Thermionic Culture Snow Petrel, Operating Manual

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Thermionic Culture Ltd, October 2019 5
3 Controls
3.1 Pad
A 20dB attenuator before the input transformer.
3.2 Input Z
Switches the input transformer from 850Ω to 2400Ω to suit
different microphones. If the Pad is used, switch to Hi.
3.3 Gain
Changes the gain of the main amplifier. Figures on front
panel are correct if Input Z is set to Lo, a low impedance
source is used, and the output feeds a 10kΩ load with no
attenuation. If input Z is set to Hi, there will be a reduction in
gain of around 6dB, depending on the microphone
impedance.
3.4 HPF
This is a 6dB/octave roll-off designed to reduce proximity
effect, being 3dB down at selected frequencies.
3.5 Air
When set to 10 will give a lift of 5dB at 10kHz, peaking at
22kHz.
3.6 O/P Trim
Reduces the output of the input stages by up to10dB. Note:
the figures on the front panel do not represent dB reduction
except 0 and 10.