REVIEW: Head-direct.com HiFiMan EF2 tube Hybrid Amp with USB DAC - Page 7

Larry, the EF2 has four A940 (http://www.fairchildsemi.com/ds/KS/KSA940.pdf) inmediately adjacent to caps. It is the heat generated by these and the two tubes I am speaking off.

I have not found it to be hot either. I've run it for 6 hours straight (at low-ish volume) and it was just warm to the touch. Would volume level, or perhaps the headphones used cause the amp to produce more heat?

I did a little A-Bing yesterday with the stock headphone out on the PC, then USB through the EF2 and I'm still a very happy camper.

One thing I've noticed though, at the very lowest volume level (just before 0), the right channel drops out. I don't normally use that volume level, so I'm only slightly disappointed in that.

Guys just because the outside of the casework does not get hot it does not mean that the internal components are cool. If you notice the manufacturer chose to spec caps rated at 105C which is a good thing to prolong their life due to the heat generated by some of the internal active components. So if you can further enhance the cooling you can prolong the life of the caps and other components.

Enough of the heat, or no heat!

The USB DAC and amp section have an additional +/-24 hours of burn in and I have to say that I am very pleased with this unit. The sound/performance you get for $189 is short of fantastic and whomever gets it should have a great bang for the buck.

I have been listening today to Renee Olstead and Madeleine Peyroux, both sound engaging and their voices have a nice warm presentation. I should also mention that although the volume pot is not an stepped attenuator it has notches. These feature is nicely implemented in that the "steps" are very close and you do not wish for in-between steps as is usually the case with true stepped attenuators.

Currently waiting for the NOS tubes while I continue to burn in the USB DAC which currently has about 50 hours of burn in while the Amp Section has about 150 hours of burn in.

After much deliberation, I'm taking the plunge on this plus a pair of Sylvania 6AK5's for my AKG K701s

(and a Pelican 1150 case to haul around the amp between offices and LAN parties, of course)

I think that'd annoy me too much. I'd like my knob to be completely free. Things like that can be a deal breaker for me sometimes.

For the last few days I have been using the EF2 as an USB DAC/Amp. The USB DAC section has 100 hours of burn in and the Amp Section has 200 hours. I am really getting to know this little unpretentious unit and I can say the sound is very engaging and smooth. It will not win a detail contest but what it lacks in hyper detail it makes up in the organic way it presents the music. Look forward trying the NOS tubes I ordered. Did I mention it is very smooth!

Hmm... I just started looking for a USB DAC and a hybrid amp for my Grado SR325i's, but this combo seems tempting. I saw it at CanJam but didn't get to listen to it. If only I had known that I would be thinking about buying it in the near future...

For those few of you who have listened to the EF2, do you think it would pair up well with my 325i's? The only other DAC I've owned was the D10 (which I sold). I liked how the 325i's sounded with the D10 DAC/amp but couldn't justify the price, so I sold it. I also eventually wanted to try a hybrid amp.

I know HeadphoneAddict said that the EF2's DAC didn't sound as good as the D10, but as long as it doesn't sound bad I'll be fine with it. I just need something better than my internal sound card. I guess the more important thing here is the amp since I wanted to try a hybrid amp with my Grados.

I'm really liking the price. I just hope it's not too bright to pair with my 325i's.

Thanks for the reply. You're opinions are always very helpful. I found that a lot of your opinions in the D10 thread prior to me listening to it was pretty accurate.

The EF2 is now topping my list as my birthday present to myself.

I concur w/ Larry, my RS-1's sound very good out of the EF2. Still waiting for the Sylvania NOS tubes.

Has anyone tried this amp with k701? Any opinions?

Anyone tried the amp with an AD900? I thought I'd want to get more kick out of the AD900's bass. Any suggestion for tube rolling for lower frequencies?