Sound Impressions
Tonality
The Continental Dual Mono tonality is incredibly smooth and natural sounding. It simply flows with a really gorgeous tube-enriched spacious midrange, organic and beautifully textured vocals, a forgiving top end, and a sprightly bass response; tighter than the usual tube offering that’s for sure.
ALO Audio has wisely avoided going knee-deep into the darker side of tube sounds with the stock NOS 6111’s, opting instead, to infuse where needed such as the mids whilst reducing where not such as that tight and snappier than normal bass line.
Character
That hybrid mix of SS and tube buffering and that amp stage wisely avoids the perils of trying to be analytically excellent and just offers a highly musical and enchanting treat. Do not get me wrong, the CDM is not overly romantic, smoothed out, or veiled.
The detail is there, perhaps not forward as say the Aurender Flow, particularly in treble performance where the CDM is a bit more rolled odd, but not as thin or soullessly presented either. The CDM has a beautiful character and that is its selling point.
Bass
The bass is tuned to sound full and detailed yet quick with a shortish decay that keeps everything tight. It is more linear than accentuated that is for sure but it does feel planted when called upon.
Throw on Laura Mvula’s “That’s Alright” and that rhythmic drum intro has plenty of authority but separation is always excellent and clean and there is no bleed into the mids whatsoever.
Mids
Mids on the Continental Dual Mono are spacious, flowing, and smooth with a slightly forward vocal presence that is sibilant-free and with excellent texture. Personally, I found the timbre to be sublime and right where I like a midrange to be in terms of striking a balance between musicality and accuracy. There is nothing sterile or claustrophobic about this midrange.
Treble
What I love most about the treble performance of the Continental Dual Mono is the lack of uneven peaking or spiking, especially around the 5-7k range. Yet at the same time, this is not a dulled-out area or veiled to mask any deficiencies in the amp performance.
Transients from mid to treble are as smooth as you like and whilst the Hugo or Flow has the edge in resolution and top-end clarity the Continental Dual Mono is no slouch either.
The tuning on the whole for the top end is for pleasurable listening; a slight roll-off, but nothing I would call shelved down or syrupy. This is a detailed but relaxed and forgiving treble performance in keeping with the smooth character the CDM embodies as a whole.
Synergy
Efficiency
The low gain setting on the Continental Dual Mono paired with the highly sensitive 64 Audio A12 is ultra-quiet with a fabulous level of control both in terms of left and right and noise.
That came as a surprise to me, to be honest. I was half expecting the usual awesome tubey sound combined with a dash of microphonics, the odd pop, and a bit of hiss using CIEMs but here we are chirping away and not a thing, not one pop.
There is not a huge amount of play in terms of gain control after all the A12 is 117db and 16 ohms so don’t expect too much. However, the smooth control from zero to full blast is very even and assured.
Dynamic Headphones
Both the Beyer T5p and the AKG K812, two cans that have their weaknesses, have excellent low noise levels on the Continental Dual Mono on high gain. I was particularly impressed with the K812 performance which I preferred over the T5p.
Musicality is excellent combined with the tube smoothness of the CDM particularly in the voicing which sounded very natural indeed. Ayo’s “Without You” has that lazy pace with a full-sounding soulful female vocal lead and supporting male vocal nipping in and out.
On the CDM/K812 pairing, both vocals were distinct yet harmonious with excellent texture and detail. The CDM also coped better than a lot of SS desktops on more strident treble-heavy tracks which can often be the weak spot of the K812.
It won’t stop that treble from shining but it did sound a lot more tolerable. Tubes really are the way to go with both of these headphones, especially on acoustics and male vocals or anything really that isn’t top-heavy.
Planar Headphones
Audeze LCD-X
No problems driving the LCD-X on high gain with the volume pot sitting comfortably way before the halfway mark in single-ended mode. Whilst I still think the current mode Bakoon HPA-01M is the best portable amp match up with the LCD-X I have heard to date the CDM offers something a little on the smoother or warmer side without messing up the speed and clarity of the LCD-X.
