SMSL’s TPA3255 All-in-One DAC/Amplifier - AL400

[Bleib]

Each has its own merits; it's best to experience them yourself.

Well, I doubt many would buy both of them..

 

[Kitty (S.M.S.L Marketing)]

"Implementation details" sounds like it has PFFB, but they don't want to go into the specifics... then this email saying no PFFB.

So which is it? To me a TPA3255 based amp without PFFB or implemented pooly is not competitive in 2025/26 market.


JSmith

Regarding PFFB: after internal testing and evaluation, our engineering team decided not to implement PFFB in this model, as we found it can have a slight negative impact on sound quality under our design targets.


That said, we fully understand the advantages of PFFB in certain applications, and we are already working on future amplifier models that will include PFFB-based designs. Those products will be announced later, and we appreciate your interest and patience.

 

[Guddu]

Regarding PFFB: after internal testing and evaluation, our engineering team decided not to implement PFFB in this model, as we found it can have a slight negative impact on sound quality under our design targets.


That said, we fully understand the advantages of PFFB in certain applications, and we are already working on future amplifier models that will include PFFB-based designs. Those products will be announced later, and we appreciate your interest and patience.

This is second time I am hearing the same explanation from a vendor w.r.t PFFB in TPA3255 design.
However AL400 already have controlled frequency response and decent Noise/Distortion.

 

[Bleib]

However AL400 already have controlled frequency response

I'm a bit curious about this, would love to see for example Erin test it with different loads
If the frequency response is OK to great this amp could be a winner in terms of price/performance ratio...

 

[chico71]

Greetings! I'm new here so this is my first post.

Very interested in the SMSL AL400.

After searching online, the online manual, and also this post, I still have not seen a definitive answer about the Low Pass/High Pass feature.

What I am searching for is an integrated amp with digital inputs and a sub out. I realize that this does have multiple options for setting the low pass that goes out to the sub.

In addition to that I am really seeking something that would also have a high pass setting that would roll off some of the lower octaves sent from the speaker terminals to a pair of bookshelf speakers.

So my question is, when you set the low pass filter up, is there an option in the settings to select a high pass that goes to the main speakers so it would essentially be a 2 way crossover?

Thank you in advance!

 

[Roland68]

Greetings! I'm new here so this is my first post.

Very interested in the SMSL AL400.

After searching online, the online manual, and also this post, I still have not seen a definitive answer about the Low Pass/High Pass feature.

What I am searching for is an integrated amp with digital inputs and a sub out. I realize that this does have multiple options for setting the low pass that goes out to the sub.

In addition to that I am really seeking something that would also have a high pass setting that would roll off some of the lower octaves sent from the speaker terminals to a pair of bookshelf speakers.

So my question is, when you set the low pass filter up, is there an option in the settings to select a high pass that goes to the main speakers so it would essentially be a 2 way crossover?

Thank you in advance!

I suspect that the only available low-pass filter is the Rohm BD37524FS-E chip. This chip doesn't offer a high-pass filter option.
If SMSL doesn't add another chip to the AL400's analog section to integrate a high-pass filter, then it's not a true 2.1 system, and the subwoofer option is essentially pointless.

Your only option would then be to add a passive high-pass filter to your speakers.

Addendum:
The BD37524FS-E has a 3-band parametric EQ, one of which is dedicated to the bass range at 60/80/100/120 Hz, which might be usable for the high-pass filter.
However, the 3-band parametric EQ is located well before the low-pass filter tap in the block diagram, so it likely affects everything and isn't usable for 2.1 operation.

 

[xlinknz]

Have I missed something how does one use headphones with the AL400...

 

[Roland68]

Have I missed something how does one use headphones with the AL400...

That's not possible, as there is neither a headphone jack nor a pre-out.

 

[xlinknz]

That's not possible, as there is neither a headphone jack nor a pre-out.

No headphone port, pre out or digital out is in my view a big omission (mistake) for device that tries to be everything including phono mm/mc

 

[Bleib]

OK, so a friend purchase this, wanting a small amp (and it is) with many features. Overall it works well but does a loud bang sound when it's turned on. This should be fixed with a firmware if possible. Just delay the ON for a bit longer

I tried the usual test, listening to the tweeter when no sound is playing from very close by. It's silent unlike A300

 

[Roland68]

OK, so a friend purchase this, wanting a small amp (and it is) with many features. Overall it works well but does a loud bang sound when it's turned on. This should be fixed with a firmware if possible. Just delay the ON for a bit longer

I tried the usual test, listening to the tweeter when no sound is playing from very close by. It's silent unlike A300

The noise in the A300 was caused by a combination of a poorly implemented display and power supply.
However, the A300 and AL400 are completely different devices and use entirely different amplifier ICs and power supplies.

