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
This is the old parts list.
| Item | Supplier | Part Number | Quantity | Price | Total |
|---|---|---|---|---|---|
| TL081 Dual Op-amp | Rapid | 82-0064 | 20 | 0.17 | 3.40 |
| 8-Pin IC Socket | Rapid | 22-0150 | 20 | 0.014 | 0.28 |
| 100nF Ceramic Capacitor | Rapid | 08-0235 | 20 | 0.014 | 0.28 |
| Dual Gang 10k Log Pot | Rapid | 65-1460 | 3 | 0.93 | 2.79 |
| Single Gang 10k Log Pot | Rapid | 65-1424 | 5 | 0.43 | 2.15 |
| 15mm Black Knobs | Rapid | 32-0270 | 8 | 0.125 | 1.00 |
| Veroboard 95x432mm | Rapid | 34-0535 | 1 | 2.40 | 2.40 |
| XLR Female (panel) | CPC | AV10285 | 4 | 0.97 | 3.88 |
| XLR Male (panel) | CPC | AV10284 | 9 | 0.97 | 8.73 |
| Mono Jack Socket | CPC | CN00002 | 16 | 0.37 | 5.92 |
| 4-pin DIN socket | Rapid | 20-0360 | 1 | 0.175 | 0.175 |
| 4-pin DIN plug | Rapid | 20-0260 | 2 | 0.13 | 0.26 |
Power Supply
Apparently, a box exists to do this, except no-ones seen it for over a year...
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.