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SMSL SA400 Power Amp - 230 WPC into 4 Ohms

AdamG247

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Maybe a typo:

“Clean power
Amplifiers are quick to brag about their output power, but that massive power means nothing if it brings noise and distortion with it. The SMSL SA400 offers clean, high-quality power at 2300 Watts x 2 per channel (4Ω)--more than enough for home theater systems of any caliber. “
 

Vini darko

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From smsl site. Looks like about 80W to me. Distortion is exponential after. I notice they proudly anouce all the chip numbers except the power amp one. I'm somewhat suspicious.
Screenshot_20210521-201444.png
 
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MediumRare

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From smsl site. Looks like about 80W to me. Distortion is exponential after. I notice they proudly anouce all the chip numbers except the power amp one. I'm somewhat suspicious. View attachment 131141
Not following you. The 1% THD+N is about 102 WPC, which is pretty close to the 110 WPC into 8 Ohms they claim. Maybe there is a burst factor to get to 110?
 

Vini darko

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It's clean to 80W so it's really a 40W amp with headroom in my book.
Edit: worth mentioning that 10W continuous into most speakers is fecking loud. With 10x power potential on tap this amp should be good to drive most speakers rather well.
 
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VMAT4

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From the descriptions I've seen it has built in tone settings as do Infineon chips. But which Infineon chip? I'm just curious. Sells for $660.
 

Jeclub

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From the descriptions I've seen it has built in tone settings as do Infineon chips. But which Infineon chip? I'm just curious. Sells for $660.

It does not look like an Infineon chip

From the Audiophonics listing: Amplifier chip and controller 2x STA516B / 1x AX5689
 

ModDIY

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STA516BE chip from ST 'Electronics, which is based on the technology of the T Amp..not young, I would look elsewhere, like the TPA3255 or the Infineon MA12070
 

jokan

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Just an FYI,

The amplifier has a fan on the underside that engages at 65 degrees Celsius.
Yes this is an old ST amplifier. The patent ran out so it's now available to the masses.
Denon, Onkyo and a few other companies used this chip-amp.

I have no comment about sound quality, construction, or anything else as I've not touched one, or heard one. But I can imagine based on my knowledge of who was using it 10-15 years ago. And we all know how Class-D keeps improving every couple of years and takes big leaps.

It looks physically nice though!

Here is Amazon Japan's description of the amplifier where I learned about the cooling fan:
https://www.amazon.co.jp/-/en/SA400...d=1&keywords=SMSL+SA400&qid=1621655351&sr=8-1
 

Toku

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The SA400's NFB is a mechanism that detects the feedback signal from the SP terminal that has passed through the output filter, performs A/D conversion with the AX5689, and performs digital calculation.
This is what we call PFFB, but SMSL doesn't seem to use the term PFFB. I confirmed this behavior with SMSL.

The output stage STA516BE is a chip with only the output part of the MOS-FET and the protection circuit such as overcurrent, and the driver AX5689 is in charge of PWM generation and signal calculation.
My understanding is that the AX5689 can work both as a full digital amplifier and as a class D amplifier.
It is unknown whether the SA400 is actually operating as a Class D amplifier or a fully digital amplifier.

If it is a full digital amplifier, I think that the input terminal may have COAX OPT I2S etc. in addition to RCA.
The actual input signals are only RCA and BT, and I think these signals are digitally converted using the AX5689 A/D converter, which has 8 channels.

Please tell us your understanding of SA400. Knowing that it was a PFFB, I suddenly wanted to buy the SA400.
 

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boXem | audio

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The SA400's NFB is a mechanism that detects the feedback signal from the SP terminal that has passed through the output filter, performs A/D conversion with the AX5689, and performs digital calculation.
This is what we call PFFB, but SMSL doesn't seem to use the term PFFB. I confirmed this behavior with SMSL.

The output stage STA516BE is a chip with only the output part of the MOS-FET and the protection circuit such as overcurrent, and the driver AX5689 is in charge of PWM generation and signal calculation.
My understanding is that the AX5689 can work both as a full digital amplifier and as a class D amplifier.
It is unknown whether the SA400 is actually operating as a Class D amplifier or a fully digital amplifier.

If it is a full digital amplifier, I think that the input terminal may have COAX OPT I2S etc. in addition to RCA.
The actual input signals are only RCA and BT, and I think these signals are digitally converted using the AX5689 A/D converter, which has 8 channels.

Please tell us your understanding of SA400. Knowing that it was a PFFB, I suddenly wanted to buy the SA400.
The AX5689 generates the PWM sent to the STA516 based on post filter feedack read through an ADC. So it operates in the digital domain.
Too bad that the only digital input is bluetooth.
I am wondering what the distortion for the 230W power figure is. Also wondering how much time these 230 W are sustained.
SNR is frankly meh.
FDA are class D BTW.
 

