The following article addresses general noise issues when using the internal mics of the R-26:
INPUT SETTINGS
- Check that the input level meter is not reaching 0dB (all the way to the right) when recording--as noise can start occurring when the inputs are overloaded. Try lowering INPUT 1 knob and/or INPUT 2 knob until the noise disappears.
POWER
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Be sure to use a Roland PSB-120 or PSB-1U power supply.
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If using a 3rd party power supply, be sure that it's compatible and that the R-26's EXT-POWER is set correctly according to page 23 of the Owner's Manual.
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If the correct power supply is being used or if batteries are being used, physically disconnect the power supply from the product and test with brand new, unused batteries for troubleshooting purposes--Alkaline batteries are recommended.
Note: Lithium batteries are not compatible.
UPDATE
- Check at the R-26 is running at the latest version:
R-26 System Update Version
FACTORY RESET
- Perform a factory reset to assure that a setting is not causing the noise:
MENU-->FACTORY RESET-->YES.
SD CARD
- Be sure that a compatible card is being used:
https://www.roland.com/us/support/knowledge_base/201973059/ - Try formatting the SD card:
https://www.roland.com/us/support/knowledge_base/201979799/ - Test with a different, compatible SD card (refer to the compatibility link above).