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The Radio Design Labs TP-HA1A is intended for use in conjunction with other modules from the RDL Format-A range, to feed a pair of headphones and provide a volume control to adjust the level. The amplifier is fed with both stereo audio and power via a standard, 4-pair, twisted pair cable such as those used in cabling buildings for IT and telecoms purposes.

The four-pair cable must be fed by a suitable RDL Format-A sender or senders, see below. The headphone amplifier has an RJ45 input socket, and a similar, parallel-connected, loop-out connector to feed additional RDL Format-A modules. Since the Format-A receivers have high impedance, bridging inputs, up to ten receiver modules may be connected to a single Format-A chain. All three signal pairs, A, B and C are connected through as is the fourth pair, which is used for power. The amplifier uses pairs B and C for the left and right audio signals, leaving pair A free for use by other Format-A modules.

All Format-A active modules require a source of power at 24V DC, with a capability to provide sufficient current for all the modules connected to the chain. The TP-HA1A is protected by an automatically resetting fuse.

The TP-HA1A is built in a metal case which mounts to a flat surface; the base plate has cut-outs to pass cables pre-wired with RJ45 plugs and apertures for mounting hardware. The top cover is removed for while mounting, then replaced and attached with a single screw.

The front panel is fitted with a single three-pole, 3.5mm jack socket and a rotary volume control.

Optional accessories: RDL Format-A sender module(s), see RDL Format-A modules, or power inserters, with power supplies, see RDL Power Supplies, or any other Format-A module which supplies power on the chain in use.


The RDL Format-A system is a proprietary scheme which links modular components together using cable types commonly used for communications and IT infrastructure, such as the Category 5 UTP cable used for Ethernet. Such a cable will have four pairs of wires, twisted together. The RDL scheme uses one pair to distribute power and three pairs, designated A, B and C, for up to three balanced, audio connections.

The audio connections over Format-A systems are analogue; for absolute clarity, please note that the fact that the type of cable used might otherwise be used for Ethernet does not imply in any way that the Format-A system uses any form of digital transmission between Format-A nodes, not Ethernet, not audio over IP, not DANTE or similar.

Note: Some RDL DANTE modules are available which have analogue inputs and outputs wired to the Format-A standard. The signals connected to those inputs and outputs must be analogue connections from other Format-A modules. The network connections to these modules will then convert the analogue Format-A signals to digital DANTE signals for transfer over the network.

For further information see:'RDL Format-A System'.

For further information see:'RDL Format-A System'.

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RDL TP-HA1A HEADPHONE AMPLIFIER Format-A connected, 1x 3.5mm jack out, volume control   Stock code:
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