PLParEQ is a 10-band Phase-Linear Parametric Equalizer of the highest quality. Each filter may assume any of many different filter characteristics, and operate in either traditional phase-warping mode, or our phase-linear mode. It uses the same internal DSP core as all of our other high-end products. Audio streams are treated in either stereo or mono. Individual filters can be applied to either or both stereo channels, middle only, or side only.

Phase Linear Operation is achieved by processing your sound in both the forward-time and reverse-time directions through classic filters - all in realtime. This completely removes the phase warping caused by IIR filtering, and applies their roll-off twice. So each filter type becomes two: one for classic IIR filtering, and the other for Phase-Linear operation.

This PC VST plugin can operate in traditional 32-bit mode (24-bit audio) or as a 64-bit plugin for Cakewalk's new Sonar 5. All internal processing is carried out in double-precision 64-bit floating point, regardless of external host mode.

For audio streams at sample rates below 80 kHz the DSP engine internally upsamples with high-quality Sinc interpolation, applies its filtering, and then downsamples back to your system sample rate.

You can run all of the filters at native sample rates higher than 80 kHz, and forego the internal upsampling conversions. Upper limits on the sample rate (> 96 kHz) are dicted primarily by your computer's capacity, and your need for high quality at the very lowest frequencies (below 100 Hz).

Individual filters can be operated as either traditional phase-warping, or phase-linear. Our algorithms employ blocked processing for phase-linear operation, and produce phase linearity by sending the signal through each filter twice - once in the forward time direction, and then again in the time reversed direction, thereby unwinding the phase back to zero.

The blocks are reassembled using very high-quality windowing and 8-fold temporal overlap. IMD resulting from phase-linear operation has been measured at below -150 dB from peak signal levels. Corner frequencies for filters can be adjusted from 10 Hz to 30 kHz at all sample rates.

Computation proceeds in double-precision floating point throughout the entire DSP core. At the last stage of conversion back to 24-bit audio, we dither with a carefully crafted white-Gaussian dither from our internal 64-bit samples to the 24-bit mantissas utilized thorughout by VST hosts. Our noise floor is typically measured at around -180 dB/Root(Hz). The Gaussian dither distribution is provably more preserving than commonly used triangular distributions.

Our tests indicate that PLParEQ requires about 5-6% of our computer speed capacity, with each additional filter enabled requiring an additional 0.5-1% at the highest quality levels. These tests were performed on a 3 GHz Pentium-4 computer with HyperThreading enabled. Different VST hosts will show varying requirements. Our tests were performed with Mackie's Tracktion 2 as the VST host. Performance on a more modern Pentium IV are likely to show improvements upon these results.