This is a review and detailed measurements of the Premium Audio Mini GaN 5 Stereo Class D power amplifier. It was kindly sent to me by a member and costs US $799 (recent price increase).
The GaN 5 comes in a compact enclosure with plenty of ventilation at the cost of decent looks:
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Beside the sole power button and blue indicator, there are two red LEDs that turn on when you power the unit on and then go off. Strangely, when the amplifier goes into protection, they do not light up and getting the unit working again requires a power cycle. I like to see protection circuits that self recover when the extreme condition goes away.
The back panel shows binding posts that are too close together for easy fitment of my large banana speaker cables. But I like the inclusion of balanced XLR inputs:
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As you see, there are also jumpers to change the gain setting although the range is not very large (26, 28 and 32). Most of my testing was with medium gain which is as shipped.
I had trouble getting the amplifier to function initially. It would simply not output anything. I played with grounding as I have seen some very low end amps cause AP to not be able to capture their output due to high level of noise (despite my use of AES-17 filter). This didn't work at first so I switched inputs to RCA. That did not work either. After some fiddling and switching back to balanced input, the amp all of a sudden started to work. Not sure how much of this is interaction with Audio Precision or design issue. Either way, it is an exception to the rule of 95% of amplifiers I have measured.
As the name indicates, this amplifier uses the new Gallium Nitride transistors (GaN) which has some advantages over classic Mosfet transistors. All else being equal, it can produce higher efficiency and better performance at expense of higher cost.
Mini GaN 5 Measurements
As noted, I started my testing in medium gain which produced near nominal 29 dB which is my standard for amplifiers. XLR input was used per introduction:
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Well, this is disappointing. Distortion is fairly high causing SINAD which is the sum of distortion+noise to be worse than a number of budget desktop amplifiers:
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Noise performance by itself is not good either:
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I had trouble getting the amplifier to go to full power for the right graph. It would shut down at just 0.7 volt input. Strangely, later on it accepted higher levels of input. I think the impulse nature of this measurement was causing it trouble. So maybe it can produce higher SNR at higher power but still, none of this is competitive.
On the other hand, crosstalk was very good:
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Multitone performance was also reasonable:
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What is not reasonable is high dependence on speaker load when it comes to frequency response:
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This is just not proper. Clearly the output filter is interacting with the load.
Power measurements were quite puzzling:
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Notice the pull back due to some protection kicking in, likely the power supply rather than the amplifier. I could not remotely get the power rating they specify using medium gain. I thought maybe low gain does better but then the pull back occurred at even low power (blue and green)! Beside lack of power, distortion is also quite high for this price class and category. We are talking about poor Audio/Video Receiver amplifier performance!
Switching to 8 ohm tamed the output a bit but power shortfall is still significant:
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This being the second amplifier I have recently tested with such power shortfall, I started to doubt my instrumentation. So I pulled out my Purifi reference design and measured it. It tracked the dashed line in the above graph from a year ago 100%. Someone had posted this from their website:
600 watts per channel??? Into 8 ohm? This is the spec from the manual:
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How on earth did they measure 600 watts when the spec is 200 watts? Strangely, that graph is nowhere to be found on their site. There is some talk about a larger amplifier of which is a shrunk version? Maybe that is the one that produced higher power but why does it say "mini" in the title of above graph?
FYI, this amplifier has the green board which I understand to be the newer design. Maybe the older red one had more power. Hard to say.
Anyway, I tried to run my max and burst power:
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In Burst mode, the amplifier would keep going into pull back and so I could not compute anything for that. Likewise the THD+N vs frequency and power could not be run. As the frequencies got lower and lower, the point where the amp would pull back would also shrink to lower and lower wattages. What I could get did not show great transfer function.
Conclusions
While I leave the door ever so slightly ajar to some interaction with Audio Precision, the measurements seem to indicate an amplifier that has both design issues and inability to meet specifications. The fact that the company took away the only measurement graph makes it suspect that maybe they had have modified the design and selling something different than what they originally intended. As it is, it is a waste of GaN technology as it brings nothing to the party but high expense.
I can't recommend the Premium Audio Mini GaN 5 amplifier.
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