[Review] MHDT - Stockholm DAC

MHDT Stockholm DAC

Stereo on steroids

Product name: MHDT Stockholm DAC.
Manufacturer: MHDT - Taiwan
Cost: 1028 USD. (Currency conversion)
(1319 USD for balanced version)

Reviewer: Nick Whetstone - TNT UK
Reviewed: October, 2012

A few years ago I reviewed the MHDT Havana DAC, with it's valve output stage. MHDT have superseded the Havana with the Stockholm DAC which is more than just a make-over model. So what's new?

At a quick glance, the Stockholm looks very much like it's predecessor but on closer inspection the review sample was considerably larger, with two valves instead of one, visible through the acrylic front panel, and ventilation apertures in the top panel. I then realised that MHDT had sent me the balanced version of the Stockholm. At 276 mm wide, it is nearly half as wide again as the non-balanced model, and will take up the best part of a whole shelf. The standard of construction, and finish is again very high, and in satin black finish it looks discreet but quite classy too with its tinted acrylic front panel. Silver finish is also available.

Details on the MHDT site state that the analogue circuit is the same as in the Havana. On the digital side, the receiver has changed from a CS8414 to a CS8416 to achieve "higher capacity of incoming S/PDIF format". The PCM56P R-2R DAC is retained and is capable of handling up to 24bits/192kHz digital signal inputs. A driver must be installed to play 24/192 material. The USB input section can be configured to be synchronous or asynchronous operation by changing the firmware.

The Stockholm sports a total of four independent digital inputs; BNC (add one star for that), USB, RCA and Toslink. The inputs are selected by small press-buttons on the front panel, and the selected input is indicated by a discreet blue light. Also on the front panel is a large but elegant toggle switch for powering the unit on and off. The rear panel also has a pair of RCA (phono) sockets for analogue output (plus the XLR sockets for balanced-output), and of course an IEC socket for mains power. Here's a summary of the specifications:

Digital Receiver CS8416
D/A converter PCM56P-J
Frequency response: 20 Hz to 18 kHz (+/-2dB)
Output impedance: 32 ohms
Output level: 1.1 Vrms
USB input 16, 24 bits 44.1 kHz or 48 kHz, 88.2kHz, 96kHz no drivers required
USB input 16, 24 bits 44.1 kHz or 176.4 kHz,192kHz (see our manual)
USB input supports Linux, Windows XP, SP2, SP3, Windows Vista, Windows 7 and Apple Mac.
USB input can be synchronous or asynchronous depends on firmware installed
All other inputs (SPDIF) 16, 24 bits 32 kHz up to 192 kHz
Dimensions clear (W x D X H) 276 x 150 x 60 mm
Dimensions w/ socket (W x D X H) 295 x 170 x 60 mm
Weight 2 kg

Sadly, it seems the days of plug-and-play are fast disappearing for this type of item. So it's even more important to read the owner's manual (available online). Apart from drivers, we now have different firmware versions to be installed too. This isn't necessarily a bad thing as it does mean that the DAC can be updated, and in these (still early) days of computer audio, that is quite useful, if not essential. The firmware can be used to change the operation of the Stockholm between synchronous (uses a one way digital connection for music replay and is considered the inferior means of connection for audio playback through a USB DAC) and asynchronous operation (technically most advanced in that it has a feedback loop so that the amount of data in the frame can be better controlled). And Windows 7 (or 8) is the recommended operating system. If Windows XP is used, it is suggested that ASIO drivers (in common with most other DAC's used with XP) are installed and used. As it comes, 'out-of-the-box' the Stockholm will work with Windows XP, W7, W8, and Ubuntu, without the need to install any software. However, it is possible to upgrade the Firmware if you want to use the DAC with USB 2.0 instead of USB1.1. And you will need to upgrade the USB drivers to play any high-resolution files greater than 24bit /96 khz.

After turning on the power, there is a delay of around 15 seconds before a relay can be heard latching on, and the unit is ready to use. This delay is quite normal for something using valves, and allows the filaments in the valves to heat up, and the valve circuit to stabilize before the output is connected, thus avoiding any strange noises. In all cases that I used the Stockholm with W8 and Ubuntu, the DAC was recognised straight away, and I was able to start playing music.

