Strymon's goal with El Capistan was to offer the most authentic tape echo experience in a modern, compact form factor. A component of that was replicating the tonal effects that the tape medium itself can have on your signal depending on the age and condition of the tape itself, as well as taking into account the significant effect of the bias setting of the tape machine. A dedicated Tape Age knob lets you decide whether you want the full bandwidth of brand new, glossy tape — or the warm top end of older well-used tape.
By adjusting the Tape Bias secondary function, you can get high-headroom, extra clean, crisp echoes at lower settings, or crunchy, saturated echoes with higher bias levels. Higher bias settings also limit the echo volume, which can be useful at very high Repeats settings when you want to create high feedback and self-oscillation effects while still keeping output level under control. For “optimal” bias, set the knob at approximately 9 o’clock.