SPA-4 is a stereo version of Ma-4 and uses the same Class A circuit. The only difference is the additional flexibility of power output and single-ended and balanced inputs. Not every music lover can accommodate two substantial power amplifiers in their music space, so a SPA-4 can solve this problem. One of the notable features of the SPA-4 is how well it works with smaller speaker designs and large speaker designs. Control level and sound level are the two key elements of SPA-4, making it a fine power amplifier.