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Distributed Volume Control System
This device is intended to use in the multi band audio systems, where power amplifiers are located close to the loudspeakers, to avoid the long acoustic cables. In this case, the interconnection cables between the crossover are long, and many people think that this is better then long speakers cables.
But it is not a good idea to send the attenuate (by the volume regulator) signal through the long wires, even using balanced connection. DVCS will solve this problem, by using electronically, digitally controlled analogue attenuator, which can be controlled remotely. Attenuator is based on MDAC1.
DVCS consists of one Control Module, which can be located at any room point, with 1-2-3-4 Output Modules and corresponding number of Input Modules. Each Input Module is 4 channel attenuator, so the total analogue channels number can be from 4 to 16. The most reasonable configuration is 2x4, i.e. 2 stereo channels with 4 frequency bands.
Output Modules and Input Module connected with the regular Ethernet 4 twisted pairs cable (CAT5) with the standard 8p8c ("RJ-45") connectors. There are two versions - active and passive. the difference is that in active version, Input Modules are "bus powered" from the Central Module. In the passive version, Input Modules are "self-powered".
The distance for active version is limited to 20m by the voltage drop in the cable.
"Crossover" and "Source" on the picture above are not exactly analog source with analog crossover. It can be also a digital source with:
2-channel DAC and analog crossover
DSP-based digital crossover with 8-channel DAC,
PC-based digital crossover with 8-channel DAC.
By the way - the best solution maybe "spitted multichannel DAC", for example two 4-channel DACs, which are located close to amplifiers and speakers, at both sides of the stereo system, and working from the one digital source with DSP or PC based digital crossover. There are some problems to implement this solution, so this will be another story. But - DVCS's control module can be the part of those system.
Volume can be controlled from the front panel or Remote Control Unit. Except the Master Volume control, thew separate volume adjustment for each channel provided. Channels number can be 4, 8, 12 or 16 - 4 channels for each Output+Input modules.
The number of connected output modules are determined automatically at each power up. Control module continuously monitor the Input modules connection (and in passive version - that the Input module is powered). This connection can be done even "on the fly", and the system will set the necessary volume after the module connection.
Control is provided by the rotary encoder and push button at the front panel, also from the Remote Control Unit.
Control Module should be powered from 12VDC power supply. 100mA is required for the passive version, but the active one require additional 400mA for each Output+Input Modules. So for 2x4 system 900mA required.
Output Module is the same for active and passive versions, except that for passive version it might be without the heatsink.
Input Module, active version:
Input Module, passive version:
Input Modules for active and passive versions shares the same PCB but some components are different:
1 We believe that nowadays Multiplying DAC (MDAC) is the best way to make the volume control (we are also believe that volume control in the digital domain is the worst case, due to resolution decreasing). DVCS use 16 bit 4 channel Texas Instrument DAC8814 MDAC.