Here is my analysis of the noise on the Audio Injector Octo. It is pretty good.
I did two experiments, connecting the DAC to the ADC using :
- Wires connecting pins to pins.
- RCA cables connecting analogue buffer output to input.
- Dynamic Range of 90 dB (arguably better)
- RCA connector harmonic distortion (1st harmonic) of -70 dB
- Without the RCA connectors (DAC pin to ADC pin connections) 1st harmonic of -Inf dB, the harmonics can't be found because they are in the noise floor.
Here is the graph of the results ... Here are the resulting audio files I recorded :
For the pin test here.
For the RCA test here.
Here is the matlab (octave) script I used for analysis :
Code: Select all
function analysis % Author : Matt Flax % Date : 2017 08 26 [xp,fs]=audioread('96kHz.test.v1.pin.wav'); [xr,fs]=audioread('96kHz.test.v1.rca.wav'); Np=size(xp,1); Nr=size(xr,1); N=min(Np,Nr) idxs=round(1*N/8):round(7.2*N/8); x=[xp(idxs,1) xr(idxs,1)]; N=length(idxs); % rescale maxs=max(abs(x)); fact=maxs(1)/maxs(2); x(:,2)=x(:,2)*fact; figure(1); clf plot(idxs/fs,x) X=20*log10(abs(fft(x/(length(idxs)/fs)))); f=linspace(0,fs,size(X,1)); figure(2); clf semilogx(f,X) grid on set(gca,'xlim',[400 10e3]) title('Audio Injector - octo pin to pin - noise measurements for a 1 kHz tone') xlabel('f (Hz)') ylabel('dB') legend('pin 2 pin','rca 2 rca') end