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 miced 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.