It could indeed be clipping. I've heard it with quite a few phono stages and I know Rushton has too.
Just as with a power amp or any amp, dynamic peaks cause phono stage problems if the power supplies can't provide enough instantaneous current to meet peak demand. What happens then is that the musical signal starts modulating the incoming power, which results in distorted waveforms until the music settles down and the power supplies can catch up again.
It gets worse on inner grooves because their shorter wavelengths are more difficult for a stylus to track cleanly and also because tracking angle error is increasing. The separate but very closely related waveforms that result can be difficult for a phono stage to keep separate and reproduce cleanly. Once it starts smearing slightly separate sounds into one, the sonics go into "fingernails on chalkboard" mode pretty quickly. ;-)
Here's a simple test for vinyl damage: "play" the suspect passage by rotating your platter BY HAND at very slow rpm, like 4-5rpm or so. The music should sound like a murky, LF growl. If there's any damage in the grooves it will usually sound like sharper, quicker clicks, much crisper and higher in frequency than the music. If you hear that and cleaning doesn't remove it, the LP's damaged.
Just as with a power amp or any amp, dynamic peaks cause phono stage problems if the power supplies can't provide enough instantaneous current to meet peak demand. What happens then is that the musical signal starts modulating the incoming power, which results in distorted waveforms until the music settles down and the power supplies can catch up again.
It gets worse on inner grooves because their shorter wavelengths are more difficult for a stylus to track cleanly and also because tracking angle error is increasing. The separate but very closely related waveforms that result can be difficult for a phono stage to keep separate and reproduce cleanly. Once it starts smearing slightly separate sounds into one, the sonics go into "fingernails on chalkboard" mode pretty quickly. ;-)
Here's a simple test for vinyl damage: "play" the suspect passage by rotating your platter BY HAND at very slow rpm, like 4-5rpm or so. The music should sound like a murky, LF growl. If there's any damage in the grooves it will usually sound like sharper, quicker clicks, much crisper and higher in frequency than the music. If you hear that and cleaning doesn't remove it, the LP's damaged.