Toku

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The AX5689 generates the PWM sent to the STA516 based on post filter feedack read through an ADC. So it operates in the digital domain.
Too bad that the only digital input is bluetooth.
I am wondering what the distortion for the 230W power figure is. Also wondering how much time these 230 W are sustained.
SNR is frankly meh.
FDA are class D BTW.
I understand that the SA400 is a fully digital amplifier from the configuration.
However, in the AX5689 data sheet, the explanation of General features says as follows.

▪ 8-channel digital Class-D amplifier controller with digital inputs

I'm very confused about describing the FDA as Class-D. Is the FDA generally represented as a Class-D group?
 

jokan

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There is way too many conflicting information about the amplifier.
One thing is this amplifier does originate from the era of T-Amplifiers. The patent for the technology expired and is now available for other companies to use.
A class D amplifier that operates and has an internal fan that kicks on at 65℃ is not efficient by any standards. Even the SNR doesn't lie.

AX5689 is an 8-channel digital Class-D amplifier controller with digital inputs, not a Class D amplifier.
https://www.axign.nl/wp-content/uploads/AX5689_ProductBrief_v1.0.pdf
Reading words like low-latency in a controller worries me because that means there is latency. They also have contradictory statements in section 3 of the first page about SNR vs the SNR as quoted by SMSL for the SA400.

The actual amplifier portion is
https://www.st.com/resource/en/datasheet/sta516be.pdf
The original date of the first release of the STA516 1st February, 2007!
This is one amplifier I would stay well clear of. The origins of the design are ancient in today's audio world. The published specs don't add up when you compare the two main parts of the amplifier design.

There is no doubt that SMSL is cranking out new amplifiers at a huge speed. They are building as many variants as possible in the hopes that one or two will hit the market. Considering the packaging that SMSL uses for their amplifier chassis's are largely the same, 2 main depth differences only and some with spikes to raise the amplifier for cooling, they are obviously going for a broad attack with the hopes that one or two of the new amplifiers will hit the market and sell well.

I'm a huge fan of the DA-9, and have contributed a great deal on the DA-9 thread. Yes, my unit had QC problems which were easily cured by myself and the amplifier is dead quiet, has an expansive soundstage compared to it's predecessor which had XLR inputs but they dodged the words balanced inputs all together because the DA-8s did NOT have balanced inputs, just XLR inputs. Even the DA-9 is playing a little bit of a trick by saying that it's a true balanced input when it is in fact using an op-amp which is not how a true balanced input works. I don't have any complaints with how the XLR input works however as it does sound better than the RCA level inputs and not because of increased gain. I think the op-amp is playing some very effective trickery to how we hear sound. I wish SMSL would publish the schematic in full, but they would never do that.

I am very comfortable saying buyer beware of this amplifier. The amount of information that I've read from the chip manufacturers themselves, and the examples for circuitry design lead me to this statement. There are too many unknowns with this amplifier. And who ever heard of an Class D amplifier from 2021 that requires forced cooling that was designed and sold as new even in the past few years. There is the Mytek Digital 2 channel that uses a heavily modified PASCAL amplifier that does run a little bit on the warm side that does have a fan, but that is an amplifier that has much more credibility and controllability of the gain settings and is a proven performer.

With a lot of the inexpensive stereo equipment on the market it's very easy to be tricked into believing something is better because it's newly announced. We have to do our own research and understand how these devices are built before we start to say things like "This amplifier produced no "hiss-noise", so it must be a good amplifier". That is a totally amateur statement. Saying that playing at 100-110db volume, well what weighting did you use? How far away was the microphone placed? What is your room like? These are all variables that must be taken into account.
It's fantastic that many companies are offering an over abundance of choice today and that the prices have come down significantly as a result. It's also very important for the buyer to be educated and to understand how to read schematics, testing procedures when the specs are published. Without some technical knowledge, it's very easy to be fooled and sold with clever marketing and pretty pictures.

I am not trashing the amplifier in any way. I do want to make that clear. I think it probably has a place in the market. Would I buy one? No. Does that mean you shouldn't buy one? No again. Read everything you can and gain an understanding of the technology behind the design, the implementation before you make a purchase. Unfortunately most of us can't hear these amplifiers for ourselves before we make a purchase, so we have to make an almost impulse purchase based on the information that is provided to us from the manufacturers. And they've proven themselves to be unreliable sources of information on not only specifications, but on simple things like quality control.

Just my more than 2 cents. The important thing that we all must do is to research, read all the documented information of chipsets, and what we can learn of the possible implementation methods of certain chips. We have to be smart. We have to learn about what the schematics of a chip tell us.

