While the DAP (portable player) market has taken away much of the market for them, there is still some interest in portable amps, as seen by a degree of interest in portable amps. ALO Audio’s Continental V5 and HeadAmp’s Pico Power still capture the interest of people who want to power more exotic full-sized headphones while traveling, for which many DAPs still don’t have sufficient power.
Some years ago I met Takanobu Kowada of Sound Potion at one of the Fujiya Avic Headphone Festivals, where he let me audition his Monolith portable amp. Most portable amps use some combination of regular batteries and an OPAMP-based circuit. Some have even made the ability to change OPAMPs a feature. However the Monolith is, very uniquely, an all-discrte component design.
For the brave, it is possible to buy the raw boards and solder the components yourself. However Sound Potion also offers a completed amp, as well as a matching case. Since the labour required to solder numerous SMD components is considerable, with the case it will end up at around the US$300 or more mark.
The amplification circuits for each channel sit on long, thin boards which are mounted vertically from the main board, and provide part of the structure for holding the batteries in place inside the case.
Rather than use AA batteries, the Monolith uses 3.7V 14500 batteries, which can give the amp up to 60 hours of running time, and a fair bit of power. To charge the batteries, an optional charging chip can be installed, whereby an external power adaptor can be used. An optional back plate, without the charging socket hole is also available for people who don’t wish to use that option.
The case itself is a basic Hammond-like thing that, with so many parts, can be a bit fiddly when it comes to changing batteries, as they are held against their spring terminals by the back of the case. I found that putting some Scotch tape to hold at least the bottom and sides together, while leaving the back plate on, helped things considerably.
This also helps if one wishes to change the gain, which by default is in its low setting, with two jumpers installed inside. To change to high gain, one removes them. Taping the case before removing the front screws allowed me to slide out the board without the whole amp falling apart.
Despite its basic looks compared to the beautiful casework of the other amps I have here, the Monolith had no trouble keeping up with the other portable amps. My current transducers for testing consist of the Campfire Andromeda and Vega, and HiFiMan RE2000 IEMs, and in full-sized headphones primarily the Focal Utopias, being sufficiently demanding of both current and voltage to get the most out of them.
What had attracted me to the amp at first was the performance with balanced armature IEMs, and it was with the current standard, the Andromedas, that it managed to punch the deep bass harder than the Pico Power when listening to When I Get My Hands On You from The New Basement Tapes, which was unexpected. The CV5 was out of the running for this test, having too much hiss for sensitive IEMs.
On the other hand, with dynamic driver IEMs, ALO Audio’s Continental V5 has the upper hand, with a more articulate presentation, but at around twice the price.
The Utopias, which are calmly revealing of the nature of every component in one’s system, were driven quite well, but the soundstage suffered from an expected degree of compression and loss of dynamics compared to my big desktop amps, which deliver the music with relaxed precision. But this was not a bad performance at all, as the amps in question are 5-20x the price.
Compared to the Pico Power and Continental V5, the Monolith was very close, only very slightly behind the more sophisticated designs in ultimate precision in areas such as bass detail and impact.
The South Potion Monolith is a unique portable amp and performs very well as an amp. Where it’s going to be of best value is for the hard-core DIYer looking for a unique project. For someone looking for a portable amp that is a bit different as well. The web site for the amp can be found here: http://soundpotion.cart.fc2.com
Gain: 2 (6dB) or 6 (16dB), switchable via internal jumpers (behind the input/output jacksl)
Suitable for headphones or IEMs 16-300 Ohms.
Playback time: 60 hours.
Power output: Not specified.
Distortion etc. Not specified.
Schematics available from here: http://www40.atwiki.jp/dkamp/pages/43.html