Universal Audio Apollo - Manual (Page 9)

Apollo Hardware Manual Front Panel 9
Front Panel
This section describes the features and functionality of all controls and visual elements on the Apollo front
panel. Note that all front panel functions, except the headphone volume knobs and power switch, can be
controlled remotely with the Console software application.
(1) Hi-Z Inputs 1 & 2
The Hi-Z (high impedance) JFET direct inputs are for connecting low-level passive devices such as electric
guitar and bass instruments into channels 1 & 2 for A/D conversion. Connect only ¼” unbalanced TS phone
plugs to these inputs; TRS plugs cannot be used.
The Hi-Z inputs have an ultra-high input impedance of 2.2 Megohms that eliminates impedance loading,
preserving the high-frequency content of signals from sources with high impedance outputs (such as electric
guitar pickups). Hi-Z input gain levels are adjusted with the Preamp control for the associated channel.
Automatic Input Detection
Hi-Z inputs 1 & 2 use the same A/D converter channels as the corresponding Mic 1 & 2 and Line 1 & 2 inputs.
When a device is plugged into a Hi-Z input, the Mic and Line inputs for the channel are overridden, the Mic/Line
switch for the channel has no effect, and the stereo link is severed (if active). To use Mic or Line inputs 1 or 2,
its corresponding Hi-Z input must be disconnected.
(2) Preamp Gain & Channel Select Knob
This “endless” rotary encoder with integrated pushbutton serves two functions. Rotating the knob adjusts the
preamp gain for the selected input channel, and pushing the knob selects which preamp channel (1 – 4) is
affected by the front panel preamp controls.
Preamp Gain
The preamp gain of analog inputs 1 – 4 is adjusted with this control. The channel to be adjusted (1 – 4) is set
with the Channel Select function. The input to be adjusted (Mic, Line, or Hi-Z) is determined by the state of the
channel’s Mic/Line switch or Hi-Z input (if connected).
Rotating the knob clockwise increases the preamp gain for the selected channel. The available gain range for
preamp channels 1 – 4 is 10 dB to 65 dB for the Mic, Line, and Hi-Z inputs.
The response of the Preamp Gain Knob is not linear; it takes more than a full revolution of the control to move
through the available range. This increases the control resolution for more precise preamp gain adjustments.
Only analog inputs 1 – 4 have input gain adjustment via the mic preamp controls. To adjust signal levels for
inputs 5 – 18, use the output level controls of the devices that are connected to those inputs.
Channel Select
Pushing the Preamp Knob changes the currently selected channel, which determines which input (1 – 4) is
adjusted by the front panel preamp controls. A channel is selected for adjustment when its Channel Select
Indicator LED (located above the channel 1 – 4 input meters; see #11 on page 11) is illuminated.