Crest Audio Introduces IPro One and IPro Two Processors

Crest Audio is introducing two new signal processors, the IPro One (mono) & IPro Two (stereo) -The IPro is a 2 space microphone or line input processor that is especially designed to optimize audio signals (low or high impedance) for recording or live applications. There are two balanced inputs, a low impedance XLR and high impedance phono, which can be used simultaneously. Phantom power (+48V), a +6 dB to +56 dB gain adjustment control, a polarity reverse switch, and a 20 dB pad are available to match (and power) whatever low impedance microphone is connected to it. Front and rear XLR input connectors allow the unit to be used on the fly or as part of a permanent install. A tunable (10-350 Hz, 12 dB per octave) low cut filter is online to remove the troublesome low frequency rumble and breath-blast noise that microphones often-encounter. The mic pre-amp is enabled with a switch so it can be turned off if the XLR input is not used. The IPro Two has two mic inputs with pan controls (to set their placement in the stereo image) and a fixed low cut filter. The stereo line input also has a balance control in addition to the other features of the IPro One.

There are two parametric equalizers in the IPro. Each has frequency, bandwidth, and level adjustments. Since a typical use for a parametric ED is to notch out an offending frequency, a deep 24 dB cut, and a 12 dB boost is available on the ]Pro One. (The IPro Two has +15/-15 dB cut and boost, which is more appropriate for stereo uses.) With a bandwidth adjustment of 1 /6 to 2 octaves, gentle or severe alterations can be made.

Each parametric equalizer has its own on/off switch to route the signal around it if it is unused. The second parametric equalizer has an additional feature. It can be moved out from the main signal path into the dynamic section's side-chain path, where it is in series with (after) the side-chain insert jack of the RMS detector. By setting it up in this mode, it can be used to define the frequencies that control the dynamics circuitry (expander, compressor, and limiter).

A key part of the IPro is its dynamics section. Using state of the art THAT Corp. integrated circuits for the voltage controlled amplifier and true RIMS detector, it has very low distortion and noise. Incorporated in the processing is a downward expander, a compressor, and a limiter. Each has an independently adjustable threshold control. The expander and compressor sections also have ratio controls. There is a side-chain insert in the detector path that can be enabled from the front panel. The expander is of soft knee topology, and has a ratio control to allow it to be used as a gentle-slope noise reduction circuit (low ratio), or a gate (high ratio). A threshold LED illuminates when the expander is active. The compressor is also soft knee, but has a more gradual knee action for even smoother transitions. It can be adjusted from no compression (1:1) to limit (infinite:1). The limiter is a compressor with a fixed infinite:1 ratio, a faster knee transition, and an LED to show when it is functioning. All have preset (program dependent) attack and release times. A twelve segment gain reduction meter displays all VCA activity (expander. compressor, and limit) so that control action is easily seen, making adjustments a snap.

Heavy compression will give the perception of darkening the signal, since the low frequency components (which have the most energy) dominate the compressor action. As the signal is compressed, the treble material is reduced at the same ratio as the bass, causing it to lose definition. To compensate for this apparent loss and to add a new sheen to signals which do not have much high frequency content, the SmarTube process was developed. This is a high frequency harmonic generator based on our SmarTube tube simulation circuitry. It adds tunable upper frequency harmonics, and will add pleasing high frequency detail not found in the source. A unique feature of the circuitry is that it behaves as a tube does in its distortion characteristics and is level dependent.

There may be an occasion when certain frequencies must be compressed then added back to the original "dry" signal, similar to using the IPro as one of the bands of a multiband compressor. A blend control was added so that this could be done without having to sacrifice an external mixer channel (if one is available) to accomplish this feat. By compressing the bass and adding it back to the original, a "fatter" sound can be created.A headphone monitoring function with an independent level adjustment is included. This is especially needed when the unit is used as a single channel recording preamp. Its signal is picked up before the main level control, and drives a front panel headphone jack. The main level control sets the Pro's main balanced and unbalanced outputs. It will adjust from "off" to +10 dB of gain. A twelve segment meter monitors either this output or the pre-amp signal, depending on the meter switch setting. The main output has both an unbalanced phone, and a XLR balanced connector on the rear panel.

An additional feature found on the IPro Two is the Track input. This is an external input with its own level control that only feeds the headphone amplifier. It is useful for listening to click tracks (or other previously recorded tracks) while recording, or a separate monitor signal during live performance.The unit is powered by an internal transformer, and has a standard IEC mains connector.