Daqarta for DOS Contents
StGen (STIM3) Stimulus:
OPL3 Synthesizer Stimulus:
Stimulus source is set to StGen for use with the STIM3 Stimulus Generator. Output Left corresponds to STIM3 DAC 0, and Right corresponds to DAC 1.
NOTE that if you are using SB16 with STIM3A, the STIM3A Output dB control takes over to allow 0.01 dB resolution over the entire SB16 attenuator range. The SB16 control is then readout-only, showing the portion of the total attenuation due to the SB16 alone.
Both controls are in dB below maximum output. Note that the maximum output on some models may be set by a thumbwheel on the back of the board. (See the Synth Level section for more information and cautions on setting the thumbwheel.)
All values other than zero are negative, but you don't need to include the minus sign when entering them directly... Daqarta will supply it automatically since there can be no values above zero.
When adjusting the output levels with the cursor keys, the up-arrow gives more output, which means the dB values become smaller (less negative).
Attempting to set a value below 120 dB (84 dB for CT417x ViBRA / WavEffects models) changes the level display to OFF and gives a much greater attenuation. The actual leakage in this state has not been measured.
The resolution of the output level controls is 2.0 dB for all models except the CT417x ViBRA / WavEffects, which use 1.5 dB steps. The step size has been found to be quite accurate. (Note that this resolution is not quite as good as that for the OPL3 synthesizer, which has an additional control in the OPL3 itself.)
In general, you should always use these output controls and leave the level controls in the STIM3 DAC submenu set to 100% wherever possible. That will insure that the stimulus has minimum distortion and maximum dynamic range. However, if you need finer resolution than 2 dB, use the STIM3 controls only to provide the difference.
For example, to create a stimulus with a level of -13.4 dB, set -12 dB here and set an equivalent -1.4 dB with the STIM3 Level control. That value turns out to be 85.1%, as tabulated in the Attenuation vs Level table in the STIM3 Help system.
Consider using Key Macros to simplify setting these uneven values.
The actual output level is greater from the Spkr output than the Line output, typically by a factor of x4 or x5. Your card may have separate outputs, or there may be a pair of jumpers to change between Spkr and Line. (See your manual.)
For CT417x ViBRA / WavEffects models, note that the DAC output is actually about 12 dB greater than the Synth output for equivalent attenuation values. You may be able to boost the synth levels by 6 dB via the O:V parameter.
OPL3 synthesizer. Note, however, that the OPL3 uses a fixed sample rate of 49.7 kHz, while the DACs must use the same rate as the ADC (45.39 kHz maximum). Just like the OPL3 outputs, the DACs are subject to modulation artifacts that result from interactions between the stimulus frequency and the sample rate.
This low frequency modulation of the stimulus is worse at higher frequencies, but typically does not become evident (as observed on an external analog oscilloscope) until the stimulus frequency approaches about 40% of the sample rate, which is 80% of the full X-axis (Nyquist) frequency.
Thus if you operate with a sample rate of 40 kHz, you will need to use special caution with stimulus frequencies above about 16 kHz. There is also an overall DAC frequency response that rolls off the highest and lowest frequencies, independent of sample rate, but at 16 kHz the output is only reduced by about 1.3 dB. The modulation artifacts will thus usually be of greater concern.
Note that you can NOT rely on Daqarta to view the modulation artifacts, since there are also analogous sampling artifacts (aliasing) associated with input digitization. The combination of both of these makes the sampled output look much worse than it really is.
Use the Line Output on your card for best response at high frequencies. This may be a separate output on some models, while on others it is obtained by setting a pair of jumpers for the single output jack.
duplex mode... it's not a control, and you can't move the cursor to this item. The DAC Bits setting is determined at start-up from the SB16.ADC configuration line (either by default to 8 bits or via the B: parameter), and used in initializing the STIM3 Stimulus Generator data formats. Since STIM3 does not allow the output format to change during operation, the DAC Bits item is for information only.
Remember that ADC and DAC bits are always opposite for most models from the SB16/32/64 families: If ADC Bits is set to 16 (the default), then DAC Bits will be 8 the same as if you had set B:D8, whereas setting ADC bits to 8 with B:8 will cause DAC Bits to be 16. Conversely, setting B:D16 will force ADC Bits to 8.
However, for CT417x ViBRA / WavEffects models, the ADC and DAC bits are independent: Setting DAC Bits via B:D16 does not affect the ADC default of 16, and you can toggle ADC Bits between 16 and 8 during operation regardless of the DAC Bits setting.
But it can produce low- to mid-frequency audio sine waves at least as good as a laboratory function generator (about 1% distortion or -40 dB), suitable for many experiments. (One SB16 was found to be only 0.1% or -60 dB.) And although it wasn't designed to do so, it can act as a very good source of pulsed or continuous random noise... which is actually very hard to obtain otherwise, and which can't be made at all with a wavetable!
Sound Blaster 16 output is AC coupled, which means that it has a series capacitor to block internal DC voltages. The output must drive a resistive load in order to allow the capacitor to charge properly.
channels. If neither individual channel is active, this will have no effect. To produce an output sound, you must set this to On, set the appropriate channel Output to On, Burst, or Gap, and set the desired Level for that channel.
This operates the same OPL3 internal gating circuits used by the individual channels, which means that setting this to Off can attenuate the output signal by only about 68 dB below that channel's Level setting. If you need more attenuation, set the individual channel Level controls to Off as well.
The positions on the left or right side of the option text indicates which output receives the channel. Where only one position is in use, only that side's output is active.
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