Probably feedback, just do some good isolating on the turntable.
Get rid of the low pass filter. Do not use it as it changes polarity and you loose micro-details, micro-dynamics, and imaging.
Some woofer pumping will be present as a good preamp will have frequency response near DC.
Get rid of the low pass filter. Do not use it as it changes polarity and you loose micro-details, micro-dynamics, and imaging.
Some woofer pumping will be present as a good preamp will have frequency response near DC.