Another TPA3255 Amplifier is Coming? Douk Audio A100 Mono/Stereo Amplifier!

[Guddu]

Thank you for your idea! I will convey that to out PD. I have consulted with one of them, for the function design of A100, they think that AUX out can connect to more audio devices for different puporses, such as another amplifier, or full-frequency active speaker, not only subwoofer (most acitve subwoofers with low and high pass filters), so they think AUX out will satisfy more usages.

Thanks, I totally understand theory behind aux out.
Subwoofers mostly use low pass filter only to process required low end or base frequencies, High pass isn’t common.
If main speakers still get full band then it is just adding of extra base on subwoofer.
But the fact is that there isn’t many smaller amps available with high pass filter or crossover yet.

 

[Guddu]

banana speaker jacks will connect to passive subwoofers and the main volume knob will adjust its output.

Do you mean passive speakers?

 

[MCH]

No, the two volume knobs are valid in all modes. In bass mode, the AUX out will only output low frequency signal, it can be adjusted by the AUX VOL knob, and the banana speaker jacks will connect to passive subwoofers and the main volume knob will adjust its output.

Can you explain a use case for this?
Do you realise that if you have subs+speakers you must have a master volume control? (=only one volume knob).
Or are you saying that the intention is to use the amp with active + passive subs, the passive having low pass filters and the active not, and the volume controls are only to adjust the relative gains? That would be a really niche use case, but hey, I am sure there is someone with such a setup, there is always someone

 

[Douk Audio]

Do you mean passive speakers?

Yeah, A100 with sub and flat modes to switch, so the banana speaker jacks can connect passive speakers or passive subwoofers in different modes.

 

[Douk Audio]

Can you explain a use case for this?
Do you realise that if you have subs+speakers you must have a master volume control? (=only one volume knob).
Or are you saying that the intention is to use the amp with active + passive subs, the passive having low pass filters and the active not, and the volume controls are only to adjust the relative gains? That would be a really niche use case, but hey, I am sure there is someone with such a setup, there is always someone

Hi, if A100 works in stereo and flat mode, it can be used to connect one pair passive speakers and one active subwoofer, the rightmost master volume knob will control the speaker output and the AUX vol knob can control the active subwoofer.
If works in bass mode, A100 can be connected to one or two passive subwoofers, depending on you select mono or stereo modes, the master volume knob is also valid and the super bass and the sw-frequency knobs will work in this mode.

 

[Douk Audio]

Thanks, I totally understand theory behind aux out.
Subwoofers mostly use low pass filter only to process required low end or base frequencies, High pass isn’t common.
If main speakers still get full band then it is just adding of extra base on subwoofer.
But the fact is that there isn’t many smaller amps available with high pass filter or crossover yet.

Thank you! It seems that I got a little. You mean that the true 2.1, the banana speaker output should add high filter pass to only get mid and high band without any bass, and if the AUX out is changed to sub out that there will only output bass to the subwoofer, so we got the true 2.1, do I understand correctly?

 

[Guddu]

Thank you! It seems that I got a little. You mean that the true 2.1, the banana speaker output should add high filter pass to only get mid and high band without any bass, and if the AUX out is changed to sub out that there will only output bass to the subwoofer, so we got the true 2.1, do I understand correctly?

I don’t know what a “true 2.1” is, however I am trying to explain what an “effective 2.1” might look like in my view.
Any 2-channel stereo with aux/pre/sub out is 2.1 channel for sure, this is what most of such products have at the moment.
Now some amplifiers have sub frequency control, that is low pass filter, to set what goes to the subwoofer out of sub-out. This is fine but 99% active subwoofers are equipped with the same low pass filter already as well.
Low pass filter on amplifier is fine, but it’s practically more useful for passive subwoofers than active.
You have stereo amplifier with aux/pre/sub out and you can definitely call it 2.1 amplifier, you are doing it and so as all other manufacturers.

Now, about High Pass Filter
While setting up a 2.1 audio topology, you are adding subwoofer because you want additional bass which you aren’t getting through the main speakers (there might be exceptions but I am putting the common situation).
After adding subwoofer, you define subwoofer frequency range on amplifier or subwoofer itself. This makes your basic subwoofer setup ready.
However, your main speakers are still getting and trying to play full 20Hz to 20KHz band. Speakers with passive crossover then can have low frequency cut off.
High Pass Filter or crossover on amplifier can help in taking this setup to next level, by defining what would go to main speakers.
- Here you can define low distortion range for speakers
- Avoid speaker and subwoofer, both playing same frequency
- This becomes critical when someone is using full range main speakers, or small satellite type speakers or if speakers don’t have passive crossovers

*** AVRs do this effectively ***

There are several posts on this topic to explain and suggest a better product to Aiyima, Fosi and other manufacturers.

