Douk A5 Budget Stereo Amplifier Review

[Douk Audio]

@Douk Audio can you post frequency response graphs of the high pass filter of version 3? Thanks

Hello, here are some frequency response graphs of the HPF

HPF knob set to the far right

HPF knob in the middle

HPF knob on the far left

Hope these helps. Any other questions just feel free to let me know.

Happy New Year!!!

 

[Blew]

Hello, here are some frequency response graphs of the HPF

Thanks for this! Any chance you could do the same for V1/V2?

 

[Schlippwhip68]

yes the PP supply bypass cap mod could help the A5 V2/V3. cheap enough to try.
but you're asking about the A5 Pro? This thread is not about the Pro model

No, an enquiry for the A5 mainly. I am interested in what this mod actually does. What’s ‘esp’ ect….?

 

[truth_soldier]

No, an enquiry for the A5 mainly. I am interested in what this mod actually does. What’s ‘esp’ ect….?

The A5 Pro (in the picture) has a different circuit layout than the A5, esp A5 V3 though there are some similarities, so there's no way to know.
Someone needs to try it, It's easy enough, I will prob try it on my V2 eventually.
I don't know what 'esp' is referring to.

 

[truth_soldier]

Hello, here are some frequency response graphs of the HPF

HPF knob set to the far right
View attachment 502712

HPF knob in the middle
View attachment 502713

HPF knob on the far left
View attachment 502714


Hope these helps. Any other questions just feel free to let me know.

Happy New Year!!!

So it's 70hz (-3db) at the middle 12 O'clock position.

 

[Schlippwhip68]

The A5 Pro (in the picture) has a different circuit layout than the A5, esp A5 V3 though there are some similarities, so there's no way to know.
Someone needs to try it, It's easy enough, I will prob try it on my V2 eventually.
I don't know what 'esp' is referring to.

Going to give this a go on a standard A5 soon. Not sure how much ‘bomb’ it will give the sound but the general consensus is that it does ‘improve’ the sound quality.

 

[Schlippwhip68]

The A5 Pro (in the picture) has a different circuit layout than the A5, esp A5 V3 though there are some similarities, so there's no way to know.
Someone needs to try it, It's easy enough, I will prob try it on my V2 eventually.
I don't know what 'esp' is referring to.

Just ordered these for the job…and a soldering kit.

 

[RandomEar]

You're adding a cap of small capacitance designed for EMI suppression in the MHz range to a DC input. The exact same 0.47 μF film capacitor is likely already installed on the AC input of the power brick that feeds the amp.

The added capacitance (0.47 μF vs 3300 μF) is irrelevant in that position. The noise suppression is useless, because the power brick already has filtering on its DC output. The DC-DC converters inside the amp powering its logic Side already have filtering on their outputs.

For the 48 V rail, there is a class D amp with switching in the 300-600 kHz region behind these caps which has its own filtering at the speaker outputs designed to suppress the switching frequencies - there's no relevant energy in the MHz range getting out of the amp, because it would fail EMI certification if there was.

This is all nonsense.

That dude claiming audible improvements from this mod in that Ali review is clueless. He installed a redundant EMI filter on the DC input voltage rail and claims a change of the sound on the output?!

 

[Maximus89]

Can i connect a passive subwoofer by running the speaker wire from the sub to one of the A5's channels. Lets say:

Passive Sub +&- speaker wire to Douk A5 Right Channel Speaker Terminal +,- then Douk A5 AUX Input to Preamp Output. Adjust crossover freq. and volume manually.

Would this be safe for the A5 to run only one channel with the other not connected to anything?

 

[Maximus89]

Crap. Just realized it's a HPF and i would need a LPF so it would just send full range to the sub correct? I do have the original amp for the passive sub which has power issues, but could i instead use the douk a5 to power, but the original amp to only do the LPF with its own built in variable phase and fixed 100hz crossover which work fine? Unfortunately the volume pot of the amp also has distortion issues, but only when its moved, its fine if i set it and never touch it.
So if i tried that: Passive sub speaker terminals to DOUK A5 right channel speaker terminal. AUX Input 3.5mm to dual rca to the output of the original amp, then original amps LPF input to Preamp Output? Run volume full max on original amp and adjust volume on the DOUK A5?

Or at this point-do i ignore AUX Input to DUAL RCA so the Left channel doesn't receive a signal and instead send DOUK A5 right channel rca mono input to dual L/R RCA LP filtered output of original amp, then L/R input of original amp to L/R output of the Preamp? In this case, the left channel is ignored right? And im now using the Douk A5 for power and volume and the original amp is using its fixed crossover point and now i can also use its variable phase? Run the volume fixed to max?

Can i connect a passive subwoofer by running the speaker wire from the sub to one of the A5's channels. Lets say:

Passive Sub +&- speaker wire to Douk A5 Right Channel Speaker Terminal +,- then Douk A5 AUX Input to Preamp Output. Adjust crossover freq. and volume manually.

Would this be safe for the A5 to run only one channel with the other not connected to anything?

 

[Schlippwhip68]

You're adding a cap of small capacitance designed for EMI suppression in the MHz range to a DC input. The exact same 0.47 μF film capacitor is likely already installed on the AC input of the power brick that feeds the amp.

