discrete YM3438 and one inside ASIC behave 1:1 on the DAC stuff part, its the YM2612 having the problem
discrete YM3438 and one inside ASIC behave 1:1 on the DAC stuff part, its the YM2612 having the problem
Oh damn, I think I need to change system when it comes to sampling music from Sega System C-2 arcade games as those use a discrete YM3438. Didn't think the discrete YM3438 would have the same DAC as Sega's ASIC-based YM3438.
By the way, here are the After Burner II samples I said I was going to send: http://www.mediafire.com/?t2j6vp5qkjavhxj
You'll notice my Audio Modded VA7 Genesis Model 1 sounds closer to the VA3 Genesis Model 1 than it does the VA3 Genesis Model 2.
Well... I got someone to build the sound module and wired it up tonight. NOTHING... no sound of any kind. Thrilled that I now have a ruined MegaDrive 2. Can anyone try and help me out with salvaging this one?
TmEE, you were right. My filter capacitors actually are 0.01uF and not 0.1uF as I thought they were. For some reason, I thought the Audio Mod needed 0.0022uF ceramic capacitors instead of 0.022uF ceramic capacitors and I bought 0.01uF capacitors instead. I thought weaker capacitors weren't supposed to filter out the audio as much? With 0.01uF capacitors, my VA7 Genesis Model 1 sounds a lot like my VA3 Genesis Model 1 to my ears, but with more audible high frequencies.
By the way, have you listened to the After Burner II clips I posted? Why does After Burner II sounds so much like it does on my VA3 Genesis Model 1 than on my VA3 Genesis Model 2 whenever I play the game on my Audio Modded VA7 Genesis Model 1 and ONLY when I don't have a 32X plugged in?
And one final question: would there be some way to make the overall audio out of the Audio Mod louder without inducing distortion? Or is that just not possible?
The higher capitance the more muffled sound will get (thus stronger filtering).
Reason why the AB songs sound like that is most probably because of overloading happening in that MD model, as it produces similiar effect though not quite it.
Making things louder is possible but that requires opamps to be powered by DC input directly which causes other kind of problems and certain death to sound parts by any kind of fault by non experienced person, margin for error becomes 0% from current 5%
So what value capacitor would be needed to get my Audio Modded VA7 Genesis Model 1 to sound like a pre-VA7 Genesis Model 1? Similarly, what value capacitor would be needed to get the clearer sound of the Genesis 3(I'm going to build an Audio Mod for my VA1 Genesis 3 - on that note, does the 315-5960 GOAC require 100Kohms at the FM inputs or is 22Kohm sufficient)?
In other words, it's a flaw with the YM3438 in the Sega 315-5487 ASIC? What would explain those notes becoming quieter when a 32X is inserted into the Genesis?Quote:
Originally Posted by TmEE
But if I build more Audio Mods and I get this same thing on my VA1 Genesis 3 and whatever Genesis Model 2 I apply the mod to(preferably one with a CXA1145 or MB3514 video encoder - I can't stand the KA2195D), most likely, I'm doing something wrong. Either that or your Audio Mod does something to make those notes more audible. Do you have After Burner II? If you do, could you check to see if those notes are audible on your MegaDrive II?
I don't recall 315-5960 needing 100Kohm resistors, Genny3 VA2 certainly does though.
There is no flaw in YM3438, YM3438 fixed the flaw in YM2612 that causes AB to sound like it sounds. 32X thing is explained by change of load on the outputs of YM due to crappiness of the mixing circuit used.
I have done some AB recordings in past, here's one http://www.fileden.com/files/2008/4/...5/AFTRBRN2.ogg.
It has been verified on spritesmind that they sound like that on MD1 because of the DAC bug in YM2612, which is later on fixed in YM3438. When you overload the outputs of YM3438 it will cause distortion which works in favor to bring out those sounds but at cost of everything else sounding bad/worse aswell.
So then, if the outputs of my VA7 Genesis Model 1 are overloaded(which they would be, from what you're saying), then what the hell did I do wrong with my amp? I did replace two resistors because I noticed when I built the Audio Mod, the YM3438's audio was too loud(and there were some resistors I couldn't find). The following resistors were replaced:Quote:
Originally Posted by TmEE
22Kohms(replaced with 25.5Kohms by means of a 20Kohm resistor put in series with a 2.2Kohm and 3.3Kohm resistor)
1Kohm(replaced with 1.1Kohms by means of two 2.2Kohm resistors put in parallel)
100ohms(replaced with 110ohms)
750ohms at the 32X PWM inputs(replaced with 294ohms by means of two 147ohm resistors in series - using 750ohm resistors made the PWM almost inaudible)
Which of those could screw up the audio coming out of the YM3438?
Also, I remember you saying that overloading the YM3438's outputs to the point of making quantization noise audible is bad for the DAC. Would keeping this Audio Mod cause the DAC in my Audio Modded VA7 Genesis Model 1 to fail prematurely?
