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

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Absolutely correct, this amp has plenty enough juice to power the LCD-2's.  Just received LCD-2's yesterday. EF2A is good for 32-300 ohms and the LCD-2's run at 60 ohms. Takes a little more juice to drive them my D2ks but stills sounds amazing being a low budget amp.
 
 
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dmwhalen

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5 for 5 on HiFiMan's customer service.  I had a faulty headphone in jack and they replaced it, no problems.
 
Quick question, what's the downside of leaving this powered on all of the time?
 
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liamstrain

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Energy consumption. Unnecessary wear on the tubes (which do burn out over time). 
 
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SgtPepper

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Holy gain batman! I had read that volumes were insane (especially with low impedance cans), but I can't even move the dial past the first notch with my Grados and HD 598!
 
I was wondering if it would be better to lower the volume in Windows or Foobar. I've read that theoretically doing so would result in a weaker signal, but would lowering the volume of one versus the other result in less of a degradation in sound quality?
 
I really love the sound of this amp with the Mullard CV4010's, lots of warmth and body.
 
Thanks
 
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liamstrain

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I don't have any issues using software to lower the input signal. It may not be "ideal" but I was unable to identify a sound difference in my own testing. 
 
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SgtPepper

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Thanks. I love this amp with my MS2i's and HD 598's, but I am wondering what headphones this amp is geared towards. The EF2A's hybrid design makes it a recommendation for low impedance cans like Grados, but its high gain is ill-suited for said headphones. This anomaly makes me wonder if the EF2A is ideal for anything, or if the lack of a gain switch is just a design flaw.
 
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I don't have any issues using software to lower the input signal. It may not be "ideal" but I was unable to identify a sound difference in my own testing. 
 
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liamstrain

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It works pretty well with low sensitivity low impedance headphones like the AKG K/Q701-K702 and some orthos (Fostex t50rp sounds nice through it). 
 
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Quote:
Holy gain batman! I had read that volumes were insane (especially with low impedance cans), but I can't even move the dial past the first notch with my Grados and HD 598!
 
I was wondering if it would be better to lower the volume in Windows or Foobar. I've read that theoretically doing so would result in a weaker signal, but would lowering the volume of one versus the other result in less of a degradation in sound quality?
 
I really love the sound of this amp with the Mullard CV4010's, lots of warmth and body.
 
Thanks
 
Strange, the 2009 model that I have can work equally well with custom IEM as it does with full size phones.
 
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TK277

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I've had the EF2A for about 2 months now and have been using it for 2 hours minimum per day, upwards to 9 hours at a time when working on design school projects.
 
For the past 2 hours I was reading this thread and started testing songs out with and without the amp. So, my mid 2009 Macbook Pro + Sennheiser HD598s vs. MBP + 598s + EF2A with stock USB and tubes.
 
I did this because Crazy*Carl's comments left me wondering how much difference I heard between the EF2A and built-in soundcard. I was frustrated because I am also very new to the audio world and at first didn't hear much of a difference. I don't hear a channel imbalance with the EF2A either (a common complaint), BUT my left ear has some slight damage. After comparing the same song about 5 times I do feel like the EF2A provides a slightly more warm tone, perhaps fuller quality to the music that I appreciate over the slight mechanical sound without it.
 
The more I read, the more I see that adding amps, dacs, and new tubes into the mix are only marginal sound differences, and they develop our sound palette over time. If someone was asking me if they should spend $170 on the EF2A I would feel bad projecting some idea about a drastic / largely noticeable difference in SQ. Most of the people I work with appreciate details though (that's part of being a designer) so I guess it would depend on who I'm talking to. So far I've been disappointed by all of my friends who say they are fine with standard earbuds or skullcandies because they "don't care that much about the quality."
 
Much to the chagrin of my bank account, today I ordered NOS matched 6AK5 Raytheon and GE 5-star tubes that are on their way and I look forward to trying them out. If I'm lucky I might nab a pair of used Grado SR60 classics to experiment with as well. I'm excited to dig further in audio with these small gains!
 
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TK277

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Received the NOS GE 5-star 6AK5 tubes today. After some warming up I've already noticed a nice subtle boost in lows and added clarity to the highs. The only negative thing I've noticed is that there's more static/noise in the quiet areas than the stock tubes. That, and I'm not sure how I'm going to get these tubes out...they're so tiny!
 
