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Sabaj A1 Desktop Amplifier Review

amirm

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#1
This is a review and detailed measurements of the Sabaj A1 desktop (small) amplifier. It was kindly sent to me by a member. Not sure if it is still in production but you can still find it for $60 or so. Main interest in testing this unit is the use of the TPA3118 class D amplifier which is used in all kinds of other devices including Genelec 8030c powered monitor!

For the price the enclosure is not half bad:

Sabaj A1 TPA3118 Desktop Amplifier stereo review.jpg


A little LED display shows the active input (there are two) and current volume level. As is typical, a laptop sized power supply provides the juice:

Sabaj A1 TPA3118 Desktop Amplifier back panel power supply  stereo review.jpg


The unit runs cool. If you overtax it, it will reset and power back on at low output level.

Sabaj A1 Measurements
As usual we start with our 5 watt dashboard:

Sabaj A1 TPA3118 Desktop Amplifier Audio Measurements.png


As you see I set the gain to 29 dB which is the "standard" I use for integrated amplifiers. Resulting SINAD is dominated by distortion and is well below average for all amps tested:

Best desktop Amplifier.png


But... if you compare it to other low cost amps in this price bracket, performance is a good 10 dB better.

Noise performance is in the same class:
Sabaj A1 TPA3118 Desktop Amplifier SNR Audio Measurements.png


Frequency response is not flat but good to see it rolling off as opposed to peaking:

Sabaj A1 TPA3118 Desktop Amplifier Frequency Response Audio Measurements.png


Crosstalk is what you expect in this type of device:
Sabaj A1 TPA3118 Desktop Amplifier  Crosstalk Audio Measurements.png


Most important is power and this is how the A1 did into 4 ohm:

Sabaj A1 TPA3118 Desktop Amplifier Power into 4 ohm Audio Measurements.png


Not a whole lot of power I am afraid. Pushing it harder didn't do any good either:

Sabaj A1 TPA3118 Desktop Amplifier Peak and Max  Power into 4 ohm Audio Measurements.png


The power supply runs out of juice and the device shuts down. May do better with a more powerful power supply.

Here it is into 8 ohm:
Sabaj A1 TPA3118 Desktop Amplifier Power into 8 ohm Audio Measurements.png


Conclusions
As a class I expect these cheap amps to be broken. The A1 is not that bad. My concern is too little power. Many small speakers are inefficient and you need more than 20 watts to get decent performance out of them. My suggestion is to save on spending money on food and flowers and save up for a better amp. But if you can't, the Sabaj A1 may do the job for you.

As it is, I can't recommend the Sabaj A1. I am too much of an audio/technology snob to go for it!

------------
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Doodski

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#3
There are undoubtedly some use cases where this would work, at least as a temporary expedient.
It's perfect for limited duty and if that protection circuitry can hang in there long term it is a ringer for applications where the power output limitation and volume setting protection circuitry are good for bedrooms, pre-teens work-desk-bench etc. I wonder how many times it can be driven into a dead short and have the protection re-engage the output.
 

3125b

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#4
That's really not a lot of power, even cheap active multimedia speakers tend to have stronger amps, even the small Eris E3.5 have 2 x 25W for example.
For very limited listening levels however, this seems like a passable amp considering the price.

Compared to that ridiculous Cord phono stage this is a real winner :)
 

Dmitri

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#5
Kind of surprised to find something like this in any Genelec product. Seems more likely a good project amp for a home brew boom box.
Adds a certain credibility to the concept of testing powered speaker amplifiers separately, if possible...to get a better sense of what you are really getting for your money.
 

Doodski

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#6
Kind of surprised to find something like this in any Genelec product. Seems more likely a good project amp for a home brew boom box.
Adds a certain credibility to the concept of testing powered speaker amplifiers separately, if possible...to get a better sense of what you are really getting for your money.
I imagine Genelec uses a higher voltage resulting in more power output.
 

ElNino

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#8
Can you do a plot with distortion by frequency? The data sheet for the TPA3118 shows that the distortion is very uneven, and increases dramatically after about 7kHz.
 
OP
amirm

amirm

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Thread Starter #10
20w? So it’s the tweeter amp for 8030?
The chip is rated up to 50 watts and that is what Genelec says about amplification power. Here, the power supply is not powerful enough for it to go that high. And may not have a heatsink for it either.
 

YSC

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#11
The chip is rated up to 50 watts and that is what Genelec says about amplification power. Here, the power supply is not powerful enough for it to go that high. And may not have a heatsink for it either.
Ic, so that’s why the genelec performs well when this got pretty poor results, implementation is the key then
 

ElNino

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#14
Ic, so that’s why the genelec performs well when this got pretty poor results, implementation is the key then
The results here aren’t out of line with the datasheet, actually. It just doesn’t hit max power, but the noise and distortion at low (~5w) power are about as good as the TPA3118 can do.
 

Sancus

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#15
So if I understand this right, this is just the one chip running in stereo mode. The 8030C has two of these, one for the woofer and one for the tweeter, in a single monitor? So it should at minimum have 4x the real power of this test. Possibly more if driving at higher voltage.
 

ElNino

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#16
So if I understand this right, this is just the one chip running in stereo mode. The 8030C has two of these, one for the woofer and one for the tweeter, in a single monitor? So it should at minimum have 4x the real power of this test. Possibly more if driving at higher voltage.
The Genelec 8030c’s max/total power consumption at full output is specced at 60w, so it’s possible they’re only using one of these. (The bass and tweeter amps are both specced at 50w, but they don’t seem to be able to produce that amount of power simultaneously,)
 

Sancus

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#17
The Genelec 8030c’s max/total power consumption at full output is specced at 60w, so it’s possible they’re only using one of these. (The bass and tweeter amps are both specced at 50w, but they don’t seem to be able to produce that amount of power simultaneously,)
Well certainly, in practice the tweeter is only covering 3khz+, which is probably never going to use more than a couple watts at maximum, especially considering the 8030C like most active monitors has boosted low frequencies compared to a passive design. So it would be pointless to actually supply equal amounts of power to the tweeter and woofer even if the chip is technically rated for that.
 

restorer-john

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#18
Most likely. It would be interesting to test the amp with higher voltages to assess its potential.
Not a good idea unless you want fireworks. The main filter cap is sailing way too close to the wind already at 25V WV.

1604806299273.png


It fails to even remotely approach any of its advertised specifications which is typical of these toy amplifiers.

1604806467948.png
 

Dmitri

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#19
Not a good idea unless you want fireworks. The main filter cap is sailing way too close to the wind already at 25V WV.

View attachment 92179

It fails to even remotely approach any of its advertised specifications which is typical of these toy amplifiers.

View attachment 92180
So this is what Genelec’s using in a $700 near field monitor? Huh. Not sure, as a company, I’d like that to get out there.....
 

restorer-john

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#20
So this is what Genelec’s using in a $700 near field monitor? Huh. Not sure, as a company, I’d like that to get out there.....
The IC can be implemented in several ways to obtain poor to quite reasonable performance and power output. This implementation is clearly in the poor category.

Avail yourself of the datasheet and look at what it can do.

The IC in question is a proven "solution" and quite robust, low cost, and reliable. High fidelity however, is not one of its attributes.
 
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