Reviewed on: SoundStage! Solo, November 2019
I measured the RH-5 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. Except as noted, I used the unbalanced output.
This chart shows the frequency response in the left and right channels at 1mW into a 32-ohm load. Channel tracking is good, with the right channel 0.015dB louder at 1kHz, and 0.095dB less roll-off in the right channel at 20kHz. Response measures -1.0dB at 20Hz, -0.53dB at 20kHz, and -5.66dB at 75kHz. This shows the unbalanced output; the balanced output was essentially the same except for -1.91dB additional roll-off at 10Hz. This measurement was taken with gain set to 3. At gain 2, output is reduced by 4.34dB at 1kHz. Gain 1 reduces the output by an additional 3.78dB.
This chart compares the Rogue’s frequency response with 1mW unbalanced output into 32-, 250-, and 600-ohm loads. Into 250 ohms, the numbers are -0.04dB, -0.45dB, and -4.85dB, respectively. Into 600 ohms, the numbers are -0.02dB, -0.45dB, and -4.78dB, respectively. The bass roll-off into 32 ohms, and the treble roll-off into all loads, isn’t impressive -- tubes at work here! -- but in both cases it’s modest enough that you’d be unlikely to notice it.
This chart shows the unbalanced output of the Rogue vs. total harmonic distortion (THD) into 32-, 250-, and 600-ohm loads at 1kHz. Rated power is 3.5W into 32 ohms; the distortion level, the frequency, and whether the spec is at the balanced or unbalanced output are all unspecified. Into 32 ohms, output is 1.9W at 0.5% THD and 2.0W at 1%; while this may (or may not) fall short of the spec, it’s certainly plenty enough power to drive any headphones to very high volume. Into 250 ohms, the output is 0.37W at 0.5% THD and 0.39W at 1%. Into 600 ohms, the numbers are 0.16W and 0.17W, respectively. Solid performance here.
Here you can see the harmonic distortion spectrum and noise floor of the Rogue, referenced to 5.66Vrms (1W) output at 600Hz into 32 ohms. This shows what I’d expect from a hybrid amp. The sonically benign (because it’s exactly one octave above the fundamental tone) second-order harmonic is stronger than we’d probably see with an all-transistor amp, but it’s not as dominant as we’d probably see in an all-tube amp.
Output impedance is rated at less than 0.1 ohm at 1kHz; I measured 0.07 ohm. This means that the output impedance of the amp will not significantly interact with the reactance of the headphones, so you’ll get consistent response no matter what type of drivers your headphones use.
. . . Brent Butterworth