My Experience With SMSL SA-160

[Rabepobemababe]

For those who are wondering about the antecedents of this amplifier, it is a Chinese Class-D stereo amplifier from the stables of Shenzhen Audio. It shares the same chip as another amplifier by SMSL, the SA-98E, which got some good reviews from aficionados.

For those who are interested in the detailed specifications of this class-D amplifier, the specifications are here:

SMSL SA-160 160WPC Digital Amplifier + Headphone Amplifier + Power Adapter - Professional Audio Store - Shenzhenaudio.com

Note that the webpage title (mistakenly) is that of power adapter for another amplifier from SMSL stables, the SA-36A. Also, the maximum power output quoted for SMSL SA-160 is with THD+N of 10%. At an acceptible THD+N of 1%, the power output would approximately be half of the maximum power output quoted.

My requirement was for a compact stereo amplifier to go with my digital piano (Casio Privia PX-150) and passive studio monitor speakers. Considering that the lowest register of a piano goes down to 27.5 Hz (A0), and the highest register goes up to 4186 Hz (C8), I needed a cost-effective amplifier with about 40 watts per channel that can truthfully reproduce these frequencies with linearity.

My digital piano's output voltage was between 500 mV to 1.5 V RMS. Since it was not full 2 Volts, I was not sure whether I could connect it directly to a power amplifier. My guess was that any stereo amplifier that I buy for this purpose needed a built-in pre-amp section, i.e., it needed to be an integrated stereo amplifier.

I was drawn to Class-D amplifiers by the glowing reviews some of them got over the net, their compact footprint, and low cost. SMSL-98E was one of them. Even their early model SMSL SA-50 got some good reviews, and one very elaborate video review that compares SMSL SA-36 and SA-50 is here:

https://www.youtube.com/watch?v=onQrfZboX3Q

Inspired by the same, I ordered an SMSL SA-160 directly from Shenzhen Audio. It took a month to arrive, and costed me Rs.7,200/- + Rs.2,150/- towards Customs charges.

I may state that my initial tilt was towards a Norge power amplifier which would have costed me about Rs.16,000/-. But the acquisition cost, looks and compact footprint of SMSL SA-160 have gotten me.

SMSL SA-160 is about the size of a 5-1/2" smart phone. It is nicely built, and the built spells quality. Its power adapter is larger than the amplifier itself.

I tested it with three different pairs of speakers that I have. The sound quality per se is quite impressive. The amplifier sounds quite neutral, and can go quite loud. But there was a problem. There was a continuous high frequency noise that is present in the background. Even when I disconnected the source, the noise was still present. This was true with all the permutations and combinations of speakers, interconnects and cables that I tried.

Considering that my hearing tops at about 14 KHz (as found in an audiometry test I had undergone a month ago), and considering that I am able to hear this noise, I am guessing that the noise is at a frequency of 13 KHz to 14 KHz. Even though the noise level is much less than the signal, it IS still audible, and would annoy any one used to a noise-free system.

This is my second hifi disappointment after the Sonus-2506 floor-standers.:sad:

Moral of the story is, never buy audio products based purely on reviews over internet (including this one).

 

[stpsycho]

I feel sorry for you.Sell it off and be careful next time

 

[cyber_cat]

What made you think you can connect instruments to these type of amps ?

PS: How did Sonus-2506 disappoint you ?

Have you connect line level devices thru the amp and played it ?

Unless you got a defective one, I don't think there is anything wrong with that amp.

 

[Rabepobemababe]

@stpsycho,

I asked a couple of friends of mine who own class-D amplifiers as to whether the high frequency noise is common with them. They said normally they are dead quite. I contacted Shenzhen Audio about my problem, and they are investigating it. I hope a solution comes through.

@cyber_cat,

There are several setups shown on Piano World - Home of the world famous Piano Forums. The most piano information on the Web, where digital pianos are hooked up to stereo amplifiers and monitor speakers for home use. I took my cue from them. A typical digital piano used for practice at home usually comes with puny speakers that are rated between 8 to 20 watts per channel, whereas an acoustic piano is much louder than that. Folks usually amplify digital pianos for practice at home.

As to the Sonus 2605 V3, I have already told my story in a thread created by <sound_cycle> on this forum.

