Simaudio isn’t a company which replaces models for the hell of it. If something is working well, it will keep on supplying it until it develops substantial improvements. That brings us to Simaudio’s Moon 230HAD Headphone Amplifier & DAC. As I write, now, it is March of 2022 and of course you can buy one of these. But you could also buy one of these back in 2017. Perhaps earlier, I don’t know.
What I do know is that I reviewed this back in late 2017, with my review appearing in Australian HI-FI in the Jan/Feb 2018, edition, v.49#01. One difference between then and now is that this was then the Simaudio Moon Neo 230HAD, and now the “Neo” element of the name has been dropped. (“Neo” equals “new”, so after four or five years, that would seem appropriate.)
Here I’m reproducing that review, as written, although not necessarily as published, and edited very lightly (eg, it doesn’t use “Neo” anymore).
And while Simaudio’s product lineup remains fairly stable over time, not everything else has. These days I do my objective measurements using an RME ADI-2 PRO FS R Black Edition analogue to digital converter, back then I used a Focusrite Forte ADC. The RME easily tops the Forte in every area of performance, including bass linearity and signal to noise, by perhaps 10dB to 12dB. So when you get to the measurements and graphs, remember that the slight bass droop is due to the test equipment, and that signal to noise, at least with 24-bit audio, might actually be better than that shown.
So, on to the review!
I’m going to jump to the conclusion briefly here. The Simaudio Moon 230HAD headphone amplifier & DAC has all the features that I consider vital for a DAC that you intend to use with a computer. It sounds great and even sometimes overlooked matters are implemented with consideration.
- The Simaudio Moon 230HAD is combined desktop headphone amplifier and DAC
- Inputs: 1 x USB Type-B, 2 x coaxial digital audio, 1 x optical digital audio, 1 x stereo analogue audio (RCA), 1 x stereo analogue audio (3.5mm, front panel)
- Outputs: 1 x 6.35mm stereo headphone (front panel); 1 x stereo analogue audio (RCA, fixed level), 1 x stereo analogue audio (RCA, variable level)
- Dimensions: 178mm wide by 76mm tall by 280mm deep
- Weight: 2.8kg
- Price: $2750
- Available at fine high fidelity retail outlets, and direct from distributor's retail division (Simaudio MOON 230HAD Headphone Amplifier & DAC)
More about the Moon 230HAD
That name’s a bid unwieldy so I’m just going to go with 230HAD. This is a relatively compact component, not designed for mounting with a stack of components. It’s only 178mm wide, and rather deeper at 280mm. It’s well built at 2.8 kilograms.
But what does it do? It’s a digital to analogue converter – suitable for use with CD transports and computers – and a headphone amplifier. Simple enough. My application is for playing audio from a computer, and it’s that on which I’ll be concentrating.
Simaudio doesn’t talk about what DAC chip or chips it employs, and I wasn’t inclined to try dismantling the unit. It’s what comes out of an audio device that’s the important thing in my view, not how it does it. Within the constraints of multiple inputs, the device has been kept simple. There is no adjustment, for example, for the slope of anti-aliasing filters and such. You’ll just have to trust that the implementation is sensible. (And check out our measurements below.)
Assuming competence on other fronts, here are the five things I consider vital for a DAC and headphone amplifier.
First, it must support basically every audiophile format. That means both PCM and DSD. Remember, things like FLAC are merely efficient ways of holding PCM, and your computer does the unpacking required to convert it into PCM. Even MP3 is created from PCM and when decoded produces PCM, and sometimes the latter is even quite similar to the former.
It is PCM (Pulse Code Modulated) and DSD (Direct Stream Digital) which are the two fundamental digital audio formats. But each now come in several resolutions. Like it or not, the great bulk of music available to us now comes as 16 bits with 44.1kHz sampling, aka the CD format. But an increasing amount of PCM is available in 24 bits and higher sampling frequencies.
Likewise, standard SACD-style Direct Stream Digital runs at 64 times the CD sampling rate, or 2.8224MHz. But now that DSD has been unshackled from the optical disc, some music is available – some even recorded natively at, 128 or even 256 times the CD sampling rate. They are known, respectively, as DSD128 and DSD256. (To find out possibly way more than you want to know about DSD, see our article “Diving Deeply into Direct Stream Digital”.)
The 230HAD supports PCM with sampling frequencies from 44.1kHz to 384kHz (including such oddities as 176.4kHz and 352.8 along the way). It also supports DSD64, DSD128 and DSD256. So, everything.
I do believe that some people are now experimenting with DSD512, and even DSD1024. If so, good luck. I’d just note that DSD tracks are not compressed. A five minute fifty second DSD256 track on my hard drive consumes just short of a gigabyte. I’m not sure that going to two or four gigabytes would be worth it for any what are almost certainly completely inaudible differences.
