Hi there, got a DDH-1 loaner thanks to my local reseller and I felt like this product would well deserve its own thread here on head-fi together with a quick review while I'm at it
The official product page can be found at http://amimuse.com/ami-musik-ddh-1/
Its user manual is available in five different languages at http://amimuse.com/support/downloads/
6moons already posted a thorough review at http://www.6moons.com/audioreviews/ami/1.html
So on the input side, we have coax / Toslink / analog line-in & USB.
Concerning the outputs, we have RCA line-out, Toslink and both 1/4" & 1/8" headphones jack.
As you can see, it's using a USB3 B connector even though it's a USB2 XMOS audio controller, I asked my reseller about this and he told me that it's a good way to be future-proof, it provides a more secure fit than a USB2 B connector and USB3 cables have to be seriously built and heavily shielded due to the ten times higher speed rate compared to USB2. It's the first time I see this trick being used and that's a really great idea IMHO, it's also fully backward compatible with USB2 B connectors of course.
Here's what it looks like in use:
So let's see what's inside, shall we:
2 boards, one for the USB conversion and one for the DAC circuitry.
Let's start by the USB board:
-XMOS chipset, supporting up to 32bit 192kHz resolution. Fully UAC2 compliant and only requiring drivers on Windows that also provide bit-transparent 32bit ASIO capabilities. These drivers are rock-solid and they come with the latest 1.63 update that's fully W8 compatible of course
-Two 1.0 ppm TCXO clocks for 44.1/48kHz multiples, some manufacturers like to go cheap and use a PLL-based single clock synthesis..this will add at least 50ps of jitter when two discrete 1.0 ppm clocks will reach as low as 2.5ps timing period jitter....über-low jitter, here I come
-IL1117 3.3V high efficiency linear regulator to feed the XMOS chip. For the record, the XMOS datasheet implementation is bus powered and uses a Semtech SC4626A switching-mode voltage regulator(with a working freq of 2.5MHz). Many/most XMOS "by-the-book" designs rely on this architecture, the Hiface 2 comes to mind. AMI took power management very seriously.
-Not USB bus powered, I can use a USB cable with the +5V pin broken. All the rage in "audiophile" USB cables is to ensure that its power lines won't pollute its data lines(some companies even sell grossly overpriced USB computer controller boards that come with a switch that can disable the +5V USB bus power). Well fear not, you can either tape or break the +5V pin and you just got yourself an "audiophile" grade USB cable
All this to say that IMHO this board uses the best of what USB audio currently has to offer and it could sell for +$500 if it came in a small box with RCA/BNC connectors for S/PDIF. I've got nothing to complain about, that 's good =)
Now for the DAC board:
-PCM1795 123dB SNR 32bit 192kHz DAC chip
-TPA6120 headamp IC
-A whole bunch of swappable opamps, whose description can be found at http://amimuse.com/support/faq/
-Nichicon audio grade caps
-Opamps are fed 20V(±10V) which a far better choice than the usual 12V and would appear to be a good compromise between SQ improvement due to the higher voltage swing(for instance most discrete opamps require at least 17V to sound their best) and an excessive amount of heat to dissipate.
-An LM78L05 5V linear regulator to feed the DAC chip & headamp IC, nice touch again!
As you can see, I've rolled the opamps.....6moons has pictures of the stock board. I decided to use some of my favorite "sociable" opamps, OPA2132P as I/V, OPA627BP(genuine for sure as they were sourced from digikey) as buffer in the very same setup as in the Eximus DP1, and two OPA132U on an adapter for the line-out.
I used dual opamps for the I/V as they are taking care of both polarities of the same channel and single opamps on adapters for stereo signals. Eventually I will solder four more OPA132U's and hear whether they'll make any difference over OPA2132P as I/V(TI make very clear in the OPA1612 datasheet that single opamps provide better signal separation than regular dual opamps)...I will also try OPA827 and OPA1611 as the former is supposedly great for I/V and I really used to enjoy the latter(TI advise using them in high-end BD players).
Opamps are just really fun and mostly harmless if you stick to unity gain stable chips and always make triple sure that everything's been soldered and inserted in the right direction.....it's just sheer fun to solder and seek any audible difference/improvement, it really is lego for grown-up OCD'ed audiophiles ^^
So I did quite a lot of listening but after a short while, I felt like the stock SMPS was holding back SQ......opamps do have a spec called PSRR and the cleaner the PSU the higher the SQ really.