I see that a number of audio enthusiasts are employing class-D & class-T, chip-based, small-footprint stereo amplifiers in their hifi setups. Like I said, SMSL SA-98E got good reviews on several forums for hifi use, and on this forum too, some one was enquiring about it. There are other brands of Chinese class-D stereo amplifiers too, which have got their following. Hence my post about my experience with SMSL SA-160.

 

[Rabepobemababe]

I was looking at the Voltage Vs. Power Output, and the Power Output Vs. THD+N graphs for the TDA7498E , the Class-D amplifier chip employed in SMSL SA-98E & SMSL SA-160, as given on the website of STMicroelectronics.

www.st.com/web/en/resource/technical/document/.../DM00044235.pdf

From the Power Output Vs. THD+N graph, it looks like the THD+N value for this chip raises sharply beyond the output of 80W per channel (@ 4 Ohms RL). Up to that point, the THD+N value is less than 0.1%. So to achieve the THD+N value recommended for hifi amplifiers (i.e., <0.1%), the power output of TDA7498E should probably be kept below 80W per channel (@4 Ohms RL).

From the Voltage Vs. Power Output graph, it looks like the power output of 80W per channel (@4 Ohms RL, and @ a THD+N value of 1%) is achieved at about 28 Volts input. Therefore for a THD+N level of less than 1%, perhaps the voltage should be even less.

Since the operational voltage range of TDA7498E is specified between 14V -38V, I am thinking of obtaining a 24V / 5A SMPS and trying it with my SMSL SA-160. I am guessing that in this arrangement, the power output of SMSL SA-160 would be somewhere around 60W per channel (@4Ohms RL), but with negligible THD+N. With the speakers of 8 Ohms nominal impedence, the output would be even less.

I intend to see whether this way the high frequency noise from the speakers connected to the SA-160 subsides.

The power brick provided with SMSL SA-160 is 36V / 5.7A. The graph shows that this will drive the TDA7498E to the limits, i.e. 160W per channel (@4 Ohms RL), but with very high THD+N. I have a feeling that this over-driving is the cause for the high frequency noise. Is my logic right?

 

[jags]

I do not have this issue with my SMSL SA-98E.

Is it possible that there is interference from the digital piano? You can try moving the amp & speakers away from the piano and see if it improves the situation.

The power brick provided with SMSL SA-160 is 36V / 5.7A. The graph shows that this will drive the TDA7498E to the limits, i.e. 160W per channel (@4 Ohms RL), but with very high THD+N. I have a feeling that this over-driving is the cause for the high frequency noise. Is my logic right?

Rapid increase in THD here is caused by clipping. It is related to output signal and not related to power supply voltage.

 

[greenhorn]

I do not have this issue with my SMSL SA-98E.

+1. I have an SMSL SA-98E, and it doesnt have any buzz that would make the music not enjoyable (there is still a slightly higher amount of residual noise if you stand next to the speaker than my other amps)

It's remarkable the crazy amount of power it puts out from a box as big as a desktop hard disk.

I stopped using it because it just didn't have the low end as the amp it replaced (a vintage sony reciever using an STK462 module), and eventually upgraded to an NAD 3020

 

[Rabepobemababe]

@jags,

I tested the SMSL SA-160 with my Denon DCD-700 AE, with the same result, i.e., high frequency noise through speakers in both the channels.

I am interested to know the power rating of the adapter you are using with the SA-98E. It was initially sold with a 32V adapter, and later with a 36V adapter.

Also, kindly tell me this:

If you disconnect the source, but keep your SA-98E switched on with its volume knob turned to maximum, say, for couple of hours without fan or air-conditioning in the room, does the SA-98E heat up?

@greenhorn,

Thanks for the observations. Some one posted on a forum that the volume knob on the SA-98E was infact an input gain adjustment (the way it is in some power amplifiers), and not a true volume control. In his case, apparently he was getting the high frequency noise (even without a source connected) as long as the gain was set below the 12 O' clock position. If he increases the gain beyond the 12 O' clock position, apparently there is no noise. With me, that is not the case. Noise is uniform irrespective of the position of the volume knob.

 

[Fantastic]

Did you check the power supply line on a scope ?
If it's clean, the noise could be the out of band switching frequency noise of the amp . This does seem rather unlikely.

Use a different supply and see if the noise changes or goes away. Need not use the same supply voltage. You are doing this to see if there is 'noise' on your current power supply.

