SP501 is a single slot 500-series class-A unit with a unique hybrid design including both vintage and modern circuits derived from TK’s flagship DP1 stereo preamp.

The TK Audio SP501 input stage is built around a high quality Swedish Lundahl transformer followed by a germanium stage that adds more harmonics. Two different output stages can be selected – either an electronically balanced stage, or a discrete transformer-balanced class-A stage sporting a heavy Carnhill output transformer. Vintage Class A mode produces a fat and punchy sound with mid-range character and a warm top end, while the electronically balanced output stage is less colored and perfect for clean amplification. A sweepable HPF from 30Hz to 400Hz allows precision crafting of the low end.

 Features

• Gain switch in 5dB steps. -25 to 80dB. +5dB to -50 with pad
  -30dB pad
• 48v phantom power
• Selectable output stage: vintage transformer balanced class-A or electronically balanced
• Germanium drive: inserts a germanium gain stage after the input stage
• Sweepable high pass filter, 30-400Hz, 12dB sloop
• Polarity switch
• Impedance switch: 1600ohm/400ohm
• Hi-Z input, instrument input with more than 2Mohm input impedance
• Output level control
• Illuminated switches, except for the phantom toggle switch