Petrúngaro Transformer Microphone Preamplifier Model NV-II

This device was designed based on the structure of pure Class “A” amplifier; this is, a one-phase design, not counter-phase, therefore avoiding crossover distortion, found in most preamplifiers that use operational amplifying circuits to handle audio signals.

This characteristic of design (Class “A”), related to the fact that audio signals pass through only six transistors, makes this equipment a one-of-a-kind in reference to its signal to noise ratio (without a doubt, the best in reference to its noise floor).

The NV-II is fitted in a 1U rack mountable chassis, and features two channels. The signal connects to the circuit passing through a transformer with permalloy — mumetal core, electrostatic screen and double primary winding. Combining these two windings enables different input impedance options (Hi and Low), thus, offering the possibility to choose between different sound “colors”, thanks to the difference in the magnetic transfer of such transformer, making this characteristic a unique variable at the moment to approach the desired sound, not only for transparency, but for color and musical character, too.

Even though these terms cannot be technically defined, when the moment comes to find a specific sound, these are the psychoacoustic appreciations that define the election of the preamplifier to be used and its setup.

Going back to the audio path, the signal passes through an input trim with 5dB steps, which is linked to an overload detector with very high impedance, indicating if the input signal reaches saturation level at any time.

For signal handling, the equipment has an output level control, that together with the trim control and the impedance (z) switch, provide three setting variables to find the desired sound. Also, it features a phantom power switch and a phase- reverse switch.

Finally, the signal comes out passing through an excellent bifilar winding transformer with flat response at up to 80 KHz, and with grain-oriented core, that makes it possible to develop output levels up to 30 dBm without distortion.

Enjoy it…

Daniel Petrúngaro