Reviewed on: SoundStage! Solo, September 2019
I measured the Nickel using a Clio 10 FW audio analyzer and a Neutrik NL-1 Minilyzer. Note that my focus with these tests is on measurements that confirm these devices’ basic functionality.
This chart shows the Nickel’s frequency response with 1mW output into 32-, 250- and 600-ohm loads. Into 32 ohms, the response measures -0.51dB at 20Hz, -0.26dB at 20kHz, and -2.80dB at 75kHz. Into 250 ohms, the numbers are -0.48dB, -0.22dB, and -2.49dB, respectively. Into 600 ohms, the numbers are -0.47dB, -0.21dB, and -2.50dB, respectively. For a tiny, portable amp like this one, these are respectable numbers.
This chart shows the matching of the Nickel’s channels at 1mW into a 32-ohm load. The right channel is 0.069dB lower in level at 1kHz than the left channel, a negligible difference, and the shapes of the response curves match precisely within the audioband.
This chart shows the output of the Nickel vs. total harmonic distortion (THD) into 32-, 250-, and 600-ohm loads at 1kHz. Rated power is 250mW into 32 ohms, THD and frequency unspecified. Output into 32 ohms is 150mW at 0.5% THD and 156mW at 1% THD; the highest output I was able to measure is 203mW at 10% THD. Output into 250 ohms is 32mW at 0.5% THD and 34mW at 1% THD. Output into 600 ohms is 14mW at 0.5% THD and 15mW at 1% THD.
Here you can see the harmonic distortion spectrum and noise floor of the Nickel, referenced to 174mW output at 600Hz into 32 ohms. The distortion is predominantly odd-order (3rd, 5th, 7th harmonics, etc.), although I had to push the amp a little past its limits to even see any even-order (2nd, 4th, 6th, etc.) harmonics.
I measured no-load gain at 5.4dB, a little lower than the rated 6.5dB. Output impedance at 1kHz measures 0.78 ohm. This means the amp’s output impedance will not interact significantly with the reactance of headphones or earphones, and thus won’t alter their frequency response.
. . . Brent Butterworth