This unit was kindly sent to me by Beach Hifi, if you’d like to purchase the SGA1 you can do so here:
This post is measurements only. A full review will be coming.
– Audio Precision APx555 B-Series Analyzer
– Van Damme Star-Quad shielded SPC XLR cables with Amphenol Connectors
– Neurochrome Dummy Load
– Full reports containing additional data and test configurations are attached
– Exact analyzer/filter configurations for each measurement are detailed in the full reports
– All measurements shown below are taken with a 32 ohm load via balanced output unless otherwise specified (single-ended reports are available below)
Reports available here:
Reports contain the following measurements:
– 200khz Bandwidth
– THD+N @ Unity gain, 700mv, 50mv
– Maximum Power test (THD+N/Watts)
– Phase Response
– Square Wave
– 1khz FFT
– 50hz FFT
– THD+N / Frequency (20-20khz and 20-30khz)
– Dynamic Range (AES17)
– IMD (SMPTE)
– IMD SMPTE vs Output Level
– Linearity (No Bandpass)
– SINAD/Output Level
– Crosstalk / Frequency
– 32 Tone FFT
– And more!
Dynamic Range (AES17): 116.7dB
This amp is a little bit interesting in that the volume control is its major bottleneck. This is an important example of why I test amps by using the inbuilt volume control manually, and NOT by just lowering the voltage from the analyzer.
Doing the latter can mean that potential issues or changes in performance that WILL be present in real world use might get missed.
Additionally, ‘0dB gain’ on balanced is actually 6dB gain.
Therefore, 4v in 4v out unity gain can’t be measured and I had to either input 4v and turn volume down by 6dB, or do 2v in with 0dB volume adjustment. Also I took the 1khz measurement at 300ohm as it began to current-limit otherwise which skewed the measurement.
1khz 2v in 4v out 300 Ohm:
1khz 4v in, -6dB vol control for 4v out 300ohm:
As you can see, as soon as the volume control chip is used, we see the 2nd and 3rd harmonic shoot up and we lose over 10dB of SINAD Performance is still good, but it’s a shame to see what otherwise seems to be a fantastic amp limited by the volume control.
Having said that, the fact that it is showing near equal parts 2nd and 3rd harmonics, and also retains high SNR, means that actually this could contribute to quite an enjoyable sound.
Typically high THD also comes with poor SNR and/or high IMD, which isn’t the case here, you get a little bit of harmonic ‘flavouring’ without much downside.
To demonstrate how much this limits performance I did the 700mv test first by leaving the volume at 0dB, and lowering the input signal to the amp, and then by putting in the normal 4v and reducing volume to 700mv.
1khz 700mv (Headphone Level) 32 Ohm, 350mv in, 700mv out:
1khz 700mv (Headphone Level) 32ohm, 4v in, -20.75dB volume reduction to 700mv:
Now whilst the SINAD figure itself hasn’t changed a huge amount, look at the actual harmonic structure. When using the amp’s volume control the harmonics are up to 20dB higher.
1khz 50mv (IEM Level) 12 Ohm:
Power @ 32 Ohm:
Power @ 300 Ohm:
DIM Level Sweep:
THD+N / Frequency (90khz bandwidth):
SINAD/THD+N vs output level:
IMD (SMPTE) vs Output Level:
1khz Square Wave: