shielding of interconnects: positive or negative

my experience using shielded and non shielded interconnects from the same manufacturer points to a disadvantage using shielded cables.

i had the opportunity to compare a shielded and non shielded version of a one meter interconnect from the Element cable company and i own a shielded and non shielded pair of interconnects manufactured by Sounstring Audio.

i found that the shielded version changes the frequency response, adding unwanted extra treble energy.

does nanyone have confirming or differing experiences in this area ?
Unless you have a RF or EMI problems an un-shielded cable frequently does sound better than shielded.

What you need is a cable that manages to shield against those things without changing the sound adversely. They do exist, several audiophile brands manage to pull it off.
Would be interesting to compare the capacitance specifications of the two cables if you have access to them. A guess is that the shielded cable had higher capacitance and this gave you the treble you did not like. If the guess turns out to line up with reality, you could try a shielded cable of lower capacitance design.