EDIT: I can confirm the two 2.2Kohm resistors put in parallel have nothing to do with the excess quantization noise. I found my 1Kohm resistors and replaced the 2.2Kohm resistors I put in parallel and the sound is still the same. I can still hear quantization noise so long as the 32X is not plugged into my VA7 Genesis Model 1. If anything, it seems like the quantization noise is LOUDER with the 1Kohm resistors instead of the two 2.2Kohm resistors in parallel. WTF? Please tell me what the hell I did wrong.
Oh, and I took a closer look at the filter caps I put instead of the 0.022uF caps and... THEY'RE 0.1uF! They're 104 caps, and I know for a fact that equals 0.1uF. You say it's supposed to really muffle the sound, but on my VA7 Genesis Model 1, it sounds like my VA3 Genesis Model 1.
EDIT 2: Might be a bit of a dumb question, but if you were to swap out the YM2612 in a Genesis Model 1 for a YM3438, would your Audio Mod work on pre-VA7 Genesis Model 1s?
You probably forgot to remove some resistors on PWM lines that you had to lower the 750ohm ones... there's 75ohm resistors on PWM (and MCD) signals that go to ground, and when you don;t remove them you'll get near inaudible PWM, plus it messes up delicate DC balance in the mixing part which can cause the problems you mention and this is not overloading related but just plain old distortions...
When something does not match up you got something wrong in 99% of cases, there's nearly no room for error...
Also what you describe as quantization noise here is not it, Q-noise is very specific kind of high freq noise mostly heard in the quietest parts of sound
When you do swap out the YM2612 for YM3438 then CCAM compatibility comes too, I am working on a CCAM 2.0 that won't require transistors but few nice opamps instead and much less resistors, but it will probably need dual polarity power supply for maximum efficiency
Okay TmEE, please explain this to me: I just rebuilt a new Audio Mod for the RetroN3 with the following tweaks:
-The 0.022uF capacitors were replaced with 0.1uF capacitors
-The 22Kohm resistors at the FM inputs were replaced with 100Kohm resistors as the FM would distort otherwise
-The 32X PWM and Sega CD PCM/CDDA inputs were omitted
-The 4558 op-amp was replaced with a TL072 op-amp
-The 1.5Kohm resistors were replaced with 3.3Kohm resistors
-The 3.3Kohm resistor to Ground at the PSG input was replaced with a 7.5Kohm resistor
-4.7Kohm resistors were added after the 100uF capacitors as the audio would become really garbled when trying to record it through my computer's audio input
And yet, I STILL get that noise in After Burner II as though the sound was produced by a YM2612 and not a YM3438(the GOAC in the RetroN3 uses a YM3438). WTF??? What am I doing wrong?
Still, the sound off the RetroN3 is near-perfect. I say near-perfect as it seems at least one of the square waves is too quiet on the TCT-6801 GOAC in the system.
I shall now record some samples from an Audio Modded RetroN3(Version 2, I should add).
EDIT: Well, isn't this F***ING NICE?! RIGHT IN THE MIDDLE OF RECORDING SAMPLES, THE CIRCUIT FAILS AND NOTHING I CHANGE MAKES IT WORK AGAIN!!! F***!!!!
EDIT 2: Got the circuit working again. For how long, I have no f***ing clue. Might have had problems with my VCC wire as I noticed when the circuit failed, the volume of the remaining audio was fluctuating quite a bit from loud and clear to quiet and distorted.
EDIT 3: I've got some audio samples recorded. Get them here: http://www.mediafire.com/?9bkh2gh92g5ekp7
I've recorded some samples from the following games:
-Thunder Force II MD
-Thunder Force III
-Thunder Force IV
-After Burner II
-G-LOC Air Battle
-Sonic the Hedgehog
Small note: the GOAC in the RetroN3 has HEAVY video noise in the audio output, so you'll hear a lot of background noise.
Now, someone tell me: is the PSG too quiet? Or are some sound channels on the GOAC's SN76489 too quiet compared to other channels?
Can't wait my mate, keep it going bro.Quote:
Originally Posted by TmEE
It involved a lot of cursing, swearing and sweating, but I managed to force this thing together today:
http://www.mastersystem.dk/stuff/pics/MD2_audio_amp.JPG
It uses an OPA2134 PA op-amp, 2SC945 transistors and sounds devine! :D
At first I tried to make a proto-print layout, but grew impatient.. too many resistors! ---> birds nest.
Hmmm, but the SMS mode has stopped working :(
This is awesome, but would look nicer with those more miniature resistors ^^
SMS mode problem is certainly interesting... only one single line from cartslot controls SMS mode.
I removed the old amp-chips. Maybe the system needs an "okay" signal from the the chips, when it switches to mono sound?
Yes, it looks awful. I'll replace it with a new circuit build on a veroboard sometime soon ;)Quote:
Originally Posted by TmEE
The left opamp is needed as it creates power on reset for the machine, you need one extra modification to bypass it so it works like in SMS. It will take time when I get it looked up though, due to lack of easy access to a clean unit