This is a review and detailed measurements of Gustard H20 balanced input and output headphone amplifier. It is on kind loan from a member. The H20 costs USD $930 but I see it on sale from shenzhenaudio for USD $840. I think it was also sold on Massdrop for $800. Either way you look at it, it is not cheap.
The H20 comes in black and silver. The unit I have for testing is the silver:
The H20 is quite heavy and large. Controls feel good although I am not a fan of relay controlled volume. There is a racket that is sharp pitched as you adjust the volume.
The two 1/4 inch jacks are not the same. The first one has a resistor inline (see measurements). The second is straight through.
On balanced XLR output, you have a choice of stereo 4-pin or dual three pin. I tested with the former.
The back panel sports a good set of connectors:
There are a set of RCA inputs to the left and two sets of XLR. There is one set of pass through XLR outputs.
Gustard has no website I can find so don't know if the unit has passed regulatory certifications or not.
Headphone Audio Measurements
I run my dashboard test using 1/4 inch output and results there were quite disappointing:
I am using XLR inputs yet we still have lots of mains noise. That aside, the dominant problem is the very high second harmonic at 2 kHz. SINAD of 90 dB is quite poor even for a cheap headphone amplifier let alone a high-end one.
The other odd thing is the gain. As you see, with maximum volume and gain switch set to highest we only have a 2 dB gain? Why so low? This is bound to cause issues for music that is recorded at low levels.
Power output using 300 ohm 1/4 inch jack is also disappointing for a unit in this class:
We don't even crack 100 milliwatts?
Notice that setting the gain to low makes no difference at all other than slightly less max power. One usually expects a lower noise floor in low gain. And bigger difference in max power.
Same situation persists with 33 ohm and 1/4 output:
Output impedance was 51 ohm out of the first 1/4 inch port, and 1.1 ohm on the second:
Balanced Output Performance
Switching to balanced output substantially improves performance. Here is the power versus THD+N for example at 50 ohm:
The H20 actually slightly beats the Massdrop THX AAA 789 in noise department. It is a negligible difference but good to see it. Power though is still less than THX amp. The specs for H20 are well above this, going up to nearly 6 watts for 64 ohm. That must be for one channel driven and even there, it is still too high relative to what I am seeing.
Measuring signal to noise ratio shows the very low noise level at max volume:
It was hard to figure out how to get the 50 millivolt results. I adjusted the volume until it got close and then dialed down the input to 2.5 volt. Results were very good but not class leading:
Frequency response was dead-flat:
Listening Tests
I am still not setup for balanced headphone listening. You all don't give me a minute to go and build my cable and I am too cheap to buy one off-the-shelf.
So I did my testing with 1/4 jack. Here, with Sennheiser HD-650 the experience was excellent with lots of bass and good power. I could turn it up to max and still tolerate it -- something I prefer not to be able to do. But good enough.
The situation with the Hifiman HE-400i was not the same. Somehow distortion would set it close to max and there simply was not enough gain there for some of my test tracks even in high gain.
Conclusions
It is clear Gustard has aimed high to build a top-end headphone amplifier. But there are some serious misses. One is the low max gain and gain settings that are so close to each other as to not be useful. Unbalanced/1/4 inch output is an afterthought with performance that is quite subpar subjectively. Objectively it was good with Sennheiser HD-650 but not with my low impedance Hifiman HE-400i. Overall, I would not buy this unit for unbalanced headphone listening.
Even with balanced output, I am struggling to find a reason to buy the H20. The massdrop THX AAA 789 has proper gain settings, and far better unbalanced output. Yes, availability is an issue with massdrop THX so another excellent option is the JDS Labs Atom. It sounds so good and has so much power that you don't need to mess with balanced cables and such. And it only costs USD $99.
Really, the JDS Labs Atom and Massdrop THX AAA 789 have changed the landscape so much that products like Gustard H20 don't stand a chance anymore. Yes, it is a heavier box than both of those combined but I can't see a reason to spend so much more money and get less. So sadly I can't recommend the H20.
------------
As always, questions, comments, recommendations, etc. are welcome.
