Map Algebra tool error

[Jorgede_la_Riva]

I am trying to use the map algebra tool and create a new raster(y) such that y= -46.7 +10*log10(original raster(tiff file)).

However whenever I do the calculations, the pixels in the new one are not oriented in the same way as the old ones, and several pixel squares are joined together in larger ones.

Any experience with this, or what would be the best way to apply this simple formula to each pixel?

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[DanPatterson_Retired]

single band tif?  type of tif (8, 16, etc bit)

range of values in the tif and the nodata value? 

(just checking to make sure that overflow/wrap/underflow isn't occurring)