Getting into LP's and startled at the big
speaker cone movements that you're seeing? Thinking a better turntable will
help? It may not! This very low frequency energy is called rumble. Much of it
is actually cut into the record groove when the master disc was made. Other
sources are mis matched tonearms, poorly damped tonearms and acoustic feedback.
Often, the only way to suppress rumble is with a really good rumble filter.
With rumble eliminated, the soundstage becomes more "still" and the bass
actually tightens up because the woofers are no longer modulating and the power
amp is no longer wasting current resources on sub audible noise.
The KAB Great Sound Escort RF-1 is a very
fine transparent rumble filter that not only suppresses very low frequency
(subsonic) energy, but also uses a unique active cancellation circuit that
effectively suppresses vertical rumble too. Your subwoofers will thank you!
Suppresses acoustic feedback too.
Two important things to know:
1. When records are made, frequencies below about 150Hz are combined to mono.
This is done to avoid large out of phase groove excursions.
2. When the
stereo stylus moves vertically, the two signals produced are equal and 180
degrees out of phase.
Therefore, below 140Hz, the music is in phase in the
lateral stylus motion, and only out of phase noise is found in the vertical
The KAB RF-1 takes advantage of this by electronically
combining the left and right channels together below 140Hz. In so doing the
filter effectively cancels vertically modulated noise. Vertical rumble comes
generally from bearing noise of the disc cutting system. But since the music
below 140hz is already mono on the disc, the musical information is
Below 20Hz, all signals are quickly attenuated at
The RF-1 is a must for vinyl enthusiasts, live DJ's and
when burning CD's for the car. You probably can't hear it, but your car woofers
are going mad with all that subsonic rumble!
The KAB RF-1 is easy to install. Place it in
between the phono preamp and control amp or in a process loop. It requires no
attendance. It is happy to remain powered up at all times.
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