Audio processing
An audio processing system has, at an input for receiving a balanced analog audio signal, an analog amplification stage having a first fixed gain and a first dynamic range. The system further includes an analog to digital conversion stage, having a second dynamic range that matches said first dynamic range of the analog amplification stage. A digital gain stage can also be provided to allow user selectable gain.
1 . An audio processing system comprising:
an input for receiving a balanced analog audio signal;
an analog amplification stage having a first dynamic range and a first fixed gain between −11 dB and +10 dB;
an analog to digital conversion stage having a second dynamic range that matches said first dynamic range of the analog amplification stage; and
a switchable attenuation stage between the input and the analog amplification stage, said switchable attenuation stage being switchable between an active state in which a fixed attenuation of an input signal is provided prior to the analog amplification stage and an inactive state in which the switchable attenuation stage provides no additional attenuation of the input signal prior to the analog amplification stage.
2 . The audio processing system as claimed in claim 1 , wherein the first fixed gain of the analog amplification stage is between −5 dB and +7 dB.
3 . The audio processing system as claimed in claim 1 , wherein the first fixed gain of the analog amplification stage is between 4 dB and 5 dB.
4 . The audio processing system as claimed in claim 1 , wherein the first fixed gain of the analog amplification stage is about 4 dB.
5 . The audio processing system as claimed in claim 1 , wherein the analog to digital conversion stage comprises a plurality of analog to digital converters (ADCs), each ADC having a third dynamic range that is lower than the second dynamic range, and wherein an output of the plurality of ADCs is digitally averaged to provide a digital output with the second dynamic range.
6 . The audio processing system as claimed in claim 1 , wherein the analog amplification stage includes:
an analog preamp stage having a second fixed gain; and
an analog attenuator stage having a third fixed gain;
wherein the second fixed gain and third fixed gain combine to provide the first fixed gain.
7 . The audio processing system as claimed in claim 1 , further comprising a digital gain stage configured to modify a digital output of the analog to digital conversion stage and apply a digital gain to the digital output from the analog to digital conversion stage.
8 . The audio processing system as claimed in claim 7 , wherein the digital gain stage is configured to receive a user selected gain level and apply digital gain to the digital output of the analog to digital conversion stage according to the user selected gain level.
9 . The audio processing system as claimed in claim 7 , wherein the digital gain stage is configured to receive a user selected gain level and apply digital gain to the digital output of the analog to digital conversion stage that matches the user selected gain level.
10 . The audio processing system as claimed in claim 7 , wherein the digital gain stage is configured to receive a user selected gain level while operating at an initial digital gain level, and in response to receiving the user selected gain level, to vary a digital gain level applied to the digital output of the analog to digital conversion stage from said initial digital gain level to the user selected gain level.
11 . The audio processing system as claimed in claim 10 , wherein the digital gain stage is configured to vary the digital gain level applied to the digital output of the analog to digital conversion stage from said initial digital gain level to the user selected gain level using any one or more of the following:
predetermined gain steps;
steps determined at least partly on the difference between the user selected gain level and the initial gain level; or
a predetermined variation function.
12 . The audio processing system as claimed in claim 7 , wherein the digital gain stage is configured to receive a dynamically varying user selected gain level and apply digital gain to the digital output of the analog to digital conversion stage that follows the dynamically varying user selected gain level.
13 . The audio processing system as claimed in claim 8 , wherein the digital gain stage includes an input device to receive the user selected gain level.
14 . The audio processing system as claimed in claim 13 , wherein the input device comprises a rotary encoder, one or more buttons, a keyboard, a switch with two or more selectable positions, or a touchscreen adapted to display a gain selection user interface element.
15 . The audio processing system as claimed in claim 7 , wherein the digital gain stage is configured to adjust the digital gain applied to the digital output of the analog to digital conversion stage in steps less than 1 dB.
16 . The audio processing system as claimed in claim 15 , wherein the digital gain stage is configured to adjust the digital gain applied to the digital output of the analog to digital conversion stage in steps more than 0.001 dB.
17 . The audio processing system as claimed in claim 16 , wherein the digital gain stage is configured to adjust the digital gain applied to the digital output of the analog to digital conversion stage in steps smaller than 0.1 dB.
18 . The audio processing system as claimed in claim 17 , wherein the digital gain stage is configured to adjust the digital gain applied to the digital output of the analog to digital conversion stage in steps larger than 0.005 dB.
19 . The audio processing system as claimed in claim 7 , wherein the digital gain stage is configured to adjust the digital gain applied to the digital output of the analog to digital conversion stage in steps at or at about 0.01 dB.
20 . The audio processing system of claim 1 , wherein said input comprises a connector for receiving a connection from a microphone.
21 . The audio processing system as claimed in claim 1 , further comprising a phantom power source connectable between the input and the analog amplification stage to power an input source.
22 . The audio processing system as claimed in claim 1 which comprises at least part of an audio processing system for a channel of a microphone preamplifier.
23 . The audio processing system as claimed in claim 22 which comprises at least part of the audio processing system for a channel of a multichannel microphone preamplifier.
24 . An audio processing device including at least one audio processing system as claimed in claim 1 .
25 . An audio processing device as claimed in claim 24 wherein the audio processing device comprises a preamplifier adapted to receive an analog signal from any one or more of the following: a microphone, musical instrument, signal generator, or audio transducer.
26 . An audio processing device including at a plurality of audio processing systems as claimed in claim 1 , wherein each audio processing system comprises an audio processing channel of the audio processing device.