We demonstrate the generation of mid-infrared radiation using a femtosecond dual-signal-wavelength optical parametric oscillator and difference frequency generation in an extracavity gallium selenide or silver gallium diselenide crystal. This system generates up to 4.3 mW of average mid-infrared power. Its spectra can be tuned to between 10.5 μm and 16.5 μm wavelength (952 cm(-1)-606 cm(-1)) with more than 50 cm(-1) spectral bandwidth. We demonstrate that the power and spectra of this system are temporally very stable.