There are very few audio circuits that use 'real' variable gain in an amp. Especially a power amp. Gain's are generally fixed as they can also affect stability. I doubt if you can easily get any commercial amp that has 'real variable gain' at the input. Such circuits can have noise compromises or very low input impedance issues.
There have been some preamps in the (distant?) past that had variable 'gain' but I don't believe it is used nowadays.

 

[Rabepobemababe]

@Fantastic,

I tried Techmate's universal adapter, the 120 watts version, which has adjustable output between 12V to 24V. At 24V, it can output 4A. This adapter has no earthing, i.e., two pin only.

The high frequency noise is still there with this adapter @24V, but much less noticeable.

Interesting observation there about variable gain on power amps! Doesn't the dual mono Pulz RS-250 actually have a variable gain knob for each channel?

 

[Fantastic]

Doesn't the dual mono Pulz RS-250 actually have a variable gain knob for each channel?

That's an independent volume control for each channel !
If you cannot get good stereo volume controls where the channel levels are matched with rotation ( particularly at low settings ), then two mono ones are better as you can adjust them separately.
Many modern amps have very good pots ( volume controls) and so even a 'balance' control is not provided for !

 

[jags]

I am interested to know the power rating of the adapter you are using with the SA-98E. It was initially sold with a 32V adapter, and later with a 36V adapter.

I got a 36V adapter.

If you disconnect the source, but keep your SA-98E switched on with its volume knob turned to maximum, say, for couple of hours without fan or air-conditioning in the room, does the SA-98E heat up?

At present, I am using my amp in a makeshift arrangement with speakers from a old Sony music system and local cables. I get speaker hum when I disconnect the source. Probably due to interference at the input cables. This hum disappears when a source is connected. I have not seen the amp getting heated up.

 

[Rabepobemababe]

In case of the SA-160, the seller website does mention that the SA-160 heating up to 40 degrees Celsius is normal. It heats up, with or without source, if the volume knob is turned beyond 9 O' clock position (with the supplied powerbrick).

The seller website says (if you can excuse the Chinglish):

"SA-160 due to greater power and volume restrictions. When in work, the shell temperature reaches about 40 ?, this is a normal phenomenon. Does not affect machine performance, please rest assured."

As to the correct power supply requirements for the TDA 7498E, I was pleasantly surprised to see a post on DIY Audio forum echoing my thoughts (and this was in connection with the SA-98E), that for it 24V is the correct voltage based on noise considerations. Apparently, some owners used a 24V Meanwell 13 Amp SMPS with the TDA 7498E with good results.

When I used the 24V/4A SMPS from Techmate, the SA-160 ran cool all through. Hence my assumption that overloading of TDA 7498E = high THD+N = heat.

In my case, today I am taking the SA-160 and its 36V/5.7Amp powerbrick for testing to a friend who specializes in power supplies for audio equipment. Most probably, the powerbrick shall be modded.

Will post the results.

 

[Rabepobemababe]

My present setup looks as below:







The 36V 5.7A power brick that came with the SA-160 could not gainfully be modded. A 24V 6A SMPS I got made from a manufacturer in Balanagar, Hyderabad too had noise problem, albiet at a much lower level than the one that accompanied the amplifier. Of the three powerbricks I used with the SA-160, the Techmate 24V 4A adapter seems to be having the least noise.

Meanwhile, I noticed that different vendors of the TDA7498E based Class-D amplifiers are marketing them with powerbricks of varying voltages and amperages, based on varying reasoning, even as all of them advertise the maximum achievable power as 160wpc with a 36V powerbrick.

One vendor on AliExpress states that 160wpc can be realistically achieved with TDA7498E only with a powerbrick of 36V and 10A, and since such a power supply is not available, they are sticking to a 32V 5A power brick.

Another vendor states that using a 36V 5.7A powerbrick damages the TDA7498E, as in many areas the domestic voltage exceeds 240V occassionally, resulting in a DC output higher than 36V from the powerbrick. He is supplying it with a 24V 6A powerbrick.

One particular vendor online is supplying a TDA7498E based amplifier with a HP 19.5V 4A laptop powerbrick.

I have now ordered what is claimed to be a custom made SMPS for TDA7498E by a Hongkong brand called Suny (imitation of "Sunny" power adapters), listed on AliExpress. This adapter is 24V 6A, and is costing me Rs.1,250/- plus Customs Duty. Even then, there is no guarantee that the noise problem would be solved!

