dominikz
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Let me share a few basic measurements of the Sabaj A1 (new 2022 version) stereo integrated amplifier. The amp is based on the popular Infineon MA12070 chip and I bought mine for $68.99 (total, shipped to EU).
A few pictures of the amp:
As you can see the power brick (Sabaj branded, 24V / 6,75A, FCC and CE markings) is bulky and the amp is quite tiny! Due to to small case all controls and ports are relatively difficult to operate as everything is cramped into a small space. The tone pots have a center indent (though not very precisely positioned - as you will see). There is unfortunately a relatively low-quality, imprecise feel to all of the pots, but apart from that build quality feels solid to me.
The tools used for measurements:
Let's dive in!
1kHz SINAD
SINAD seems to be limited by the rising noise and distortion (with frequency). A few other amps based on the same chip exhibit similar behavior (e.g. SMSL A100 measured by @amirm), and it appears to be related to the implementation of the output filter - i.e. if there is no choke/inductor on the outputs the amp will show this kind of behavior. Still - pretty solid result for such a cheap amp, IMHO!
It is implied that in this kind of implementation a loudspeaker inductance will act as part of the output filter and help with the rising distortion and noise. To see if there is any improvement I measured 1kHz response @ ~150mW into a pure resistive load and a real loudspeaker (Revel M16):
As you can see, with a loudspeaker the result is slightly worse (rather than better) so it seems to me proper output filter implementation is important for MA12070-based amps.
[EDIT 2022-05-22] Multitone response
Here's the multitone response (5W into 4Ohm, one channel driven), for this I used the very nice Multitone Analyzer tool by @pkane:
The result (10,4 bits) seems very similar to that of the SMSL A100 (I guess that's as expected).
Frequency response and load (in)dependence
As we can see there is around -0,7dB droop at 20Hz and around -0,2dB at 20kHz which is not too bad.
Please note that the above response is the flattest I could get, and it is actually with the tone controls set very slightly below the center-indentation. At the center-indent position there is 2,8dB bass boost and 0,3dB treble boost (see next section for more information).
We saw above there is very little load dependency with this amp. Based on the measured voltage with 4 Ohm and 8 Ohm resistive loads I calculated and plotted the output impedance:
Output impedance appears to be around 0,06 Ohm, which equals to an 8Ohm damping factor of about 125, and it appears to be pretty constant with frequency. All of this means that the amp's frequency response should be pretty stable against any kind of load.
To test this I measured the frequency response when the amp is driving a complex load of a real loudspeaker (Revel M16), and I compared the result to an amp with a very high output impedance (Denon RCD-N9 Ceol):
Please note that both amp's responses are normalized to the response when driving a pure resistive 4Ohm load. As you can see the Sabaj A1 2022 frequency response deviates from flat by about 0,1dB when driving this loudspeaker, while Denon deviations are >1dB with the same loudspeaker.
Tone controls
As I mentioned above, the center indentation of the tone controls is not very precise and doesn't give the flattest response. Here's a plot showing the range of the controls:
Power into 4Ohms (20kHz BW, one channel driven)
The 80W power rating by the manufacturer seems overly optimistic, as with just one channel driven I got to only about 64W RMS at 10% THD into my 4,1Ohm resistive dummy load.
Power into 8Ohms (20kHz BW, one channel driven)
The 40W manufacturer rated power is almost reached (I measure 37W) when driving my 8,2Ohm resistive dummy load, if I allow 10% THD (again, this is only one channel driven).
There's not a lot of power in this tiny amp, but the results seem comparable to other amps with the same chip.
Power vs distortion into 4Ohms (45kHz BW, one channel driven)
Here we see the typical rise of distortion with frequency, from 5kHz onward.
Conclusion
All-in-all I'd say this is a very nice little amp given the low price. Performance is solid and in line with many other similar amps with the same chip. A few implementations seems to perform slightly better (e.g. Loxije A30 and Topping PA3s - perhaps due to the output filter implementation?), but those seem to to also cost more.
Listening to the amp I thought it sounded good - or should I say transparent - just as most other amps I listened to.
The power was in my opinion more than enough to listen to my Revel M16 at 2,3m distance in a 18m2 open living room - though it is a residential building so I can't really blast the music anyway.
[EDIT 2022-05-22] Updated power graphs with correct scaling for the x-axis.
[EDIT 2022-05-24] Updated output impedance and 45kHz BW THD vs power plot with equivalent, but nicer-looking versions. Note that additional BT measurements are available in post #5 (only SBC is supported).
