15IPS mkii change resonant filter

Part of the distinctive sound of tape that the 15IPS is a resonant high-pass filter in the very low frequencies, sometimes known as the "head bump." Vintage tape machines had a wide range of curves in the low frequencies. Head bumps at 15 inches per second varied in the range of <1dB to 4dB and roughly 30Hz to 70Hz. The 15IPS is designed to have a head bump of 3dB with a corner frequency of 47Hz.


If you want to modify or remove this bump while keeping the compression and distortion character, simply change or remove R7. The resistor specifications are through-hole, metal film, 1% tolerance, 1/4 watt.


R7 Value Corner Freq Bump Amount
15k (stock) 47Hz 3dB
22k 45Hz 1.5dB
27k 43Hz 1dB
Remove  None None

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