animalstyle
Offline
killadelphia

I have tried just about every model of the Genesis looking for the best audio.  I used the Crystal Clear Audio mod from tiido at first, then i switched to the unmodded model 3 which was a bit tighter and cleaner sounding (didn't matter that it was mono because i was using TFM - which didn't support panning).  It's also possible to stereo mod the model 3...  Recently, I bought a good High Definition Graphics model (from madgearstore) and did a full electrolytic capacitor replacement.  I have to admit - there is a little more signal to noise ratio but overall the sound is much fuller.  I remeber having a model one and loving playing it with my headphones on when i was like 12.  There is definitely more bass and the thing doesn't sound computery or digital.  That was basically my gripe with both the CCAM and the model 3.  I might as well have been using a really accurate emulator.  Both the model 2 and 3 have ASIC versions of the YM2612 which means you won't see the actual chips on the board and I think the sound suffers because of it.  On the High Definition Graphics model one there is a dedicated YM2612 and for some reason the PSG master system chip sounds way better.  If you're looking to replace the caps you will need:

7X  47uf 16v
13X  10uf 16v
6X  1uf 50v
9X  100uf 10v
4X  220uf 10v

When you replace the caps - the voltages do not matter so much...  you just don't want to go down in volatge - up is fine.  I bought a cap kit from Jameco but after reading about HIFI audio amplifiers I had another thought.  Why not replace the caps in the audio section with some really hi-fi stuff:  Like some Black Gate or Elna Silmic caps.  After reading this article i think the problem with the audio output is not really the original schematic...  its probably the horrible components the units shipped with.  I know that from modding tons of Boss pedals they make a great product and overtime ship shittier and shittier parts inside to cut costs and make a more profit.  A lot of the complaints with noise on the Genesis come from electrolytic capacitor drain over time so you start to hear unwanted AC noise, VDP noise, and general tone harshness.  It's much more apparent on an FM machine than on the NES' 2A03 because those don't actually need an amplifier for line level on a mixer.  The FM chips need really amazing amplifiers with very accurate capacitor filtering.

Last edited by animalstyle (Nov 17, 2013 4:01 am)

metropeak
Offline

Yep, the older the Genesis models have the best full sound quality for exactly the reasons you describe. As for your idea about the capacitors, why not instead simply have an isolated power circuit for the YM2612, might be a cheaper way for the same benefit?

I personally think a bit of noise adds authenticity, but clean FM sounds great too wink

animalstyle
Offline
killadelphia

I forgot to mention I actually replaced the huge cap in the wall wart too...  which did help some noise go by by.  I also tried to isolate the YM2612's power supply as well but i failed and then ran into some monetary issues - it was hella difficult but i probably went about it the wrong way.  I think the noise is not really being picked up by the YM2612 because those chips are pretty solid and are found in many many expensive keyboards of the 80s - i think its actually the CXA-1034 or the CXA-1145 that's the culprit.  I think that's why tiido basically ripped his out.  I don't mind the sound of that op-amp...  it's dirty in the right frequencies and i also like the capacitor values - it think it filters out some of the high frequency harshness of the tinny sounding FM.  Although - it doesn't help that CXA-1145 is both an audio amp and a video encoder...  doing both of those so close to eachother in an IC could probably lead to some noisey results.

Last edited by animalstyle (Nov 17, 2013 6:02 am)

freezedream
Offline
Adelaide, Australia

First of all, I think your complaint about the sound being more or less "computery" is a bit odd. What are you expecting exactly? This is a digital synth chip in a video game console, not a state-of-the-art professional analogue synthesizer.

Secondly, I'm not positive about this, but I was under the impression that some of the noise comes from the poor quality DACs inside the YM2612, which you can't change. Actually, it seems this is the case. Have a look on wiki.

I think CCAM actually bypasses the amp and filter section as a better sounding equivalent.

For me, the inherent noise, though it's really a design flaw, is part of the sound character of the synth.

Finally, TFM does supported panning. I've used it for every track I made in it.

DSC
Offline
animalstyle wrote:

I have tried just about every model of the Genesis looking for the best audio.  I used the Crystal Clear Audio mod from tiido at first, then i switched to the unmodded model 3 which was a bit tighter and cleaner sounding (didn't matter that it was mono because i was using TFM - which didn't support panning).  It's also possible to stereo mod the model 3...  Recently, I bought a good High Definition Graphics model (from madgearstore) and did a full electrolytic capacitor replacement.  I have to admit - there is a little more signal to noise ratio but overall the sound is much fuller.  I remeber having a model one and loving playing it with my headphones on when i was like 12.  There is definitely more bass and the thing doesn't sound computery or digital.  That was basically my gripe with both the CCAM and the model 3.  I might as well have been using a really accurate emulator.  Both the model 2 and 3 have ASIC versions of the YM2612 which means you won't see the actual chips on the board and I think the sound suffers because of it.  On the High Definition Graphics model one there is a dedicated YM2612 and for some reason the PSG master system chip sounds way better.  If you're looking to replace the caps you will need:

7X  47uf 16v
13X  10uf 16v
6X  1uf 50v
9X  100uf 10v
4X  220uf 10v

When you replace the caps - the voltages do not matter so much...  you just don't want to go down in volatge - up is fine.  I bought a cap kit from Jameco but after reading about HIFI audio amplifiers I had another thought.  Why not replace the caps in the audio section with some really hi-fi stuff:  Like some Black Gate or Elna Silmic caps.  After reading this article i think the problem with the audio output is not really the original schematic...  its probably the horrible components the units shipped with.  I know that from modding tons of Boss pedals they make a great product and overtime ship shittier and shittier parts inside to cut costs and make a more profit.  A lot of the complaints with noise on the Genesis come from electrolytic capacitor drain over time so you start to hear unwanted AC noise, VDP noise, and general tone harshness.  It's much more apparent on an FM machine than on the NES' 2A03 because those don't actually need an amplifier for line level on a mixer.  The FM chips need really amazing amplifiers with very accurate capacitor filtering.

