The original L9 IN/OUT module for the TD9 tape recorder was developed at Stellavox towards the end of the 1970s. Signal balancing was carried out using transformers, as was common at the time. These transformers also had the pleasant side effect of galvanic isolation, which is less important today, since TD9 recorders run exclusively as installed units in studios around the world, where ground loops can be excluded by planned and controlled ground flow. What remains, however, are the shortcomings of the transformer: poorer transient behaviour, more distortion and a reduced dynamic. Furthermore, with micro-electronic surface-mount devices (SMD) unavailable at the time, it was not possible to build both original amplifier units with single components (discrete circuit) because of the reduced space.
Looking at the past and at today’s technical possibilities, we came up with the idea of developing a new module for what may well be the world’s best tape recorder. Beating excellence is of course a challenge! However, we believe to have significantly improved the TD9’s reproduction quality by eliminating the bottleneck created by the transformers.