Douk A5 Budget Stereo Amplifier Review

[effj]

Hello Community,

The attached graphs are frequency analyses of the Douk A5 (V1) high-pass filter (HPF). There are separate files for the left and right channels. Each curve (26 total) corresponds to an approximate setting on the HPF knob.

Unsure of the correctness of the A5's HPF implementation and of how to manually calibrate it to sync with my subwoofer, I decided to measure it with a loopback apparatus using the hardware I have on-hand:

• Topping RD3 DAC connected to a Windows PC
• Douk A5 (V1) connected single-ended to the Topping RD3
• DS18 VX2HL speaker-level to line-level converter connected to the Douk A5 speaker terminals
• Behringer UCA222 USB audio interface connected single-ended to the DS18 VX2HL line-level outputs and via USB to the Windows PC

Using a custom-cut front panel template in order to hand-adjust the Douk A5 HPF at uniform intervals, I output a sine sweep (5 Hz to 5 kHz) repeatedly through the Topping DAC, generated WAV files from the input of the Behringer UCA222 interface, then generated the attached graphs from the FFT curves of all the WAV files.

Notes on the HPF setting numbers:

• 0 means off
• 1 means on but the lowest setting
• 2 thru 24 correspond to notches on the front panel template relative to the lowest setting
• 25 corresponds to the highest setting

Regards

 

[chasmo57]

Thank you for the effort.
If I counted the template correctly there are 32 "spokes" total. Between "on/30" and "200hz" I count 25 positions corresponding to the curves in the graph.
I have sketched the template star on paper and assigned a number to each spoke corresponding to the graph to help me visualize where to place the pointer between 7:00 and 5:00 on the HPF.
The curves are kinda crowded below 80hz, but it's still serviceable for my application.

 

[Blew]

The attached graphs are frequency analyses of the Douk A5 (V1) high-pass filter (HPF). There are separate files for the left and right channels. Each curve (26 total) corresponds to an approximate setting on the HPF knob.

Thanks, that's very interesting stuff! Am I missing something or is the filter curve next to useless for rolling off at 80Hz, as is commonly used for subwoofer integration? The filter either rolls off too early or rolls off too slowly.

Your measurements correlate with Amir's measurement of the filter at the centre position, which would be number 13 on your scale. According to your measurements, it appears that any filter setting above that setting produces much less desirable results!

 

[effj]

Am I missing something or is the filter curve next to useless for rolling off at 80Hz, as is commonly used for subwoofer integration? The filter either rolls off too early or rolls off too slowly.

Yeah, seems like it attenuates a larger band of frequencies the higher you set it (perhaps exponentially?). Attached is a linear graph that might help, too. The graphs in my first post have a logarithmic frequency scale. If I were to choose a setting for 80Hz, personally, I'd probably choose something between 6 and 9 based off these findings. I'm no expert on any of this, though, so would love other opinions.

 

[avl2]

Yeah, seems like it attenuates a larger band of frequencies the higher you set it (perhaps exponentially?). Attached is a linear graph that might help, too. The graphs in my first post have a logarithmic frequency scale. If I were to choose a setting for 80Hz, personally, I'd probably choose something between 6 and 9 based off these findings. I'm no expert on any of this, though, so would love other opinions.

thank you for the measurements!

I tried to relate your numbered positions to a typical watch face position:

probably not 100% correct, only estimated, any correction remark welcome!

as it was in message : until 12 o´clock happens almost no change in freq. response once the HPF is activated

in my view for typical cases (of main and sub) the correct setting or the most relevant range is between 12 o´clock and 2 o´clock

question: how to interpret your Y axis ? what means the magnitude ? 1.0 unit change in magnitude corresponds to how many dB ?

 

[effj]

question: how to interpret your Y axis ? what means the magnitude ? 1.0 unit change in magnitude corresponds to how many dB ?

The y-axis has the absolute values of the raw magnitudes from a NumPy FFT applied to the WAV files. Note the "1e7" in the top-left; they're actually in the range of 0 - 30,000,000. If someone more familiar with this kind of analysis wants to normalize those values, I can provide the WAV files and Python code upon request. I think the graphs themselves are more useful than the numbers, at the moment, because they show you the trends and the curves relative to each other.

 

[chasmo57]

Too bad the lower settings are so crowded. I agree that an expanded 'Y'-axis shown in relative dB scale would be helpful in interpreting the graph.
Thanks for everyone's efforts.

 

[Blew]

The y-axis has the absolute values of the raw magnitudes from a NumPy FFT applied to the WAV files.

Is the magnitude in logarithmic scale?

 

[riemerra]

I see your mention that the PFFB (post filter feedback) reduced output impedance. Since some amplifiers have problematic output impedance, I would be interested to see impedance by frequency curves if they are readily available. Thanks for the very informative review. I bought the Douk A5 Pro and am having fun listening to music and learning about HiFi.

