diff --git a/pyvo/dal/params.py b/pyvo/dal/params.py
index fce246dc..b6ebbca2 100644
--- a/pyvo/dal/params.py
+++ b/pyvo/dal/params.py
@@ -367,18 +367,12 @@ def _validate_pos(self, pos):
                     self._validate_ra(m)
 
     def _validate_ra(self, ra):
-        if isinstance(ra, str):
-            ra = Unit(ra)
-        if not isinstance(ra, Quantity):
-            ra = ra * u.deg
+        ra = Quantity(ra, u.deg)
         if ra.to(u.deg).value < 0 or ra.to(u.deg).value > 360.0:
             raise ValueError('Invalid ra: {}'.format(ra))
 
     def _validate_dec(self, dec):
-        if isinstance(dec, str):
-            dec = Unit(dec)
-        if not isinstance(dec, Quantity):
-            dec = dec * u.deg
+        dec = Quantity(dec, u.deg)
         if dec.to(u.deg).value < -90.0 or dec.to(u.deg).value > 90.0:
             raise ValueError('Invalid dec: {}'.format(dec))
 
@@ -418,15 +412,12 @@ def get_dal_format(self, val):
             raise ValueError('Invalid interval: min({}) > max({})'.format(
                 low, high))
         if self._unit:
-            if isinstance(low, str):
-                low = Unit(low)
             if not isinstance(low, Quantity):
-                low = low * self._unit
+                low = u.Quantity(low, self._unit)
             low = low.to(self._unit, equivalencies=self._equivalencies).value
-            if isinstance(high, str):
-                high = Unit(high)
+
             if not isinstance(high, Quantity):
-                high = high * self._unit
+                high = Quantity(high, self._unit)
             high = high.to(self._unit, equivalencies=self._equivalencies).value
 
             if low > high: