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Douk Audio TPA3255 Amplifier with HPF is Coming! Let's Shape it Together!

Douk Audio

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Audio Company
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Hello all ASR members,

Recently we have launched a series of TPA3255 digital amplifiers, and we have also received a lot of feedback from audiophiles about adding high-pass filtering.
Therefore, we have done some research and designed an A5. The following are the functions and appearances that have been temporarily determined. Please take the time to have a look, share your thoughts and shape it together!

Here are some highlights of the A5:
1. With acrylic window design on the top just like our DAC-Q11.
2. Easy to switch the op-amps, just take off the acrylic window and no need to remove screws.
3. Three backlight colors can be displayed individually and also can be mixed freely: blue/green/orange, the color switch is inside the A5 but easy to select and mix from the window.
4. Add HPF filter, the range can be adjusted from 60Hz to 6KHz.
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Here are some questions that need your suggestions:
1. What range of the HPF filter adjustment is better and suitable for most audiophiles' use?
2. What power adapter is better to match with the A5 considering performance and cost performance? Below is the estimated price:
A5 with 32V5A power adapter, $79.99
A5 with 36V5A power adapter, $89.99
A5 with 48V5A power adapter, $99.99
Which one do you prefer?


Basic Function and Parameters
Audio input: stereo L/R RCA
Audio output: Banana speaker jacks / 3.5mm AUX
Max power output in theory: 300W*2 (4 ohms, THD10%)
Frequency response range: 20Hz-20kHz (±1dB)
THD+N: 0.007%
SNR: ≥110dB
Working voltage: DC 24-48V

Of course, other suggestions are also welcome. Thank you for sharing your opinions in advance!
 
Why not follow the TPA3255 data sheet below and build one with PFFB (and maybe even add a notch filter removing the unavoidable >20kHz peaking ?)
Making a TP3255 amp load independent is more desirable, at the very least to ASR members looking for a cheap, powerful, small sized amp.


Ah... just noticed they already have a PFFB 3255 amp... the A100 ... never mind.
 
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Hi,
Nice to see these sort of questions coming up in an open forum.

Since you ask:
Frequency and load independence please (20Hz to 20kHz, and stable into 4Ohm loads).
Balanced input.
Deliver the rated performance as specified in the data sheets.
As @solderdude says, it's the LPF that is interesting - taking a load off the amp when a sub is handling the lower frequencies.

Stop talking about Op Amps, just fit ones that work.
Also, how safe is a 300W amp where you can just open a lid?

(Balanced input, not output!, edited)
 
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@Douk Audio is the second knob for the HPF adjustment?
If yes, I would propose to instead of that prominent knob on the front that someone would easily turn accidentally, have a smaller knob, even at the back.
@solderdude I believe what they are proposing is a high pass filter at the speaker output. Douk can confirm though.
 
Fantastic. About time this was done...

Great to see manufacturers addressing the subwoofer crossover/HPF issue. It's definitely not rocket science.
Good on ya's!
 
I’d second the suggestion for PFFB. It will become mandatory in future for this type of amp (I wouldn’t buy one without it)

You HPF frequency range is too high. I’d want it to go down to at least 40Hz, and 6KHz is way higher than needed. Assuming you are aiming at sub integration, then it doesn’t need to go higher than about 250Hz. Then with a few numbers on the dial, it would be possible to eyeball the frequency well enough just by position. This would not be viable with a 6Khz range, as all the interesting frequencies would be in just 5% of the dial position.
 
Also, how safe is a 300W amp where you can just open a lid?

(Balanced input, not output!, edited)
And who would take the lid off & reach into it while it is operating?
Don't care about balanced anything, in being involved in audio since 1975, I never had a hum/buzz, whatever: using RCA runs as long as 12 feet that wasn't fixable.
Don't care about PFFB, either.
Adjustable HPF 40 HZ to 200 HZ is likely all that is needed there.
For $20 more than the 32V one, I'll take the 48V power adapter.
What is power at 1% THD? That, to me, would be a bigger question.
 