The added capacitance (0.47 μF vs 3300 μF) is irrelevant in that position. The noise suppression is useless, because the power brick already has filtering on its DC output. The DC-DC converters inside the amp powering its logic Side already have filtering on their outputs.

For the 48 V rail, there is a class D amp with switching in the 300-600 kHz region behind these caps which has its own filtering at the speaker outputs designed to suppress the switching frequencies - there's no relevant energy in the MHz range getting out of the amp, because it would fail EMI certification if there was.

This is all nonsense.

That dude claiming audible improvements from this mod in that Ali review is clueless. He installed a redundant EMI filter on the DC input voltage rail and claims a change of the sound on the output?!

Excellent RandomEar!

 

[truth_soldier]

The exact same 0.47 μF film capacitor is likely already installed on the AC input of the power brick that feeds the amp.

It's possible this mod is NOT redundant and can be an improvement.
TI recommended 1uF ceramic caps near the TPA3255 inputs, it must be for a reason.
I think these are not present in the A5 so this mod maybe compensates for that?

 

[RandomEar]

I'm not gonna invest half an hour of my life to list all the errors of your 10 s AI output. Please also read the AI policy.

Suffice to say that while some of it is correct, many points are false or talk about totally different parts of the circuit, making the statements irrelevant. AI sounds smart and convincing, but that doesn't mean its correct. This is a good example.

And

Results: cleaner power, less harshness, better soundstage at high volumes

just shows that AI is mostly the sum of its training data. In case of audio, that is a lot of subjective stuff from forums and reviewers. Hence: Bullshit in, bullshit out.

 

[Douk Audio]

Thanks for this! Any chance you could do the same for V1/V2?

Sorry, we are unable to provide V1/V2 versions for the test. Currently, all inventory of the A5 in our Shenzhen warehouse is V3; the next batch will be V4. Our engineers do not have V1 or V2 versions on hands to do this test.

 

[MCH]

It's possible this mod is NOT redundant and can be an improvement.
TI recommended 1uF ceramic caps near the TPA3255 inputs, it must be for a reason.

Near meaning really near, as close as possible to the pins. That cap in the mod is way too far away

I think these are not present in the A5 so this mod maybe compensates for that?

Yes they are, they are C50 C52 in my version (v3)

 

[Schlippwhip68]

I'm not gonna invest half an hour of my life to list all the errors of your 10 s AI output. Please also read the AI policy.

Suffice to say that while some of it is correct, many points are false or talk about totally different parts of the circuit, making the statements irrelevant. AI sounds smart and convincing, but that doesn't mean its correct. This is a good example.

And

just shows that AI is mostly the sum of its training data. In case of audio, that is a lot of subjective stuff from forums and reviewers. Hence: Bullshit in, bullshit out.

My own searches with ‘baby AI’ is one of a mostly milk teething. It does not have a full set of molars yet. I found very sketchy results but how it’s working it’s not surprising. Data dredging is dragging up all sorts of chuck away comments that it formulates into the best opinion it can. It’s like the Jeet Kun do of info but it’s not picking the best bits quite yet as Bruce Lee would do but it does deliver a little faster than an one inch punch.

 

[truth_soldier]

I'm not gonna invest half an hour of my life to list all the errors of your 10 s AI output. Please also read the AI policy.

Suffice to say that while some of it is correct, many points are false or talk about totally different parts of the circuit, making the statements irrelevant. AI sounds smart and convincing, but that doesn't mean its correct. This is a good example.

And

just shows that AI is mostly the sum of its training data. In case of audio, that is a lot of subjective stuff from forums and reviewers. Hence: Bullshit in, bullshit out.

I realize all that and caveated that it's not necessarily completely correct - though maybe has some truth and good points in it.
the point is not to pit AI against you in an argument, it's to debate the points and possibly dig into the info for the purpose of learning.
and... I deleted the AI content because after I thought about it, and this site's frowning on posting AI content.

"the sum of training data" to me means that it's just a better search engine and as such it may be finding more information than any one person - including you - knows about. I think we should all be open to possibly learning something that we didn't know. ie, be skeptical but open to learn.

 

[truth_soldier]

AI sounds smart and convincing, but that doesn't mean its correct.

the same can be said for you and your opinions.

let's just say I'm skeptical that your statement about what a power supply "likely" has in it means that adding this particular cap value must be redundant.
But I'm also not blindly believing what one person thinks they hear from that one cap addition. I think it's worth trying to see what happens.

 

[truth_soldier]

Yes they are, they are C50 C52 in my version (v3)

are those in the same path as the big 3300uF supply rail cap? Cool if so.

That cap in the mod is way too far away

OK fine, you may be right.

that said, I'm willing to try this easy mod and if I can't hear any difference, I'll say so.

I can already hear the replies about "blind testing"

 

[spookym]

the same can be said for you and your opinions.

It isn't the same though.

People can feel free to disagree with each other's opinions, the issue is that people can paste large amounts of AI output with very little effort and it takes a disproportionate amount of time to wade through it all and refute all the errors.