The Burl B1D is an all-discrete, Class-A 500 Series mic preamplifier designed for a thick and thunderous sound with pretty much any microphone you can throw at it. The signal path is free from capacitors, giving it an especially clear tone that yields an outrageously punchy sound for drums and bass. The BX4 iron output transformer produces a slightly darker, warmer sound with tremendous bottom octave emphasis when compared to the B1. The B1D provides up to 70dB of gain and features a -30dB pad for especially hot signals. Dig into the input gain and back off the output level for more input transformer saturation, or flip into the low-impedance mode when you're using ribbon mics...or both.