is cleaner, that model don't suck up as much of the clock, and the YM2612 is able to produce a high-range..

I had discovered this, as when I used a crystal of my own, severed the connection going to the YM2612, and used my own, the audio was good again, but, I can't guarantee this works for ALL YM2612's, I only tested my one Genesis 1 model (has a license screen, and does NOT say HD graphics)...

As for the Genesis 2, this is a totally different reason. The YM2612 in it is a CLONE, and lives inside the 315 chipset.

**Joe Redifer** · 11-09-2006, 08:55 PM

That is interesting. I'd like to hear some side-by-side comparisons.

evildragon · 11-09-2006, 09:01 PM

I will record some, as soon as I put my music studio computer back together (it's the master recorder, it records HD audio, 24-bit 192KHz range..)

evildragon · 11-09-2006, 09:09 PM

Actually, for the time being, I'll just record it with my iPod later tonight (mono recording, but you'll here the difference)..

evildragon · 11-09-2006, 09:38 PM

Here you go Joe.. While mono, you can very clearly hear the difference.. Also notice, while it's on it's own isolated clock crystal, the 60Hz noise, is COMPLETELY gone (i haven't figured out why yet -- Because I thought the 60Hz noise came from the PSG as that lives in the VDP)

Before: http://blackevilweredragon.spymac.com/before.wav
After: http://blackevilweredragon.spymac.com/after.wav

**Joe Redifer** · 11-09-2006, 10:19 PM

I seriously hope you have those mixed up, because the "After" sounds HORRIBLE!

Gentlegamer · 11-09-2006, 10:22 PM

Quote:

Originally Posted by Joe Redifer

I seriously hope you have those mixed up, because the "After" sounds HORRIBLE!

I think he did . . .

evildragon · 11-09-2006, 10:26 PM

They were recorded via my iPods headphone jack, the iPod has a PreAmp that can't be disabled (and I think it's EQ kicks in)..

But if you notice, after the song ends, the before has a "fuzzyness" sound to it, where the After, sounds very very clean..

evildragon · 11-09-2006, 10:28 PM

Quote:

Originally Posted by Joe Redifer

I seriously hope you have those mixed up, because the "After" sounds HORRIBLE!

The after is the after, the before is the before..

If you think the 60Hz noise in the BEFORE is perfectly fine, then perhaps you need to hear this thing live...

The after is much cleaner, all the noise is completely gone, and is able even to go to low-volumes (as the crystal is isolated, and clean, so it can also produce very low sound, without "kicking-out")...

**Joe Redifer** · 11-09-2006, 10:32 PM

iPods are hardly even acceptable to play back sounds of any kind, and they most certainly aren't good recorders. I suggest waiting until you can record with your real computer. Don't compress 'em (48000 16-bit stereo is fine).

evildragon · 11-09-2006, 10:41 PM

Here, these sounds are more simple to hear, from the iPod recording, before I can get the music studio running again.. (notice the after does have a VERY small hiss, it's there, but VERY minimal)

http://blackevilweredragon.spymac.com/before2.wav
http://blackevilweredragon.spymac.com/after2.wav

http://blackevilweredragon.spymac.com/before3.wav
http://blackevilweredragon.spymac.com/after3.wav

I'll record any thing you want, for a before and after.. I have the following carts: MK, MK3, Sonic, Sonic 2, Sonic Spinball, Doom (why should I even bother with that one?), Knuckles Chaotix

**Joe Redifer** · 11-09-2006, 10:52 PM

The "boing" seems to have a good noticeable difference, but the "clang" seems to have an extra layer of high-pitched static on the "after". Then again I am not comparing with headphones, only Marantz floor-standing 3-way speakers with 12-inch woofers and a tuned port.

evildragon · 11-09-2006, 11:13 PM

That is something I noticed.. When I used it's own isolated crystal, it's frequency range is MUCH higher..

For example, most sounds on the Genesis YM2612, with the "shared" crystal, looses the ability to produce sounds over 30KHz (it's there, but it gets sorta interpolated).. With it's own crystal, it seems to produce up to 44KHz (around there is more like it), so it seems to sounds slightly different.. Also, it can go much lower too, with it's own crystal (due to noise being in the low frequency before, it distorts it, now it's very clean)..

With the "after", this is technically how it's "supposed" to sound, as the YM2612 datasheet specifies it's OWN crystal (which SEGA neglected to do, to cut production cost)... it probably sounds so different, because the programmers took this into consideration (with the shared crystal).. I'm just more surprised how much the reduction of the hiss is...

