Wait, how do you know this amp has high residual noise? You have one?
From the measurements. You can convert the dynamic range measurement to residual noise. You can also add in the contribution from your DAC to get a feel for what the total residual noise at your speaker terminals looks like. In this case because of the poor amplifier performance residual noise will likely be dominated by the amp not the DAC.
Here is an example.
Let's say we have a pretty decent DAC that has 115 dB dynamic range at 2 V output.
residual noise at DAC output = dac_vout x 10^(-DR/20) = 2 x 10^(-115/20) = 3.56 uV
Now multiply that by the amplifier gain, assuming 29 dB we get...
DAC residual noise at amplifier output = dac_noise x 10^(gain/20) = 3.56 x 10^(29/20) = 100 uV
Now let's look at the amplifier. We have 76 dB dynamic range at 5 W in to 4 ohms. First we need to calculate the amplifier output voltage at 5 W.
amp output voltage = sqrt(P x R) = sqrt (5 x 4) = 4.47 V
Now we can convert the output voltage to residual noise.
amp residual noise = amp_vout x 10^(-DR/20) = 4.47 x 10^(-76/20) = 708 uV
Now calculate total noise from DAC / amplifier combination at speaker terminals.
total noise = sqrt(amp_noise^2 + amplified_dac_noise^2) = sqrt(708^2 + 110^2) = 715 uV
Again I've done measurements at the speaker terminals of my own system and correlated them with whether or not I have audible hiss. For me that threshold is around 150 uV. This thread has more details ->
https://www.audiosciencereview.com/...m-china-with-topping-performance.24768/page-2.
Michael