How to Use C700: Volume and Echo Delay Settings
Now we will cover the section at the bottom of the plugin interface, section C, which mainly concerns global volume and the SNES's built-in echo delay feature. Although the echo delay settings are global, each sample has its own toggle to disable/enable echo delay for that sample. That toggle can be automated on a per-channel basis as well, using MIDI CC#91; read about C700 MIDI CCs here.
Let's dig in! Echo delay, in particular, is one of the most distinct features of this soundchip.
Volume Sliders
The sliders at the bottom left, "Main" and "Echo", affect the global volume output of the plugin – Main governs the "dry" volume of your song while Echo governs the echo delay's volume. The left (L) and right (R) stereo can be controlled separately in both cases. C700 defaults to a Main volume of 64, which can comfortably be raised to the maximum value of 127 in most cases!
You will notice that the range of values also includes negative numbers; negative numbers invert the phase of the waveform (meaning where the wave would go up it instead goes down, and vice versa). If both numbers are negative or positive, this has no practical meaning; however, a positive and negative number (as in our example for Echo, L = 50 while R = -50) will cause sound to be canceled out if played back in a mono setup (in which one speaker mixes L and R into a single audio output). C700 defaults to these values for the Echo volume sliders, so if you want your music to be mono-compatible, make sure to change these values to match one another. Note that there is a timbral difference in the positive-negative echo setting though – in stereo, it will have a wider, "surround-like" effect.
Here's some Echo slider examples to illustrate the difference in sound:
EXAMPLE 1: C700 default echo sliders values (50 and -50):
EXAMPLE 2: Equal echo slider values:
EXAMPLE 3: Example 1 but mixed down to mono (i.e. no delay is heard):
Echo Delay
The whole rest of this pane is devoted to echo delay settings, so let's learn everything there is to learn about this key aspect of the SNES sound. A few parameters can be controlled: Delay Time, or the length of time between delay notes triggering; Feedback, or the volume that gets fed back into the delay to keep the effect going; and Filter, which lets you control the prevalence of a few frequency ranges within the echo delay.
Delay Time
The Delay Time setting, which affects the amount of time between delays occurring, can be controlled in increments of 16ms (milliseconds), ranging from 0ms to 240ms. For example, if set to maximum, the following would occur: [note] - [240 milliseconds] - [first delay note] - [240 milliseconds] - [second delay note], and so on. At a value of only 16ms, the space between delays will be quite low.
Crucially, each increment of 16ms takes up 2KB of your allotted 64KB of space, meaning that the higher you set your Delay Time, the less space you will have for samples (and potentially song data, if you are making .spc rather than .smc). At the maximum setting of 240ms, this effect takes up a whopping 30KB of space!
At the bottom-right of C700, you will see an indication of how much space is being taken up by echo delay, samples, and sound driver. (In the screenshot at the top of the page, it says "12522 bytes", which is about 12.5KB.) Watch the amount change as you move the Delay Time slider. If you exceed 64KB, this indicator will turn red until you've cut back enough size. You may have to restart your DAW as well if you enter the red zone – playback will often sound glitchy after experiencing this.
Interestingly, the 0ms setting does produce additional sound and is not the same as disabling echo delay entirely. It can be used in conjunction with the Filter setting (described below) to provide a sort of EQ boost, though you lose the ability to utilize longer echo delay at the same time by doing this. Below is an isolated example of 0ms Delay Time. In the example, Main volume is set to 0, so only Echo is heard, and exactly one slider from the Filter setting is being raised & lowered at a time.
Feedback
The Feedback setting is a single knob that determines the volume of sound to "feed back" into the echo delay to keep the effect going. In practice this means the higher you turn this knob, the longer the delay will keep occurring. Turning it to maximum will make the delay perpetual, while turning it to 0 will make it so there is exactly one delay and then it stops. Most likely, you will want to choose a space in between.
Note that the available range is -128 to 127, much like the Echo (and Main) sliders. A negative value inverts the phase and slightly alters the sound. Experiment with what sounds best to you on any given song! Be careful of causing a feedback loop with large values; be ready to mute volume.
Filter
The Filter setting (also called the "FIR filter") lets you control how prominent certain frequency ranges are within the echo delay effect. Five sliders are available to control, and by default, all are raised to maximum, meaning the default echo delay will apply fully across all frequencies. On the left is the lowest frequency range; on the right is the highest. Turning one down all the way will remove that frequency range from the echo delay.
Loosely the five sliders correspond to (in Hz) 0k, 4k, 8k, 12k, and 16k (higher Hz = higher pitch). Eight boxes above are also available for value input (-128 to 127), but only use these if you know what you're doing; they control the actual values the SNES uses to determine this stuff, while the sliders offer an easier, more intuitive approach. (You will notice that the sliders affect multiple values when modified.) You may be able to achieve different sounds with value input, but be careful of feedback loops resulting from wonky settings, especially when the sum of values is very negative or very positive.
Generally speaking, you can get away with louder, more intense echo delay if you turn down the highest-frequency sliders, but depending on the sounds you're applying the echo to, it may instead be helpful to turn down the lowest one, clearing away mud in lower frequencies. It is fruitful to experiment with these values on individual songs.
As mentioned above in the "Delay Time" section, if Delay Time is set to 0ms, these sliders can be used as a makeshift EQ setting. Check out the example shown above to hear what each frequency range sounds like.