Here's the stock SMPS brick:
So I plugged a linear 12V linear PSU(lucky me it was the same barrel connector size), as you can see there is no question that it's no SMPS due to the much higher weight and fixed input voltage:
Well, now we're talking! After PSU & opamp rolling, this little shiny box becomes hard to believe.....I A/B'ed it against the built-in DAC of the Eximus DP1(2.5ppm TCXO driven XMOS/dual-mono PCM1794/OPA2132P/OPA627AP):
Well, the similarities in design were very hard to miss. The DP1 DAC section goes through some discrete "diamond" buffering so the sound is sweeter and more forgiving when OTOH the pimped DDH1 presents the naked truth and a less colored but just as 3D sounding soundstage. I seriously did not expect this and I'm honestly floored by how the DDH1 is now performing after those minor modifications
Surely, OPA627 has been a long time favorite of audiophiles for a good reason....its musicality and effortless -yet very detailed- presentation are the reason why it's still being used in new designs. Some ppl claim OPA827 to be an improvement but that doesn't match my experience at all. Also many people buy cheap 627's from ebay, too bad it's the most counterfeit opamp..
You can read in this review that OPA627 is a real treat through headphones, and it's also undoubtedly part of the reason why the DP1 sounds so great to many ppl(including me ^^).
This highly skilled DIY designer ran an opamps shoot-out and wrote the following:
OPA132 [..] (2132) in DIP packages, [..] A very good chip to start with. Indeed, you may be so happy with it that you stop looking at other chips!
OPA627 [..] The first thing I noticed is the cleanliness of the sound. With this chip in the test amplifier, I heard known problems in a low-end portable source more clearly [..]
The 627 also seems to do better on recordings with room ambience: it reveals details about the acoustic space that the OPA132/134 chips will hide, making them sound "flat" in comparison. But these two chips are more alike than different. Both have the characteristic laid-back and dark Burr-Brown sound, and both are very tolerant, stable chips.
He of course made sure that all opamps were stable and used within a proper surrounding design. Implementation is everything and rolled blindly in an unfit circuit OPA132 can sound "grainy" and OPA627 dark and veiled.....let me tell you that this is not the case here, it's working just as well as it does in the DP1 to my ears
I ran those tests through the widely acclaimed headamp of the DP1, so I also tried if off an old SONY AVR:
Well, it still sounds really fantastic tbh.....of course the headamp of this AVR is based on NJM4565(even worse than 4580 apparently) and its volume control is digitally attenuated so it's not quite audiophile grade, yet the 3D SS, clarity and thick deep bass of the DDH1 keep impressing me
Whenever I'll have the opportunity, I will try the DDH1 with <$500 serious headamps and will report back.
Of course it also sounds good stock but NJM2114(an improved 5532) and LM49860(a higher grade LM4562) on swappable sockets really begged to be rolled for more expansive chips. Actually, manufacturers do have to make a living so when they use OPA627 or AD797 you are basically paying a lot more than if you bought them yourself and rolled them on your own.
My original intent was to find an XMOS DAC with serious clocking, swappable opamps, a fixed volume line output and great power regulation....the DDH1 does just that and then some
I also tried the built-in headamp but of course it's no competition with the DP1 headamp or any other $1K headamp I played around with in the past......we're on head-fi and a TPA6120 headamp without discrete buffering or a more elaborated surrounding design will have a hard time impressing the most demanding amongst us. This said, it's very capable considering that it's thrown-in with the DAC and I got solid bass response out of it. It really is a vanilla TPA6120 implementation as far as my eyes and my ears can tell.
Of course you can use the line input together with the pot as a preamp and it also comes with a Toslink output.
There's a "variable / fixed" switch at the back of the unit that toggles the front pot onto the line-out, you can see a relay right behind the pot and can hear it clicking when activating this switch.
I didn't try its S/PDIF capabilities because again this protocol is broken by design(the galvanic isolation of Toslink costing at least 1000 ps of jitter) and it would be a shame to leave this high-end 1ppm XMOS based asynchronous USB input unused, 6moons used the Toslink input in their review if you feel like checking it out. This said, S/PDIF inputs are great to plug a TV tuner, game console or CD player when you can't be hassled to turn on your computer.
All this to say that once slightly modified, it's really hard to believe that this little monster sells for $550....again, last year you were lucky to get a bus powered USB to S/PDIF transport for this kind of money, in 2013 you get a most impressive sounding and cleverly well-built self-powered standalone DAC for the same price....and you can even play around with rolling as much as you like
I see that AMI is a young company and that this would be their first product, my reseller told me that he will also stock their forthcoming products and I can hardly wait to hear what that'll be all about.
Hope you had as much fun reading this short review as I had writing it, this little thing and personally I'm definitely pulling the trigger on it
Edited by leeperry - 9/26/13 at 3:40am