Yes, it’s more than just a head­phone am­pli­fier, it’s also a full-fea­tured DAC that can han­dle DSD.

Australian HIFI - - CONTENTS -

Be­fore start­ing this re­view, I am go­ing to briefly jump to its con­clu­sion. The Si­mau­dio Moon Neo 230HD head­phone am­pli­fier/DSD DAC has all the fea­tures that I con­sider vi­tal for a DAC that you in­tend to use with a com­puter. It sounds great and per­fectly han­dles datas­tream is­sues that many other DACs do not han­dle well at all.


The full name of this DAC is a bit un­wieldy so I’m just go­ing to go with 230HD for the re­main­der of this re­view. It’s a rel­a­tively com­pact com­po­nent, not de­signed for mount­ing with a stack of com­po­nents. It’s only 178mm wide, and rather deeper at 280mm. It weighs 2.8 kilo­grams, so it’s a solid bit of kit.

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.)

As­sum­ing com­pe­tence on other fronts, here are the five things I con­sider vi­tal for a DAC/Head­phone am­pli­fier.

First, it must sup­port ev­ery au­dio­phile for­mat. That means both PCM and DSD. Re­mem­ber, codecs such as 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 quite sim­i­lar to the for­mer.

It is PCM (Pulse Code Mod­u­lated) and DSD (Di­rect Stream Dig­i­tal) that 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 at 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 times or even 256 times the CD sam­pling rate. They are known, re­spec­tively, as DSD128 and DSD256.

The 230HAD sup­ports PCM with sam­pling fre­quen­cies from 44.1kHz to 384kHz (in­clud­ing such odd­i­ties as 176.4kHz and 352.8kHz 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, be­cause DSD tracks are not com­pressed, so a five minute fifty-sec­ond DSD256 track will con­sume just short of a gi­ga­byte of space on your hard drive. I’m not sure that go­ing to two or four gi­ga­bytes would be worth it for what are al­most cer­tainly go­ing to be com­pletely in­audi­ble dif­fer­ences.

The sec­ond vi­tal re­quire­ment for a DAC/ Head­phone am­pli­fier is that it must have a low 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. A high-im­ped­ance out­put acts as a volt­age di­vider, with the 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 head­phone

I do be­lieve some peo­ple are now ex­per­i­ment­ing with DSD512 and DSD256. If so, good luck...

amps with a high out­put im­ped­ance will vary by fre­quency, which will mean a wonky fre­quency re­sponse. The 230HAD has a spec­i­fied out­put im­ped­ance of 1.25Ω, 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 600Ω, 200mW into 300Ω, and a full watt into 50Ω. 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 the 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 the line out­puts, so that any noise that does make it into the in­ter­con­nects is well down by com­par­i­son. If a sin­gle vol­ume con­trol is used to man­age 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 be­ing played at too high a vol­ume level.

The 230HD 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.

Fifth, the DAC re­ally ought to clearly in­di­cate what for­mat is play­ing. This is some­thing that is ig­nored ‘way too of­ten, and it doesn’t re­ally mat­ter if you’re us­ing the DAC with a CD trans­port. But com­puter dig­i­tal au­dio is tricky. Things can go wrong. A small er­ror in set-up. The wrong au­dio player soft­ware. Fail­ure to prop­erly in­stall the rel­e­vant plug-ins. Any of these mis­takes 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 230HD has a clever sys­tem with five LEDs that in com­bi­na­tion in­di­cate un­am­bigu­ously which sig­nal it is re­ceiv­ing, cov­er­ing ev­ery­thing from 16-bit/44.1kHz PCM to DSD256. Of course, there’s more to the 230HD than those things. Yes, you can plug in trans­ports and such. There are two coax­ial dig­i­tal au­dio 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 20Hz–20kHz ±0.1dB, and 5Hz–100kHz –3dB, and a sig­nal-to-noise ra­tio of 115dB at ‘full out­put’. The DAC sec­tion’s re­sponse is quoted as 20Hz–20kHz ±0.2dB and 2Hz–72kHz –3dB, and its S/N ra­tio at 114dB, sim­i­larly ref­er­enced to ‘full out­put’. It is rated to sup­port head­phones with im­ped­ances from 20–600 .

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.


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 fully de­ploy—see wp­blog/?p=4511.)

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 DoP (DSD over PCM), a sys­tem that dis­guises the DSD sig­nal as high-res­o­lu­tion PCM. The DAC recog­nises that this pur­ported PCM con­tains DSD within it and treats 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—and my desk­top com­puter’s nearfield speaker sys­tem, which is based around a pair of KEF LS50 loud­speak­ers and a Krix Seis­mix 1 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.

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 mi­cro­phones 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. These usu­ally tend to be rather bright, but the 230HAD seemed to tame their 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 balanced out their oc­ca­sional light­ness.

All five of the head­phones I used were smooth, con­trolled, and as able to be driven as high as they could man­age. Any vol­ume lim­i­ta­tions lay in the ca­pac­ity of the head­phones, not in the abil­ity of the 230HAD to de­liver fine mu­sic.

What I had in mind specif­i­cally when I men­tioned ‘datas­tream is­sues’ at the head of this ar­ti­cle is switch­ing noise. As I’m writ­ing this para­graph I have 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 dig­i­tal for­mats, it does so with­out any switch­ing noise. That is not al­ways the case, even with some very 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 half-way 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 the 230HAD 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.


With the bulk of your mu­sic, which will have 16-bits of res­o­lu­tion and 44.1kHz sam­pling, this DAC’s fre­quency re­sponse will be­gin a very gen­tle roll-off slightly be­low 10kHz and be down by al­most 0.4dB at 20kHz. At 21kHz the out­put is down by only 1.3dB.

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.

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.

(For all the fore­go­ing, ig­nore the 0.2dB droop at 20Hz. That’s in­tro­duced by my mea­sur­ing rig.)

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 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 it is in your price range, do au­di­tion it. Take your own favourite head­phones, just to be cer­tain. I think you’ll like it. Stephen Daw­son


In­puts: 1×USB Type-B, 2×coax­ial dig­i­tal au­dio, 1×op­ti­cal dig­i­tal au­dio, 1×stereo ana­logue au­dio (RCA), 1×stereo ana­logue au­dio (3.5mm, front panel)

Out­puts: 1×6.35mm stereo head­phone (front panel); 1×stereo ana­logue au­dio (RCA, fixed level), 1×stereo ana­logue au­dio (RCA, vari­able level) Di­men­sions (WHD): 178×76×280mm Weight: 2.8kg


Brand: Moon by Si­mau­dio Model: Neo 230HAD Cat­e­gory: Head­phone Am­pli­fier/DAC RRP: $2,099 War­ranty: Three Years Dis­trib­u­tor: BusiSoft AV Pty Ltd Ad­dress: 158 Christ­mas Street F air­field VIC 3078 TF: 1300 888 602 T2: (03) 9810 2900 E: W: • Ex­cel­lent head­phone

am­pli­fier • Ex­cel­lent sig­nal sup­port • Vis­ual as­sur­ance of dig­i­tal

sig­nal for­mat • Some (in­audi­ble) noise from

com­puter break­through • Balanced out­puts

Graph 4: Noise floor when con­nected to lap­top run­ning on bat­tery (white trace) vs lap­top run­ning on mains power (green trace). See copy.

Graph 2: Fre­quency Re­sponse us­ing 24-bit/96kHz data.

Graph 3: Fre­quency Re­sponse us­ing 24-bit/192kHz data.

Graph 1: Fre­quency Re­sponse us­ing 16-bit/44.1kHz data.

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