One set of specifications for advertising, and another set of specifications for realistic use, seem to be the norm with respect to the TDA7498E. Moreover, the 160wpc is advertised at 4 Ohms and @10% THD+N. The continuous wattage would not, I suppose, exceed 50-60wpc at 4 Ohms. At 8 Ohms, it would be slightly more than half of that wattage, i.e., not more than 30 wpc. If that is the case, then why not buy the conservatively rated and tried & tested CA AM-5, and why go for a Chinese cigarette case amplifier at all? By now, in addition to what I have originally spent on the SA-160, I have spent about Rs.5,000/-. on trying out different power supplies with the amplifier. I wonder if I am throwing my good money over bad money. Rs.12,000/- would have got me a brand new CA AM-5 amplifier. Rs.13,000/- could have got me a dual mono Pulz RS-250. Rs.16,000/- could have got me a Norge Power Amplifier, all of which are decent sounding, tried and tested amplifiers.

Other than a small form factor, there really seems to be no advantage in going in for a Chinese Class-D cigarette pack sized amplifier for my requirement.

 

[jags]

I wonder if I am throwing my good money over bad money.

I am afraid this might be the case. I think it might be better to cut the loss and move on when facing issues with such (direct import Chinese) products.

 

[Fantastic]

Why are the speakers so high up ?
Besides they are pointing straight ahead.
If the speakers are up there due to space issues or small kids (!) at least they should 'point' downwards to the listener. If not you would loose a very large part of the direct HF sounds. Off axis performance at HF is always several dB down. In this case it should be at it's worst. Here the HF would consist mostly of reflected sounds.

Just bringing the speakers down to keep the listener on axis will be equivalent to changing to a 'great' amp and 'super' cables ! All you need to do is bring the speakers down !

 

[Rabepobemababe]

@Fantastic,

1.It would suffice if the speakers here are able to reproduce truthfully upto the highest note of the piano, which is at 4186 Hz. Frequencies beyond 4186 Hz hardly matter. There might be few harmonics of the treble clef of the piano in the frequecies beyond 4186 Hz, but they will be several dB lower.

2.In piano, you always listen to the reflected sounds more. In a grand piano, the lid is supposed to provide the reflections. In an upright piano the walls behind and the ceiling above provide the reflections, and you will almost never hear direct sounds (because the front portion of an upright piano towards the player is closed completely, and sound emanates from the rear and the top). So the reflected sound is OK as far as the piano is concerned. You would see in quite a number of digital pianos, speakers facing down towards the feet of the player / floor. Also, in several amplified speakers meant to be used with digital pianos, you would not see tweeters.

3.I am actually looking to get rid of the high frequency whine here. Thanks to the higher placement of the speakers, the high frequency whine is somewhat less than what it otherwise would be.

4.Yes, there is a space constraint. The speakers when placed at ear level would protrude by about 1-1/2 feet into the room. Since it is a 12' x 12' bedroom, of which 6' x 6-1/2' is occupied by the bed, there is a good chance of people bumping into the speakers while walking around the bed if I place the speakers at ear level. I consulted the designer of these speakers before placing them high on the shelves. Unfortunately, due to the size and weight of the speakers, I could not source mounts that would hold them pointed down. A design was given by a well known installer in Hyderabad, where powder coated iron shelves with speakers pointing straight ahead were shown as the only option. So I went ahead, and got the shelves made with plywood.

But for the high frequency whine, the set up sounds quite good as of now, and closely mimics an upright piano. All I need now is to get rid of the HF whine, either by sourcing a good power supply, or by replacing the amplifier altogether.

@jags,

Yes, I am seriously considering CA Topaz AM5. I also had a telephonic conversation with our esteemed forum member, Hifipal4all, and he seems to be having a used NAD, which might also be a good option for me.

 

[darmstadtium]

Hi Rabepobemababe

did you manage to find a solution ?

 

[Rabepobemababe]

@darmstadtium,

No. So far, no joy.

Shenzhen Audio says it is a problem with the main board, and they will ship a replacement board. It is yet to happen, and when it happens, it will take another month for the shipment to reach me, not to speak of the Customs Duty by Indian Customs.

 

[greenhorn]

I believe the enclosure uses some fancy screws - you'll need one of those hex shaped heads to open it