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... or a switched outlet. That is what I spec'd for my hifi room. 
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Douk A5 Budget Stereo Amplifier Review
- Thread starter amirm
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PoorAudioGuy
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Please help me decide: this or Fosi V3 for running a pair of DBR62s?
Subjectivity alert.
Today I fired up my old Arcam Alpha 7, soon 30 year old amp and I was shocked how it sounds more transparent and dynamic in comparison to douk A5. Even with 40W per channel, especially higher volumes sound so much better. I've been using 48V 10A psu for A5 last few months.
Today I fired up my old Arcam Alpha 7, soon 30 year old amp and I was shocked how it sounds more transparent and dynamic in comparison to douk A5. Even with 40W per channel, especially higher volumes sound so much better. I've been using 48V 10A psu for A5 last few months.
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The Douk Audio A5 is currently on sale at Amazon (USA) for Prime members only.
An A5 with a 32 volt, 5 amp power supply is $79.99
An A5 with a 48 volt, 5 amp power supply is $99.99
An A5 with a 32 volt, 5 amp power supply is $79.99
An A5 with a 48 volt, 5 amp power supply is $99.99
This is a review and detailed measurements of the Douk Audio A5 stereo class D amplifier. It was sent to me by the company and costs US $99.99 as of this writing on Amazon including free shipping.
View attachment 435558
I really like the look of the unit. The control on the right turns the amp on and adjusts the volume. The knob on the left adjusts a high-pass filter which is nice to have to tailor the bass response for typical bookshelf speakers this amp will be driving. And allowing subwoofer integration (although you have to bring your own splitter). Back panel is what you expect:
View attachment 435559
While the unit is rated up to 48 volts, the supplied power supply as you see is rated at 32 volts @ 5 amps. The terminals are rather small but I still managed to attach my chunky locking banana plugs into them.
As an interesting touch, a plexiglass cover is easily removed to change op-amps but also change switches which change the RGB lighting inside!
View attachment 435560
Give the market segment they are going after, the lighting is a low cost differentiation.
If you are not familiar with amplifier measurements, please watch my tutorial on it:
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Douk Audio A5 Amplifier Measurements
As usual, we start with our 1 kHz tone into 4 ohm load at 5 watts to bring out both noise and distortion:
View attachment 435563
That's above average performance and better than I expected:
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I had not realized the A5 at this price had PFFB (post filter feedback) which reduces output impedance and load dependency until I measured frequency response:
View attachment 435566
I was also surprised by the good performance of the high-pass filter at the setting I used. There is no ringing despite high attenuation. Very nice!
Another pleasant surprise was again, above average channel separation:
View attachment 435567
The implementation is not perfect though as there is more high frequency distortion as seen in our intermodulation distortion tests:
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Noise performance is excellent especially for the class:
View attachment 435570
Power is fitting with price but more modest than the more expensive competitors (from memory):
View attachment 435571
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These chip based implementations are quite robust, not even turning on protection as I beat it in my "FTC like" full bandwidth and longer term test (45 seconds or so):
View attachment 435575
EDIT: forgot power vs frequency:
View attachment 435605
Reactive loads don't matter to it either, going all the way down to 2 ohm (NOTE: both channels driven but only one channel loaded):
View attachment 435576
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The amplifier was stable almost at power up:
View attachment 435578
I didn't realize the volume control was also the power switch so I just disconnected the AC cable for on/off noise test:
View attachment 435579
Conclusions
Our journey into these pocket/desktop amps started around this $100 price range but without PFFB feature. This caused high frequency variations which we accepted as a trade off to get such a low cost. Companies then stepped up and implemented PFFB but the cost was increased. Douk A5 disrupts this market by providing PFFB at the $100 price mark. There is a bit of high frequency distortion penalty there but otherwise, the rest of tests show excellent engineering, put a big smile on my face!
I am happy to recommend the Douk Audio A5 stereo amplifier.
