How to Increase Bass Pedal Response in a Hammond Organ
Hammond organists play bass lines by stepping on a series of pedals while playing the organ. This creates a bass accompaniment for the chords and melodies that they are playing with their hands. Sometimes the bass pedal notes can lack clarity or volume. By modifying the amplifier attached to the Hammond organ, you can increase the volume and tone clarity of the bass pedals for a thicker and more audible sound.
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Instructions
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Turn off your Hammond organ. Let it cool off for 20 minutes so that the amplifier's vacuum tubes aren't hot.
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Unscrew the back panel of the organ. Use a cross-head screwdriver to tighten the screws governing the tension of the bass pedal return springs. When you press a Hammond organ bass pedal with your foot, you depress a spring. When you remove your foot, the spring returns the pedal to the starting position. If the spring is loose, the pedal will not return fully. This means you can't accurately play the bass notes, which can lead to poor bass response.
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Unscrew the back panel of the tone cabinet with a cross-head screwdriver. Pull the amplifier chassis toward you and remove the tubes from their sockets on top of the lid. Pull the tubes vertically so that the pins slide out of the tube socket. Don't twist and pull.
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The glass on worn out tubes has a dull appearance Inspect the tubes. The tube configuration differs between models. For example, the Hammond B3 tone cabinet has eight tubes, arranged as follows: One 6X4 tube, one 12BH7 tube, one 12AX7 tube, two 6AU6 tubes, two 6C4 tubes and one 12AU7. Look for tubes with a brownish discoloration. This is a sign of a burned out filament. When tubes burn out, certain frequency ranges diminish. A burned out tube is a likely cause of poor bass response. If the burned out tube is part of a pair, replace both tubes so that they are biased correctly. Never replace one from a pair. This puts undue strain on the new tube as it compensates for the wear on the existing tube.
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Remove the lid of the chassis. Inspect the circuit board for loose wiring. If any of the tube sockets are poorly wired to the circuit board, this can diminish the bass response, especially if it is the socket for the 12AX7 tube. The Bio Audio Works website describes this tube as having "good bite and definition." If this tube is not correctly connected to the circuit board, the tone will lack definition. Disconnect loose wires with a soldering iron and reconnect them securely.
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Tips & Warnings
Always wear latex gloves to handle vacuum tubes. This protects the glass.
Attach the screws to a piece of electrical tape to prevent them rolling away. Attach them in the order you removed them so you can put each screw back in the original hole.
Modifying any part of your Hammond organ may void the warranty.
References
Resources
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