Here's another before and after.. It's the intro to MK3.. (i lowered the volume slightly to remove the possible chance of clipping)

http://blackevilweredragon.spymac.com/before4.wav
http://blackevilweredragon.spymac.com/after4.wav

I think MK3 benefitted the most here from an isolated Crystal.. (and I just confirmed with the neighbor ex-sega employee.. The hiss WAS being generated from the YM2612s DAC, and the hiss isn't just a 60Hz hum, it's the high frequency that "backfires" or "interference" from the Moto, and ends up with a un-clean FM sounds as the DAC doesn't know what "silence" is.. He said that when I introduced an isolated crystal, I also introduced much higher SNR, as the DAC knows silence now.. The PSG is silent as it is, it's got isolation in the VDP chip, for that very reason...

evildragon · 11-09-2006, 11:18 PM

Quote:

Originally Posted by megadriveworld

Wouldn't it have been better to post this in the existing thread evildragon, instead of creating a complete new one. What you're are talking about here is tied in with the thread subject I created yesterday.

You're thread was about recordings..

Mine is all about the problem, with particular small samples to explain "why"... I didn't see any comparison between the threads, besides they both are about the quality of the sound.. (but no comparison for "why", and possibly how to "fix" it...)

If a mod wants to merge it, then sure, do it, i don't care..

**Joe Redifer** · 11-10-2006, 01:12 AM

That was a pretty decent example. You need some more games, though. And good ones. I'd like to see if you could get rid of the constant high frequency noise in After Burner.... for the 32X.

11-09-2006, 08:35 PM	#1
evildragon The Black Dragon Fantasy Zone Resident Join Date: Oct 2006 Location: Oviedo, FL Age: 23 Posts: 4,021 Rep Power: 20	Sega Genesis Audio Quality - The Problem I have been tinkering around, and have found out why later models of the Genesis have crappier audio than the original that does NOT have the License screen. Joe Redifer, I know you are going to love to know why it happens.. On the original model, on the circuit, the crystal they used has a very powerful output.. This crystal powers both the CPU and YM2612.. For the CPU, it sets the speed.. For the YM2612, it sets the DAC (not the 6th channel DAC, I am talking about the FM DACs), so it can produce a steady audio wave. On this original Genesis model, it was fine, because as stated, the crystal used was powerful, and produced a VERY clean clock. On later models of the Genesis, while they used the same crystal, it was a cheaper model. It produced a slightly noisier clock. To the CPU, this is fine, to the YM2612, this was a disaster, it made the DAC clock itself down, to be able to produce anything. This limits it's highest frequency sound it can do. Why does this happen? Because Mr. Moto 68k sucks up a LOT of the clock. This is why people that have put in a 68k10, report the audio is cleaner, that model don't suck up as much of the clock, and the YM2612 is able to produce a high-range.. I had discovered this, as when I used a crystal of my own, severed the connection going to the YM2612, and used my own, the audio was good again, but, I can't guarantee this works for ALL YM2612's, I only tested my one Genesis 1 model (has a license screen, and does NOT say HD graphics)... As for the Genesis 2, this is a totally different reason. The YM2612 in it is a CLONE, and lives inside the 315 chipset.

11-09-2006, 09:38 PM	#5
evildragon The Black Dragon Fantasy Zone Resident Join Date: Oct 2006 Location: Oviedo, FL Age: 23 Posts: 4,021 Rep Power: 20	Here you go Joe.. While mono, you can very clearly hear the difference.. Also notice, while it's on it's own isolated clock crystal, the 60Hz noise, is COMPLETELY gone (i haven't figured out why yet -- Because I thought the 60Hz noise came from the PSG as that lives in the VDP) Before: http://blackevilweredragon.spymac.com/before.wav After: http://blackevilweredragon.spymac.com/after.wav Last edited by evildragon; 11-09-2006 at 09:50 PM.