I certainly think the slightly thinner more agile personality of the LCD-X is a better match with the fuller-sounding CDM than the more resolving but slightly thinner-sounding Hugo and Flow. I like my mids thick, loud, and proud with a natural but slightly forward vocal presence.
The CDM offers that more convincingly than the Flow which is a bit more stand-offish and lacking in character.
Audeze LCD-2 Rev 2
The LCD-2 Rev 2 required a tiny bit more power than the LCD-X, around 10-15% more but nothing the CDM couldn’t handle easily on high gain. I honestly thought the shelved-down treble of the non-Fazor edition LCD-2 would favor something like the Aurender Flow with its more agile and extended treble.
In reality, the CDM once again outshone the Flow in the midrange and vocals, especially on rock. I do think though after some heavy a/b’ing that the Flow has a bit more sub-bass weight and extension on the LCD-2 than the CDM which has a richer and fuller mid-bass response.
Hifiman HE560
Hifiman’s HE560 required a little more juice, about 55 to 60% single-ended on the volume pot using the CDM DAC out from Foobar. The CDM won’t change the slightly thin but accurate signature of the HE560, get a HE400i if you want thick and musical.
That slight roll-off in the treble though does keep the HE560 free of any nasty peaks or sounding shrill or sharp. That is critical in enjoying the HE560 for me. The more open and detailed midrange of the HE560 combined with the rich tones of the CDM actually sounds really excellent.
Hot Chocolates’ “Everyone’s a Winner” and that 1970’s rack-mount phaser/flanger-induced guitar intro sounds assuredly fat and detailed on the HE560 as it should do. Errol Brown’s vocals are clear and detailed and that synth swirl around the center-focused guitar does a really fine job of demonstrating the excellent width and separation of the CDM soundstage.
Select Comparisons
Aurender Flow
Technical
Physically they are quite similar in shape and size with the Flow being the slightly thicker of the two and having that ripple-type design and big volume knob on top. The Flow also has a few more tricks up its sleeve than the CDM including a tidy little GUI on top for display info on interface choice, output selection, and sample rate.
The Flow also packs in SSD storage for carrying around your library and being able to use it as a typical memory drive when plugged into any PC or MAC. I never really felt that to be a huge bonus given SSD costs but they are dropping so it’s becoming more interesting.
DAC
Like the CDM it has a built-in DAC with a USB interface for sampling rates including PCM, SACD, and DSD. Unlike the CDM the Flow uses an ESS9018K2M Sabre DAC which is the mobile version of the main desktop ESS9018 chip but with similar tonalities.
The Flow can also decode up to DSD128, unlike the CDM which tops out at DSD64. Both need proprietary drivers to make that happen, the Flow with XMOS and the CDM with C Media. The Flow edges it in terms of DAC technology with it being able to interface with the likes of JRiver and Foobar for playback and track selection physical hardware buttons.
Both units run similar battery times of around 5-7 hours depending on usage conditions with the CDM edging it a bit on pure amplification only.
I/O
The CDM, though lacking in an optical jack that the Flow has, does seem to have better I/O options. The Flow can I/O analog and digital but it’s through a series of differing cable which comes as accessories. I am not a huge fan of the loss of the headphone jack and carrying cables for ‘this and that’ becomes a slight pain.
The CDM, however, has balanced 2.5mm TRSS, 3.5mm outputs, and line, stereo, and USB inputs. Personally optical is okay, and appeals to the AK fans but USB is just as good these days especially for hi-resolution playback, if not better. Both are adept at that with their USB interfacing.
Tuning
Tonally though things are a bit different and this might sway a few people also. Clarity and resolution is the Flow’s strong point with absolutely excellent control and extension both ways. It’s not sharp, the ESS chip is very well implemented in the Flow so it does have a very even and precise feel to its sound.
Its one weakness is that it tends to have a slightly mundane midrange with vocals lacking in fullness and character. The top and bottom are assured, planted, and non-peaky but the midrange is nothing special and vocals only seem to perform on operatic or classical where it’s not so essential to have a guttural performance.
