There are at least two ways of achieving sub-sample delay. One is to simply over-sample the signal and then delay it by the wanted sub-sample amount. The over-sampling is equivalent to creating new samples in-between the existing samples utilizing the prior sample values and then using a low-pass filter on the resulting signal. Low-pass filters generate artifacts, resulting at minimum in pre/post-echo for linear phase filters.
The second alternative is to perform a FFT, multiplying the phase response with a linear phase response corresponding to the delay amount. My question is: what are the artifacts involved in this procedure? I would think that they would be the same, but can't find a low-pass filter anywhere.