Early 775's did not have DSP as a stock item. It was installed as an option.
Not sure what the S/N was when the DSP unit was made standard. In any case a
straight 775 would not have the DSP unit unless optioned in like the extra
filters while a 775DSP was built with DSP installed.
My unit S/N 1005 has the DSP installed as an option.
Very nice radio.
73
Dan R