AIYIMA A07 TPA3255 Amplifier with MW RS-100-24 SMPS Power Supply
I have just received the Mean Well RS-100-24 SMPS power supply, connected it to AIYIMA A07 and made a set of measurements and some listening. As the amplifier must be paired with a power supply and these 2 units make a complete amplifier, and the behaviour of the class D amplifier with a SMPS power supply is quite special, I have decided to open this new thread and not to make even bigger mismatch in my original review/measurement thread,
https://www.audiosciencereview.com/...-measurements-and-review-lm4562-option.19155/
The power supply used in this new test thread is switched mode power supply Mean Well RS-100-24, rated at 24V/4.5A (108W). As there is a trim pot to fine tune output voltage, I have set it to 27.0V output voltage, which is close to maximum, which I measured 27.45V (OCV).
There are 3 screw terminals to connect mains input (230V, L, N, PE) and -V and +V output DC terminals, each having 2 screws. I have used 1 pair of output terminals to supply the amplifier, and to the other pair I connected 47nF/1000V capacitor to reduce output HF noise a bit. This capacitor was also used to connect oscilloscope probe for ripple measurements.
The unit is small, 159 x 97 x 38mm.
It should be connected and operated by a qualified personnel, for the reason of bare screws connected to dangerous mains voltage. It should be covered in a vented box in case that supposed to be used with the amplifier, with safety standards fulfilled (diameter and placement of vents).
Okay, I first measured the PSU ripple when connected to the amplifier. Without any input signal, the ripple looks like this
The ripple is about 42mVp-p and sawtooth frequency is about 70kHz.
When both channels of the amplifier were driven to 2 x 37W/4ohm, the ripple looked like this
About 250mVp-p and the SMPS switching frequency is modulated by H2 of the input 1kHz signal. Still not bad.
Then I measured the usual
THD and THD+N (SINAD) at 1kHz/5W/4ohm (both channels driven)
We can see quite low THD=0.0014% and SINAD=86.74 dB and very good suppression of mains hum multiples.
THD and THD+N at 1kHz 2x27W/4ohm
Decent spectrum, considering the chip used.
THD and THD+N at 1kHz 2x54W/4ohm
Still nice!
However going a bit higher to 2x57W/4ohm, the power supply switched off itself, most probably because its output current limit has just been exceeded. So this is the limit of A07+RS-100-24 combo.
THD vs. amplitude at 100Hz, 1kHz and 6kHz / 4ohm, both channels driven, SMPS
So far so good up to some 2x55 – 2x60W/4ohm. Then, the SMPS PSU overcurrent control is activated and the DC supply voltage falls to zero. We can see the “knee” at about 65W, the output voltage is dramatically decreased and the distortion is dramatically increased.
If we make the same test with my 25V/270VA unregulated power supply, we do not see this collapse, however the output power is a bit lower and the spectrum is less clean, especially the mains power components (and the PSU is huge).
Conclusions
I think that the amp behaves nicely with this Mean Well SMPS, except for the moment when the overcurrent protection might be activated. It is also necessary to bear safety rules of the PSU implementation in mind. For the amplifier, this lower supply voltage is an advantage re inside temperature and life time expected. The amp itself is not able to give much more than 2x50W, because after some time it is switched off by its temperature protection and with e.g. 48V power supply this happens much much earlier.
I have just received the Mean Well RS-100-24 SMPS power supply, connected it to AIYIMA A07 and made a set of measurements and some listening. As the amplifier must be paired with a power supply and these 2 units make a complete amplifier, and the behaviour of the class D amplifier with a SMPS power supply is quite special, I have decided to open this new thread and not to make even bigger mismatch in my original review/measurement thread,
https://www.audiosciencereview.com/...-measurements-and-review-lm4562-option.19155/
The power supply used in this new test thread is switched mode power supply Mean Well RS-100-24, rated at 24V/4.5A (108W). As there is a trim pot to fine tune output voltage, I have set it to 27.0V output voltage, which is close to maximum, which I measured 27.45V (OCV).
There are 3 screw terminals to connect mains input (230V, L, N, PE) and -V and +V output DC terminals, each having 2 screws. I have used 1 pair of output terminals to supply the amplifier, and to the other pair I connected 47nF/1000V capacitor to reduce output HF noise a bit. This capacitor was also used to connect oscilloscope probe for ripple measurements.
The unit is small, 159 x 97 x 38mm.
It should be connected and operated by a qualified personnel, for the reason of bare screws connected to dangerous mains voltage. It should be covered in a vented box in case that supposed to be used with the amplifier, with safety standards fulfilled (diameter and placement of vents).
Okay, I first measured the PSU ripple when connected to the amplifier. Without any input signal, the ripple looks like this
The ripple is about 42mVp-p and sawtooth frequency is about 70kHz.
When both channels of the amplifier were driven to 2 x 37W/4ohm, the ripple looked like this
About 250mVp-p and the SMPS switching frequency is modulated by H2 of the input 1kHz signal. Still not bad.
Then I measured the usual
THD and THD+N (SINAD) at 1kHz/5W/4ohm (both channels driven)
We can see quite low THD=0.0014% and SINAD=86.74 dB and very good suppression of mains hum multiples.
THD and THD+N at 1kHz 2x27W/4ohm
Decent spectrum, considering the chip used.
THD and THD+N at 1kHz 2x54W/4ohm
Still nice!
However going a bit higher to 2x57W/4ohm, the power supply switched off itself, most probably because its output current limit has just been exceeded. So this is the limit of A07+RS-100-24 combo.
THD vs. amplitude at 100Hz, 1kHz and 6kHz / 4ohm, both channels driven, SMPS
So far so good up to some 2x55 – 2x60W/4ohm. Then, the SMPS PSU overcurrent control is activated and the DC supply voltage falls to zero. We can see the “knee” at about 65W, the output voltage is dramatically decreased and the distortion is dramatically increased.
If we make the same test with my 25V/270VA unregulated power supply, we do not see this collapse, however the output power is a bit lower and the spectrum is less clean, especially the mains power components (and the PSU is huge).
Conclusions
I think that the amp behaves nicely with this Mean Well SMPS, except for the moment when the overcurrent protection might be activated. It is also necessary to bear safety rules of the PSU implementation in mind. For the amplifier, this lower supply voltage is an advantage re inside temperature and life time expected. The amp itself is not able to give much more than 2x50W, because after some time it is switched off by its temperature protection and with e.g. 48V power supply this happens much much earlier.
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