EDIT: video review of Douk A5 posted as well:
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When you comment Distortion rising with frequency is typical of architecture are you referring to PFFB? …
and implying that while PFFB has a couple of advantages it has more distortion at higher frequencies than amplifiers with the same chip but without PFFB?
across the frequency range, or much/ more in the treble?
I was looking for multi-way desktop amplification. They needed to be small. No true multi-channel amps were available and/or satisfactory, so I decided that multiple 2-channel amps were the only considerations. Amir's review of the A5 prompted me to buy. Got lucky with Amazon sale price. I bought three and made distortion measurements with REW, Topping D50 III and E1DA ADCiso. I measured both channels of all three. Unit-to-unit consistency was excellent. There was only one slight outlier for noise floor.
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What PCB version your A5 are?
I have no Topping D50 III and E1DA ADCiso, but my Focusrite loop connection THD and noise are still 30 dB less than I get from A5 in my measurements.
If you look at Amirm measurements at 1 kHz then there is dominating 3dr harmonic, in my measurement 2nd harmonic. Like A5 V1 and V2 are totally different amps.
I see a Ver:V3 label on the boards.
F**k, Amazon.de is selling old V2 version and V3 seems better.
I made also 1 kHz stepped sinus measurements with original NE5532P opamp and LM4562NA. No difference in total THD, but there is difference in higher harmonics levels in higher than 1W power. Cursor is at about 5W on images.
Original
with LM4562
I made also 1 kHz stepped sinus measurements with original NE5532P opamp and LM4562NA. No difference in total THD, but there is difference in higher harmonics levels in higher than 1W power. Cursor is at about 5W on images.
Original
with LM4562
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I believe that those harmonic levels will be inaudible until close to 0dBFS point. I also ran RTAs on them. The results were similar to those by Amir. HD3 dominates in all of mine. I only ran a frequency response on one channel of one unit. There was a slight rise at the top end on my 4-ohm load that looks more like Amir's test for an 8-ohm load. But that isn't an issue for me.
Roland68
Major Contributor
That's quite normal. It always takes some time for a production batch to be distributed to the various Amazon warehouses. And every manufacturer who is somewhat organized will operate on a "first in, first out" principle at their own warehouse.
As a result, there will always be a point where the Amazon devices might be slightly older than those at the manufacturer's warehouse (or in one of their own stores). This is a perfectly normal logistical issue.
Needed to use some coupons and got one of these for 35eur during the last AliExpress sales. Turned out to be v3. Is it worth measuring the frequency response of the high pass filter or has it been done or assumed it is the same?
The one difference I see at first sight is the capacitors at the output, but I have not checked in detail.
Full PCB, surprisingly dirty back side and detail of the sandwiched chip, for the heatsink aficionados.
I am curious about the glossy coating of the block sandwiching the chip, that my knife test confirms metallic.
Don't tell me that it is the same on the side in contact with the chip.....
Yes it is.
The one difference I see at first sight is the capacitors at the output, but I have not checked in detail.
Full PCB, surprisingly dirty back side and detail of the sandwiched chip, for the heatsink aficionados.
I am curious about the glossy coating of the block sandwiching the chip, that my knife test confirms metallic.
Don't tell me that it is the same on the side in contact with the chip.....
Yes it is.
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Is known, what is different in V1, V2 and V3, besides heat sink, HPF and HPF scale markings?
I am sure there must be deference in amplifier components or schematic, other way is not possible to get so different THD figures and THD harmonic composition.
I am sure there must be deference in amplifier components or schematic, other way is not possible to get so different THD figures and THD harmonic composition.
Roland68
Major Contributor
If I compare TI PFFB circuit for TPA3255 and image then components in red circle fits directly as feedback resistors, values are directly from TI suggestion .
Rest resistors are Douk specific, strangely number and values of them are not symmetric.
TI suggestion:
Rest resistors are Douk specific, strangely number and values of them are not symmetric.
TI suggestion:
Most are logic ones. The differences between versions seem to be in the components between two of the LEDs
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