Crystal Clear Audio Mod for Sega Mega Drive 2 & Genesis 2, version 1.0

[KillerBean2]

Lower end of the signal suffers and constant levels are no longer possible...

So much for that dream then

No big loss though. The "normal" CCAM sounds amazing anyway

[CathodeRayTubes]

Back when I was in grade school I figured out that the model2 had poor sound and that the model 1 sounded better, I remember my friends having a genesis and I wanting one but at the time I had the snes and my parents wouldnt buy me a genesis then, later a couple of years down the road I remember another friend of mine getting what ended up being a VA7 genesis and I noticed that the sound was really bad on his and thought it had something wrong with it. Then he model 2 came out and I was like man this sux cause now if I finally talk my parents into buying one it would be a model 2, back in those days it was hard to find consoles 2nd hand. To make a long story short I ended up with a model 2 years later for free which suffers from the poor audio. And as of now I own a couple of model1s and a jvc x eye. And now I wish I could have had tiidos ccam back then. I am temped to pick up another model 2 since I long since sold mine and try tiidos mod.

[KillerBean2]

Btw, if any of you guys are thinking about finding a good alternative to the 4558D, I highly recommend OPA2134.

It's designed specifically for high quality audio applications, and it's specified to run on a supply as low as +/-2.5v DC. A perfect fit for the CCAM.

It's relatively expensive, but compared to some of the other offerings from Burr Brown (now Texas Instruments) or Analog Devices, it's a steal!

Just be careful if you find it cheap on eBay. There's a high risk that it's a fake. A lot of re-branded general-purpose op-amps are floating around on EvilBay.

[KillerBean2]

I've been trying to dust off my old analog electronics skills in order to understand how the CCAM works, but I'm getting nowhere fast.

The part after the positive inputs on the op-amps makes sense to me. Q-point set at 2.5v, gain of 4.7 and output impedance of 100 Ohms, right?

And the 22nF caps cut off the unwanted stuff above audio frequencies?

The transistors themselves are set up as voltage followers and only have a buffer function?

I don't think I'll get any further with my analysis before I know the characteristics of the FM/PSG outputs. Do any of you guys have some info on DC offset, amplitude and impedance? TmEE, help!

[TmEE]

Transistors act as buffers, 0.022pF caps remove inaudible freqs that would otherwise strain the opamp (which results in garbled highs).
Vref is 2.5V so the opamp has good swing in the power supply range. Gain I dont remember by heart, output impedance should be that (unless the opamp has something internally affecting stuff too)

In all honesty, most of the CCAM came out from trial and error :P

(but I have one final sound mod cooking that works on all models with discrete Z80, that includes MD1 !)

[KillerBean2]

In all honesty, most of the CCAM came out from trial and error :P

Guess I'll just have to do my analysis that way too

On a side note, do you know if the 315-5660 has a separate suppy input for the DAC(s)? Like AVcc on the YM-2612 in the MD1.

[TmEE]

That is what the bridged resistors are :P

[KillerBean2]

I did some probing with my multimeter yesterday and came to the same conclusion

You actually raise the voltage form ~4v to 5v. Is that on purpose?

I figure I'll have to replace the DAC supply with something super clean/steady if I am to do a ridiculous overkill CCAM.
Like I've seen you mention somewhere: You can't make delicious pancakes out of a turd

[TmEE]

I have DAC supply separated in my MD aswell as PSG supply, it helps too ^^

And voltage raise makes stuff sound nicer, and louder. Better noise floor you know :P

[KillerBean2]

Awesome

Is the PSG supply pin 177 on the 315-5660?

Btw, took the liberty to redraw the schematic. IMO this version is a little easier to navigate:

[omp]

Very nice work on the schematic there! Neat and easy to read, one VERY minor thing is you have 2 OUTL. It is obvious that the lower one is OUTR though just a minor thing.

[KillerBean2]

Fixed

[palonso4373]

Hey do you know if I can play sega megadrive games on my sega genesis how can I do it ????

[MaxWar]

Hey do you know if I can play sega megadrive games on my sega genesis how can I do it ????

This is quite Off topic my friend, this thread is about an audio mod for the console.
And here, i googled it for you.
http://www.sega-16.com/forum/showthr...-Drive-Genesis

[firage]

Can anyone tell me if there is a good smd equivalent to the 2sc945 transistor? I have for the most part completed the smd version of my board but I can not find any c945 smd transistors. Is there an easy to find equivalent out there? My board looks great but those transistors stick out way to much. It looks bad with such a nice low profile board with only four components sticking up.

Did you find something that works, retrogamer? This thing is going to rock, can't wait.