Ver. 1.1 - ©Phædrus Audio Ltd. 2011 All rights reserved.
PHI
Application and connections
Simple
DI units utilise a transformer to balance the unbalanced signal and
feed it to the microphone input of your mixer or microphone preamplifier.
This technique
provides a
reasonably high-
impedance as
presented to the instrument; typically a
few tens of thousands of ohms. Adequate
for a keyboard, for example: at a push,
sufficient for a bass guitar. But the tone
of an electric guitar is completely destroyed, unless it drives an impedance hundreds of times
greater than can ever be provided by a transformer. The only answer is to present the instrument
with the very high input impedance, such as it "sees" when plugged into a valve amp' (see
Voicing
and the valve amplifier
section above). This is the role of the Phædrus Audio PHI DI-Box. The dual
valve (tube) stage acts as an impedance-converter, presenting the instrument input with an
impedance of approximately 1MΩ. The output of the unit then feeds the microphone input of your
mixer, computer interface, or your PHAB preamplifier.
The Phædrus Audio PHI DI-Box is connected as shown in the diagrams above. Ensure that the
"LOUDSPEAKER/INSTRUMENT" switch is in the "INSTRUMENT" position. However, note that
feeding the output of the PHI into the studio console will negate some of the benefits of the
PHI’s unique character. Use a premium-quality microphone preamplifier (such as Phædrus Audio’s
PHAB) for the very best resul ts as shown below.