11-09-2006, 11:13 PM	#13
evildragon The Black Dragon Fantasy Zone Resident Join Date: Oct 2006 Location: Oviedo, FL Age: 23 Posts: 4,021 Rep Power: 20	That is something I noticed.. When I used it's own isolated crystal, it's frequency range is MUCH higher.. For example, most sounds on the Genesis YM2612, with the "shared" crystal, looses the ability to produce sounds over 30KHz (it's there, but it gets sorta interpolated).. With it's own crystal, it seems to produce up to 44KHz (around there is more like it), so it seems to sounds slightly different.. Also, it can go much lower too, with it's own crystal (due to noise being in the low frequency before, it distorts it, now it's very clean).. With the "after", this is technically how it's "supposed" to sound, as the YM2612 datasheet specifies it's OWN crystal (which SEGA neglected to do, to cut production cost)... it probably sounds so different, because the programmers took this into consideration (with the shared crystal).. I'm just more surprised how much the reduction of the hiss is... Here's another before and after.. It's the intro to MK3.. (i lowered the volume slightly to remove the possible chance of clipping) http://blackevilweredragon.spymac.com/before4.wav http://blackevilweredragon.spymac.com/after4.wav I think MK3 benefitted the most here from an isolated Crystal.. (and I just confirmed with the neighbor ex-sega employee.. The hiss WAS being generated from the YM2612s DAC, and the hiss isn't just a 60Hz hum, it's the high frequency that "backfires" or "interference" from the Moto, and ends up with a un-clean FM sounds as the DAC doesn't know what "silence" is.. He said that when I introduced an isolated crystal, I also introduced much higher SNR, as the DAC knows silence now.. The PSG is silent as it is, it's got isolation in the VDP chip, for that very reason... Last edited by evildragon; 11-09-2006 at 11:21 PM.

11-09-2006, 08:55 PM	#2
Joe Redifer Join Date: Dec 2005 Location: Denver, CO - USA Posts: 9,759 Rep Power: 50	That is interesting. I'd like to hear some side-by-side comparisons.

11-09-2006, 09:01 PM	#3
evildragon The Black Dragon Fantasy Zone Resident Join Date: Oct 2006 Location: Oviedo, FL Age: 23 Posts: 4,021 Rep Power: 20	I will record some, as soon as I put my music studio computer back together (it's the master recorder, it records HD audio, 24-bit 192KHz range..)

11-09-2006, 09:09 PM	#4
evildragon The Black Dragon Fantasy Zone Resident Join Date: Oct 2006 Location: Oviedo, FL Age: 23 Posts: 4,021 Rep Power: 20	Actually, for the time being, I'll just record it with my iPod later tonight (mono recording, but you'll here the difference)..

11-09-2006, 10:19 PM	#6
Joe Redifer Join Date: Dec 2005 Location: Denver, CO - USA Posts: 9,759 Rep Power: 50	I seriously hope you have those mixed up, because the "After" sounds HORRIBLE!

11-09-2006, 10:26 PM	#8
evildragon The Black Dragon Fantasy Zone Resident Join Date: Oct 2006 Location: Oviedo, FL Age: 23 Posts: 4,021 Rep Power: 20	They were recorded via my iPods headphone jack, the iPod has a PreAmp that can't be disabled (and I think it's EQ kicks in).. But if you notice, after the song ends, the before has a "fuzzyness" sound to it, where the After, sounds very very clean..

11-09-2006, 10:32 PM	#10
Joe Redifer Join Date: Dec 2005 Location: Denver, CO - USA Posts: 9,759 Rep Power: 50	iPods are hardly even acceptable to play back sounds of any kind, and they most certainly aren't good recorders. I suggest waiting until you can record with your real computer. Don't compress 'em (48000 16-bit stereo is fine).

11-09-2006, 10:41 PM	#11
evildragon The Black Dragon Fantasy Zone Resident Join Date: Oct 2006 Location: Oviedo, FL Age: 23 Posts: 4,021 Rep Power: 20	Here, these sounds are more simple to hear, from the iPod recording, before I can get the music studio running again.. (notice the after does have a VERY small hiss, it's there, but VERY minimal) http://blackevilweredragon.spymac.com/before2.wav http://blackevilweredragon.spymac.com/after2.wav http://blackevilweredragon.spymac.com/before3.wav http://blackevilweredragon.spymac.com/after3.wav I'll record any thing you want, for a before and after.. I have the following carts: MK, MK3, Sonic, Sonic 2, Sonic Spinball, Doom (why should I even bother with that one?), Knuckles Chaotix

11-09-2006, 10:52 PM	#12
Joe Redifer Join Date: Dec 2005 Location: Denver, CO - USA Posts: 9,759 Rep Power: 50	The "boing" seems to have a good noticeable difference, but the "clang" seems to have an extra layer of high-pitched static on the "after". Then again I am not comparing with headphones, only Marantz floor-standing 3-way speakers with 12-inch woofers and a tuned port.

11-10-2006, 01:12 AM	#15
Joe Redifer Join Date: Dec 2005 Location: Denver, CO - USA Posts: 9,759 Rep Power: 50	That was a pretty decent example. You need some more games, though. And good ones. I'd like to see if you could get rid of the constant high frequency noise in After Burner.... for the 32X.

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