REVIEW: Head-direct.com HiFiMan EF2 tube Hybrid Amp with USB DAC - Page 11

The Amp without much burn-in sounds nicer than the DAC without burn-in - the DAC itself only needed 24-48 hours to open up in clarity and detail, and I did 250 on the amp with most of the improvement in the first 100-150). With burn-in the amp becomes less bright and the bass fills in nicely, while the DAC burn-in improves clarity and detail of the DAC section. My EF2 had about 24 hours on it when I took it home from CanJam.

Also, the internal DAC output level is lower than some other DACs with a "hot" output like Pico DAC only or Apogee mini-DAC, and is closer to the lower levels of the D10 line-out. So it wont play quite as loud using the internal DAC as it does with the Pico DAC-only or Apogee mini-DAC. But typically that only affects the position on the volume knob needed to achieve the same volume levels.

With most phones the power level is just a little below the EF1, but with those new HiFiMan prototype RE5 orthodynamic phones the EF1 was much better at driving their low 4-8 ohm impedance load. With Grado and Denon the volumes can be quite loud, and still fairly loud even with 300 ohm HD600 and HD800. It beats most portable amps for power, excluding maybe the 3MOVE or SR-71.

I think that Skylab posted what the various equivalent tubes would be.

Maybe you could try a Shure or Westone headphone volume attenuator between the EF2 and the powered speakers.

I answered this in the other thread you posted in. "I feed the RCA into my Amphora and the mini to my EF2 with a mini-RCA cable, and both outputs are active at the same time with no switches, so if the amps are both on then the sound comes out of both of them."

You can feed the RCA into the EF2, and the mini to the powered speakers just fine, but you have to control the speaker volume via the speakers or with a volume attenuator.