Based on the Portico 5017 Mobile Pre, the Rupert Neve Designs 517 provides world-class, transformer-coupled preamp, compressor, and DI circuitry, with Vari-phase, Silk and DI/mic blending capabilities in a 500 series model.
 
As the first 500 series module designed by Mr. Rupert Neve, the 517 incorporates outstanding sonic quality with an indispensable feature set.
 
Mic Pre and Instrument Amplifier
The 517's mic pre includes 66dB gain, and is based on the Portico 5017 design. The mic pre also incorporates a polarity reverse switch and phantom power. The separate instrument amplifier includes 30dB of gain, a ground lift, variable phase and an instrument Thru connection.
 
Blended Use
Used as a single channel device for instruments, the 517 can be used to phase align, combine and compress direct and amplified signals. To achieve this, use the DI for the instrument's direct signal and the mic preamp for the speaker cabinet signal. The blend control is used for mixing direct and amplified signals to achieve the desired tonal blend between the two sources, and the variphase is used to minimize or extenuate phase cancellations between the two signals. To compress the blended signal, the internal compressor jumper must be set to the blend path (this is the default setting). This technique could also be used to create a single, mixed output of a guitar and vocals.
 
The Compressor
Based around a new LDR (light dependent resister) design, the 517?s opto-coupler compressor has been simplified to a single threshold control with auto make up gain. By default, the compressor is set to a fixed 2:1 ratio with fixed attack and release. To set the compressor, simply dial the threshold control down until the desired amount of compression is achieved. An LED light indicates when the compressor is active.
 
Vari-Phase
In addition to the standard polarity reverse, the 517's vari-phase control may be used to adjust phase incrementally. This control is useful any time two signals derived from the same source are combined.For instance, even with careful placement, the combination of close miced drums and overheads, can often yield hollow sounding results. By using the variable phase adjust, the direct signal can be phase rotated until the signals are naturally aligned.This technique is also extremely useful when combined with the internal blend control on instruments. A bassist, using both direct and miked signals can blend the two into a single output, using the vari-phase to reach an optimal alignment. By adjusting the phase in the 517, the musician or engineer can find the absolute best mic position without regard to the phase relation to the direct signal.
 
Silk
Much could be written about this feature, suffice to say, that it gives a subtle option to enhance sound quality in the direction of vintage modules. The silk button reduces negative feedback and adjusts the frequency spectrum to provide a very sweet and musical performance. Try it and make your own judgment.
 
The Features
Gain - 0 - 66dB in 6dB increments
Compressor - Single-knob opto-coupler compressor with 2:1 ratio
Blend - Determines balance of mic and DI inputs
Instrument gain - 0 - 30dB on instrument input
Phantom power - 48V
Silk - Adds nostalgic warmth and presence when engaged
Instrument input - Front-panel TRS input and passive-through for Hi-Z sources
Threshold - When signals exceed threshold level, gain is reduced at a controlled 2:1 ratio with fixed attack and release time constants
Indicators - Signal presence and clipping on both mic and DI signals, as well as compressor activation.
 
The Specs
Frequency Response - Main Output, no load, -0.2dB @ 10Hz -3dB @ 160kHz
Noise measured at main output, unweighted, 22Hz - 22kHz, terminated 150 ohm: Gain at unity - better than -100dBu; gain at 66dB: better than -62dBu EquivalentInput Noise - better than -128dBu, noise factor 1.5dB
Maximum output level from 20Hz to 40kHz - +23dBu
Total Harmonic Distortion and Noise - @ 1kHz, +20 dBu output 
Main Output - Better than 0.001% @ 20Hz, +20 dBu output
Main Output - Better than 0.002%
Silk Engaged - Better than 0.2% Second harmonic
Crosstalk - Measured channel to channel: Better than -90dB @ 15kHz.
Phantom Power - +48 Volts DC +/- 1%