It's a Dumble ODS style amp (non HRM) with a few departures from the Dumble circuit. The most notable of these is a built-in tube buffered series/parallel effects loop and spring reverb. It has the traits most associated with this style amp - warm cleans, creamy overdrive, smooth top end, rich harmonic content, notes bloom effortlessly into harmonic feedback even when set clean, wide dynamic range, and lots of tone shaping control. The non HRM ODS work great for almost any style of music except metal. It's a fantastic amp for blues and classic rock.