The Signal Transfer Company

The Signal Transfer Low-Noise Balanced Input Card

Low noise balanced input card
The conventional balanced input stage built with 10K resistors and a 5532 op-amp has a far worse noise performance than a simple unbalanced input, and is also much noisier than any of our power amplifier designs. Its output noise is approximately -104 dBu.
The Signal Transfer low-noise balanced input card solves this problem by the use of a multiple amplifier array that causes the noise from each amplifier to partially cancel, and in a similar way improves the common-mode rejection ratio; this array is driven by a multiple-buffer structure that allows the input impedance to be much higher than usual, preventing loading of external equipment and also further improving the CMRR. The elegant design does not require selected or exotic components. The noise output is less than -115 dBu.

The principle of operation is fully described in the Fifth edition of Douglas Self's book "The Audio Power Amplifier Design Handbook".

This card handles a single channel, so that the two required for stereo can be spaced apart to minimise interchannel crosstalk.

  • PCB 008: 19:80 each
  • Kit 008: 38:00 each
  • Built and tested: 58:00 each

F E A T U R E S

S P E C I F I C A T I O N S

C O N N E C T O R S

Graph of THD at 5 Vrms and 10 Vrms. Testgear AP SYS-2702.