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HiFiMan EF2A trouble

post #1 of 9
Thread Starter 



I bought my second HiFiMan tube USB DAC amp it being the EF2A unit. I sold my first to purchase some headphones I had my eye on. These amps come standard with the Chinese 6J1 tubes. I'm after the best audiophile experience so on the first amp I bought NOS Sylvania compatible tubes. It sounded awesome. For the second EF2A amp I bought some valve electronic CV4010 KQDD/K tubes based on compatibility threads here. At first everthing was cool. I.m plugging the amps USB into my Dell Inspiron with iTunes.


Now I'm getting a strong hiss when the song ends and crackling interference which can and will turn to pure white noise. It's hard on the ears when that happens, I changed back to the 6J1's thinking maybe a bad tube. Music was good then bang it came again. It seems as though when I turn everthing off and then power back up it does ok for a few minutes, but then back to bad.


I called Head Direct for advice. The woman told me the president says not to use any other tubes than what's shipped with it. I can't accept that and told her as such. She still wouldn't help. So is tube rolling a no no wit HiFiMan amps? My successful experience withe first amp tells me no. As of right now I would not buy from Head Direct due to such inadequate customer service. I wasn't being a jerk. I was just trying to get some help.


Any ideas Guys? Thanks.

post #2 of 9
Thread Starter 

Well while I was writing the above post I got a message from head direct to have my paperwork ready to show it's still in warranty and return it. This is what should have been explained in the first place rather than the BS about the tubes it came with. Arrrrggghhh.

post #3 of 9

I agree that it would be helpful if Head-Direct would post/include usage guidelines so you would know what you can and cannot do with their equipment. I have rolled the tube in my EF5 with no discernible problems, perhaps it has to do with the built-in DAC in the EF2A. Hopefully you are within their 30 day return policy, otherwise a warranty claim should be valid for a year.

Edited by grokit - 6/14/10 at 2:52pm
post #4 of 9
Thread Starter 

Ok Everyone,


As is the route of isolating the problem in electronics, I hooked the amp usb into my main PC USB hub. The amp performed perfectly. Just like I remember. It really is a great amp. I had a spare USB hub which I plugged into the dell then connected the amp usb to it. Works perfect. I called Head Direct back and told them how I fixed it. They were very, very nice and told me to call right away if I noticed any further trouble. All is well now. The fix is just strange though. I think maybe this is a Dell USB port problem? This laptop is questionable anyway. I tried going economy due to the times, but that's exactly what I got. An economy piece of s**t, LOL.

post #5 of 9

Yes, there can be differences in USB ports for sure. Glad you are enjoying your EF2A again.


Head-Direct always seems to come around to doing the right thing by their customers from my experience with them.

Edited by grokit - 6/14/10 at 4:22pm
post #6 of 9

I have a fairly new HiFiMAN EF2a with rolled tubes, about 3 weeks old, and it's sounding brilliant with my Sennheiser HD580s and IE8s with an Audioquest Forest USB DAC cable.


I was pretty dismayed when I picked up my headphones and heard a distinct crackling and/or whooshing sound instead of music, and no amount of plugging/unplugging and power cycling the device was able to cure it. I tried different tubes, but no luck.


After reading this post, I decided to try plugging it into a different USB port on my Macbook Pro 17", and sure enough it solved the problem!


I don't know if the USB port just went bad or what, but troubleshooting it is my next step.

post #7 of 9

So glad I found this thread as I will sometimes have the same problem with my amp.  Only happens off of USB, not RCA, and only if I happen to open other programs or search engines - everything's going along nicely and getting immersed in the music and then WHAM!!!!  solid stream of white noise that'll really hurt the ears.


If I do a power cycle on the amp, there is still crackling that overshadows the music and it only goes away if I restart the computer.


If I just use the computer as source and don't do anything else with it, the sound is great.  I've swapped in some Tung-Sols and the sound is superior, but the event still happens as it did with stock tubes, so I assumed it was a USB problem.  I was thinking of trying a hub, so I'm thrilled to see I was on the right track with that.


Anyone have any experiences like this and if so, is one hub as good as another?  Also, how does a hub correct this problem?  I kinda figured the hub would just be an extension of whatever USB port it is attached to, therefore it would replicate any properties (in this case problems) of the port to which it is plugged.  Is my thinking flawed here?


And what about a wireless USB hub?  That way, I can just hook the amp directly to that and route the music files from DAS or any device connected to the network.  Anyone done that?


Edited by TigreNegrito - 1/9/12 at 7:13pm
post #8 of 9

Okay, three or four hours into running the HF2A from the laptop via a USB hub and no feedback/white noise issues yet.  And I'm running multiple applications, just as I should be able to do.  There is one issue that is still keeping me cautiously optimistic.  When I listen to Pandora and the EF2A is plugged in (directly to computer or through the new hub) the data for the individual track's remaining playtime is affected.  It starts out at some insanely long time (20 or 30 minutes) and then rapidly counts down until it reaches the correct playtime.  This takes a few seconds to happen and the audio quality (such that it it) is unaffected, nevertheless it is a glitch I only notice with this unit, not the Fiio or TBH (a clocking issue in the DAC?).  I'll continue to test it out within my 30 day window to decide if I'm going to keep it or not, and keep you posted accordingly. 


Just have to reiterate that the Tung Sols are supremely better tubes for this amp with the Q701's and I'm loving how the range is now complete instead of the balance shifted towards the highs as it was before.

post #9 of 9

I've also experience the same issue from time to time. Reconnecting USB cured it.

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