This is a review and detailed measurements of the SMSL SH-9 THX headphone amplifier. Product was just released and will be available shortly. The sample I have was kindly sent to me by SHENZHENAUDIO and costs US $290.
The market for high performance headphone amplifiers has become quite crowded but SH-9 sets itself apart with a gorgeous digital display and volume control:
A 256-step attenuator using resistor ladder implements volume control which should result in perfect channel matching (see measurement later). Typical of these systems, the volume control changes a bit slow compared to analog counterparts. The chatter of relays controlling which resistors are being used is rather quiet which is a relief.
The back side shows that there is only input and no pass through/pre-amp mode:
As you will see in the measurements, the 4 pin XLR output is NOT balanced in the sense that it doesn't provide higher output level compared to 1/4 headphone jack. There is balanced input as you see which is important to keep possibility of ground loops low. As long as there is enough output, it does not matter whether there is or is not a balanced (properly called differential) output.
SMSL SH-9 Measurements
As usual, we measure the unity gain of the unit with feeding it 4 volts and getting 4 volts out. The low gain mode is 0 dB which makes this task easy:
This is superb performance and provably transparent to the source. Ranking is way up there:
Noise performance is excellent as well:
50 mv output which forces the output attenuation is good but not state of the art:
Frequency response is dead flat as we like to see:
Here is our power versus distortion starting at 300 ohm:
My threshold for desktop products here is 100 milliwatts and the SH-9 sails way past that to 226 milliwatts. So it should have no trouble driving high impedance headphones.
Switching to the other extreme at 33 ohm we get similarly excellent performance:
Using the XLR output with balanced load shows that there is no more output to be had:
As you see the drop THX amp in balanced mode can produce much more power. But SH-9 beats it in noise department and by good bit.
Finally, the key differentiation for SH-9: channel balance:
SMSL SH-9 Headphone Listening Test
I tested the SH-9 with my killer load: the Ether CX with its 25 ohm impedance and low efficiency. The SH-9 had no trouble whatsoever driving it with authority with no sign of distortion to any loudness level you wanted. Likewise it took the Sennheiser HD-650 headphone's neck and drove it to skull resonating levels with ease.
dfjk jkkk jdkfj kkkkk.... what ...
Oops, sorry about that. A screw had come loose inside my head as a result of the above testing. Tightened that and all is well now.
Conclusions
The SMSL SH-9 Joins other instrument grade, ultra-fidelity headphone camp. It mates nicely to its DAC sibling, the SMSL SU-9. It has an attractive, high contrast high resolution display with accurate digital volume control. The cost is also quite attractive. Misses are few which is lower power due to lack of balanced output, soft control buttons, and slow volume control.
I love differentiation without sacrificing performance which SMSL SH-9 brings. I am happy to put the SH-9 on my recommended list.
------------
As always, questions, comments, recommendations, etc. are welcome.
Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
The market for high performance headphone amplifiers has become quite crowded but SH-9 sets itself apart with a gorgeous digital display and volume control:
A 256-step attenuator using resistor ladder implements volume control which should result in perfect channel matching (see measurement later). Typical of these systems, the volume control changes a bit slow compared to analog counterparts. The chatter of relays controlling which resistors are being used is rather quiet which is a relief.
The back side shows that there is only input and no pass through/pre-amp mode:
As you will see in the measurements, the 4 pin XLR output is NOT balanced in the sense that it doesn't provide higher output level compared to 1/4 headphone jack. There is balanced input as you see which is important to keep possibility of ground loops low. As long as there is enough output, it does not matter whether there is or is not a balanced (properly called differential) output.
SMSL SH-9 Measurements
As usual, we measure the unity gain of the unit with feeding it 4 volts and getting 4 volts out. The low gain mode is 0 dB which makes this task easy:
This is superb performance and provably transparent to the source. Ranking is way up there:
Noise performance is excellent as well:
50 mv output which forces the output attenuation is good but not state of the art:
Frequency response is dead flat as we like to see:
Here is our power versus distortion starting at 300 ohm:
My threshold for desktop products here is 100 milliwatts and the SH-9 sails way past that to 226 milliwatts. So it should have no trouble driving high impedance headphones.
Switching to the other extreme at 33 ohm we get similarly excellent performance:
Using the XLR output with balanced load shows that there is no more output to be had:
As you see the drop THX amp in balanced mode can produce much more power. But SH-9 beats it in noise department and by good bit.
Finally, the key differentiation for SH-9: channel balance:
SMSL SH-9 Headphone Listening Test
I tested the SH-9 with my killer load: the Ether CX with its 25 ohm impedance and low efficiency. The SH-9 had no trouble whatsoever driving it with authority with no sign of distortion to any loudness level you wanted. Likewise it took the Sennheiser HD-650 headphone's neck and drove it to skull resonating levels with ease.
dfjk jkkk jdkfj kkkkk.... what ...
Oops, sorry about that. A screw had come loose inside my head as a result of the above testing. Tightened that and all is well now.
Conclusions
The SMSL SH-9 Joins other instrument grade, ultra-fidelity headphone camp. It mates nicely to its DAC sibling, the SMSL SU-9. It has an attractive, high contrast high resolution display with accurate digital volume control. The cost is also quite attractive. Misses are few which is lower power due to lack of balanced output, soft control buttons, and slow volume control.
I love differentiation without sacrificing performance which SMSL SH-9 brings. I am happy to put the SH-9 on my recommended list.
------------
As always, questions, comments, recommendations, etc. are welcome.
Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
