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 amplifier circuit can include an amplifier and a resistor network coupled to the amplifier. The resistor network can include a range resistor coupled in parallel to a resistor string, and one or more switches coupled to the resistor string. The resistor network can be used to calibrate gain and common mode rejection ratio (CMRR) of the amplifier circuit.

Various methods and circuital arrangements for biasing one or more gates of stacked transistors of an amplifier are presented, where the amplifier can have a varying supply voltage that varies according to a control voltage. The control voltage can be related to a desired output power of the amplifier and/or to an envelope signal of an input signal to the amplifier. Particular biasing for selectively controlling the stacked transistors to operate in either a saturation region or a triode region is also presented. Benefits of such controlling, including increased linear response of an output power of the amplifier, are also discussed.

A variable gain amplifier (1) includes: a signal transmission circuit (10, 20) including amplifying transistor units (11.sub.1 to 11.sub.N, and 21.sub.1 to 21.sub.N) connected in parallel between a signal input port (2P, 2N) and a signal output port (3P, 3N); a load circuit (40) connected between a supply line of power supply voltage (VDD) and an output end of the signal transmission circuit (10, 20); a signal short circuit (30) including a short-circuit transistor unit (31) connected between the supply line of the power supply voltage (VDD) and an input end of the signal transmission circuit (10, 20), a constant-current source circuit (42), and a transistor control circuit (46). The transistor control circuit (46) selects transistor units to be turned on, from among the amplifying transistor units (11.sub.1 to 11.sub.N, and 21.sub.1 to 21.sub.N) and the short-circuit transistor unit (31), and supplies control voltages for turning on the selected transistor units.

A variable gain amplifier (1) includes: a signal transmission circuit (10, 20) including amplifying transistor units (11.sub.1 to 11.sub.N, and 21.sub.1 to 21.sub.N) connected in parallel between a signal input port (2P, 2N) and a signal output port (3P, 3N); a load circuit (40) connected between a supply line of power supply voltage (VDD) and an output end of the signal transmission circuit (10, 20); a signal short circuit (30) including a short-circuit transistor unit (31) connected between the supply line of the power supply voltage (VDD) and an input end of the signal transmission circuit (10, 20), a constant-current source circuit (42), and a transistor control circuit (46). The transistor control circuit (46) selects transistor units to be turned on, from among the amplifying transistor units (11.sub.1 to 11.sub.N, and 21.sub.1 to 21.sub.N) and the short-circuit transistor unit (31), and supplies control voltages for turning on the selected transistor units.

An integration unit IU for tuning an OEM sound system augmented with aftermarket components, such as an amplifier or a subwoofer. The integration unit is contained in a small housing that can be installed inconspicuously in most vehicles without removing the original head unit. The unit may comprise a DSP-based active line output converter that is configured to automatically detect the frequency response and phase of the OEM head unit. The unit performs various algorithms to detect and analyze crossovers, EQ, time delay, and allpass filters and then matches left and right audio channels. The IU may allow for low bass correction detecting and defeating the factory high pass filter. Still further, the IU can correct the various filters to ensure a clean, uncolored audio signal for the augmented components.

Embodiments described herein related a moldable mounting wireless speaker system which provides a secure wireless communication link between a set of wireless speakers and a selected host mobile device once a pairing code is established. The system includes a set of wireless speakers, Bluetooth module, processor, and infrared transceiver module enclosed within a hermetically sealed housing and located at each end of a flexible and moldable mounting strip comprised of a plurality of spherical connectors. The system is configured to receive both infrared and radio frequency inputs and convert to a digital signal to initially authenticate the pairing code by attempting to match the pairing code from the host mobile device with a plurality of stored pairing codes within the memory. Once authenticated, a light emitting diode will be illuminated and visible through a translucent portion of the housing to indicate that the secure communication link is established. The user may then secure and bend the system to a variety of objects using the securing grips located around each of the spherical connectors.

Embodiments described herein related a moldable mounting wireless speaker system which provides a secure wireless communication link between a set of wireless speakers and a selected host mobile device once a pairing code is established. The system includes a set of wireless speakers, Bluetooth module, processor, and infrared transceiver module enclosed within a hermetically sealed housing and located at each end of a flexible and moldable mounting strip comprised of a plurality of spherical connectors. The system is configured to receive both infrared and radio frequency inputs and convert to a digital signal to initially authenticate the pairing code by attempting to match the pairing code from the host mobile device with a plurality of stored pairing codes within the memory. Once authenticated, a light emitting diode will be illuminated and visible through a translucent portion of the housing to indicate that the secure communication link is established. The user may then secure and bend the system to a variety of objects using the securing grips located around each of the spherical connectors.

Techniques for optimizing a player based on the addition of a second player are disclosed. In an embodiment, when a first player no longer needs to play certain audio frequencies due to the addition of a second player, the gain of the first player is automatically increased as part of the setup process. In another embodiment, when a first player needs to play certain audio frequencies, for example due to the removal of a second player, the gain of the first player is automatically decreased. Many other embodiments are disclosed.

Techniques for optimizing a player based on the addition of a second player are disclosed. In an embodiment, when a first player no longer needs to play certain audio frequencies due to the addition of a second player, the gain of the first player is automatically increased as part of the setup process. In another embodiment, when a first player needs to play certain audio frequencies, for example due to the removal of a second player, the gain of the first player is automatically decreased. Many other embodiments are disclosed.