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High Level
IRIS has seven pairs of main HIGH LEVEL inputs, selected by
Inputs
the seven (oval) KEYS to the right of the phono KEY. All of these
(Oval Key inputs proceed at unity gain to the attenuator/line-amplifier
selected) system, which has a maximum gain of 20dB.
Main Outputs The MAIN output jacks are used to feed the power amplifier.
and
Their low output impedance of 316 ohms allows driving long
Mono switch
cables if necessary.
The usual ground thumbscrew is provided for turntable-frame
grounding via the extra ground wire provided on most turn-
tables.
All of these basically identical inputs are selectable by the input
KEY switches. The KEY switches activate a digital system
which effects audio-signal selection by FET switches, followed
by matched J-FET buffers.
Excepting phono, all input impedances, for the entire preampli-
fier, are in the 15-28k ohms range.
To get you to the basic operation of IRIS as quickly as possible,
we have deferred the discussion of EPL and TAPE loops to a
later section.
The MONO switch effects a passive combining of the stereo
channels into monaural, fed through the attenuator system to
both line amplifiers. Although rarely used today, this switch is
provided for the optimum reproduction of treasured mono
recordings, and can be employed to check for exact system
balance.
It is highly recommended that where you may have a constant
monaural source, such as a mono TV, that you secure a
“Y”
splitter from an electronics store and feed both preamp chan-
nels in parallel. This makes remote operation easier, and
avoids accidentally leaving MONO engaged when you switch
back to a stereo source.