SMSL SA-S1 low volume noise

Hello all.

I just received a SMSL SA-S1 from MarcMarts Ebay store. A neat little package that looks and sounds great, aside from one disturbing issue:
It has an audible noise (so called pink noise) on low volumes up to 12 o'clock volume knob position. It recedes on max volume, but is still there. This phenomenon remains with and without rca cables attached to a music source. I have tried 2 different switch mode power supplies. One 12V 1,5 A from an Audio Pro portable ipod dock. It should be of good quality. The other one a rather expensive multi voltage power supply Switchat nätaggregat - 72*W > Ställbar utspänning | Kjell.com

My first step will be to give the seller a chance to correct this. If this fails, I would welcome suggestions as how to fix this issue myself. Could this for example be resolved with some kind of filtering, a cap on the dc input?

Best regards.
 
So I tried to contact their support, and I got answers!

"Dear friend,
Good day. Thanks very much for your message.
We feel sorry for the late reply.It takes us some time to contact with our professional colleagues.And he suggests that you could have a try to break the AUDIO IN signal wires behind the amplifier,then open the amplifier and turn the sound to maximum.After doing that,if there's noise insist,please don't hesitate to tell us.Thanks~!

If there is any question or problem, please feel free to contact us.
Thanks&Best regards,
Marcmart"

A bad case of google translate it seems. My interpretation was that I should disconnect the Audio in, turn the amp on and crank the volume up to max. Of course, this would not help.

If I was to take them on their words I even could try to open the case. I will avoid this as that would mean breaking the warranty seal. I am awaiting their next reply.
 
Hi Nigel. Thanks for the suggestions.

I suppose the only way to turn down the gain without opening the case and thereby voiding warranty is to turn the volume counter clockwise. Oddly enough it has the most noise on the lowest volume setting, from 7 o'clock to 11 o'clock. When I crank it up, it is dead silent.

The RC filter formula was a bit above my engineering skills :) But I guess F is a frequency cut off point, R a resistance value and C a capacitor value. Out of curiosity, how will this filter work? Will it attenuate the noise without sacrificing the audible frequency spectra?

Good news is that MarcMart has offered to ship me a replacement unit :)
 
Set the filter frequency for around 30KHz.
Put a resistor in series with the input then after the resistor put the capacitor to ground.
This will filter out RF and noise above 30KHz.

This filter is commonly used on the front end of amplifiers.

The input impedance of the amp is important when determining the RC values.
 
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after contacting marc mart with details of the problem. they replied saying to replace the capacitor shown in the pic with a red arrow with a 104 (0.1uf) capacitor as i said previously i've never worked on a pcb before so i am making them promise to replace it if i fudge the job up before i go ahead and open the thing up. any advice on this would be greatly appreaciated
[IMGDEAD]http://postimage.org/image/9dskaobl5/[/IMGDEAD]
 
Got my replacement

So, I finally got my replacement SMSL SA S1 amplifier. As I tested it i was initially glad that it was dead silent. Then came the cold shower. The bass response was horribly weak and somewhat distorted. I was nearly howling with rage and about to throw the junk through my window but got to my senses and started troubleshooting.
I switched between different speakers, and compared the sound from sources such as laptops and smartphones. I tried different rooms and setups, and even compared the sound to my trusty old Denon 2105.
The reason for the bad sound in my first test was because of a Dolby sound effect feature on my laptop that was on by default. A truly retarded equalization. I recently reinstalled this Lenovo laptop of mine and missed to remove the soundprocessing. I also like to think that the sound somehow got better by warming up the amp. Anyhow, this SMSL amp is well worth the money, despite the fact that I got a faulty amp to begin with. It keeps up fairly well with my Denon amp. One thing that is disturbing is that it works as a an FM radio Jammer and severely scrambles the reception of my radio in the same room. Perhaps it could be dealt with if I soldered some small pF caps across the speaker outputs. When and if I open the case I will probably see if I can find room for some reservoir caps as well.
 
One thing that is disturbing is that it works as a an FM radio Jammer and severely scrambles the reception of my radio in the same room. Perhaps it could be dealt with if I soldered some small pF caps across the speaker outputs. When and if I open the case I will probably see if I can find room for some reservoir caps as well.
I have 2 of the SML-SA-S1 units and a cheaper Lepai 2020A+ all using the same chip. I could not get any sort of FM reception just like you. I tried adding ferrite beads, changing power supplies, adding a isolation transformer to no avail.
Perhaps this problem is known, I seem to remember that they were advertised as being good for connecting to digital components.
 
Try connecting the negative of the power supply, the negative of the RCA inputs, and chassis/casing to common EARTH ground (connected to ground on 3-pin wall power). I had a similar hiss that went away after I did this. I think the negative of the audio input is especially susceptible to noise pickup when not properly grounded if not being driven by true balanced input line drivers.
 
Replaced C23 - Unit works fine!

Thanks to all, i modified my unit according to [FONT=verdana, tahoma, arial][FONT=verdana, tahoma, arial][FONT=verdana, tahoma, arial]posted image from 'ostrichmilkman' with the original tantal capacitors value of 1nF (101T) in mind i tried to get a value as close, but still larger to get the wanted result (= no noise) I'm now @ 4,7nF (472) with good result. No noise and no noticeable negative change to the sound. Pictures @ [/FONT][/FONT][/FONT][FONT=verdana, tahoma, arial][FONT=verdana, tahoma, arial][FONT=verdana, tahoma, arial][FONT=verdana, tahoma, arial][FONT=verdana, tahoma, arial]http://195.84.101.101/~goranl/projects/nad_stereo/SMSL_amp/[/FONT][/FONT] [/FONT][/FONT][/FONT]
 
Glad you were able to fix the problem. My unit did not have a problem with the Tantalum cap, but with a channel imbalance at low volumes. Rather than request a replacement amp, I asked SMSL for a replacement volume pot, which they promptly sent to me. After installing the replacement pot, both channels are now balanced and the sound quality is quite impressive. I definitely prefer this over my modified Sonic Impact 5065 Gen 2 T-amp and the Arjen Helder TA2020 MkIII T-amp. It's smoother, equally dynamic and the soundstage is more three dimensional. I initially had my doubts about the ERO MKT1813 input caps, but after about 80 hours of playing time, the amp has really opened up and the bright treble has smoothed out, while the bass and midrange have become fuller and better defined.