6 - Sample Edit

Parametric Equalizer

O The Start and End points	Parametric Equalizer
	Parametric EQ allows you adjust the individual parameters of the filter.
are “remembered” from module	Boost/Cut controls “how much” of the signal will be boosted or cut. Center
to module so that you can	Frequency sets the center frequency to be boosted or cut, and the
perform successive operations	Bandwidth control sets the width of the band to be boosted or cut. The
on the same section of the	three parameters are diagrammed on the following page.
sample.	The parametric equalizer is a digital (non real-time) equivalent of an analog
	equalizer with +12 dB of boost and a whopping -48 dB of cut. Center
	frequency and bandwidth controls are accurate, precise and have an excep-
	tionally wide range.

OThe left and right cursor v To Filter a Sample:

	buttons will change the start	1.	Press the Sample Edit key. The LED illuminates and the main sample
	and end points so that they fall
			edit screen appears.
	on positive zero-crossing points
		2.	Select the sample that you want to equalize using the Data Entry
	in the waveform. This will
	minimize clicks in the sound		Control, INC/DEC keys, or the numeric keypad.
	when processing only part of a	3.	Press the Tools 3 function key (F4). Another row of function keys
	sample.		appears.
		4. Press the ParEQ function key (F3). The following screen appears.

OIf the sample is stereo, a • The Select Section display controls are identical to the controls in

pop up dialog box will ask you	Truncate. See Truncate for a full description of the controls.
to select left, right or both sides.	5. Specify the Start and End points for the portion of the sample to be
	EQ'ed using the Data Entry Control, left/right cursor keys, INC/DEC
O Holding down the Enter	keys or the numeric keypad.
	6. Press OK to continue on to the next page of options or Cancel to cancel
key while turning the Data Entry	the operation.
Control allows “fine tuning” of
the value by one number per
click.

EOS 4.0 Software Manual 225

6 - Sample Edit

Parametric Equalizer

O A standard analog parametric equalizer may be useful in order to locate the frequencies which need EQ. The digital EQ can then be used to actually filter the sample with ultra-low noise and phase linear response.

If you pressed OK, the parametric equalizer parameters are displayed.

+12 dB	Freq.
	Boost

Amplitude	Bandwidth
	0 dB
	Cut
	-48 dB

Frequency

•Gain: Controls “how much” boost or cut will be applied to the signal.

•Center Frequency: Selects the center frequency to be boosted or cut.

•Bandwidth: Sets the width of the band to be boosted or cut.

7.Specify the parametric equalizer parameters using the Data Entry Control or the INC/DEC keys.

•Coarse/Fine: Fast forward through the values using Coarse, then switch to Fine for single digit editing.

8.Press OK to process the sample section or Cancel to cancel the operation.

226 E-MU Systems

6 - Sample Edit

FIR (Phase Linear Filter)

O Holding down the Enter key while turning the Data Entry Control allows “fine tuning” of the value by one number per click.

FIR (Phase Linear Filter)

The phase linear filter was originally developed on the EIII to separate the attack and sustain portions of piano samples. Ordinary filters cause serious phase distortion at the cutoff point. This FIR filter has much less phase distortion than a typical filter and so is better suited for sample splicing. The phase linear filter acts on the ENTIRE sample, unlike the parametric filter which can filter any portion of the sample. This ensures strict phaselinearity. There are five types of phase linear filters available: Lowpass,

Highpass, Bandpass, Allpass and Notch.

The Points parameter determines the Quality or Q of the filter. The larger the Point value, the more the filter behaves like an ideal filter and the steeper the filter slope. The Points parameter is variable from 5 to 99.

The Frequency parameter determines the cutoff frequency of the filter and is calibrated in Hertz. When Bandpass or Notch filters are selected, a second frequency field appears to allow you to specify the frequencies on either side of the passband or notch.

The Allpass filter is a special purpose filter that is used to add delay to a sample before it is recombined with a filtered sample. Recombining allows you to perform band-splitting or frequency boosting instead of frequency attenuation.

v To Filter a Sample:

1.Press the Sample Edit key. The LED illuminates and the main sample edit screen appears.

2.Select the sample that you want to equalize using the Data Entry Control, INC/DEC keys, or the numeric keypad.

3.Press the Tools 3 function key (F4). Another row of function keys appears.

4.Press the FIR function key (F4). The following screen appears.

5.Select the filter Type: Lowpass, Highpass, bandpass, Notch or Allpass.

6.Set the filter slope by adjusting the Points parameter. The higher the number, the steeper the filter slope.

7.Set the Frequency parameter to the desired frequency. If you chose the Bandpass or Notch filters, the Frequency 2 field will appear, allowing you to set the lower frequency in the range.

8.Press OK to filter the sample or Cancel to cancel the operation.

EOS 4.0 Software Manual 227

6 - Sample Edit

FIR (Phase Linear Filter)

• Alternate Filter Responses

Low Shelving Boost - Add Lowpass with original signal.

High Shelving Boost - Add Highpass with original signal.

Band Boost - Add Bandpass with original signal.

	+20dB
	+10dB				Filter Size and Slope
	0dB
Attenuation	-10dB							5 points
	-20dB
			99 points
	-30dB
	-40dB
	-50dB
	-60dB
	-70dB
	-80dB
	0	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9	1
				Frequency			(rad x pi)

This chart shows the relationship between the filter Points and Slope.

The Allpass filter can be used to achieve complex formants, notches or frequency boosts by copying, filtering and adding the original sample to the filtered version. When adding filtered signals with the FIR, each signal must be processed through the same number of points to preserve phaselinearity. The diagram below shows the incorrect and correct ways to add signals together.

	Creating a Low Frequency Boost EQ
Sample	Low Pass
	50 Pts.
	Sum
Copy of	Signals Add
Sample	Out of Phase

Sample	Low Pass	Sum
	50 Pts.

	Copy of	All Pass
	Sample
		50 Pts.

Signals Add

In Phase

The signal is passed through the Phase-linear filter and recombined with the original signal to create a low frequency boost. Because of the filtering, the two signals are now out of phase. The Allpass filter, set to the same point size, is used to correct the problem.

228 E-MU Systems