TK Audio SP-501



500-series Class A preamp

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SKU: TKA-SP501 Categories: , ,
Brands: TK Audio
TK Audio


TK Audio SP-501

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 midrange crunch of the germanium sound of the mid 60’s, the low mid punch and thick sound associated with British Class A from the early 70’s as well as the more modern tone from the 80’s and 90’s are finally all available in a single unit.

SP501’s 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.

  • Lundahl input transformer
  • Carnhill output transformer
  • Selectable germanium circuit for extra harmonics
  • Sweepable high-pass filter, 30-400Hz, 12dB/oct
  • Hi-Z instrument input
  • Selectable output stages, electronically balanced or discrete class-A

Power requirement: +130mA / -130mA
Input impedance: 1600 / 400 ohm
Instrument input impedance: Higher than 2Mohm
Max output level: +24dBu


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
Specifications and components may be changed or updated without further notice.