Superpower = Super Low Noise
SPJ78@12V RMS noise voltage measurement
Total unweighted noise across the audio band of 20Hz to 20KHz measures 8µVrms. (see below). This RMS value is noise measured for a +12V out Superpower, which equates to <1PPM of noise per volt out. 3.3V output devices have noise of approximately 4µVrms. Note: Voltage scale was adjusted to reflect a gain of 1000 in the measurement system.
Comparison of Six Regulators
Noise of six regulators is shown here. These measurements were all made with the same test fixture (above) at the same testing session. Some are common monolithic parts (LM317, LM7812), some are newer, higher quality monolithics and some are "boutique" regulators like Superpower.
A noise spectrum shown below is from a Superpower with 12V out with no external load. Sample
rate was 39.063KHz with 4K samples using a Blackman-Harris window.
Sixteen sample sets are averaged to smooth the graph.
Superpower noise spectrum
Superpower noise spectrum at 480mA load
Above is the same noise measurement made with the Superpower delivering a 480mA load. With a gain of 60dB due to the test setup, the measured values were all scaled down by 60dB (= divide by 1000), so, e.g. a value at -60dB became -120dB.
While total noise is slightly higher due to load induced noise, the RMS measurement remains about 8µV and peak-to-peak about 55µV.To overcome noise floor limitations of the data capture instrument, a low noise preamp with a gain of 1000 is used to boost the noise to be measured:
The test fixture also performs a bandpass function, limiting the measurement to the audio bandwidth of interest:
Bandwidth of noise test fixture
Spectrum of measurement system
Basic noise floor of the measurement system including the gain-of-1000 amplifier shown above.
Vertical scale has been adjusted by -60dB to account for the gain.