A power switch 307a is provided between a bias generation circuit 301 and a high potential power source, or a power switch 307b is provided between the bias generation circuit 301 and a low potential power source. A bias potential Vb output from the bias generation circuit 301 is held by a potential holding circuit 300. The bias potential Vb held by the potential holding circuit 300 is input to a bias generation circuit 301a, and a bias potential Vb2 output from the bias generation circuit 301a on which an input signal IN is superimposed is input to an amplifier circuit 302. The potential holding circuit 300 is constituted of a capacitor 306 and a switch 305 formed of, for example, a transistor with a low off-state current that is formed using a wide band gap oxide semiconductor. Structures other than the above structure are claimed.

A novel phantom-powered inline preamplifier is configured to provide selective processing of a sound source signal by intelligently determining the need for a low or high impedance matching and transformer coupling, based on high fidelity requirements of a particular sound source signal. For example, the phantom-powered inline preamplifier can intelligently detect a microphone-originating sound source signal and automatically route the microphone-originating sound source signal to a low impedance matching circuit pathway that leads to a phantom-powered output terminal for an optimal hi-fidelity processing specific to the microphone-originating sound source signal. Likewise, the phantom-powered inline preamplifier can intelligently detect a musical instrument-originating sound source signal and automatically route the musical instrument-originating sound source signal to a high impedance matching circuit pathway and optionally couple to an instrument transformer, which leads to the phantom-powered output terminal for an optimal hi-fidelity processing specific to the musical instrument-originating sound source signal.

A novel phantom-powered inline preamplifier is configured to provide selective processing of a sound source signal by intelligently determining the need for a low or high impedance matching and transformer coupling, based on high fidelity requirements of a particular sound source signal. For example, the phantom-powered inline preamplifier can intelligently detect a microphone-originating sound source signal and automatically route the microphone-originating sound source signal to a low impedance matching circuit pathway that leads to a phantom-powered output terminal for an optimal hi-fidelity processing specific to the microphone-originating sound source signal. Likewise, the phantom-powered inline preamplifier can intelligently detect a musical instrument-originating sound source signal and automatically route the musical instrument-originating sound source signal to a high impedance matching circuit pathway and optionally couple to an instrument transformer, which leads to the phantom-powered output terminal for an optimal hi-fidelity processing specific to the musical instrument-originating sound source signal.

Provided is a preamplifying circuit, including a first amplifier and a second amplifier sequentially connected in series, wherein an output end of the second amplifier is connected to a circuit output end, and an input end of the first amplifier is connected to a circuit input end. The preamplifying circuit further includes a positive feedback branch including a diode group and a third amplifier, wherein one end of the diode group is connected to the input end of the first amplifier. The positive feedback circuit can positively feed part of signals back to the other end of the diode group, so that voltage drops at two ends of the diode group can be reduced, and harmonic distortion caused by nonlinearity of the diode group is reduced. Thus, the sound quality detected by a microphone sensor is improved.

The present invention discloses a bias compensation circuit. The bias compensation circuit includes a detecting circuit, including a diode-connected transistor circuit, with a first end for receiving a first current, and a second end coupled to a first reference voltage end; and a first diode circuit, with a first end for receiving a second current, and a second end coupled to the first reference voltage end; wherein the detecting circuit provides a first voltage level according to the diode-connected transistor circuit, and provides a second voltage level according to the first diode circuit; a voltage-current converting circuit, coupled to the detecting circuit, for generating a first reference current according to the first voltage level and the second voltage level; and a bias circuit, coupled to the voltage-current converting circuit, for receiving the first reference current, to provide a bias voltage level according to the first reference current.

Processes and systems for producing glass fibers having regions devoid of glass using submerged combustion melters, including feeding a vitrifiable feed material into a feed inlet of a melting zone of a melter vessel, and heating the vitrifiable material with at least one burner directing combustion products of an oxidant and a first fuel into the melting zone under a level of the molten material in the zone. One or more of the burners is configured to impart heat and turbulence to the molten material, producing a turbulent molten material comprising a plurality of bubbles suspended in the molten material, the bubbles comprising at least some of the combustion products, and optionally other gas species introduced by the burners. The molten material and bubbles are drawn through a bushing fluidly connected to a forehearth to produce a glass fiber comprising a plurality of interior regions substantially devoid of glass.

Processes and systems for producing glass fibers having regions devoid of glass using submerged combustion melters, including feeding a vitrifiable feed material into a feed inlet of a melting zone of a melter vessel, and heating the vitrifiable material with at least one burner directing combustion products of an oxidant and a first fuel into the melting zone under a level of the molten material in the zone. One or more of the burners is configured to impart heat and turbulence to the molten material, producing a turbulent molten material comprising a plurality of bubbles suspended in the molten material, the bubbles comprising at least some of the combustion products, and optionally other gas species introduced by the burners. The molten material and bubbles are drawn through a bushing fluidly connected to a forehearth to produce a glass fiber comprising a plurality of interior regions substantially devoid of glass.

An example playback device includes a first interface for receiving a first audio signal from a first audio source; a second interface for receiving a second audio signal from a second audio source; and a processor configured to: cause the playback device to playback the second audio signal; determine that the first audio signal is present at the first interface; in response to determining that the first audio signal is present at the first interface, (i) cease playback of the second audio signal being played by the playback device and (ii) cause the playback device to playback the first audio signal; receive an instruction to stop the playback device from playing the first audio signal while the first audio signal is still present at the first interface; and arm the playback device such that a subsequent presence of the first audio signal at the first interface causes the playback device to play the first audio signal.

An example playback device includes a first interface for receiving a first audio signal from a first audio source; a second interface for receiving a second audio signal from a second audio source; and a processor configured to: cause the playback device to playback the second audio signal; determine that the first audio signal is present at the first interface; in response to determining that the first audio signal is present at the first interface, (i) cease playback of the second audio signal being played by the playback device and (ii) cause the playback device to playback the first audio signal; receive an instruction to stop the playback device from playing the first audio signal while the first audio signal is still present at the first interface; and arm the playback device such that a subsequent presence of the first audio signal at the first interface causes the playback device to play the first audio signal.

An amplification circuit includes a filter circuit, an amplifier, a capacitor, a bypass line, and a switch circuit that includes a first FET and a second FET connected in series between one end and the other end of the bypass line, a first resistance element connected in series to a gate of the first FET, and a second resistance element connected in series to a gate of the second FET. A first control signal is supplied to the gate of the first FET. A second control signal is supplied to the gate of the second FET. A product of a gate length and a gate width of the first FET and a resistance value of the first resistance element is smaller than a product of a gate length and a gate width of the second FET and a resistance value of the second resistance element.