I'm a huge SMSL fan, and will continue to buy SMSL product as long as the quality control doesn't go way-way down. It is also my greatest concern as they will be announcing yet another "new headphone" amplifier in the coming days. Making this many new models with an existing workforce will cause strain on quality control, even if they employ many new employees. You have to train them. You have to oversee the work.

Please bare in mind that "hiss-noise" is something that shouldn't exist in even tube amplifier if designed correctly. It shouldn't be audible, unless your tweeters are 105+db/watt efficient. You really shouldn't have any issues with "hiss-noise" if all of your components are set-up correctly, and gain matched properly. Gain is not a volume control. It is to match one devices output with another's input. These youtube experts are not all created equal. Not all of them have the technical knowledge to properly test equipment.
 

boXem | audio

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I understand that the SA400 is a fully digital amplifier from the configuration.
However, in the AX5689 data sheet, the explanation of General features says as follows.

▪ 8-channel digital Class-D amplifier controller with digital inputs

I'm very confused about describing the FDA as Class-D. Is the FDA generally represented as a Class-D group?
Fully digital amplifier is marketing techno babble. Doesn't exist in real world and creates confusion.
The amplification part is analogue. It can't be digital.
The classical class D amplifier is analog input - > modulator generating pwm - > FET driver - > FETs - > output filter.
So called FDA are PCM input - > PCM to PWM converter - > FET driver - > FETs - > output filter.
What makes an amplifier to be called "class D" is the PWM - > FET driver - > FETs part, which is completely analog. So an FDA is not "fully digital".
 

Premonition

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Fully digital amplifier is marketing techno babble. Doesn't exist in real world and creates confusion.
The amplification part is analogue. It can't be digital.
The classical class D amplifier is analog input - > modulator generating pwm - > FET driver - > FETs - > output filter.
So called FDA are PCM input - > PCM to PWM converter - > FET driver - > FETs - > output filter.
What makes an amplifier to be called "class D" is the PWM - > FET driver - > FETs part, which is completely analog. So an FDA is not "fully digital".
Thanks for the great explanation, my understanding is that these "fully digital" amplifiers call themselves digital because it skips the DA conversion process and skips to PWM. So is PWM considered digital or analog? Wouldnt a wave generated by PCM be jagged instead of smooth?

In this case, if the amplifier requires analog inputs meaning DAC-> RCA/XLR -> ADC -> PCM to PWM converter, is it not counter-intuitive to convert D->A->D->PWM instead of connecting directly digitally?

What is the point of it then, I assume that the AD conversion creates more problems than using a modulator to generate PWM from an analog signal. I have the SMSL AD18 which sounds truly horrific to me in analog, and if the SA400 uses the same process it's hard to imagine it sounding good
 

boXem | audio

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Thanks for the great explanation, my understanding is that these "fully digital" amplifiers call themselves digital because it skips the DA conversion process and skips to PWM. So is PWM considered digital or analog? Wouldnt a wave generated by PCM be jagged instead of smooth?

In this case, if the amplifier requires analog inputs meaning DAC-> RCA/XLR -> ADC -> PCM to PWM converter, is it not counter-intuitive to convert D->A->D->PWM instead of connecting directly digitally?

What is the point of it then, I assume that the AD conversion creates more problems than using a modulator to generate PWM from an analog signal. I have the SMSL AD18 which sounds truly horrific to me in analog, and if the SA400 uses the same process it's hard to imagine it sounding good
PWM is a square ware with fixed frequency and variable duty cycle. Something completely analog.
Using a classical FDA for an amplifier with analog inputs is indeed quite disputable. In the case of the AX5689 the interest of using such chip is that the control loop is done in the digital domain, which in principle allows more complex loops than in the analog domain. But for this, you need people with very good knowledge in control theory. The other advantage is that the needed PCB area is much smaller than for an analog control loop, making the manufacturing of class D amplifiers with post filter feedback cheaper.
 

bud947

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When I saw a lot of comments trashing this amp because of the STA516BE I thought they were missing the point.
AX5689 is the supposed game changer here not STA516BE. But I do think that SMSL made some very questionable choices here.
This would have been better as a FDA with XLR/analog as an addition. The feebdack loop feeded with two 12070 or TPA3255 and coax + I2S inputs would have been a better design imho, but I guess we simply have to wait for technical reviews with measurements.

I was torn between March Audio P122, SMSL SA400 and SMSL DA9 and finally went with Sabaj A20a (very similar to DA9). DA9/A20a were much more straightforward and appealing to me on a design standpoint (and also cheaper). At 650 usd the SA400 is competing with march audio that are very good and well known class D amps.
 
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