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Think about adding something that your competitors don't have. An example could be loudness functionality. Whether that function in itself would be a selling point, I don't know. I like it anyway. :)

A TPA3255 based amp with PFFB plus sub out with LP filter set to 80 Hz plus with it i action, plugged in then automatic HP filter set to 80 Hz to the speakers. As said, loundness function and remote control plus as much power as can be squeezed out of the TPA3255 chip. Preferably stable to 3 Ohms to be on the safe side. Preferably with an integrated power supply in the amplifier.
Okay, now we may be talking about different prices than what you at Doku Audio are thinking about, but still. In any case, such a TPA3255 amplifier with good SINAD (rather a little more power than lower SINAD, say SINAD 90-95) can certainly sell for at least $250 - $300 :)
Douk Audio, please note this is what I would like but not at all sure this would appeal to others.

A reliable and stable amp. Perform extensive endurance tests. Run the crap out of a number to see what they can handle when you push the pedal to the metal when it then has to handle really low Ohms at max power for a long time. You probably already do that today when you test new amplifiers, but I mention it anyway.
 
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Also, how safe is a 300W amp where you can just open a lid?

No more dangerous than the exposed speaker terminals, assuming the power supply is external. 48V falls in the category of SELV (Safety extra low voltage)
 
The PP voltage between the terminals (with 48VDC) can be almost 96Vpp AC so 34VACrms which is considered safe for adults (50VAC 1Hz-1kHz) but not for children (25VAC) < 3sec. acc to IEC TS 60479-1
IEC 60364-4-41:2005
EN 50110-1 ed. 3: 2013
EN 50122-1 ed. 2: 2015
The output voltage is isolated from mains anyway so could only be references to ground, which would be 17VAC in that case at best on 24VDC.
 
I suppose I don't see the point of some of the things you're contemplating. Make this an amp. As others have said stable into at least 4Ohm, frequency and load independence getting the most Watts as possible. 12v trigger. Forget opamp swapping and HPF and LFF and even sub out. Make a proper matching DAC/ preamp with volume control, PEQ and your low and high filters and sub out. It's like you're trying to build a half integrated amp, if you want it all in one box then build it accordingly.
 
The PP voltage between the terminals (with 48VDC) can be almost 96Vpp AC so 34VACrms
Or 48V AC RMS if someone amplifies a square wave. So 48V DC internally, Max 48VAC externally - both SELV.
 
I wouldn't use my tongue between the LS posts to see if there is any voltage on it at full power though. :D
 
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I wouldn't use my tongue between the LS posts to see if there is any voltage on it at full power though. :D
No, but you probably also wouldn’t do it on a 9V PP3 battery either. I certainly wouldn’t…. Any more :D
 
No, but you probably also wouldn’t do it on a 9V PP3 battery either. I certainly wouldn’t…. Any more :D
I once showed a Chinese women (in Saipan) that, to check her 9 volt PP3 (which was dead) that you stick it on your tongue & I demonstrated with the dead battery.
Then, I opened the new one & knowing what they do, I made sure to hold very still & demonstrated again. I said yes, this is a good one. You check so that you will know the difference. She stuck it on her tongue, dropped the battery & slapped me: in one motion, I think.
 
FINALLY! THANK YOU DOUK! It is about time companies to start adding HPF, a must-have for my desktop setup. Many of the suggestions here are great. What my ideal amp is one with a HPF subwoofer output, auto on/off, and a volume bypass. I pray that we get there ... hopefully. Sure, Balanced + RCA and PFFB will be even better. I do agree that the adjustable frequency range is too high; the numbers antcollinet suggested are appropriate.
 
What I wish is PFFB, mono mode to use is as monobloc and volume bypass switch
 
Off topic but a high powered sub amp for all of us who have dead sub amps and powered sub speakers such as Definitive Technology BP7004's is sorely needed.
 
Good separation of bindning post (not those little ones like fosi V3).
Fixed Op amps, use the best one for you design.
2 power supply, 32 and 48 are more than enough IMHO.
No easy open lid, dangerous.
PFFB, is the trend now :)

Not sure about those 2 knobbs in the front, I guess volume and bass? Keep Volume in front and bass on the back, we will not be moving that one a lot of times.
 
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