Generator dB Slider Dialog

Macros: dB_L, dB_R, dB_Trk

After the mixer has been calibrated, you can select the Use dB option in the Attenuator Options dialog (wide button just below the volume controls on the main Signal Generator dialog). After you do that, the small'Vol' button between the Left and Right volume controls is replaced with 'dB', which you can click to open the dB Slider dialog.

Unlike the Volume dialog, this has only one large pair of sliders with associated edit controls. There is also an additional Track option via 3 radio buttons between the sliders.

The slider operation is dependent upon other settings in the Attenuator Options dialog. If you set the dB Relative / User Units button to 'dB Relative', the edit controls (mirroring the main Generator Volume edit controls) will be in dB relative to maximum output. Values will thus run negative from 0 dB. If you set 'dB User Units' with User Units active, the maximum value will be whatever value you have specified in the User Units Calibration dialog for each Left and Right Output. The slider title and labels will show 'dB' or 'dB:Volt' (or whatever unit you used) accordingly.

If you have loaded a Spkr.CAL file for a channel, and its SPL button is active, then whenever User Units is active the dB slider will be calibrated in SPL units. Without the .CAL file, you can force SPL units by setting the Units Name to "Pa" to enable the SPL button.

When you set Use Level, the Max control below it specifies the maximum amount of attenuation that Level will add. The default value is 96 dB. That amount will likewise extend the range of the slider controls.

The Atten Scroll Step only applies to scrolling the edit controls when Use Level is active; the sliders always use 1 dB steps.

One final consideration regarding Use Level operation: When this is active, a change in volume usually requires Daqarta to compute new waveform levels in order to hit the desired volume exactly. The Stream Level controls don't change visibly, but their effective values are adjusted and the output waveform is recomputed just as though Level had been changed directly.

Sound output is stopped momentarily and restarted from the beginning with the new waveform; it does not just continue where it left off. This causes a discontinuity in the waveform, which results in a click. A single click may not be a problem when entering a value into an edit control, but a whole stream of clicks can be very annoying while moving a slider over any appreciable distance. You can avoid these clicks by leaving Use Level off, and relying upon the native resolution of the mixer hardware.

The Track radio buttons allow two different modes besides Off (which gives normal independent Left and Right operation). Track Equal mode is similar to the single Track mode available in the uncalibrated Volume slider dialog: Any attenuation you set on either channel is set identically on the other.

Track Rel maintains the a constant dB difference between the channels, behaving like an ideal Balance control. To use this mode, first use Track Off to set the two channels independently, such that they have the desired difference between them. Then set Track Rel and that difference will be maintained as you change either attenuator.

There are a couple of points to consider when using Track Rel. Ideally, you should have Use Level active so that Daqarta can create any arbitrary volume in case the attenuators can't hit it exactly. This may entail the clicking behavior noted above.

Also, note that the total control range can't be exceeded. Suppose, for example, that you set Right to be 3 dB louder than Left. If you move Left to -3 dB, then Right will be forced to 0 dB. If you then move Left to -2 dB, Right can't go to +1 dB (in dB Relative mode), so it just remains at 0 dB. Now when you reduce the Left volume, there will only be a 2 dB difference between channels.

A similar situation happens in reverse at the low end of the range. Again, if Right is 3 dB louder than Left, you can't move it any lower than 3 dB from the bottom because Left can't be driven lower than Mute. If you do, then the difference between the channels will necessarily be reduced.

Macro Notes:

Note that the following macro commands assume that Use dB is active. If not, the macro will abort with an error message. To be safe, give a UseCal=dB command before using these.

dB_L=6 sets the Left Generator output to -6 dB. Note that 0 is loudest, and all entered values are assumed negative. (If you enter a sign, it is ignored.) Use dB_R to set the Right Generator output.

Unless Use Level is active, the resultant dB setting will be the closest value allowed by your sound card. (The actual value will be shown.) Different sound cards may have different dB step sizes, and the size is not constant over the whole attenuation range.

If Use Level is active, dB values will be exactly as entered.

Alternatively, db_L=>1 will make the Left Generator output one step louder (less negative) and dB_L=>-1 will make it one step softer (more negative). Unless Use Level is active, these steps will be the smallest steps allowed by your card at that point in its range.

If Use Level is active, the step size is determined by the Scroll Step setting.

dB_Trk=Off sets the Track mode to Off, so the Left and Right dB controls are independent. dB_Trk=Equ sets them to Equal, so changing one causes the other to change to match. dB_Trk=Rel sets Rel so the two channels maintain a constant relative difference. (Or nearly so, if Use Level is not active.)

See also Generator Volume/dB Slider Button, Attenuator Calibration, Signal Generator Control Dialog