JED audio devices

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T461 front

T461 audio connections

T461 relay and +12 volt output

JED T461 audio controller (four stereo channels), eight optional relays.

The T461 is a 1RU high 19-inch rack mount unit, with four line level stereo RCA pairs as inputs and one line level RCA pair as output. It has an RS232 input and a 240 volt IEC mains connector. A 12-volt power output can power the T460R (and any other attached equipment. All connections are on the rear, and on the front are four LED channel indicators and screw-driver adjustable pre-scaler trim pots, one for each stereo pair.

Recent software can permanently allocate channel 4 as a "microphone" channel, which can be turned ON from a T460R before the projector turns on (e.g. at the start of a lecture, and the volume set using the T460R volume control keys. Pressing ON again turns on the projector and program audio (from the lower three channels is mixed with the microphone (on channel 4) allowing the lecturer to comment on the program on the screen. A dummy channel on the T460R is able to be allocated for microphone level control while the projector is running, allowing dynamic level changes. Pressing OFF turns off the projector, but allows the microphone to still be active until the OFF is pressed again.

An option for the T461 adds 8 outputs (-R8).  It has eight relay contact outputs which can be used to control screen up/down functions, projector "dipper", room lighting pre-set selects, etc. The relays are also controlled via the RS232 secondary link from the T460R to the T461. The relay states are indicated by LEDs on the front panel of the T461. Control options include control of a C-Bus or a Dynalite lighting control system, or Quest, Kramer or Extron video switching systems.

JED T441 audio controller (two stereo channels, four mono channels)

The T441 is a small boxed audio attenuator/mixer which switches and controls line-level audio in a small A/V room installation. It is powered from the same 12 volt adaptor which runs T440's etc.

It has two main modes and an auxiliary mode of operation: A DIP switch on the end selects modes:

• In stereo mode, there are two stereo input pairs which are typically a computer stereo pair and an A/V stereo pair from a DVD/VCR, (although this can be selected via an option switch to be both computer sources, both with stereo audio). These are switched to an RCA pair on the back to feed into the room PA system. The default setup in a T440 selects these audio channels automatically for, say, Code:0, 9 or A keyboards; or

• In mono mode, the four RCA inputs are regarded as separate line inputs, which could be from two computers in mono and two A/V signals each in mono. These are switched to one of the rear RCA connectors to the room mono PA. This is used if T440, OPT4 is set and one needs to select between, and control, 4 audio channels;

• In the third mode, the first RCA input pair is regarded as two mono channels, and are used for two computer channels selected by T440 Computer:1 and Computer:2 respectively. The other (stereo) input is selected by Video:1 and  is passed in stereo to the two outputs. (At the moment, if this mode is to be used, it needs to be ordered as a "Mode 3" T441:The next PCB rev will use switches to select it. This mode came as an unintended bonus!)   

Note: The T441 is code compatible with the T461, so the T460 can drive it too, if an application only needs two stereo/four mono channels.

The RS232 codes are available, so it can be driven from foreign controllers with an RS232 port. The T441 is code compatible with the T461, and is just simple ASCII strings 7 characters long.

T465 Microphone pre-amp and three-channel mixer. T465 PDF data sheet

This unit, mounted in a matching Clipsal panel similar to the T460R, has two volume controls on the front, and is positioned in the stereo line output from the T461 (or projector audio output) to the PA amplifier. This allows a lectern microphone and an audience participation / roving radio mic channel input as well. Mic and radio audio operates independently of the T460R On or Off state (so a lecture can begin before turning on the projector via the T460R).

It is powered by a 12 volt source, e.g. the 12 volt regulated power available from the back of a T461, or a PAK12/1A plug-pack. (It draws 75mA)

The left hand volume control is for the microphone input, and this is added to both channels equally. Rear preset switches allows the gain for the microphone channel to be preset in 6 steps of 10dB (0 to 50db). Inputs can be balanced or unbalanced (a switch on the back can ground one channel). Phantom power at 12 volts can be connected to the balanced microphone inputs to power a phantom-powered microphone preamplifier. Another switch controls a base-cut switch to reduce breath pops, etc.

It also takes a radio microphone input (or any other line input, e.g. a CD player), and mixes it to both channels as well, via the right-hand volume control.

The advantage of such an audio control panel is that the lecturer does not need access to mic volume controls on the audio amplifier (which might be across the room in a secure rack), and can control the roving mic channel from the lectern as well.

A rear stereo log pot allows the T461/projector input level to be preset. (This signal level is adjustable via the "volume" buttons on the T460R.)

A second stereo output is available to feed a cassette tape recorder to allow taping of lectures.