A few pictures of the amp:
As you can see the power brick (Sabaj branded, 24V / 6,75A, FCC and CE markings) is bulky and the amp is quite tiny! Due to to small case all controls and ports are relatively difficult to operate as everything is cramped into a small space. The tone pots have a center indent (though not very precisely positioned - as you will see). There is unfortunately a relatively low-quality, imprecise feel to all of the pots, but apart from that build quality feels solid to me.
The tools used for measurements:
- Topping E50 DAC as signal generator (USB input, RCA outputs), 192kHz sample rate and 32bit depth
- E1DA Cosmos ADC (2,5mm TRRS Aux input), 192kHz sample rate and 32bit depth
- Asio4All drivers (192kHz sample rate)
- REW software for measurements
- Google Sheets for impedance calculations
- DIY resistive dummy load
- Revel M16 loudspeaker for complex load test
Let's dive in!
1kHz SINAD
SINAD seems to be limited by the rising noise and distortion (with frequency). A few other amps based on the same chip exhibit similar behavior (e.g. SMSL A100 measured by @amirm), and it appears to be related to the implementation of the output filter - i.e. if there is no choke/inductor on the outputs the amp will show this kind of behavior. Still - pretty solid result for such a cheap amp, IMHO!
It is implied that in this kind of implementation a loudspeaker inductance will act as part of the output filter and help with the rising distortion and noise. To see if there is any improvement I measured 1kHz response @ ~150mW into a pure resistive load and a real loudspeaker (Revel M16):
As you can see, with a loudspeaker the result is slightly worse (rather than better) so it seems to me proper output filter implementation is important for MA12070-based amps.
[EDIT 2022-05-22] Multitone response
Here's the multitone response (5W into 4Ohm, one channel driven), for this I used the very nice Multitone Analyzer tool by @pkane:
The result (10,4 bits) seems very similar to that of the SMSL A100 (I guess that's as expected).
Frequency response and load (in)dependence
As we can see there is around -0,7dB droop at 20Hz and around -0,2dB at 20kHz which is not too bad.
Please note that the above response is the flattest I could get, and it is actually with the tone controls set very slightly below the center-indentation. At the center-indent position there is 2,8dB bass boost and 0,3dB treble boost (see next section for more information).
We saw above there is very little load dependency with this amp. Based on the measured voltage with 4 Ohm and 8 Ohm resistive loads I calculated and plotted the output impedance:
Output impedance appears to be around 0,06 Ohm, which equals to an 8Ohm damping factor of about 125, and it appears to be pretty constant with frequency. All of this means that the amp's frequency response should be pretty stable against any kind of load.
To test this I measured the frequency response when the amp is driving a complex load of a real loudspeaker (Revel M16), and I compared the result to an amp with a very high output impedance (Denon RCD-N9 Ceol):
Please note that both amp's responses are normalized to the response when driving a pure resistive 4Ohm load. As you can see the Sabaj A1 2022 frequency response deviates from flat by about 0,1dB when driving this loudspeaker, while Denon deviations are >1dB with the same loudspeaker.
Tone controls
As I mentioned above, the center indentation of the tone controls is not very precise and doesn't give the flattest response. Here's a plot showing the range of the controls:
Power into 4Ohms (20kHz BW, one channel driven)
The 80W power rating by the manufacturer seems overly optimistic, as with just one channel driven I got to only about 64W RMS at 10% THD into my 4,1Ohm resistive dummy load.
Power into 8Ohms (20kHz BW, one channel driven)
The 40W manufacturer rated power is almost reached (I measure 37W) when driving my 8,2Ohm resistive dummy load, if I allow 10% THD (again, this is only one channel driven).
There's not a lot of power in this tiny amp, but the results seem comparable to other amps with the same chip.
Power vs distortion into 4Ohms (45kHz BW, one channel driven)
Here we see the typical rise of distortion with frequency, from 5kHz onward.
Conclusion
All-in-all I'd say this is a very nice little amp given the low price. Performance is solid and in line with many other similar amps with the same chip. A few implementations seems to perform slightly better (e.g. Loxije A30 and Topping PA3s - perhaps due to the output filter implementation?), but those seem to to also cost more.
Listening to the amp I thought it sounded good - or should I say transparent - just as most other amps I listened to.
The power was in my opinion more than enough to listen to my Revel M16 at 2,3m distance in a 18m2 open living room - though it is a residential building so I can't really blast the music anyway.
[EDIT 2022-05-22] Updated power graphs with correct scaling for the x-axis.
[EDIT 2022-05-24] Updated output impedance and 45kHz BW THD vs power plot with equivalent, but nicer-looking versions. Note that additional BT measurements are available in post #5 (only SBC is supported).
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