There is a myth that the AV Famicom is too quiet when it mixes internal audio with external audio. The myth goes that the external cartridge audio drowns out the internal audio from the console and gives an unbalanced and unfair impression of what the programmer intended the music and sound effects to sound like. The conclusion is that an original Famicom, preferably an earlier model, is the ideal way to experience Famicom audio. However, this conclusion is too simplistic and the internal/external mix is not as extreme on standard Nintendo Famicoms and AV Famicoms as one may be led to believe.
Of course Famicom audio has its own problems. The first problem is that genuine Famicom audio is encoded into RF and decoded in a TV. The baseline audio has a buzz and the output of the audio sounds like it was run through an oppressive low-pass filter. The second problem is that playing a Famicom with its RF video and hardwired controllers is something of a chore.
I have made some recordings of several games which use Famicom expansion audio and internal Famicom audio. The games in question are :
Zelda no Densetsu (Famicom Disk System, The Legend of Zelda)
Akumajou Densetsu (Konami VRC6, Castlevania III: Dracula's Curse)
Zelda no Densetsu was being run off a real FDS RAM Adapter and Akumajou Densetsu was run off a real cart.
The AV Famicom is a HVCN-CPU-02 with laser marked 2A03H and 2C02H CPU and PPU. This is a very late AV Famicom. Nintendo stopped manufacturing AV Famicoms in 2003.
The Famicom is a HVC-CPU-07 with 2A03E and 2C02E CPU and PPU. This is a very common Famicom. It has the AV board connected via a ribbon cable, not soldered to the main PCB via the RF shield. Nintendo made this model with revision E and G CPU and PPU chips from 1984 until 1988. In 1988 it switched to the HVC-GPM-0x motherboards, which have the RF shield soldered to both PCBs. These Famicoms tend to have audio like the AV Famicom.
Most of the Famicom Disk System games were released from 1986-1989, so they would tend have been programmed for the older Famicoms. Akumajou Densetsu and Rolling Thunder were released in 1989, so they too may have used the older Famicoms for development and testing. Other games like Lagrange Point (1991) and Gimmick (1992) were released well into the newer Famicom production, so they may have been intended for later systems.
Both consoles are unmodded as far as sound goes.
The AV Famicom is being recorded through a Nintendo-manufactured Stereo AV cable.
The Famicom, set to Japan Channel 2, U.S. Channel 96, is being routed to a VCR via a well-shielded coaxial cable. The VCR then separates the RF into composite video and separate audio. The audio output through the RCA jack is being recorded.
The Famicom/NES internal audio has five channels mixed into a single monaural output, rectangle, rectangle, triangle, noise & PCM. The VRC6 has three audio channels, also mixed into a single monaural output, rectangle, rectangle, sawtooth. The FDS has one wavetable audio channel.
In some clips, the expansion sound is used only for music. In other clips, it is used only for sound effects. In Zelda, the FDS channel is combined with the internal audio for the opening music, but most of the game uses just the internal audio for music. The FDS channel handles many of the sound effects. In Akumajou Densetsu, the three VRC6 channels are used solely for music
Famicom Zelda no Densetsu Level 3 :