Why don't all phono preamps include a rumble filter?

louisl,
Have you inspected and lubricated the main bearing lately?  My HW-19 MK IV had no audible rumble at any volume.  The Technics in stock form may be more immune to feedback.  Could it be that you are referring to acoustic feedback as rumble?  As noted, there are solutions for that.

My personal experience is that a rumble filter is a band-aide (and a poor one at that) for not correcting isolation/vibration issues. I learned that the hard way and now have a KAB RF-1 Rumble Filter sitting unused (and unneeded) in my closet.

@dwette...……………………

Agreed, but sometimes it is the ONLY option after all else fails.

@stereo5 In the end, my primary problem – after I got isolation under control otherwise – was the tonearm. I was using a Clearaudio Magnify. The magnetic bearing caused severe woofer pumping on certain recordings. After doing everything else I could to isolate the problem I finally changed to a tonearm with mechanical (precision ball) bearings. That was the night and day difference that finally solved my rumble issues. I also had to correct some isolation issues, and now I can play bass heavy records at high volume (and that’s with Confidence C2s and a pair of RELs) with no rumble issues at all (unless the record itself is mastered badly in that regard...rare for my collection).

infrasonic rumble can destroy you woofers. especially when listenning at high volumes! My NAD phono preamp does not need a rumble filter as it always cuts those ultrasonic noises. With my former phono preamp (ATOLL) woofers were moving excessivly producing infrasonic bass.