Netmux audio breakout

Roger will have a new replacement by the end of 2010, to be named Harry. Harry will do pretty much what Roger did, but will have newer chips, and some nice added features. BAsically, Hrry's job will be to convert any "finished" audio source, i.e. vidserv, sound desk to whatever they are needed as somewhere else, like vidserv, stream, and Desk. So, a format convertor.

Input Sources

Source	Stereo?	Balenced?	Level	Adjustable?
Vidserv	Yes	No	-10dBV	Yes
Analogue Tuner	Yes	No	1V	No
Digital Tuner	Yes	No	1V or -10dBV	No or Yes
Sound Desk	Yes	Yes	+4dBu	No*
No	No	?	No

By adjustable Rihard meant whether there is a control that can be used to vary the signal level. The sound desk is not adjustable because the meters on the output show a fixed reading for a given signal level, and we always mix to the same point on the meters. It doesn't actually matter because the sound desk will be the reference level to align all the other sources to anyway.

Processing

These are the connections to other pieces of equipment hidden behind the breakout box, which are used to control and process the audio. Mux connections

Practically the whole point of this box being here.

Net Mux inputs are balenced, on 25pin D connectors and do not have individual level controls

Net Mux outputs are balenced assuming the inputs are, buffered (to give two outputs) and have "Master" level control potentiometers.

Question: Do unused inputs get shorted to ground? Answer Richard thought not; otherwise vidserv loopthrough wouldn't work, but he was not sure. We'd have to check this.

Compressor Connections

We currently use one channel of a dual channel compressor to compress everything. Logically using one channel to compress 'stream' and the other to compress 'net' makes sense, since they would potentially have different sources in the future.

Compressor inputs can be balenced or unbalenced, the outputs are balenced and will drive unbalenced, and the whole device can be switched between -10dBV and +4dBu levels (affects inputs and outputs). There is also an output level control on the front panel.

Outputs Loop-through outputs

Unaltered (buffered) outputs

Signal	Destination	Stereo?	Balenced?	Adjustable?
Vidserv	Sound Desk	Yes	Yes	Yes
Analogue Tuner	Sound Desk	No	Yes	Yes
Digital Tuner	Sound Desk	No	Yes	Yes
Spare / OB	Sound Desk	No	Yes	Yes
Sound Desk	Control Room Amp	Yes	No	No

Outputs are marked as Balenced if they are capable of accepting balenced signals (they obviously can take unbalenced as well), and Adjustable if they have a trim control to compensate for the level of the input signal. Tuners are shown as Mono because they are only on the sound desk as a conveience, and have historically been mono.

Main Outputs

These carry the output signals from the Mux, and are controlled by the mux settings

Signal	Destination	Stereo?	Balenced?	Adjustable?
Net Sound	Network	No	Yes	Yes
Net Sound	Local TVs	No	No	Yes
Net Sound	Control Room Amp	Yes	No	No
Net Sound	Campus Stream	No	No	No
Net Sound	Net audio VU	No	No	Yes
Stream Sound	Stream	No	No	No
Stream Sound	Control Room Amp	Yes	No	No
Stream Sound	Stream audio VU	No	No	Yes

Outputs marked Stereo are not truly stereo, but have stereo inputs so both channels need to be driven, preferably without special splitter cables. Campus Stream and Stream Sound to Control Room Amp are included for future flexibility, and the two VU outputs are so we can put VU bargraphs alongside the monitors on the rack. They are classed as "adjustable" because they don't need their own level control pots on the breakout, we can fit trimmers on the VU meters to set up the 0dB level to match our desired ouput level to network.

Block Diagram

apparently, one used to exist, but has been lost over time. The whole thing will probably change anyway.

Circuit Details

Text description, will hopefully also have pictures from the old website.

Parts List

Also probably horrendously out of date, we probably have most of it anyway as remnants from what was bought ~2006.

Power Supply

I have no idea what box this is referring to, maybe we never bought it. I'm considering a PC PSU, since they have +/- 12V, instead of the 15V suggested, and making suitable alterations to the circuitry. The only problems with this are that the output voltages won't be adjustable for fine adjustment. Also, the motherboards wouldn't use as high a current on the -12V rail as on the +12V rail, so the + and - 12V won't be symmetric.

Wiring Details

Tables straight from the old website, probably needs comparing during the holdiay with Net Mux inputs/Outputs just in case it's been changed.