The RA1 from Grado is a reference-quality headphone amplifier designed specifically to drive Grado headphones. Machined from a solid block of mahogany, this amp sounds as good as it looks. The front of the amp features a volume knob and a 1/4" stereo output, while the rear features an on/off switch and a pair of gold-plated RCA phono inputs for accepting a line-level stereo source.