Review and Measurements of SMSL SP200 THX HP Amp

[trl]

I contacted to the hifi-express store, where I bought from the Smsl sp200 about the hiss noise with earphone, especially with low impedance earphones like the kz as10 that has impedance of 14 ohms and after 4 days and two messages they replied,
"14Ω< 16Ω
The headset is too sensitive to hear the current sound of the thx module，not suggest to connect it with KZ AS10."
This is really upsetting response, the funny part is that before I bought the AMP from them I ask them if the AMP work with earphone that has minimum impedance of 8 and they said "yes,it can" .After I told them that they told me the I need to get a "Impedance noise reduction rod " which is a 3.5mm Impedance Adapter . I ask them for a replacement or a refund as I got a defective AMP but they still did not reply.

Sorry to hear that.

However, 14Ω impedance has nothing to do with the sensitivity of the headphones. We could have 14Ω earphones with a sensitivity of 115dB/V and 32Ω headphones with a sensitivity of 125dB/V.

Regarding your KZ AS10, per manufacturer specs, these IEMs have 14Ohms impedance, 105dB/mW or 125.5dB/V sensitivity (indeed, very high!), although per https://reference-audio-analyzer.pro/en/report/hp/kz-as10.php your headphones are having an impedance of about 17Ohms and a sensitivity of over 132dB/V (extremely high, you might need to purchase Geshelli Archer 2 to drive them without background noise).

 

[or965]

Sorry to hear that.

However, 14Ω impedance has nothing to do with the sensitivity of the headphones. We could have 14Ω earphones with a sensitivity of 115dB/V and 32Ω headphones with a sensitivity of 125dB/V.

Regarding your KZ AS10, per manufacturer specs, these IEMs have 14Ohms impedance, 105dB/mW or 125.5dB/V sensitivity (indeed, very high!), although per https://reference-audio-analyzer.pro/en/report/hp/kz-as10.php your headphones are having an impedance of about 17Ohms and a sensitivity of over 132dB/V (extremely high, you might need to purchase Geshelli Archer 2 to drive them without background noise).

Thanks you for the response but I can not understand it quite well, does a AMP with high power cause hiss noise with sensitive earphones ?
,If there was a lower gain on the SMSL sp200, then I will not hear hiss noise ? I want to know if an AMP like Schiit Heresy that has two gain,one very low gain 0db ,and one high gain 15db will not has hiss noise or that high power AMP will have noise with sensitive earphones no matter of what gain they have. I saw that the Schiit Heresy max power at low gain 33 Ohm is 111 milliwatts and on high gain is 2.37 watts .

 

[trl]

But SMSL sp200 already has a Low-Gain switch and this is a +6dB amplification (2X), while other headamps are having a 0dB amplification in their Low-Gain mode (1X). Heresy has a 0dB (or 1X) amplification in Low-Gain, but depending on the internal circuitry and schematic this might mean a lower background noise or might not.

Maybe this graph will help:

50mV SNR​

 

[jaraheel]

hello everyone! I just purchased one from Apos and it arrived today. Though when switching from JDS Atom to this one (connected via rca input from my Mac) I noticed a hissing sound. The noise is not there with the Atom. Does that mean the SP200 needs to be returned, or should I experiment with different cables? I am using HD660s headphones.

 

[Veri]

hello everyone! I just purchased one from Apos and it arrived today. Though when switching from JDS Atom to this one (connected via rca input from my Mac) I noticed a hissing sound. The noise is not there with the Atom. Does that mean the SP200 needs to be returned, or should I experiment with different cables? I am using HD660s headphones.

Other people here fixed the problem with RCA to XLR cable, into the XLR inputs.

 

[jaraheel]

Other people here fixed the problem with RCA to XLR cable, into the XLR inputs.

thank you so much for the reply. Can you please point me to a single RCA to dual male XLR cable for this job?

 

[trl]

I noticed a hissing sound

Does this noise changes when switching between the low/high gain?

Can you please point me to a single RCA to dual male XLR cable for this job?

https://www.crutchfield.com/S-06ghNGEnE6O/p_979GXM133/Hosa-RCA-to-XLR-Adapter.html should do, but measure with a multimeter the pin-out. Usually, one of the two hot-wires from the XLR will need to be shorted to GND, to minimize the interferences:

Source: http://4.opposed.menke-bahr.de/rca-to-xlr-wiring.html.​

 

[jaraheel]

Does this noise changes when switching between the low/high gain?


https://www.crutchfield.com/S-06ghNGEnE6O/p_979GXM133/Hosa-RCA-to-XLR-Adapter.html should do, but measure with a multimeter the pin-out. Usually, one of the two hot-wires from the XLR will need to be shorted to GND, to minimize the interferences:

Source: http://4.opposed.menke-bahr.de/rca-to-xlr-wiring.html.​

Thanks for the reply.
It does change in ‘volume’ when switching between high and low gain settings, like the noise is being amplified correspondingly.

 

[trl]

OK, so when using the lowest gain setting and volume somewhere around 10 o'clock is there still that noise audible?
Can you unplug the interconnects and try to see if the noise disappears?

 

[jaraheel]

OK, so when using the lowest gain setting and volume somewhere around 10 o'clock is there still that noise audible?
Can you unplug the interconnects and try to see if the noise disappears?

yes some noise is still audible when using lowest gain setting at 10 o'clock volume knob.

the noise disappears when the interconnects are unplugged.

