thanks for the reply, but I only have a standard license. Can't use spatial analysis.
You can do this using Python by converting the raster into numpy array. In case it is large, see the second example on the same page that handles larger raster datasets: ArcGIS Help (10.2, 10.2.1, and 10.2.2)
No Spatial Analyst extension required.
You can run Raster to ASCII, load/modify spaced-delimited file in spreadsheet software (Excel, perhaps), then convert back to raster with ASCII to Raster. No Arc licensing required.
* Xander's Python solution will avoid most of the file conversion glitches and headaches, though.
If you have more than 16384 columns in your raster, Excel won't do it for you..., but I like the creativity of the answer.
or you can run Raster to point, add a column/attribute to the point feature class, calculate the elevation, then convert it back using Point to raster with the appropriate value field and using the original DEM as a snap raster/source for the pixel size.
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Using ArcPRO, the Rastercalculator will work. The expression is "Raster.tif'*3.2808.