According to many books I have read, a דגש קל can only be present in the letters ב, ג, ד, כ, פ and ת. The Ashkenazi מסורה for pronunciations of the letters ג and ד without a דגש קל has been lost. I have heard that the letter "ג" without a דגש קל is pronounced like the english letter "j" in some Sephardic customs. However, I have neither heard nor read about how a "ד" without a דגש קל is pronounced. Can somebody transliterate it into english?
According to the predominant Yemenite custom, a “ד" without a דגש קל is pronounced as “th” (as in “the”). The authenticity of this tradition can be seen in Brachos יג, where we are instructed to elongate the pronunciation of the ״ד״ in the אחד of שמע. This is nearly impossible to do when following the prevalent traditions of the Ashkenazim and Sefardim, who have lost the tradition regarding the pronunciation of a “ד.” (Therefore, it is very likely that the Jews of Babylonia pronounced ״ד״ as a “th” sound.)