According to the manual, the ImAmp supports op-amp rolling, and so I set out to play around with some different op-amps. Opening the case is relatively easy, simply unscrewing two screws on the top and two on the front panel side, and the cover can be removed. Inside, I find the layout to be very clean. Most of the parts are an SMD type, with brand name capacitors such as Wima and Os-Con and the Korean brand Sam Young. You will also find a Burr Brown OPA2134 op-amp placed on a socket.
The stock opamp is the OPA2134, and is actually pretty good, but I also tried some different opamps with the ImAmp:
- OPA2134 (Stock): Generally laid back, nice big soundstage.
- AD825 (single channel SOIC package, with an adaptor): Generally laid back, bigger soundstage than OPA2134, nice open sound, a little grainy.
- LT1364 (DIP Package): Forward sound. Very smooth. Not as spacious as the AD825, but smoother and cleaner at the top frequencies.
- OPA2107 (DIP Package): Slightly lush, full midrange.
- LME49720 (Metal TO-99 Package): Very tubey, thick midrange.
Other than those, I also tried the ImAmp with the AD8066 and AD797 op-amps, but for some reason they don’t work on the ImAmp.
On battery power, the amplifier runs at a lower ±6~±8V, while it runs on a higher ±10V on external power. I really don’t notice any performance differences with the walwart on, except when I needed to run the amplifier while battery level is low. The external power supply that’s supplied with the ImAmp supports a worldwide voltage from 100V to 240V, so you can take it for international travelling and have a decent amplifier for listening at the hotel room.
I briefly compared the ImAmp on the stock OPA2134 with the built in amplifiers of the Audinst HUD-MX1, the Nuforce uDAC, and the Dr. DAC DX2, the Ibasso D10, and found the ImAmp to fare better with a smoother and more musical sound than the rest.
Overall, the ImAmp has slightly warm sound with a pleasing midrange, with a slightly relaxed treble that results in a likeable sound that’s not fatiguing for long term listening. At this price range, the ImAmp is actually very fun sounding, and the sound is tuned to work well with a wide range of music genres. Some amplifiers like the D10 emphasizes the treble, and may sound more lively, but it’s actually less refined in the treble area. The uDAC also has some coloration in the treble and bass, although it is a little more punchy than the ImAmp. When compared to the built in amplifiers of the HUD-MX1 or the Dr. DACs, I find the ImAmp to deliver a more solid power and overall smoother sound. I have been listening with the ImAmp with a ton of headphones, and I never found a glaring coloration.
For the price that it’s selling for, it does make a fun and good sounding little amplifier. Think of an amplifier that you can take to the campus, office, travelling, and with enough gain to cover just about most headphones. The sound signature is generally pleasing, without any dryness, harshness, or any other nasty thing often heard on cheaper amplifiers.
Equipment used for review:
Headphones: Beyerdynamic T1, Sennheiser HD800, Etymotics ER4S, JH16Pro
Source: Ipod Classic 120GB
Amplifiers: Audiotrak ImAmp