[and if this is the wrong thread for tube rolling the EF2/A I apologize, let me know where that is if there is one!]
 
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Quote:
I've had the EF2A for about 2 months now and have been using it for 2 hours minimum per day, upwards to 9 hours at a time when working on design school projects.
 
For the past 2 hours I was reading this thread and started testing songs out with and without the amp. So, my mid 2009 Macbook Pro + Sennheiser HD598s vs. MBP + 598s + EF2A with stock USB and tubes.
 
I did this because Crazy*Carl's comments left me wondering how much difference I heard between the EF2A and built-in soundcard. I was frustrated because I am also very new to the audio world and at first didn't hear much of a difference. I don't hear a channel imbalance with the EF2A either (a common complaint), BUT my left ear has some slight damage. After comparing the same song about 5 times I do feel like the EF2A provides a slightly more warm tone, perhaps fuller quality to the music that I appreciate over the slight mechanical sound without it.
 
The more I read, the more I see that adding amps, dacs, and new tubes into the mix are only marginal sound differences, and they develop our sound palette over time. If someone was asking me if they should spend $170 on the EF2A I would feel bad projecting some idea about a drastic / largely noticeable difference in SQ. Most of the people I work with appreciate details though (that's part of being a designer) so I guess it would depend on who I'm talking to. So far I've been disappointed by all of my friends who say they are fine with standard earbuds or skullcandies because they "don't care that much about the quality."
 
Much to the chagrin of my bank account, today I ordered NOS matched 6AK5 Raytheon and GE 5-star tubes that are on their way and I look forward to trying them out. If I'm lucky I might nab a pair of used Grado SR60 classics to experiment with as well. I'm excited to dig further in audio with these small gains!
 
To me the headphones are the most important part of the equation, then source and amp.  The conversion for electrical to mechanical or back, like with microphone, phono cartridge, or headphone/speaker is the hardest part to get right.  The HD598 are okay but not the most resolving headphones out there, and so improvements in source and amp will make a smaller difference than if you were using HD600, LCD-2, HE-500 or HD800.  
 
But even then, the differences between a $100 amp and $200 amp won't be much greater than improving that to a $500 amp.  On the other hand, comparing the bottom rung amp to the top of the line amp will be more striking than comparing incremental improvements, but we're talking about much bigger price jumps.  The nice thing about the EF2 amp is that with mid-fi and even hi-fi headphones the amp won't let you down, much, vs more costly ones.
 
Again, I think the EF2 amp is better than it's DAC, and that could be the weak link rather than the phones if your PC has a good sound card.
 
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Quote:

 
Received the NOS GE 5-star 6AK5 tubes today. After some warming up I've already noticed a nice subtle boost in lows and added clarity to the highs. The only negative thing I've noticed is that there's more static/noise in the quiet areas than the stock tubes. That, and I'm not sure how I'm going to get these tubes out...they're so tiny!
 
[and if this is the wrong thread for tube rolling the EF2/A I apologize, let me know where that is if there is one!]
 
When the tubes are cooled down you can wrap a rubber band around the top part of the tube to help you get a grip on the tubes and pull them out.
 
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liamstrain

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Quote:
 
When the tubes are cooled down you can wrap a rubber band around the top part of the tube to help you get a grip on the tubes and pull them out.
 
Yup. This works well. 
 
You can also unscrew the plexi top, if needed.
 
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TK277

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Quote:
 
To me the headphones are the most important part of the equation, then source and amp.  The conversion for electrical to mechanical or back, like with microphone, phono cartridge, or headphone/speaker is the hardest part to get right.  The HD598 are okay but not the most resolving headphones out there, and so improvements in source and amp will make a smaller difference than if you were using HD600, LCD-2, HE-500 or HD800.  
 
But even then, the differences between a $100 amp and $200 amp won't be much greater than improving that to a $500 amp.  On the other hand, comparing the bottom rung amp to the top of the line amp will be more striking than comparing incremental improvements, but we're talking about much bigger price jumps.  The nice thing about the EF2 amp is that with mid-fi and even hi-fi headphones the amp won't let you down, much, vs more costly ones.
 
Again, I think the EF2 amp is better than it's DAC, and that could be the weak link rather than the phones if your PC has a good sound card.
Makes sense, thanks. :)
Quote:
 
When the tubes are cooled down you can wrap a rubber band around the top part of the tube to help you get a grip on the tubes and pull them out.
I'll give this a try when I need to get them out, thanks!
 
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