One more thing. I didn't mention
THD+N yet.
This plot is different in that the x-axis is output voltage and the y-axis is THD+N (%), which means total harmonic distortion plus noise.
While the harmonic spectrum shows harmonics and noise in great detail, it only shows this at a fixed output voltage and load. In the THD+N plot this spectrum is converted into a single number and that is done over and over again with rising voltage and different loads.
The way it is calculated is by summing the power of the harmonics and noise (everything else) and dividing it by the power of the fundamental. The resulting percentages can also be converted into dB:
10% = -20 dB
1% = -40 dB
0.1% = -60 dB
0.05% = -66 dB
0.01% = -80 dB
Since higher load impedance means the amp has to provide less current you'll generally see lower THD+N with such loads.
At low voltages noise starts to dominate, at high voltage the amp will reach its clipping point at some point (where the line shoots up). If this point, for example, is at 2 V then the amp can output about 250 mW (= 2*2/16) into 16 ohms.
Quote:
How would you say the e17 alpen score, xnor? (I own this amp) Thanks.
Well, it seems to have problems with nonlinear distortion. What's weird is that in the measurement with 150 ohms it has higher THD+N than with more difficult loads. It seems to be quite a bit happier with 16 ohm IEMs. But keep in mind that you won't need high voltages to reach ear-splitting levels with IEMs and at low voltages the THD+N doesn't look so good.