 

[Bleib]

The noise in the A300 was caused by a combination of a poorly implemented display and power supply.
However, the A300 and AL400 are completely different devices and use entirely different amplifier ICs and power supplies.

I know, I almost sent my A300 to SMSL to have change the firmware because of the display noise issue but decided to return the whole unit instead.
Told friend that he likely would receive a better unit. With his floorstanders turning the AL400 amp is quite loud.
EQ, remote etc all work great otherwise. Ventilation on top and at the bottom

 

[Bleib]

Also curious, does the amp have the DRE switch on or off?

On the Distortion of Cirrus Logic CS431xx-Based Devices: A Comparative Review

another fiio product has now implemented DRE switch

www.audiosciencereview.com

 

[JSmith]

Regarding PFFB: after internal testing and evaluation, our engineering team decided not to implement PFFB in this model, as we found it can have a slight negative impact on sound quality under our design targets.

What do you mean?


JSmith

 

[NTK]

Regarding PFFB: after internal testing and evaluation, our engineering team decided not to implement PFFB in this model, as we found it can have a slight negative impact on sound quality under our design targets.


That said, we fully understand the advantages of PFFB in certain applications, and we are already working on future amplifier models that will include PFFB-based designs. Those products will be announced later, and we appreciate your interest and patience.

That would be very impressive if SMSL can achieve this frequency response without PFFB, which is flat to well within ±1/2 dB to ~40 kHz.
But I am curious (and suspicious). The vertical scale is "RMS Level (dBV)" and 0 dBV is 1 V. Was the measurement done with nominal 1 Vrms output (= 1/8 W @ 8 Ω and 1/4 W @ 4 Ω)? Why chose this level and not the usual 1 W?

Source: https://www.smsl-audio.com/portal/product/detail/id/935.html

 

[perceptionist]

That would be very impressive if SMSL can achieve this frequency response without PFFB, which is flat to well within ±1/2 dB to ~40 kHz.
But I am curious (and suspicious). The vertical scale is "RMS Level (dBV)" and 0 dBV is 1 V. Was the measurement done with nominal 1 Vrms output (= 1/8 W @ 8 Ω and 1/4 W @ 4 Ω)? Why chose this level and not the usual 1 W?

View attachment 503813
Source: https://www.smsl-audio.com/portal/product/detail/id/935.h

That would be very impressive if SMSL can achieve this frequency response without PFFB, which is flat to well within ±1/2 dB to ~40 kHz.
But I am curious (and suspicious). The vertical scale is "RMS Level (dBV)" and 0 dBV is 1 V. Was the measurement done with nominal 1 Vrms output (= 1/8 W @ 8 Ω and 1/4 W @ 4 Ω)? Why chose this level and not the usual 1 W?

View attachment 503813
Source: https://www.smsl-audio.com/portal/product/detail/id/935.html

What matters is whether they can achieve flat FR under different loads.

 

[NTK]

What matters is whether they can achieve flat FR under different loads.

My interpretation is that there are 2 curves. "AL400" is 4 Ω and the "8ohm" is 8 Ω.

 

[perceptionist]

My interpretation is that there are 2 curves. "AL400" is 4 Ω and the "8ohm" is 8 Ω.

The flattest FR of TPA3255 ever recorded by @amirm are from 3e audio a7, wiim vibelink and amp ultra, all of which implemented PFFB and none of the FR are ruler flat. I'll wait for amirm's or Erin's review.

 

[Audionaut]

Overall it works well but does a loud bang sound when it's turned on.

That's terrible, and I can't stand it.
The Douk A5 costs around 60 euros and has a relay built in. The measurements are very good, and it has a lot of power on a 48V 10A power supply.
But of course, you can also buy this SMSL if you want to have a switch-on noise.

 

[Bleib]

That's terrible, and I can't stand it.
The Douk A5 costs around 60 euros and has a relay built in. The measurements are very good, and it has a lot of power on a 48V 10A power supply.
But of course, you can also buy this SMSL if you want to have a switch-on noise.

I should add that he (my friend) connected the amp to different speakers and it's much quieter. And I don't know why because spec wise they are both about same sensitivity, both big floorstanders.
So it seems the loud noise doesn't always happen.

I'll borrow it from him and try it with my Guru floorstanders... if I have time do some superficial comparison with TP RA3 (= Topping PA5 II)