Author Topic: Resistor for NES expansion audio mod?  (Read 10405 times)

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Offline The Iron Goat

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Resistor for NES expansion audio mod?
« on: June 04, 2013, 06:41 PM »
Got my NES EDN8 (woo-hoo!), and I'm about to mod a front loader for expansion audio. Should I use a 47k-ohm, two 47s in series, or a single 100? I've read differing recommendations, and I'm wondering which would provide the closest audio mix to an original Famicom.

Offline Redifer

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Re: Resistor for NES expansion audio mod?
« Reply #1 on: June 05, 2013, 02:01 AM »
I first tried a single 47k and the expansion audio was too loud on Castlevania 3 or whatever they call it in Japan. When you defeat the boss, you could *barely* hear it groan at all. Listening to recordings of how the game is supposed to sound on a real Famicom as well as the Sharp Twin Famicom that I had in my possession, I knew 47k was wrong. So I did 2 47k's in series and it was really close to the recordings and the Twin Famicom (though it sounded better than the Twin due to the filter on the motherboard that softens the audio before output). It now sounds perfect with the real JP Castlevania 3 cartridge.

Sounds like ass with the Everdrive N8, hopefully the N8 audio will be fixed someday both in volume and quality.
« Last Edit: June 05, 2013, 02:03 AM by Redifer »

Offline The_Atomik_Punk!

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Re: Resistor for NES expansion audio mod?
« Reply #2 on: June 05, 2013, 11:12 PM »
Hey Joe, thanks for your insight regarding which caps/values are producing accurate sound with real hardware. I myself am using my NES N8 on my NES frontloader, and am only concerned with adding famicom channels with my N8 configuration (not real carts).

I'm understanding that I don't have to modify my N8, as my 72-pin connector can access the extra channels fine if I solder those caps in series on the NES board? It doesn't matter for someone with my setup, as those channels aren't right now anyways.

I have virtually no understanding of these hardware concepts, but is it possible that Krikzz can "emulate" the increased audio channels in a future update with the existing hardware of the N8 on a NES, i.e no soldering required? I'm aware that the extra channels are not currently emulated properly by the N8, and I'm in no rush myself to have a quick solution for the few games if a feature improvement is on the horizon. I personally prefer almost all of the NES soundtracks of games over their famicom counterparts ( the two Zeldas come to mind in particular). I'm mainly interested in some of those awesome Sunsoft soundtracks, like U-four-ia and Gimmik! that we missed out on.

As an aside Joe, have you tested your mod with any FDS games in your collection? Kid Icarus comes to mind. After checking out all of the regional audio comparisons to see if I've been missing anything, the title screen intro on the FDS Kid Icarus floors me. It utilizes the extra channels to great subtlety,  adding richness and a beautiful counter-point melody that simply cannot be done on the NES- absolutely enchanting: http://www.youtube.com/watch?v=p08wyrAYMrs

That composition has single-handedly convinced me to eventually find a way to access those extra channels. To my ears,  without question the single best example of famicom audio superiority over the NES version.  Castlevania 3 is the example I always hear cited when extolling the benefits of the Famicom audio hardware.  I personally don't prefer the famicom Castelvania 3 audio- while "fuller" (more instrumentation), I find it lacks the dynamics/percussive impact of the NES version, and dilutes the melody with needless complexity. Sounds like a good "tech demo" to me. Your insight would be appreciated, Joe!
« Last Edit: June 05, 2013, 11:39 PM by 3aleksandar3 »

Offline parasyte

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Re: Resistor for NES expansion audio mod?
« Reply #3 on: June 06, 2013, 12:39 AM »
[1][...]I'm understanding that I don't have to modify my N8, as my 72-pin connector can access the extra channels fine if I solder those caps in series on the NES board?[...]
[2]I have virtually no understanding of these hardware concepts, but is it possible that Krikzz can "emulate" the increased audio channels in a future update with the existing hardware of the N8 on a NES, i.e no soldering required? [...]
[3]As an aside Joe, have you tested your mod with any FDS games in your collection?[...]

In order:
1) No caps need be soldered, it's just a simple resistor. You could also use a potentiometer to give you a dial to set the expansion audio just right, even a clicky one if you wanted to get fancy and disable the mod easily. The other option would be to buy an ENIO EXP board, that will plug on the EXP connector of the NES and contains 2x47kOhm resistors already in place. If you have too little resistance on the circuit the EDN8 can switch over to using a lower level output to sound more in line with your console's output.
2) It's not possible. On the Famicom, the cart had an audio in and audio out pin on the connector. The audio would go from 2A02->Cart->Output circuit, so the chip in the cart was responsible for mixing. The NES has no such pins on the connector, so there is no way to get audio from a cart to the audio out without modifying the console.
3) EDN8 FDS audio is known to be inaccurate. It works, but it sounds like ass. I understand the Retrousb powerpak is no better at it. Krikzz has mentioned that he wants to improve 2C33 sound though.

Offline Redifer

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Re: Resistor for NES expansion audio mod?
« Reply #4 on: June 06, 2013, 01:40 AM »
   3aleksandar3, I don't have a Famicom Disk System that I can hook up to my US NES to test the sound. But like Parasyte mentioned, the FDS sound on the Everdrive N8 is inaccurate. Hell, it's barely even there even on the N8's highest volume setting. Hopefully this will be fixed soon.

Offline The_Atomik_Punk!

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Re: Resistor for NES expansion audio mod?
« Reply #5 on: June 06, 2013, 02:30 AM »
Thanks guys for your insight. I'll be waiting for Krikzz to add proper audio support before I proceed with the mod.  I wasn't aware that this feature was never implemented with the Powerpak, hopefully it's not too much of a hassle for Krikzz to improve 2C33 sound.

Offline Tighe

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Re: Resistor for NES expansion audio mod?
« Reply #6 on: October 18, 2015, 07:12 PM »
Correct me if I am wrong, but aren't the same pins on the cartridge connector as is on the expansion slot?  So couldn't the resister be installed on the everdrive instead?

Offline Enzo1960

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Re: Resistor for NES expansion audio mod?
« Reply #7 on: October 22, 2015, 06:08 PM »
I own an EverdriveN8 NES version, and obviously a NES (italian PAL version).
My doubt about audio modification is:
Have it sense since ALL carts with audio expansion are jap Famicom games, that have problems to runs on PAL NES?

Offline Johnny23b

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Re: Resistor for NES expansion audio mod?
« Reply #8 on: October 23, 2015, 12:12 AM »
I own an EverdriveN8 NES version, and obviously a NES (italian PAL version).
My doubt about audio modification is:
Have it sense since ALL carts with audio expansion are jap Famicom games, that have problems to runs on PAL NES?

Rather not, I would buy a NTSC NES or AV Famicom.

Offline Enzo1960

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Re: Resistor for NES expansion audio mod?
« Reply #9 on: July 18, 2016, 06:46 PM »
I correct myself. It has sense. NOW. Because I just modded my PAL NES to NTSC, changing quartz, CPU, PPU, now all Japan and Usa games runs fine, altough in black & white!
But this can be solves with a dual standard (crt) tv...