My second vital requirement is that it must have a low headphone output impedance. This is not so much for such things as damping factor, but to allow you to use any set of headphones without worrying about their impedance curve. High impedance outputs act as a voltage divider, with the amount of power burning off as heat in the output, rather than producing sound in the headphones, depending on the impedance of the headphones. Some headphones have an even impedance across all frequencies. Some don’t and can vary widely somewhat like loudspeakers. For those, the amount of power provided by high impedance headphone amps will vary by frequency, which means a wonky frequency response. The 230HAD has a specified output impedance of 1.25 ohms, which is perfectly satisfactory.
Third, high power and gain at the headphone output. High power again means that you don’t have to worry so much about your choice of headphones. There’ll be plenty on tap. The output of this unit is rated at 100mW into 600 ohms, 200mW into 300 ohms, and a full watt into 50 ohms. They translate, respectively, into 20dB, 23dB and 30dB of volume above the sensitivity rating of the headphones (when specified, as most are, as dB for 1mW input). I doubt you’re going to find any headphones which 230HAD will not drive beyond all reasonable limits.
Gain? We’ll get to that.
Fourth, fixed level line outputs. Or separate volume controls for line and headphone output. I’d far rather have the full two volts output available to line outputs, so that any noise that does make it into the interconnects is well down by comparison. If a single volume control managed both line and headphone outputs, though, then there’s the danger that one might forget and put on the headphones while the output is set to full volume. And you’ll always need to disconnect the headphones when you’re using the line level, lest they simply blow up from too high a volume.
The 230HAD has two sets of line level outputs: fixed and variable. The latter is controlled by the volume control. That’s even better because you have the option of skipping a pre-amp if you want.
My fifth vital requirement is that the DAC clearly indicates what format is playing. This is something that is ignored way too often. It doesn’t really matter if you’re using the DAC with a CD transport. But computer digital audio is tricky. A small error in setup. The wrong audio player software. A failure to properly install the relevant plug-ins. Any of these can result in your expensive, natively recorded DSD256 tracks being delivered to the DAC in 16 bits and 48kHz PCM, and you not realising it, or perhaps being vaguely discomforted by the sound but not knowing why.
The 230HAD has a clever system with five LEDs that in combination indicate unambiguously which signal it is receiving, covering everything from 16/44.1 PCM to DSD256.
Of course, there’s more to the 230HAD than those things. Yes, you can plug in CD transports and such. There are two coaxial digital audio inputs and one optical digital audio input. Those are restricted to a maximum of 24 bit, 192kHz PCM and DSD128. The higher resolution signals are limited to the USB connection. There are also rear panel analogue inputs, and a front panel 3.5mm analogue input, so you can use the headphone amp with analogue sources. LEDs on the front panel indicate which input is in use. A button cycles through them. An infrared remote control, borrowed from some of Simaudio’s other products, can cycle through also, but it offers both directions. It also controls the volume (by means of a motor on the volume control) and switches between standby and on. The other keys on the remote aren’t used.
The headphone amp section has a rated frequency response of 20-20kHz +/-0.1dB, and 5 to 100kHz -3dB, and a signal to noise ratio of 115dB at “full output”. The DAC section’s response is quoted as 20 to 20kHz +/-0.2dB and 2 to 72kHz -3dB, and its SNR at 114dB, similarly referenced to “full output”. It is rated to support headphones with impedances from 20 to 600 ohms.
Is there anything missing? Fans of balanced headphones – or for that matter, balanced interconnects to your main amplifier – will be disappointed. Other than that, no.
Listening via the Moon 230HAD
I used the Moon 230HAD with both a Windows computer and a Mac. The Mac required no drivers. Since my computers are running the most recent version of Windows 10 – the Fall Creators update (version 1709) – it kind of didn’t for them as well. But Microsoft still seems to be developing the drivers for USB Audio Class 2, so they were very limited and wouldn’t even allow the selection of a sampling frequency. To really take advantage of this DAC with a Windows computer you should install the appropriate drivers which you download from the Simaudio website. These put in place both ASIO and WASAPI drivers.
With the Mac I used Audirvana Plus software and with Windows I used Foobar2000 for playing music. The latter has the advantage of being utterly free, but the disadvantage of taking some working out to do things like deliver Direct Stream Digital in a pure format to the DAC. (Audirvana Plus also takes some deep digging in the Mac Terminal interface, fiddling with operating system permissions, to confidently employ some high resolution formats.)
In both cases, though, I did configure the players to deliver the audio in bit perfect format. That is, they extracted the original PCM from their FLAC compression schemes and fed the bits without any processing to the DAC. With Foobar2000, the DSD was delivered using the DoP system – that disguises the DSD as high resolution PCM. The DAC recognised that this purported PCM contains DSD within it and treated the stream appropriately.
