I recently reviewed the SMSL SP200 THX headphone amplifier and gave it very high marks for excellence in performance. Given that this product was not yet available, I accepted the opportunity to review. Same happens with offers from other manufacturers. Invariably someone after the review wonders if I have received a "golden sample," i.e. a handpicked unit to measure well. My answer is that the chances of that is very low but that if there is some doubt, people should send another one and we can verify. Well, that has happened. A member ordered a SP200 and kindly sent it to me for evaluation.
For this assessment, I am just performing some spot checks as opposed to re-running all the tests. If there are differences, these tests should easily show them.
Let's start with our dashboard view using the same settings as the review unit:
SINAD which represents noise and distortion relative to our source signal is only 1 dB down. I see variations like this and more in products I test. There is always some variability with respect to temperature, environment, run to run variation in measurement, etc. So this is definitely within the accuracy limit of our measurements.
What I can't explain is the spectrum of distortion products changed. Here it is from the review unit:
We are still below -130 dB but the role of 2nd and 3rd harmonics has changed.
Next I tested the signal to noise ratio for the same input and output level:
We see a 1.7 dB difference which likely the reason SINAD changed similar amount. Again, nothing to worry about.
Let's see how our power curve relative to THD+N looks with 300 ohm load:
Performance is as identical as you can get. Both high and low gain product the same power and very low distortion and noise.
The one element that I thought would have variation would be the analog volume control. So I tested channel balance:
This is quite different than the review sample. First, the level would not change for quite a while and once it started to change, it fell apart a lot sooner than the review unit. You can only get 30 dB of attenuation before channel balance becomes extreme relative to 70 dB before.
Hard to tell if this is an outlier, typical of these analog controls, the one I got was hand picked or what. If you are going to use sensitive IEMs, this may be an issue for you.
Conclusions
I see little evidence of SMSL having picked a special unit to send me. Performance is as superb as the review unit. Volume control has some issues but as mentioned, I think there are other explanations for this than a golden sample.
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As always, questions, comments, recommendations, etc. are welcome.
If you like to support articles like this, please donate using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
For this assessment, I am just performing some spot checks as opposed to re-running all the tests. If there are differences, these tests should easily show them.
Let's start with our dashboard view using the same settings as the review unit:
SINAD which represents noise and distortion relative to our source signal is only 1 dB down. I see variations like this and more in products I test. There is always some variability with respect to temperature, environment, run to run variation in measurement, etc. So this is definitely within the accuracy limit of our measurements.
What I can't explain is the spectrum of distortion products changed. Here it is from the review unit:
We are still below -130 dB but the role of 2nd and 3rd harmonics has changed.
Next I tested the signal to noise ratio for the same input and output level:
We see a 1.7 dB difference which likely the reason SINAD changed similar amount. Again, nothing to worry about.
Let's see how our power curve relative to THD+N looks with 300 ohm load:
Performance is as identical as you can get. Both high and low gain product the same power and very low distortion and noise.
The one element that I thought would have variation would be the analog volume control. So I tested channel balance:
This is quite different than the review sample. First, the level would not change for quite a while and once it started to change, it fell apart a lot sooner than the review unit. You can only get 30 dB of attenuation before channel balance becomes extreme relative to 70 dB before.
Hard to tell if this is an outlier, typical of these analog controls, the one I got was hand picked or what. If you are going to use sensitive IEMs, this may be an issue for you.
Conclusions
I see little evidence of SMSL having picked a special unit to send me. Performance is as superb as the review unit. Volume control has some issues but as mentioned, I think there are other explanations for this than a golden sample.
------------
As always, questions, comments, recommendations, etc. are welcome.
If you like to support articles like this, please donate using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
