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Even if you have the best turntable in the world, there's still rumble coming from your records.

In fact, if you could spin the record in midair using antigravity, and read the record grooves using a laser, you'd still hear rumble. Why? Because the record was produced on a turntable with rumble, and that rumble was copied right into the record itself!

Precision Audio Restoration has developed a unique device, the DERUMBLEIZER, which, unlike a conventional rumble filter, reduces audible rumble almost 3 octaves higher, leaving the music totally intact!
It not only reduces the rumble coming from the turntable and record, but also reduces acoustic feedback and floor vibrations. (DJs and those who like their music loud, take note)

The picture below is about 20 seconds of a 50Hz tone from a test record. The red trace on top simulates music, and the green trace simulates rumble. The Derumbleizer was switched in at the middle. You see the "rumble" dramatically reduced by using the Derumbleizer.

the Derumbleizer at work

The red trace above is the record groove moving laterally, like music does, and the green trace is the record groove moving vertically, like rumble does. Both traces are actual screenshots from the sound files, and are not retouched in any way.

The Derumbleizer works by comparing the phase of the bass coming from the record. Since most rumble is vertical movement of the stylus, (needle) which makes out-of-phase bass, and most music is lateral movements, which makes in-phase bass, and there's little or no out-of-phase bass music anyway, the rumble can be "easily" canceled.

The music in both channels coming from the record is split into two frequency bands: bass and everything else. The phase of the bass is checked. In-phase bass music is kept, out-of-phase bass rumble is canceled. The bass without rumble is then added back to the "everything else" channels. During this process, the bass is made monophonic.

block diagram for the Derumbleizer

DON'T PANIC! Bass is monophonic anyway, so nothing is being done that changes how the music sounds to your ears. (Okay, there may be one or two records with bass in one channel only, but the Derumbleizer will still remove the rumble, and at the right volume to sound as if it were still coming from one speaker.) Besides, your ears can't localize bass anyway, and if you have a subwoofer, you're hearing monophonic bass already.

The Derumbleizer comes with a high performance RIAA phono preamp built in to connect directly to your turntable with a moving magnet cartridge, and to stereos without a phono input, or to a computer sound card.
A moving-coil version is being developed, as well as a Signal Processor which can be used with your own phono preamp, or in the tape loop of your amplifier.

"It works excellently and I am most pleased with it. certainly does remove any hint of rumble!"

-- David C., Van Nuys, CA


In phase (music) signals:
Gain (Derumbleizer section): unity, +/-0.5db, 10-50,000Hz
Gain (Preamp section): 36db
Phase shift (Derumbleizer section): 0 degrees, +/-2.0, 10-50,000Hz

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Mailing address:
Precision Audio Restoration
14419 Greenwood Ave. N., Suite A, Box 321
Seattle, WA 98133
Call 206-387-5662 or email to receive
directions to purchase a Derumbleizer personally
By appointment only.

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