~ :: using the dpcm channel :: ~

NT2 uses instruments, similar to .XI instruments in how several samples can be loaded into one instrument. You'll need to have 5 samples (with each one 1 half-tone higher than the one before it) of the same sound if you want to have a usable frequency range from one sample.

There is no instrument file saving, so the best way to save your instruments is to save them in a blank .NED.

The NES's DPCM frequency control is only 4-bits (yeesh). If sample #1 is a C note, then you should set sample #1's frequency value for C-2 (or any other octave) to $C in the sample editor. Now things start to get weird. Set E-2 to $D, G-2 to $E, and C-3 to $F (all of them using sample #1). This is where the half-tone higher samples come in, and if you understood what I was just talking about then you can probably see the pattern that you'll need to follow. This technique should work fine, as long as sample #1 plays a C note when the frequency value is $C. It's not known if Nintendo designed certain values to be notes, or if it's just blind luck that they are.

Here's some diagrams to explain NT2's DPCM instrument interface. This example covers a 5-sample melodic instrument (with sequential half-tone advancements by each succeeding sample # explained above), so pay special attention to this specific note-table scheme if you plan to utilize such instruments in your NED's:

Sample frequency:

Playback speed:

0

C-8

1

D-8

2

E-8

3

F-8

4

G-8

5

A-8

6

B-8

7

C-9

8

D-9

9

F-9

A

G-9

B

A-9

C

C-10

D

E-10

E

G-10

F

C-11

Remember that any instrument settings you set for normal instruments will have no effect on the DPCM channel. Effects such as volume and pitch slides, etc. can't be done with the NES's DMA method of using samples. They are stored in ROM, and are played as-is. The maximum amount of sample data you can use without bankswitching is 16378 bytes. It wouldn't be too hard to write the code to do bankswitching to get more, but would depend on how the samples were arranged. Contact Memblers if you're wanting to try something like this.

Also, due to the filtering on the NES's sound the PCM channel is significantly quieter and cleaner sounding than most emulators to date. On a real NES, if the pulse channels are too loud, they can easily drown out the PCM samples. Personally, when I use samples I keep my pulse channel volumes below 8 because of this.

Return to tips menu...