Another cheap PFFB stereo amp!

[dpuopolo]

Douk Audio has a new cheap PFFB amp looks interesting in that you can take the top cover off to easily change op amps. 100 bucks with a 32 volt power supply.

Amazon.com

 

[staticV3]

Selling the unit with a 35V5A supply and advertising "300 Watts x2", without caveat or note regarding PSUs, has got to be illegal.

The best case scenario with that 32V5A PSU will be 2x110W (4Ω, 1% THD).

 

[Bruce Morgen]

Douk Audio A5

 

[Roland68]

If the Douk Audio A5 actually outputs the unfiltered and volume-controlled signal via the Aux output (no high pass), and the adjustable high pass filtering for the internal amplifier works well, then any user with an active subwoofer could build a functioning and useful 2.1 system.

This would make Douk Audio one of the few (or the only?) manufacturers who have understood this and integrated it into an inexpensive TPA3255 amplifier.

 

[somebodyelse]

Selling the unit with a 35V5A supply and advertising "300 Watts x2", without caveat or note regarding PSUs, has got to be illegal.

The best case scenario with that 32V5A PSU will be 2x110W (4Ω, 1% THD).

The Amazon listing is just plain deceptive. Their web site listing from #3 above has a table for power output:

Power Output Table of The A5

Power Supply	Speaker Impedance	Rated Output Power
32V/5A	4Ω	78W+78W
	6Ω	71W+71W
	8Ω	65W+65W
36V/6A	4Ω	107W+107W
	6Ω	100W+100W
	8Ω	94W+94W
48V/5A	4Ω	120W+120W
	6Ω	110W+110W
	8Ω	102W+102W
48V/10A	4Ω	250W+250W
	6Ω	210W+210W
	8Ω	185W+185W

Note that distortion level isn't mentioned (1% maybe?) and none reach the headline 300W figure.

@Douk Audio care to comment?

 

[TonyJZX]

i mean that chart is quite clear and does not deviate from the competiton

$100 and 100w at 8 ohm on a 48v/5a is about on the money

say take off 25w for safety and 75w is probably beleiveable


i'm not sure how i feel about the super prominent 30-250hz cut off knob on the front

i think having a permanent 30hz lowest cut is ok given most of us do not have 20-20 speakers but its a weird choice to always have that on the front - it's ok if you keep changing mains

 

[Douk Audio]

Thank you for mentioning me, I will reply these questions tomorrow and let my colleague responsible for Amazon to modify their page soon.

 

[Douk Audio]

The Amazon listing is just plain deceptive. Their web site listing from #3 above has a table for power output:

Note that distortion level isn't mentioned (1% maybe?) and none reach the headline 300W figure.

@Douk Audio care to comment?

Hi, the Amazon page added the power output table already. Thank you for pointing out this.
By the way, the distortion of the A5 is below:
4Ω, 1% distortion: 195W
8Ω, 1% distortion: 100W
Distortion: 0.002% (4Ω/8Ω, 5W)
Hope this helps.

 

[somebodyelse]

Hi, the Amazon page added the power output table already. Thank you for pointing out this.
By the way, the distortion of the A5 is below:
4Ω, 1% distortion: 195W
8Ω, 1% distortion: 100W
Distortion: 0.002% (4Ω/8Ω, 5W)
Hope this helps.

The power output table is there if you go looking for it, but not on screen by default. Meanwhile the headline still says "300 Watts x2" and the "About this item" says:

300W×2 Power with Premium Components: Powered by the TPA3255 chip and premium components, A5 delivers distortion-free audio with ultra-low THD (0.002%)

The table that is shown by default says:

Max. output power:	300W × 2 (4Ω)
Matched speaker impedance:	4-8Ω
THD+N:	0.002%

The amp is supplied with a 32V 5A supply, so as supplied it can't output 300W.

To be fair almost everyone using a TPA3255 uses the 300W x2 claim without a load, distortion figure or supply voltage specified, but that doesn't make it any less misleading. They're all clearly violating the FCC amplifier rule for listings in the US.

 

[Tell]

The power output table is there if you go looking for it, but not on screen by default. Meanwhile the headline still says "300 Watts x2" and the "About this item" says:

The table that is shown by default says:

The amp is supplied with a 32V 5A supply, so as supplied it can't output 300W.

To be fair almost everyone using a TPA3255 uses the 300W x2 claim without a load, distortion figure or supply voltage specified, but that doesn't make it any less misleading. They're all clearly violating the FCC amplifier rule for listings in the US.

Personally I don't care for the FCC rules at all (both because I'm not in the US bot also because they are just bad and doesn't apply for any kind of real world use), but I do agree that having a table showing 300Wx2 and a THD+N at 0.002% is extremely misleading. Sure you might maybe be able to push out 300W with the right power supply, but _never_ at a THD+N at 0.002%, not even close.

 

[Roland68]

i'm not sure how i feel about the super prominent 30-250hz cut off knob on the front

i think having a permanent 30hz lowest cut is ok given most of us do not have 20-20 speakers but its a weird choice to always have that on the front - it's ok if you keep changing mains

On any large/full size amplifier the setting for a high pass filter is on the front panel if there is one.
Why should it be on the back of such a small amplifier, which is already crowded and difficult to reach.

 

[Zek]

Is it true that the high pass filter is always on and cannot be turned off?

 

[Old_School_Brad]

To be fair almost everyone using a TPA3255 uses the 300W x2 claim without a load, distortion figure or supply voltage specified, but that doesn't make it any less misleading. They're all clearly violating the FCC amplifier rule for listings in the US.

Good comment. I’m curious to hear what @Douk Audio thinks about this, actually.

 

[Tell]

Is it true that the high pass filter is always on and cannot be turned off?

If you look closely on the HP filter dial you will see that it says "Off" just next to "30Hz", so if you turn it all the way to 30Hz and a bit more you'll probably hear a click and then the HP filter is off.

 

[Roland68]

If you look closely on the HP filter dial you will see that it says "Off" just next to "30Hz", so if you turn it all the way to 30Hz and a bit more you'll probably hear a click and then the HP filter is off.

Thanks for the tip, I hadn't seen that.

Is it true that the high pass filter is always on and cannot be turned off?

What difference would that make at 30 Hz? Any reasonably normal speaker would only benefit from it.
Even monster speakers like Visaton's Monitor 890 MK III with 2 very strong 30s basses have -10 dB at 30 Hz.