 

[effj]

Is the magnitude in logarithmic scale?

Linear

 

[Blew]

Linear

Shouldn't it be in logarithmic scale, given that dB is logarithmic? What does the graph look like when both axes are logarithmic?

 

[effj]

Shouldn't it be in logarithmic scale, given that dB is logarithmic? What does the graph look like when both axes are logarithmic?

I don't think the question is should or shouldn't the y-axis be logarithmic. What I have done above is for the purposes of understanding the behavior of the Douk A5's high-pass filter and as guidance for adjusting the knob. If making the y-axis logarithmic would be more useful, I don't have a problem with someone doing that. However, I am not the person to do it; as someone with limited experience creating and interpreting audio graphs, my ignorance would show if I went into any further depth. Am happy to share anything I have, though, if someone more knowledgeable wants to get involved.

 

[chasmo57]

Thanks again for your efforts. Now I guess it's up to those with the ability to graph it in a way we're accustomed to seeing/reading -much obliged!

 

[Pasarski]

Oh dear, such a journey with this product and the company. Bought an unit this March. It started acting funny and messing up my digital cable TV channels when close to the TV.

I've had a lengthy conversation with the support but no resolution. They finally watched the video I shot that shows my TV going mad when turning the device on and their answer is:

"Hello, we just found your email.
After checking, we found that the video freezes may be due to a decoding issue or a problem with the input device's memory.
Please check.
Or, you can try playing the video again without installing our software. Thank you."

I don't even understand what they're suggesting and what software they're talking (maybe a translation error ) and don't have the will power to continue the chat with them, been doing that since May and it's been really messy from the beginning.

So I'm giving up with the product and the company and leaving a warning here for everybody who is planning to use the device near digital cable TV.

 

[chasmo57]

I bought three units back in April, (V2).
No problems so far (knock on wood) and they're plugged in next to my TV/antenna.
Amazon's return policy allows return of defective product. If you bought direct from Douk, be persistent. It would be a shame to lose your investment.

 

[chasmo57]

Oh dear, such a journey with this product and the company. Bought an unit this March. It started acting funny and messing up my digital cable TV channels when close to the TV.

I've had a lengthy conversation with the support but no resolution. They finally watched the video I shot that shows my TV going mad when turning the device on and their answer is:

"Hello, we just found your email.
After checking, we found that the video freezes may be due to a decoding issue or a problem with the input device's memory.
Please check.
Or, you can try playing the video again without installing our software. Thank you."

I don't even understand what they're suggesting and what software they're talking (maybe a translation error ) and don't have the will power to continue the chat with them, been doing that since May and it's been really messy from the beginning.

So I'm giving up with the product and the company and leaving a warning here for everybody who is planning to use the device near digital cable TV.

Try using a different power source. It sounds like a defective SMPS. Good luck!

 

[Pasarski]

Try using a different power source. It sounds like a defective SMPS. Good luck!

Sounds plausible. I bought the PSU separately and now thinking of it, a SMPS definitely seems more potential interference source than an audio amplifier.

 

[RFS]

After so many great reviews, I purchased a unit on Amazon for $75 to use in a 2.1 office system. First, out of curiosity, I compared it with three different speakers driven by more expensive Outlaw and Marantz amps I had on hand. The Douk sounded decidedly soft in comparison with less punch, decreased transient response, and a smaller sense of scale.

It’s great for cost though. Sound is clear, soundstage is very good and it is perfectly enjoyable - just not a giant killer.

 

[Blew]

After so many great reviews, I purchased a unit on Amazon for $75 to use in a 2.1 office system. First, out of curiosity, I compared it with three different speakers driven by more expensive Outlaw and Marantz amps I had on hand. The Douk sounded decidedly soft in comparison with less punch, decreased transient response, and a smaller sense of scale.

It’s great for cost though. Sound is clear, soundstage is very good and it is perfectly enjoyable - just not a giant killer.

Your Marantz and Outlaw amps may just be more powerful amps. Did your Douk come with the standard 32 volt power supply? It maxes out at 33 watts using the 32 volt power supply with 8 ohm speakers. Which speakers did you test it with? Was the HPF turned off?

Mine sounds much "punchier" than my old Marantz AVR which is rated at 100 watts with the same 8-ohm speakers. I am using the 48 volt power supply on the Douk though.

 

[RFS]

Your Marantz and Outlaw amps may just be more powerful amps. Did your Douk come with the standard 32 volt power supply? It maxes out at 33 watts using the 32 volt power supply with 8 ohm speakers. Which speakers did you test it with? Was the HPF turned off?

Mine sounds much "punchier" than my old Marantz AVR which is rated at 100 watts with the same 8-ohm speakers. I am using the 48 volt power supply on the Douk though.