Hammond 1140-LN-D 40K to 2.4K Step-Down Line Input Transformer, 4:1

The 1140-LN-D is a 4:1 step-down line input transformer from the 1140 Series of studio grade impedance matching transformers. It is designed for input stages with wide bandwidth and low distortion, and the drawing notes it can be used to match high impedance inputs to low secondary source impedances. Audio equipment designers building line inputs are the main audience.

The impedance ratio is 40K:2.4K with a 4:1 turns ratio. Rated figures are +21 dBu maximum input at 20 Hz, 0.060% THD at 20 Hz and a response of -0.12 dB at 20 Hz and +0.06 dB at 20 kHz. The drawing gives typical 42K primary input impedance and 225 secondary output impedance at 1 kHz and +4 dBu, 70 dB common mode rejection at 60 Hz and 65 dB at 3 kHz, and THD of 0.007% at 1 kHz and 0.001% at 20 Hz (-20 dBu).

A nickel alloy core provides the bandwidth, and the mu metal can provides excellent shielding. DCR is 1.96 K on the primary and 95 on the secondary at 20 °C; capacitance to shield and case is 525 pF primary and 640 pF secondary; dielectric strength is 500 Vrms.

The 1140-LN-D mounts to a chassis with colour-coded leads: brown/orange primary, green and green/yellow secondary, grey shield and violet can ground. It is RoHS and REACH compliant, made in Canada and ships at 0.2 lbs (0.09 kg).