The Stockholm will require quite a bit of burning in, MHDT suggest up to a month for the valve output stage to sound optimal. I left it playing music over several days before starting serious auditioning but still felt that it was getting better as the days passed. Now perhaps the hardest part of any review is to describe the sound of something. Apart from our lack of vocabulary to describe sound exactly, it is always difficult to know how much other parts of a system are influencing the sound, and how much the item under review is. With USB DAC's matters get even more complicated because the computer source will have a noticeable effect on the sound. I used the Stockholm with JPlay, JRiver Media Jukebox (both latest versions), and Ubuntu/Exhaile. As an example, the difference between Jukebox on W8 and Exhaile on Ubuntu made the Stockholm sound like two different DAC's! A bit of investigation into Jukebox revealed that it no longer supports features like ASIO and WASAPI so I guess that is why it sounded rather inferior to Exhaile (and more so, JPlay). Another quirk was that it sounded so much closer to JPlay from Exhaile than a couple of other high-end DACs that I was reviewing at the same time. Anyway, I will describe the sound as how it sounded at its best, and suggest that if you want optimum performance from your USB DAC that you avoid Jukebox. In fairness Jukebox is freeware, and JRiver sells their Media Centre software that has the features missing in Jukebox, to achieve much better audio playback.

I liked the Havana DAC and found the sonic signature of the Stockholm quite similar. It's a very 'strong' presentation with a thumping, but well-controlled bass. The bass is also fast and tuneful although not the fastest I've heard. There always seems to be a trade-off between how much bass there is, and how fast it sounds. Rather like a motor vehicle where you can have a truck that carries a huge load but can't move as quickly as a car that can't carry the heavy load. So not the best PRaT I've heard but by no means poor.

I noticed that 'strength' in the portrayal of the Q Sound effects on the 'Amused to Death' album. Not only were they very well located out into the room, but they were also remarkably tangible. The tangibility extended through the mid-range and top end too producing a good sound-stage with plenty of depth to it. Imaging was also strong with it being easy to locate performers and instruments within the sound stage. There was plenty of 'air' at the top end, in fact sometimes I felt a bit too much. On some recordings there was a kind of high-frequency noise (eg tape-hiss from the original recording) which the Stockholm seemed to be exaggerating. I did notice that more on Ubuntu/Exhaile than JPlay so obviously the playback from the computers was having some effect.

This 'strength' (or boldness) of presentation seemed to dominate a little and I think that the Stockholm will need careful partnering as regards amplifiers to sound it's best. With a solid-state amplifier it appeared to lack a little of the nuance that I was hearing from the JKDAC32 and Human Audio Tabla/Mutu that I had for review at the same time. When partnered with a valve amplifier, the results were a lot more balanced, and I felt that the DAC really showed what it was capable of. If you feel that your system is a bit laid back, the Stockholm could be just what you need.

I played some high-resolution files through the Stockholm and found what I do with most DAC's that can play these files, ie a lot depends on the track being played as to whether I sit there thinking 'wow'. I find that the more complex tracks do benefit more from hi-res, with full orchestral classical music being a good example. The Stockholm produced a larger and more detailed sound stage with a 24/192 recording of a Tchaikovsky Hopek, with crisper imaging, and a greater sense of 'being there'.

The Stockholm doesn't have to be used with a USB input of course and I tried it with a couple of CD players, The sound didn't change much although I felt that it was more on par with the JRiver Jukebox presentation, and not quite up with how good that it sounded using JPlay. In other words, I felt that a computer source showed it off to better effect than the CDP's did.

Summing up, the Stockholm is a quality piece of hi-fi. Well made, attractive and with much attention to detail. It's also versatile with it's range of inputs. With its valve output stage it will happily play into most (if not all) amplifiers, and if you are controlling the volume from a computer source, then you can connect a power amplifier to the Stockholm and have a two-unit hi-fi system (plus computer source). If you need a balanced source, that option is available too. I can recommend the Stockholm, but it does need to be partnered with the right amplifier, and in my experience, that will be a valve amplifier. Also keep in mind that this DAC is upgradeable through its firmware, and its performance may be improved in the future. As it stands, it is certainly a capable DAC. If you are looking to add some oomph to your system, the Stockholm will certainly do that, and with the right amplifier, it will certainly produce a great sound.

Addendum

A few weeks after completing and submitting this review, I was still using the Stockholm. Almost overnight, it went from sounding as I described it above into another league. The sound stage opened out further, the sound became much more 'natural', and the level of detail increased. All that with much more nuance. I guess that the valve buffer finally burned in, a bit later than I was anticipating. Anyway, I would now place the Stockholm DAC up with the best that I've heard, and can strongly recommend it.