Author Topic: Another Expansion Audio question (ED N8[fami] -> adapter -> NESRGB -> Toploader)  (Read 2085 times)

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Offline avramce

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Hi all,

I've researched the topic pretty extensively, feel that I have my system wired up properly, but I do not appear to be getting Expanded Audio out of my Toploader.  Looking for any input or clarification on my setup.

Hardware:
N8 [famicom edition] from StoneAgeGamer
60 -> 72 pin adapter [pulled from a Gyromite cart]
NES Toploader NES-101
NESRGB

My understanding:
Based on https://wiki.nesdev.com/w/index.php/Cartridge_connector - Expanded Audio comes out from pin JP#46 on the N8
The goal is we want to wire JP#46 to the audio out of the NESRGB for the Expanded Audio, so we wire JP#46 to US#51 on the adapter (wire only, no resistor) [We wire to US#51, because US#54 is not connected on the Toploader?]

Now, for the console side modification:
We need to get the input from cart slot pin US#51, and wire it to the audio output through a resistor.  I've seen a wide variety of suggestions, but nesdev was suggesting a middle ground, so I used a 47K.  At the moment, I am collecting CPU pin 1&2 into the NESRGB for mixing, and put it out to the multiout port on my system, so I wired cart pin US#51 to the NESRGB audio out through the 47K resistor.

I've checked all my connections, I have solid conductivity from JP#46 all the way to NESRGB#AudioOut, and I'm seeing a load of 47k from end to end.  I've been testing with Gimmick using the latest RC7 firmware, yet, I'm not getting anything like the audio in this video: https://www.youtube.com/watch?v=CCEm1pcGJNU

Any feedback or suggestions would be greatly appreciated.

Offline avramce

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Well, I played around with it for about an hour, and figured I should report my findings.  So, the main point of my frustration is the desire to use the NESRGB's onboard audio circuit (wiring CPU#1 and CPU#2 to NESRGB#AudioA and NESRGB#AudioB) to take advantage of the built-in Audio Amplifier.  I hooked the US#51 to the NESRGB#AudioOut through a 47K resistor, and was unable to hear any external audio, then I saw a suggestion that I should try a 1.2K resistor instead. 

I wired the US#51 and GND to an audio jack, and confirmed that I am getting External Audio before dropping the resistor value, and after much trial and error, I ended up wiring the US#51 to the NESRGB#AudioOut without any resistor.  Doing so, I can actually get ExternalAudio over my Multiout, but only after cracking the N8's mixer to 200% for VRC6 and Sunsoft's 5B.  My guess is the built-in amplifer has such a high gain that it drowns out the External Audio no matter how I try to mix it.

Going off a post I saw on reddit, I might end up bypassing the audio amplifier in favor of 1uF capacitors like you would see on any standard AV mod.  Depending on the volume witnessed doing that, I'll play it by ear and throw on a resistor between US#51 and the Audio Out and get a good mix.

Offline avramce

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On last follow-up:

So, I just reversed the findings from the trial and error and came up with the bright idea of applying the load of the resistor to the output of the NESRGB#AudioOut and wiring the US#51 directly to the Audio Out on the multiout port.  Doing so, I achieve a mixing level that I am happy with and all mixers on the N8 audio settings can sit happily at 100%.  For what it is worth, I ended up passing the NESRGB#AudioOut through a 1K resistor before mixing it with the external audio.

Forgive the sloppy work, but I'm happy that this install is over and I can finally enjoy some Gimmick or Akumajou Densetsu  :D