– Audio Precision APx555 B-Series Analyzer
– Amplifier was warmed up for 6 hours before measuring.
– AudioQuest Mackenzie RCA interconnects
– Neurochrome Headphone Dummy Load
– Full reports containing additional data and test configurations are attached
– Exact analyzer configurations for each measurement are detailed in the full reports
– All measurements shown below are taken with a 32 ohm load in low gain unless otherwise specified
Reports available here (These contain 2v, 700mv and 50mv test results, please check you’re looking at the right ones when comparing!):
Gain: 20.8dB (High), 14.2dB (Med), 0dB (Low)
Output impedance: 0.17 Ohm
As an auxilliary note: Artem asked me to test the maximum input level of this amp and I was able to input just over 11V (The max the analyzer will output) with no reduction in performance. So you can happily use this with even very ‘hot’ output dacs/preamps.
1khz 2v input 32 ohm (Low Gain Pot Maxed):
If there’s an amp that disproves the ‘well measuring stuff sounds sterile’ trope, this is certainly it!
This is an amp that in my opinion sounds very warm and lush, but doesn’t sacrifice THD+N performance.
THD+N / Frequency:
SINAD/THD+N vs output level:
IMD (SMPTE) vs Output Level:
Crosstalk is the main area where this amp could seemingly use a bit of improvement. Though Artem from Rebel has said that he will be sending a tweaked design over at somepoint to lower crosstalk so I’ll post as soon as I’ve tested it!
1khz Square Wave:
Note: I unfortunately had the reference level set wrong during this test as I’d left the value for balanced 4v in, not unbalanced 2v.
As such, the actual content is shifted down by 6dB, but otherwise still accurate.