NTP 179/400

The NTP 179-400 accommodates a high-quality VCA module manufactured by NTP, which has resulted in the production of a limiter with quite outstanding performance in respect of noise and distortion. The features of the instrument include transformer balanced input and output stages. The input contains a ZFT transformer stage. The ZFT module is a unique NTP design which practically eliminates low frequency distortion due to iron-core saturation. As for the dynamic behaviour, the design of the limiter benefits from the experience gained from the manufacture of earlier FET-type limiters. To ensure smooth operation, a 1 ms attack time has been chosen. This, however, implies a risk of overloading in the event of transients. Thus the 1 ms attack function is combined with an instantaneous soft clipping circuit. Dynamic distortion often encountered with limiter amplifiers is kept at a minimum due to the dual-time cons- tant, programme-dependent recovery function. The recovery time constants are pre-selected for the best performance on most programme sources. To meet special requirements, however, the limiter includes facilities for changing the time constants via the connector. To further increase the versatility of this limiter amplifier, the gain and limiter threshold levels are adjustable by means of front-panel switches. The switchable pre-emphasis may also be selected in the front panel.