Guess what? Boating season is right around the corner! Our little boat decided to take a ride on its own on a high tide and storm last winter. So I need another one. Hope to set it up so that I can measure audio gear while riding it. So please donate generously so that I can buy a large and stable boat using either:
Patreon: https://www.patreon.com/audiosciencereview), or
upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
The H20 comes in black and silver. The unit I have for testing is the silver:
The H20 is quite heavy and large. Controls feel good although I am not a fan of relay controlled volume. There is a racket that is sharp pitched as you adjust the volume.
The two 1/4 inch jacks are not the same. The first one has a resistor inline (see measurements). The second is straight through.
On balanced XLR output, you have a choice of stereo 4-pin or dual three pin. I tested with the former.
The back panel sports a good set of connectors:
Gustard has no website I can find so don't know if the unit has passed regulatory certifications or not.
Headphone Audio Measurements
I run my dashboard test using 1/4 inch output and results there were quite disappointing:
I am using XLR inputs yet we still have lots of mains noise. That aside, the dominant problem is the very high second harmonic at 2 kHz. SINAD of 90 dB is quite poor even for a cheap headphone amplifier let alone a high-end one.
The other odd thing is the gain. As you see, with maximum volume and gain switch set to highest we only have a 2 dB gain? Why so low? This is bound to cause issues for music that is recorded at low levels.
Power output using 300 ohm 1/4 inch jack is also disappointing for a unit in this class:
We don't even crack 100 milliwatts?
Notice that setting the gain to low makes no difference at all other than slightly less max power. One usually expects a lower noise floor in low gain. And bigger difference in max power.
Same situation persists with 33 ohm and 1/4 output:
Output impedance was 51 ohm out of the first 1/4 inch port, and 1.1 ohm on the second:
Balanced Output Performance
Switching to balanced output substantially improves performance. Here is the power versus THD+N for example at 50 ohm:
The H20 actually slightly beats the Massdrop THX AAA 789 in noise department. It is a negligible difference but good to see it. Power though is still less than THX amp. The specs for H20 are well above this, going up to nearly 6 watts for 64 ohm. That must be for one channel driven and even there, it is still too high relative to what I am seeing.
Measuring signal to noise ratio shows the very low noise level at max volume:
It was hard to figure out how to get the 50 millivolt results. I adjusted the volume until it got close and then dialed down the input to 2.5 volt. Results were very good but not class leading:
Frequency response was dead-flat:
Listening Tests
I am still not setup for balanced headphone listening. You all don't give me a minute to go and build my cable and I am too cheap to buy one off-the-shelf.
So I did my testing with 1/4 jack. Here, with Sennheiser HD-650 the experience was excellent with lots of bass and good power. I could turn it up to max and still tolerate it -- something I prefer not to be able to do. But good enough.
The situation with the Hifiman HE-400i was not the same. Somehow distortion would set it close to max and there simply was not enough gain there for some of my test tracks even in high gain.
Conclusions
It is clear Gustard has aimed high to build a top-end headphone amplifier. But there are some serious misses. One is the low max gain and gain settings that are so close to each other as to not be useful. Unbalanced/1/4 inch output is an afterthought with performance that is quite subpar subjectively. Objectively it was good with Sennheiser HD-650 but not with my low impedance Hifiman HE-400i. Overall, I would not buy this unit for unbalanced headphone listening.
Even with balanced output, I am struggling to find a reason to buy the H20. The massdrop THX AAA 789 has proper gain settings, and far better unbalanced output. Yes, availability is an issue with massdrop THX so another excellent option is the JDS Labs Atom. It sounds so good and has so much power that you don't need to mess with balanced cables and such. And it only costs USD $99.
Really, the JDS Labs Atom and Massdrop THX AAA 789 have changed the landscape so much that products like Gustard H20 don't stand a chance anymore. Yes, it is a heavier box than both of those combined but I can't see a reason to spend so much more money and get less. So sadly I can't recommend the H20.
------------
As always, questions, comments, recommendations, etc. are welcome.
Guess what? Boating season is right around the corner! Our little boat decided to take a ride on its own on a high tide and storm last winter. So I need another one. Hope to set it up so that I can measure audio gear while riding it. So please donate generously so that I can buy a large and stable boat using either:
Patreon: https://www.patreon.com/audiosciencereview), or
upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).