* pls excuse typos, not easy to type all this on phone with fat fingers

 

[PlasticDoc]

It is a secret now~

There have been vendors on ASR who have also tried to hide their bad designs behind a "secret".

Other vendors use sandpaper to erase the manufacturer markings on the soldered components (making bad design repair much harder), or encapsulate part of the components on resin blocks (causing thermal problems later and again making bad design repair much harder).

It would be more amusing if you dropped the "secret" and just called it something like "a poorly implemented PFFB".

The PROGNOSIS for the Douk Audio A100 is RESERVED.

 

[TonyJZX]

yeah i agree with the guy who says... "who's the product for???"

and the other thought i have is... "are there competitive products in a similar price range that is more customer focussed?"

i mean this marketplace is bursting with competant and well priced designs.

 

[Douk Audio]

There have been vendors on ASR who have also tried to hide their bad designs behind a "secret".

Other vendors use sandpaper to erase the manufacturer markings on the soldered components (making bad design repair much harder), or encapsulate part of the components on resin blocks (causing thermal problems later and again making bad design repair much harder).

It would be more amusing if you dropped the "secret" and just called it something like "a poorly implemented PFFB".

The PROGNOSIS for the Douk Audio A100 is RESERVED.

Hi, no worries, Douk Audio won't do that. I said it's a secret just because it is a pomotion point when we are going to release it.
As for a poorly implemented PFFB, the SNR reaches 115db, we cannot say that it is very excellent since the function and circuir design of the A100 is more complicated than other TPA3255 amplifiers on sale, so 115db for A100 is the best our engineers can do now. Of course, we will try our best to improve it in the following production if possible.

 

[Douk Audio]

yeah i agree with the guy who says... "who's the product for???"

and the other thought i have is... "are there competitive products in a similar price range that is more customer focussed?"

i mean this marketplace is bursting with competant and well priced designs.

Yeah, The market is very competitive and we appreciate the competition that helps us grow faster, at the same time, it also allows consumers to buy better products at lower prices, which is exactly what we want to see. May I know your specific thoughts on pricing and competitive products? For example, what is the price, what features does the product have, and other requirements?

 

[Douk Audio]

I don’t know what a “true 2.1” is, however I am trying to explain what an “effective 2.1” might look like in my view.
Any 2-channel stereo with aux/pre/sub out is 2.1 channel for sure, this is what most of such products have at the moment.
Now some amplifiers have sub frequency control, that is low pass filter, to set what goes to the subwoofer out of sub-out. This is fine but 99% active subwoofers are equipped with the same low pass filter already as well.
Low pass filter on amplifier is fine, but it’s practically more useful for passive subwoofers than active.
You have stereo amplifier with aux/pre/sub out and you can definitely call it 2.1 amplifier, you are doing it and so as all other manufacturers.

Now, about High Pass Filter
While setting up a 2.1 audio topology, you are adding subwoofer because you want additional bass which you aren’t getting through the main speakers (there might be exceptions but I am putting the common situation).
After adding subwoofer, you define subwoofer frequency range on amplifier or subwoofer itself. This makes your basic subwoofer setup ready.
However, your main speakers are still getting and trying to play full 20Hz to 20KHz band. Speakers with passive crossover then can have low frequency cut off.
High Pass Filter or crossover on amplifier can help in taking this setup to next level, by defining what would go to main speakers.
- Here you can define low distortion range for speakers
- Avoid speaker and subwoofer, both playing same frequency
- This becomes critical when someone is using full range main speakers, or small satellite type speakers or if speakers don’t have passive crossovers

*** AVRs do this effectively ***

There are several posts on this topic to explain and suggest a better product to Aiyima, Fosi and other manufacturers.

* pls excuse typos, not easy to type all this on phone with fat fingers

Hi, thank you so much for your detailed explanation, I think I got it! We haven't designed such an amplifier with a high pass filter not yet. I will convey your article to our PD manager and engineers, maybe they will take this into account in their product design and see if they can come up with a suitable product in the near future.
I totally understand how difficult it is to type such a long reply on the phone! Thank you again for your time and patience!

