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Review and Measurements of Gustard A20H DAC & AMP


Major Contributor
Central Scrutinizer
Mar 9, 2016
Riverview, FL
peace of technology
I'm always entertained seeing a new, possibly usable, and interesting phrase accidentally coined.


Senior Member
King of Mods
Feb 28, 2018
Iasi, RO
Problem with such designs is they usually cost more and there is little they can offer to justify that, unless you can find pleasure in owning such "exotic" peace of technology.
We all know that inside opamps there are transistors, so not sure why call this design as "exotic". That's an old debate of discrete vs. integrated amplifiers.

Inside my Yamaha A-S701 there are no opamps in signal path, from INPUT to SPEAKERS (only Sub-out has opamps in LPF) and I like when there are companies out there able to build amplifiers by using their original design (this amp has all harmonics lower than -90dB, noise is non-existent @1m away from speakers - volume to the max w. no music playing). Same opamp free design is inside my Burson Conductor and this why I purchased both of the above amps, because I prefer to invest in R&D and not in copy-paste designs from manufacturer's datasheet, and an outer case made by a 3rd party company. I like new designs, innovation and originality...but that's just me probably. :)

However, I do love original designs opamp-based too, like:
- Chu-Moy (even Grado adopted the same schematic)
- Objective2 (first pot in-the-middle design and great way to create the output buffers)
- Per-Anders/sjostromaudio designs (he's mixing opamps with transistors, great output buffers, extremely low-noise PSUs, impressive designs done from scratch)
- Tom/Neurochrome designs (interesting how SMPS are followed by LPSU, original designs and interesting way to parallel output buffers, extremely good measurement numbers)
- THX789 (original output buffers, interesting protection, quite an original design).


New Member
Mar 9, 2019
The (probably) official specs of the A20H, extracted and “validated” through google translate from a few different Chinese sources 2 years ago, before I bought my own unit :)

MAX POWER (RMS) balanced / unbalanced
16 ohm n/a / 1200mW
32 ohm 2400mW / 600mW
150 ohm 530mW / 133mW
300 ohm 266mW / 67mW (SENNHEISER HD650)
600 ohm 133mW / 33mW

When listening to the different outputs I would say that these figures really represents the superiority of the “balanced” output and I really think the unbalanced jack shouldn’t be used at all and probably should have been removed entirely by Gustard in the first place:) When driving HD650 (or HD800) from an Objective2 amp with A20H in DAC-mode it outperforms the unbalanced jack with some good margin. The difference is comparable to the DX3 Pro comparison in this review. BUT in balanced mode, I really feel it outshines the O2 in all regards by a huge margin, really night and day-difference making it impossible to appreciate the O2 with the HD650 anymore… :( And actually, I haven’t listened to any amplifier more suitable for driving the HD650/HD800 (/probably HD800S also), at least when trying to match it to my personal taste / hearing-curve etc. The only amps coming close are other balanced amps in higher price ranges (which I haven't been able to test for long enough time) or subjectively maybe an expensive DIY semi-tube amp (unbalanced) owned by a friend. For me I would describe the benefits of the A20H-balanced as more analogue / and somewhat “tubey” in its character but still with less distortion and absolutely black background. I suppose the completely discrete design is both responsible for the worse distortion measurements etc. but also for the pleasant analogue and somewhat Sennheiser-ish “long time listenable” sound-character. (I'm convinced that it should be possible to mimic analogue Vinyl/Tube-sound characteristics with some advanced distortion filters digitally applied... probably sounding better than "real" analogue sound :D ) But probably also because of the assumed benefits of “balanced” amping with supposedly better authority/control through push/pull-control of the drivers, and the stereo separation => benefitting the soundstage and depth of the HD650 and enhancing the stage of the HD800 further. Maybe also due to my balanced cables being many times more expensive than their stock unbalanced counterparts... Sadly it’s difficult to really A/B-test because of fast cable switching issues (I don’t want to destroy expensive cables by re-termination) and because normal hardware setups naturally give vastly different specs and characteristics between balanced/unbalanced outputs from the same amplifier.

I also own the HE400i (rev2) which I don’t like much (Focus Pad A and “the grill mode” turns them from bad to somewhat usable, but still not “reliable” as HD650.. some songs they handle well but others are kind of, a little bit... extremely bad presented :) ) But with those cans the benefits over the O2, my iFi iDSD nano or my AudioLab 6000A is not as apparent and mostly focused to the bass control. But I haven't really given it much time because I don’t use them normally.

With HD650 the vastly different sounding Sabre 9018-Dac of the AudioLab 6000A with its rather good integrated unbalanced headphone amp makes a cleaner but thinner, far more “non-analogue”, uninteresting and tiering impression compared to the Gustard, both with my HD650 and my KAM Near field active studio speakers. Also, the DAC of the iFi iDSD nano gives a very plain and boring sound whatever amp it drives and also my Odac is clearly inferior in the same regard compared to the A20H DAC.
Last edited:
Jun 20, 2018
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