• CD-DA can be used as a sound source on the Saturn, but there are some things you need to be careful about when playing CDs.
  First, CD-DA data is always input to SCSP, mixed under the same control as other sounds, and then output, so when playing CD-DA, the mixing balance and localization settings must be adjusted. You have to do it right.

• Please note that if you make a mistake in the settings, the sound may be clipped, distorted, or not output correctly in stereo.

• Basically, CD-DA is handled in exactly the same way as one note of PCM sound source from SCSP's point of view, so if you fully understand the function of "MIXER register", you will avoid mistakes. I think.

• Here I would like to briefly explain how to play CD-DA in stereo.
  The following is the basics for handling SCSP digital mixers, so please read it if you are working with SCSP.

• The path from when CD-DA is input to SCSP until it is output is shown in Figure 3.1 , so we will explain it based on that.

Figure 3.1 CD-DA pathway

• As shown in Figure 3.1, CD-DA first undergoes output level control, then panning (localization between LR) processing, and then mixing processing with other sound sources (PCM/FM sound with built-in SCSP). are received and combined into a stereo output.
  Finally, the output level is controlled by MVOL (master volume), and the signal is output.

• There are five registers that must be set to output CD-DA.

  First, "EFSDL16/17" to balance the level between each sound source, "EFPAN16/17" to specify the localization of each sound source, and finally "MVOL" to adjust the output level.

• ~The register named SDL is a register that adjusts the level balance of each sound, and is similar to a slide fader on a mixer.

• Volume control in SCSP is basically a damping adjustment type. Attenuation adjustment type is a method in which the volume is adjusted to reduce the volume when balancing with other sound sources.

  The reason for using this method is that the Saturn is not equipped with an amplifier, so it is not possible to increase the volume, so if you cannot adjust the dynamic range to be as wide as possible, the volume will be very low. This is because it will happen.

• ~The register named PAN is a register that adjusts the localization of each sound, and is equivalent to a panpot in a mixer.

• The panpot can be set in 31 steps between left and right.

• This register is used to adjust not only the CD-DA but also all Saturn sound output levels. (4-bit configuration)

• If you set this register value to "0H", no sound will be output at all, so if you want to output sound, be sure to set it to a value other than "0H".
  Normally, set it to “FH” (= 0 [dB] = no attenuation = maximum volume).

• Based on the above, I would like to explain the settings for outputting CD-DA.

• First, set the CD output level.

  If only the CD-DA is outputting sound, there is no other sound to mix, so the level can be set to 0 [dB], so set EFSDL16/17 to "7H".

  If you want to play other sounds, lower the level to avoid overflow. (Incidentally, decreasing the value will decrease the volume.)

• Next, set the panpot (stereo position).

  What you need to be careful about when outputting CD-DA is that when it comes to CD-DA, it is divided into LR (left and right channels) and input to SCSP, but on the SCSP side, the sound is the same as the PCM sound source / FM sound source. Therefore, if you do not set the panning correctly so that the L channel side is L and the R channel side is R, it may not actually be output in stereo even if the CD-DA is stereo. I'll put it away.

  Therefore, set "1FH" to "EFPAN16" and "0FH" to "EFPAN17". (Please refer to the "Mixer" section below for data regarding the stereo position relative to the register settings.

• Next, set the master volume (“MVOL”).

  This is the final stage master volume, so for now, set it to the maximum volume, "FH."

  A summary of the settings so far is shown in Table 3.1 below.

• With the above settings, you will be able to output CD-DA.

However, if you want to make it monaural, please set the EFSDL value to one smaller than the value for stereo settings.