 

[Douk Audio]

Here is the inside of the A100, do you have any ideas or questions about it?

 

[Guddu]

Hi, thank you so much for your detailed explanation, I think I got it! We haven't designed such an amplifier with a high pass filter not yet. I will convey your article to our PD manager and engineers, maybe they will take this into account in their product design and see if they can come up with a suitable product in the near future.
I totally understand how difficult it is to type such a long reply on the phone! Thank you again for your time and patience!

Here is recent review by Erin, and you can hear him recommending the same thing as I did above and explained.
@4:30 Sub-Woofer integration and Low Pass & High Pass filters.

 

[PlasticDoc]

Hi, no worries, Douk Audio won't do that. I said it's a secret just because it is a pomotion point when we are going to release it.
As for a poorly implemented PFFB, the SNR reaches 115db, we cannot say that it is very excellent since the function and circuir design of the A100 is more complicated than other TPA3255 amplifiers on sale, so 115db for A100 is the best our engineers can do now.

In fact, this seems to be another red flag: when an audio manufacturer gives numbers in terms of SNR instead of SINAD, it sometimes means they are trying to hide poor distortion performance.

In ASR, the main measure of amplifier accuracy is usually SINAD not SNR and there is a good reason for that.

a) SINAD = Signal + Noise + Distortion to Noise + Distortion [(S+N+D)/(N+D)]. When expressed in dB it becames: SINAD (dB) = 20 log [(Vsignal +Vnoise+Vdistortion)/(Vnoise+Vdistortion)].

b) SNR = Signal plus Noise to Noise ratio [(S+N)/N]

Good TPA3255 PFFB based amplifiers, i.e. those that manufacturers can brag about, which seems to be what you are trying to do here at ASR, have a SINAD of 95dB or better.

 

[activewire]

A power amp should turn itself ON/OFF with the source component - needs 12V trigger (opto isolated to prevent ground loop) also (ideally) auto signal sense on/off (and make certain no POP when comes on/off)
No front volume controls wanted!!!! The source component handles this, I do NOT want that on my power amp
Your Aux-out function (stereo? really?!?) makes no sense! Either:
- Please just Delete this entirely
- or, MUCH less desirable: make this a proper 2.1, which means LFE (mono RCA!!!) sub out (possibly with adj frequency? but most active subs would have this built in so probably not needed/wanted in the amp) AND MUST HAVE high pass filter for the main output (definitely need adj freq for this)

 

[TonyJZX]

yeah look i mean this amp will probably not find a place with many people here

to me it looks like the amps you install inside arcade and poker machines... it has a place but i doubt it works well in many domestic environments

 

[Eleo]

yeah look i mean this amp will probably not find a place with many people here

to me it looks like the amps you install inside arcade and poker machines... it has a place but i doubt it works well in many domestic environments

Please look at the data included with first post. They seem to me in line with other Tpa3255 PFFB implementations.

 

[Douk Audio]

In fact, this seems to be another red flag: when an audio manufacturer gives numbers in terms of SNR instead of SINAD, it sometimes means they are trying to hide poor distortion performance.

In ASR, the main measure of amplifier accuracy is usually SINAD not SNR and there is a good reason for that.

a) SINAD = Signal + Noise + Distortion to Noise + Distortion [(S+N+D)/(N+D)]. When expressed in dB it becames: SINAD (dB) = 20 log [(Vsignal +Vnoise+Vdistortion)/(Vnoise+Vdistortion)].

b) SNR = Signal plus Noise to Noise ratio [(S+N)/N]

Good TPA3255 PFFB based amplifiers, i.e. those that manufacturers can brag about, which seems to be what you are trying to do here at ASR, have a SINAD of 95dB or better.

Hi, thank you for pointing out this! We have noted the SINAD in the test data. At the beginning, it was above 91db just like the following picture shows

Then after circuit optimization, SINAD has been updated to above 94db now.

Of course, we know that's not enough, our engineer will continue to work hard to see if they can improve it in the future production.

 

[Douk Audio]

Here is recent review by Erin, and you can hear him recommending the same thing as I did above and explained.
@4:30 Sub-Woofer integration and Low Pass & High Pass filters.

Thank you! I have sent it to our PD and engineers as well. Any updates I will let you know as soon as possible.