DAC/ADC not at full range.

My frequency from the NCO is 3 MHz. I send the signal from the first DAC into the ADC then feed back out through the second DAC, as follows:

assign comb2 = {~sin_out[13],sin_out[12:0]};

assign comb = {ADC_DA[13:0]};

Where comb and comb2 are the DAC output pins. It's coming out as a sin wave at the correct frequency just attenuated. I'm measuring the output of the 2 DACS with the same oscilloscope, high input impedance. Is it right to say that the output impedance of my DAC is high, so is attenuated by half at the ADC input?(given that the SMA has Zo of 50 ohms).