This is very helpful information.  Cap values are very helpful.  I have a couple of GenMDM's and was looking to modify a couple of consoles here very soon.

animalstyle
Offline
killadelphia
freezedream wrote:

First of all, I think your complaint about the sound being more or less "computery" is a bit odd. What are you expecting exactly? This is a digital synth chip in a video game console, not a state-of-the-art professional analogue synthesizer.

yes it's a digital chip that is a descendant of the high quality yamaha OPN family.  There is a diference between hearing the actual YM2612 and the ASIC version's approximation in later models.

freezedream wrote:

Secondly, I'm not positive about this, but I was under the impression that some of the noise comes from the poor quality DACs inside the YM2612, which you can't change. Actually, it seems this is the case. Have a look on wiki.

My friend luis made a hardware VGM player on a breadboard with the isolated chips + arduino at @partty.  That thing sounded amazingly clean.  There was no VDP noise and just about no AC hum.  Electrolytic caps have a life span of about 10 years...  less if they're shitty.

freezedream wrote:

I think CCAM actually bypasses the amp and filter section as a better sounding equivalent.

The original filter actually chills out the tin on the high parts of the FM because of the built in design flaws of the DAC in the actual chip (in your wiki article) - i like that better.

freezedream wrote:

For me, the inherent noise, though it's really a design flaw, is part of the sound character of the synth.

again - it's probably not all the chip itself because you find OPN chips in high quality keyboards.  I realize that the wiki is talking about one specific type of noise when channels are blended together.  What I'm talking about is the general hiss, hum and VDP noise funneling through the sound chip.  You basically hear AC line leakage and VDP noise when the processor crunches (i love that sound actually - its nice when it's subtle but annoying when your caps are old).

freezedream wrote:

Finally, TFM does supported panning. I've used it for every track I made in it.

the first version of TFM did not support panning and when the option was added later... you couldn't hear it inside the tracker.


Seriously - recapping your High Definition Graphics model one sounds really really nice.  The bass sounds better to me too.

Last edited by animalstyle (Dec 6, 2013 6:21 pm)

wedanced
Offline
San Francisco

The genesis really needs a good sound comparison page. the current ones are kinda meehh and very incomplete. would love to see this in full swing.

Theta_Frost
Offline
Milwaukee, WI

Idk, this is pretty good.  It's missing board revisions but that's about it.

http://milkcrate.com.au/_other/sega_comparisons/

wedanced
Offline
San Francisco

nah that guy, while the most complete available, still is missing model 3 and different sound mods available.

animalstyle
Offline
killadelphia

yea - the problem is all the damn board revisions.  not all models and boards are equal - makes getting every detail a much more daunting task than the gameboy.  someone with a bunch of money should do it tongue

If someone does do it should they compare square waves like Weixelbaum, though?  would that even make sense for an FM synth?

yea - model 3 isn't on Little Scale's page either - and I think it has a better output by itself than any model 2 (even modded).  Only downside is the mono output.

Last edited by animalstyle (Dec 13, 2013 5:43 pm)

wedanced
Offline
San Francisco

I think the model 3 has a stereo mod that can be done. It actually does sound fantastic in general too. Not sure why it doesn't get the love it deserves.

The revisions really are a bitch. I would be willing to run the test myself if people were down to send me units to barrow. I have 2 model 2s that were given to me and access to one other hi deff model ones. 

Weeeeee can doooo it if we pool our resources.

iNFOTOXIN
Offline
Dublin, Ireland

Helpful thread thanks, been trying to figure out the best option for this. Think I'll give re-capping a go. smile

Slight aside, but does anyone know how easy it would be to split off the SN76489 to a separate output? / What exactly I'd have to do?

_-_-
Offline

I've got a couple of mega drives at home now and maybe one more I could borrow. I would be up for making a sound comparison, but I'd need some help from anyone who's got a different machine than I to make it more complete. I have a borrowed everdrive as well, so I could play some VGMs. Although I would probably construct some sort of "test sound" / pattern. I will most probably do this.

It would be a part of my secret wiki that currently is a wip cataloguing all the different nanoloop versions in a reader friendly way.

Last edited by _-_- (Dec 13, 2013 11:46 pm)

ultramega
Offline
Boston, MA

i've got like 15 high definition graphics models.. i did a bunch of research into this using board schematics i found online. theres an amp for the headphone port on the front and theres another dual op amp that amplifies the merged audio channels and something else from some other part of the board, if you pull that 2nd amp completely the genesis wont boot

I assume this dual op amp working on completely different signals is introducing some noise, its an LM317 or something like that, dirty amplifier really not meant for audio from my research.

I havn't done exhaustive testing, but i picked up the L and R audio channel before they were merged and put them through my own LM317 on a separate board and it sounded pretty good, my next tests were gonna involve using a dual op amp meant for audio.

i really dunno what i'm talking about though, learned through experience, sorry if what i'm saying is dumb

ultramega
Offline
Boston, MA

I lied i got 10 HD graphics 5 normal, I'd like to contribute to figuring this out.. if there is any value to the stuff I did

animalstyle
Offline
killadelphia
iNFOTOXIN wrote:

Helpful thread thanks, been trying to figure out the best option for this. Think I'll give re-capping a go. smile

Slight aside, but does anyone know how easy it would be to split off the SN76489 to a separate output? / What exactly I'd have to do?

it's pretty easy to "prosound" just the master system chip.  I did it.  maybe have a look at emu-docs.org.