Pro-Ject Phono Box S3B Phono PreamplifierPhono Box S3 B Entry Level True Balanced Phono Stage A New Access to High End Features. THE NEW PHONO BOX S3 B The Phono Box S3 B is an entry level phono preamplifier that offers a fully balanced design in a neat, small package. Weve packed this tiny chassis to the brim with high end features. One of those is our new True Balanced Connection. At Pro Ject, balanced connections were exclusive to our RS range of products until now. The Phono Box S3 B