How to Switch the Tubes in an Electro Harmonix Pedal
Electro Harmonix is a musical instrument accessory manufacturer specializing in vacuum tubes and effects units. The company claims to be the world's leading manufacturer of vacuum tubes. There is a range of Electro Harmonix pedals that feature vacuum tubes. The Black Finger optical compressor and the Tube EQ are two popular models in the range. Although the company uses top quality tubes in their pedals, you may wish to customize your pedal by swapping the tubes. You can achieve cleaner sounds or more distortion from your pedals by switching the tubes.
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Instructions
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1
Source suitable replacement tubes. The stock tubes for all Electro Harmonix pedals are made by Electro Harmonix. For example, the Black Finger pedal has two 12AX7 vacuum tubes. According to the Tube Store website, these tubes have a gain factor of 100. Establish what you would like to achieve from swapping the tubes. If you would like to reduce the gain of the pedal, consider going for a tube with a lower gain factor such as a Sovtek 5751, which has a gain factor of 70. Check the manufacturer specifications to ensure that you are swapping for a compatible tube. The Tube Store website has a gain factor chart which explains the relative gain of various tube types.
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2
Switch off and unplug your Electro Harmonix pedal. It is very dangerous to remove tubes when the unit is powered, and you also risk damaging your pedal. Once you have unplugged the unit, leave it for 20 minutes so that the tubes can cool off. They are more likely to shatter if touched when hot.
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3
Remove the tube shield. Unscrew the bolts that attach the tube shield to the front of the pedal housing.
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Remove the tube. Simply pull the tube upwards, and it will pop out from its socket. It is tempting to twist the tube out as you would when removing a light bulb but this is not necessary. If the tube is still operational, put it in a safe place and keep it is a spare.
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Put on a pair of latex gloves before you put in the new tube. Oils from your skin can create hot spots on the tube glass. These hot spots can create an uneven distribution of heat across the surface of the glass, which can cause the tube to shatter. If you do plan to keep your old tubes, put on the gloves before removing them.
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Power up and test the pedal. Do this carefully as your tube shield is not in place to protect the tubes. The first thing you should listen out for is correct operation. There should be no hiss or crackling. Then listen out for the change in sound that you were aiming for when you picked your new tubes.
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Replace the tube shield. Because the pedals are foot operated, it is important to keep the tubes secure. Ensure that you replace the tube shield and fit it securely back on to the front of the pedal.
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Tips & Warnings
While the tube shield is not attached, clean away any dust that has gathered underneath it before replacing the tubes.
Ensure that the replacement tubes are compatible. Some tubes may cause the pedal to malfunction if they are too high or too low-powered.
References
Resources
- Photo Credit old vacuum tubes image by Dmitry Rukhlenko from Fotolia.com