 

[trl]

the noise disappears when the interconnects are unplugged.

This is odd and might need investigated by the manufacturer, as you're not the only one on this forum complaining because of this noise (@or965).

What audio source (DAC) is connected to sp200?
With balanced cables connected only to the sp200, but disconnected from the audio source (DAC) is the noise still there?

Some manufacturers do not tied up XLR plugs ground to the audio ground of the circuit to prevent future possible ground loops. Like Veri said, perhaps using the RCA might help, because RCA is tied up to the GND for sure. This might help perhaps if both sp200 and your DAC are having floating grounds, but also might help in case of a ground loop. Ideally, audio ground and chassis ground should be separate, but strange noises might appear when the audio-source's grounding is different than amplifier's grounding.

 

[ninetylol]

I had some noise problems too. Solved it with 2 steps:

1. DAC had noisy power from PC USB ports. Fixed it with a separate clean power source for the DAC.
2. Strangely 44,1khz 16 Bit gave me noise even when nothing was playing. Changing to 44,1khz 24 Bit removed the noise completely.

This Was using RCA and optical to DAC.

 

[trl]

1. DAC had noisy power from PC USB ports. Fixed it with a separate clean power source for the DAC.

What DAC? What power source have you used, please?

 

[ninetylol]

What DAC? What power source have you used, please?

I Was using the Loxjie D10 and used the Topping P50 which removed a groundloop I had before, also removed some humming noise. In combination with the 44,1khz 24 Bit setting i had no noise at all even with High gain and full volume on the SP200.

Since then I upgraded to the Topping D50S, because that P50 stack is so hot

 

[jaraheel]

This is odd and might need investigated by the manufacturer, as you're not the only one on this forum complaining because of this noise (@or965).

What audio source (DAC) is connected to sp200?
With balanced cables connected only to the sp200, but disconnected from the audio source (DAC) is the noise still there?

Some manufacturers do not tied up XLR plugs ground to the audio ground of the circuit to prevent future possible ground loops. Like Veri said, perhaps using the RCA might help, because RCA is tied up to the GND for sure. This might help perhaps if both sp200 and your DAC are having floating grounds, but also might help in case of a ground loop. Ideally, audio ground and chassis ground should be separate, but strange noises might appear when the audio-source's grounding is different than amplifier's grounding.

- The audio source is just a Mac PC via audio out (no DAC)
- I am using RCA cables currently
- When the RCA cables are plugged in the amp but not in the computer, then there is no noise. Does that mean the amp is amplifying the noise output by the source? But then the Atom amp does not have this noise

 

[ninetylol]

- The audio source is just a Mac PC via audio out (no DAC)
- I am using RCA cables currently
- When the RCA cables are plugged in the amp but not in the computer, then there is no noise. Does that mean the amp is amplifying the noise output by the source? But then the Atom amp does not have this noise

Maybe try changing the bit rate to 24 Bit as I mentioned before?

 

[Veri]

thank you so much for the reply. Can you please point me to a single RCA to dual male XLR cable for this job?

I would try the monoprice RCA to XLR cable.

 

[jaraheel]

Maybe try changing the bit rate to 24 Bit as I mentioned before?

that did not help

 

[or965]

@trl
I got the same hiss sound with RCA input contacted to the topping d50 and without it .
Hifi-express, the shop that I bought the SMSL sp200 waste my time, after 15 emails between me an the seller I opened a paypal dispute because the seller only accept that I will return it but I need to pay the return shipping .After I opened the dispute, I really thought that he want to help me, he try to fully understand how I am using the AMP and ask me to unplug the DAC input to see if the issue is from my DAC .I said to him that I already tested it and it happen without input from the DAC .After it he said that he will buy the earphones that I experience the highest volume of hiss noise .I was really surprised because I told him before that I have many earphones that has the hiss noise with low gain. After few days he email me this
"I have received my KZ as10, and I have tried it with SP200.
When it is low, I can't hear the hissing noise.
When it is high, I can hear the noise.
I have tried it with my other headphones like moondrop, sony. It doesn't have any noise.
And I have connected with the KZ company.
They said that is normal, This headset has a better resolution and clear sound quality. The front end you are pairing with has a current sound, and the current cannot be avoided if it is charged. Just more or less. The earphone is of high sensitivity. High gain makes the current sound more pronounced.
Recommend you used it with the low."

After that email I told him that I already mention on the previews emails that the hiss noise is noticeable on low gain and and sent him a picture of the knob position as he requested in the previews emails . I also told him that I do not use the high gain as this earphones never need this power, the volume is very loud with low gain on 10 o'clock knob position .
I only found out that the seller does not try to really help me when he email me this "they always has this noise" and explain me that it is normal, he contradict himself by said now that it has hiss noise on both low gain and high gain .
The worst part that he even does not want to pay only a small part of the returns shipping fee,I ask him to pay only 13 USD of return shipping although it cost me to ship it with insured shipping much more,a 47 USD .Then he tell me that he will pay 20 USD and send me a 20 USD offer on the paypal dispute .If I accept this offer, it mean for paypal that I agreed to keep the AMP for a 20 USD refund, the dispute will be closed and no one can assure me that he will return the rest of the money when he will receive the returned AMP .I so disappointment with this seller, I will never buy anything from him again .

 

[jaraheel]

can any one here confirm that their unit does not produce any hissing sound? I am wondering if I should request a replacement or a refund..