Cable data

The table below helps you select the correct gauge of wire for your loop amplifier. The type of wire is not too important, though experience has shown that a stranded cable with tri-rated insulation is probably the easiest to install and most robust in use. So for example, an ILD122 amplifier when using a 1.5mm² loop cable, will work with a minimum length down to 17m and a maximum length of up to 90m. Any length in-between these two values should work fine though beware of working right at the limits of cable size. If in doubt, use a different size of cable such that the total loop length is well within the minimum and maximum lengths.

Cable / Wire Data ILD20 ILD122 ILD252 (USA) ILD9
Length (m) Length (m) Length (m) Length (m)
Wire
gauge

mm²
Resistance |Z| @ Min Max Min Max Min Max Min Max
Ω per 1.6 KHz DC 1.6 KHz DC 1.6 KHz DC 1.6 KHz DC 1.6 KHz
100ft 100m Ω/m 0.2Ω 1.2Ω 0.2Ω 0.3Ω 2.72Ω 0.4Ω 3.75Ω
0.5 1.051 3.448 0.0399 6 29 6 50 9 68 12 94
0.75 0.701 2.299 0.0305 9 44 9 65 13 89 17 123
1.0 0.526 1.724 0.0265 12 57 12 76 17 102 23 142
1.5 0.350 1.149 0.0223 17 67 17 90 26 122 35 168
2.5 0.210 0.690 0.0194 29 77 29 103 44 140 58 194
4.0 0.131 0.431 0.0186 X X 46 108 70 146 93 202
FB 1.8* 0.292 0.958 0.0150 21 100 21 133 31 181 42 250
AWG wire Ω/100ft Length (ft) Length (ft) Length (ft) Length (ft)
22 7x30 1.482 4.861 1.603 13 67 13 125 20 169 27 234
20 7x28 0.933 3.062 1.117 21 107 21 179 32 243 43 336
18 16x30 0.648 2.127 0.892 31 154 31 224 46 304 62 420
16 26x30 0.399 1.309 0.706 50 251 50 283 75 384 100 531
14 41x30 0.253 0.830 0.607 79 395 79 330 119 447 158 618
12 65x30 0.160 0.523 0.574 X X 125 348 188 472 251 653
10 65x28 0.101 0.330 0.561 X X 199 357 298 483 398 669
FB 1.8* 0.292 0.958 0.458 69 343 69 437 103 592 137 819
Cable / Wire Data ILD100 ILD300 ILD500
Length (m) Length (m) Length (m)
Wire
gauge

mm²
Resistance |Z| @ Min Max Min Max Min Max
Ω per 1.6 KHz DC 1.6 KHz DC 1.6 KHz DC 1.6 KHz
100ft 100m Ω/m 0.2Ω 1.0Ω 0.2Ω 1.3Ω 0.3Ω 2.0Ω
0.5 1.051 3.448 0.0399 6 23 6 33 9 55
0.75 0.701 2.299 0.0305 9 29 9 43 13 72
1.0 0.526 1.724 0.0265 12 34 12 49 17 83
1.5 0.350 1.149 0.0223 17 40 17 58 26 99
2.5 0.210 0.690 0.0194 29 46 29 67 44 114
4.0 0.131 0.431 0.0186 X X 46 70 70 118
FB 1.8* 0.292 0.958 0.0150 21 60 21 87 31 147
AWG wire Ω/100ft Length (ft) Length (ft) Length (ft)
22 7x30 1.482 4.861 1.603 13 54 13 81 20 135
20 7x28 0.933 3.062 1.117 21 81 21 116 32 197
18 16x30 0.648 2.127 0.892 31 101 31 146 46 247
16 26x30 0.399 1.309 0.706 50 128 50 184 75 312
14 41x30 0.253 0.830 0.607 79 148 79 214 119 363
12 65x30 0.160 0.523 0.574 X X 125 226 188 383
10 65x28 0.101 0.330 0.561 X X 199 232 298 392
FB 1.8* 0.292 0.958 0.458 69 197 69 284 103 481

* FB 1.8 is Flat Copper Tape

Table Notes

The table above gives comprehensive information on the minimum and maximum length of cable of a particular wire gauge that can be used with specific Ampetronic loop drivers. Each driver has a specified minimum resistance and maximum impedance at 1.6KHz which can be driven at full current.

Feeder Cable

The values given in the table ignore the resistance of the feeder cable (the cable connecting the loop to the loop driver) which is normally very low. If the situation is marginal, or where very long feeder cables are involved, additional design must be done to compensate. Feeder cable should always be tightly twisted to ensure that the reactive component is very low resulting in a low magnetic field near to the equipment. Use of shielded cable has no real advantages as magnetic radiation is not affected. Parallel wire cable (eg Fig 8) as used by some loudspeaker manufacturers is not recommended. Very often, the wire gauge of the feeder will be similar to the actual loop cable.

The actual feeder length is double the physical length for resistance (send and return). This is important when calculating the total resistance of the system.

Star Quad Feeder Cables

For very long feeder cables, the recommendation is to use a 4-core round cable in a "star quad" configuration. Optimum cable size is 1.5mm² / 2.5mm² (14AWG / 16AWG). The opposing cores are connected together, providing a very low resistance and inductance with little magnetic radiation. This style of cable is often used for 3-phase + earth power connection of machinery.

UK style is 3184Y, harmonised H05VV-F. Similar UL approved cable is SV-3, UL recognised 4097. Total resistance of 100m of 3184Y cable, 2.5mm² per core is 0.69Ω (4-core 14AWG cable is 0.252Ω/100ft). This is well inside the capabilities of the Ampetronic loop drivers.

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