I split my listening between several sets of headphones, a variety of proper room stereo systems – I tend to use quite a few over time – and my desktop computer near-field system, which is based around a pair of KEF LS50 loudspeakers and a Krix Seismix 1 eight-inch subwoofer. Aside from checking out the variable level outputs to make sure nothing untoward happened with them, I relied on the fixed level outputs.
The sound delivered through the speaker systems was of the highest quality. There was no noise. At all. Stereo imaging was as good as it gets. Detail was first class. Everything in the music was revealed without veil, whether to the good or bad.
I’ve been accumulating some natively recorded high resolution PCM and DSD tracks of late, and the level of transparency with those was truly astonishing. It sounded to me as though the microphones capturing the sound were connected via wire directly to my sound system. All points in the chain – the ADC at their end, the Internet, the 230HAD at my end – all of them disappeared. The sound was entirely dependent upon their microphone and my speakers and amplifier.
As for headphones, the 230HAD took total control over all of them – even such seemingly mismatched gear as Sennheiser Momentum In-Ear earbuds. They tend to be rather bright, but the 230HAD seemed to tame that top end somewhat. Likewise, when I later pulled out my old Sennheiser HD350 headphones to check the gain situation, I found a welcome body in the deeper bass regions which balanced out their occasional lightness.
All five of the headphones I used were smooth, controlled, and able to be driven as high in level as they could manage. Any volume limitations lay in the capacity of the headphones, not the ability of the 230HAD to deliver fine music.
What I had in mind specifically when I mentioned “sometimes overlooked matters” at the top of this article is switching noise. As I’m writing this paragraph, I have a Foobar2000 playing a list of tracks in the following formats: 16/44.1 PCM, DSD64, DSD128, DSD256, 24/352.8 PCM, 24/384 PCM. And you know what? As each track draws to a close, there’s a moment of silence and then the next track starts playing. In other words, as the DAC switches between radically different formats, it does so without any switching noise. That is not always the case, even with some more expensive DACs.
As for gain, let me say that it was ample. To check I played the rip of my old Seiji Ozawa/Boston Symphony recording of Vivaldi’s “Four Seasons” on Telarc. This is recorded at a sometimes problematically low level. I plugged in my twenty-year-old Sennheiser HD535 headphones – which are really fairly insensitive, and played the music in Foobar2000 with the volume slider set to slightly quieter than -20dB (I normally have it set to 0dB). Rotating the 230HAD’s volume control to the maximum position produced a very satisfying level. Returning Foobar2000’s level control to the normal 0dB, it was difficult to rotate the 230HAD’s level control to much more than the halfway point before the sound level was ludicrously and inappropriately high.
There was one small usability issue. Putting the 230HAD into standby stops the signal, but it seems that it leaves the USB and DAC circuitry fired up. At least the computers thought that it remained on, so they’d just keep on playing into, well, nothing, rather than switching automatically over to another audio device.
And to be really picky, if it were mine I’d put a white dot on the volume control. The indent in the black knob isn’t very easy to make out.
Measuring the Moon 230HAD
With the bulk of your music, the stuff with 16 bits of resolution and 44.1kHz sampling, this DAC begins a very gentle roll off slightly below 10kHz and is down by almost 0.4dB at 20kHz. At 21kHz, the output is down by only 1.3 decibels. Here’s what that looks like on a frequency response graph:
For 96kHz sampling, the output is down by less than 0.2dB at 20kHz, and only gets to -1dB at 43.5kHz, at which point it hits the brick wall. Here’s the graph:
With 192kHz sampling, the filter is much the same as for 96kHz, but extended into a smooth roll off. It’s down by 0.2dB at 20kHz, 1dB at 45kHz, 2dB at 58kHz and 3dB at 65kHz. Again, here's the graph:
(For all the above, ignore the 0.2dB droop at 20 hertz. That’s the measuring rig.) Now, let's check out noise with 24-bit audio:
My measurement environment doesn’t really let me plumb the very extremes of what some equipment can manage. Still, I measured an A-weighted noise level of -106.2dB. But that was when the computer I was using – a Microsoft Surface Pro 4 – was running from its internal battery. When docked, so it was connected to power, but not to the wired network, the noise level rose to -100.2dB, mostly due to midrange and bass noise breaking through. I don’t know if it’s possible, but ideally at least a DAC would somehow isolate its analogue output entirely from electrical noise delivered over its digital input. DACs work with computers, and computers are noisy.
The Simaudio Moon Neo series 230HAD is a wonderful device, both as a system DAC and a headphone amplifier. If this is in your price range, do audition it. Take your own favourite headphones, just to be certain. I think you’ll like it.