Enter the CDM. The CDM is the very opposite of the Flow in many respects, as it is all about the mids and presenting something full, rich, and smooth sounding without messing up the detail.
I do not think it extends as well as the Flow but it certainly has a much more pleasing top end and a fuller-sounding mid-bass response that makes the CDM that bit more musical. I
f you need the resolution and detail of an ESS chip with the bells and whistles, then the Flow is pretty darn good. If you want something more musical, with more character and dynamics then the CDM is the better choice.
Bakoon HPA-01M
Technical
These are two quite different beasts, to be honest, and not just as pure amp versus amp/DAC. The Bakoon is also a SATRI circuit-designed portable amp with both a current signal and voltage-based output scheme from an analog line-in.
They are both roughly the same size but the lower heat and slightly slimmer profile of the Bakoon make it just a little bit more portable. Battery wise both amps have similar ratings with the Bakoon edging ahead by about 1-2 hours at most. That’s impressive though for the CDM which throws a DAC into the mix and still keeps up with a pure amp solution.
Efficiency
The main edge the CDM has over the Bakoon is really the ability to cope with highly sensitive gear such as IEMs and low impedance cans which the Bakoon has problems with at low gain levels. The Bakoon left and right balance is all over the place on really low volume levels and noise floors are much too high on either current or voltage output.
It makes it quite difficult to recommend for earphone use unless you go with some high-impedance earphones but even then left-right balance won’t be good. Pot scratching is the norm also for the first 15 minutes with the Bakoon until the circuits settle down when powering up from the cold.
Now you could argue that the tubes on the CDM need a little time to warm also but there is zero scratching when powered up and zero microphonics also so for me the CDM amp is just that bit more refined as a pure amp.
On the plus side, the Bakoon is the king of planar-portable amps for me and puts in a much better shift than the more laid back smoother Continental Dual Mono. Do not get me wrong, the CDM sounds excellent with the likes of the LCD-X, but the Bakoon has much stronger dynamics and impact when paired in current mode.
The ALO Audio Continental Dual Mono though is the more flexible of the two for everything else from IEM to regular dynamic headphones and tube lovers are doubtlessly going to prefer its smoother musical tones.
Our Verdict
The Continental Dual Mono DAC/Amp for me is a very special transportable piece of gear that combines the magic of tubes with solid-state sensibilities and the price I find, to be honest fair.
I do like to have a pop now and then at overpriced gear but the Continental Dual Mono is machined to a very high standard and produces a wonderful sound that is neither bloated, dry, or sharp. It’s just simply put a very natural-sounding signature that gels wonderfully well with quite a lot of gear.
It doesn’t aim to be the neutral king, nor does it claim to be the pinnacle of analytical excellence. There are other tools out there for that kind of job such as the Hugo and in some instances the Aurender Flow.
But what it does have is a very musical and rich sound signature that combines the magic of tubes with a little dose of solid-state sensibility to keep it tight and clean enough for both SS and tube camps to enjoy.
It’s a very smart move by ALO Audio to load it with a tube “light” 6111 and not go all out. It makes the Continental Dual Mono a very flexible performer with a wide variety of headphones as well as earphones. That low noise level and sensitivity were a big surprise for me with CIEMs, I did not think it would have that level of dexterity but there you go, you learn something new every day.
The bonus is the tube rolling, the ability to pack in a different sound with a different set of tubes for the price of a New York popcorn and cinema ticket. Those who want to go deeper into the tube world can within 30 minutes and it can make all the difference.
ALO Audio Continental Dual Mono Technical Specifications
RMS per channel, both channels are driven:
Single entry
- 80mW into 32 ohms
- 95mW into 50 ohms
- 75mW into 150 ohms
- 60mW into 300 ohms
Balanced
- 125mW into 32 ohms
- 145mW into 50 ohms
- 110mW into 150 ohms
- 95mW into 300 ohms
- Input impedance SE: 10k
- Input impedance BAL: 50k
- Output impedance SE and BAL: < 1 Ohm
