I had always thought that the problem that cartridge expansion sound (such as the disk system's RAM adapter, the Konami VRC6 and VRC7, and the Namco 163 chips) being too loud was only introduced with the AV Famicom. It turns out that it was introduced earlier with the HVC-CPU-GPM-01 revision of the original Famicom's main PCB. The following video compares Zelda 1's title screen music between several Famicom revisions:
http://nicoviewer.net/sm14264546
Notice the change in relative sound channel volumes after the HVC-CPU-07 revision. According to this page:
http://offgao.blog112.fc2.com/blog-entry-20.html
PCB revision HVC-CPU-07 was used in Famicoms up until 1987, and other blog posts mention that by 1989, revision HVC-CPU-GPM-02 was used, so that expansion sound will be louder for Famicoms produced in 1988 and later. I wonder which one should be considered "correct"? For pre-1988 games, the choice is clear; for later games such as Akumajou Densetsu, not so much.
And I can attest that the Sharp Twin Famicom tends to distort quite easily.
http://nicoviewer.net/sm14264546
Notice the change in relative sound channel volumes after the HVC-CPU-07 revision. According to this page:
http://offgao.blog112.fc2.com/blog-entry-20.html
PCB revision HVC-CPU-07 was used in Famicoms up until 1987, and other blog posts mention that by 1989, revision HVC-CPU-GPM-02 was used, so that expansion sound will be louder for Famicoms produced in 1988 and later. I wonder which one should be considered "correct"? For pre-1988 games, the choice is clear; for later games such as Akumajou Densetsu, not so much.
And I can attest that the Sharp Twin Famicom tends to distort quite easily.