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REVIEW: Head-direct.com HiFiMan EF2 tube Hybrid Amp with USB DAC - Page 80

post #1186 of 1318
Quote:
Originally Posted by Nananine View Post

I purchased an EF2A a month and a half ago and I really like it.  Unfortunately, a day ago the amplifier end of the amp stopped working.  The tubes don't glow and I don't get any amplifier gain.  Does anyone know why this could be happening?


Check to make sure the tubes are seated properly. Otherwise, you may have a defective unit. Hifiman has good customer service, so contact them if it doesn't work.

 

post #1187 of 1318

They're definitely seated properly, so my amp may be defective.  This is happening way to close to the release of Battlefield 3 :(

post #1188 of 1318

I'm with Calipilot - if it was just one tube, I'd suggest a faulty tube and replacement as the first check - but both tubes out sounds like something in the circuit somewhere... contact Hifiman. 

post #1189 of 1318
Thread Starter 

Could be the wall wart - maybe it's as simple as replacing the power supply?

 

You can't tell if it's only the amp that is not working simply because the DAC still shows up on the computer, since the DAC is powered by the computer even if the amp's PSU is bad.

post #1190 of 1318
Do you think an alternative and better PSU is needed?
If so, what PSU do you recommend?
post #1191 of 1318
Thread Starter 

I've never tried an alternative PSU.  I think this might use a wallwart that puts out AC power, and not many aftermarket ones like that are out there.  I'd have to double check on that.  Haven't you contacted customer service yet, after this many weeks?

post #1192 of 1318

Hi:

 

I'm having a problem with my newly purchased EF2A.  It doesn't work using the USB port.

 

When I plug it into my iMac (2 years old, 2.8GHz Intel Core i7, 8GB RAM, OSX 10.7.2) or my older MacBook Pro (2006, 15") I get the following message:

 

 

"Because a USB device was drawing too much power from your computer, one or more of your USB devices have been disabled.

 

To prevent damaging your computer, the USB device drawing too much power has been disabled. Other devices may have also been disabled. When you disconnect the device drawing too much power, your other USB devices will be enabled again."

 

 

I've tried:

- three different USB cables

- a powered (Dynex USB 2.0 4 port) USB hub

- a crappy old Windows XP Pro computer

- a Windows Vista Computer

 

No luck with any combinations of the above.

 

The amp DOES work when I run my CD player through the RCA inputs.

 

I'm in a conversation with Head-Direct customer service (they're the ones that suggested the powered

USB hub) as well, but thought I'd post here to see.

 

My understanding is that to set it up for the Mac, you:

- plug it into an unused USB port

- select it as the device for sound output from System Preferences->Sound->Output

Is that correct?

 

 

Any suggestions?  Thanks in advance.

post #1193 of 1318

Since it is happening on multiple OS/Platforms, I would guess it's a defect in the Amp.  I did read a thread around here, however, that specifically said NOT to use the front or side USB ports on Macs as they are sharing power with the keyboard/mouse and when they powercycle after periods of non-use, it creates an audio skip in the SQ.  I don't know if that would be related to your problem or not, but maybe try hooking up to the rear ports?  I'm just running off of a cheap little netbook, but I get a HUGE SQ difference if I use the USB ports on the left versus the one on the right, and I'm guessing it's for the same reason.  I never get error messages though.  Hope you get it all figured out, as it is a nice product!


Edited by TigreNegrito - 1/6/12 at 4:04pm
post #1194 of 1318

Thanks.  I'd heard about the possible issues with USB ports being shared with other things (keyboard, mouse), so I tried a number of different ones.

 

I think this is a problem with the amp. as well.  Hopefully Head-Direct will do right by me.

post #1195 of 1318

The guys around here all seem to think so!  Good luck!

post #1196 of 1318

Anyone recommends this amp with low impedance IEMs??

Thanks.

post #1197 of 1318

kalla - no. It is an OTL tube output, which means it has a fairly high gain, and high output impedence. It does not really do well at all with low impedance headphones of any type, typically causing you to turn down the volume dial very low (where there can be a channel imbalance), and/or poor electrical damping of the headphone which can affect bass clarity and quality (sounding boomy and muddy).

 

It is a great value in tube amp and dac for mid to higher impedance cans, but for low, I think it is a bit lacking (as would be just about any OTL tube amp at any price).


Edited by liamstrain - 1/26/12 at 4:15pm
post #1198 of 1318
Thread Starter 
Quote:
Originally Posted by liamstrain View Post

kalla - no. It is an OTL tube output, which means it has a fairly high gain, and high output impedence. It does not really do well at all with low impedance headphones of any type, typically causing you to turn down the volume dial very low (where there can be a channel imbalance), and/or poor electrical damping of the headphone which can affect bass clarity and quality (sounding boomy and muddy).

 

It is a great value in tube amp and dac for mid to higher impedance cans, but for low, I think it is a bit lacking (as would be just about any OTL tube amp at any price).


Ummmm... I don't agree with any of that. My understanding is this is a tube hybrid amp like the EF1 that proceeded it and the EF5 that came after, not OTL. I've used mine with a wide variety of headphones and IEM, including my custom IEM, and have no problems with low or high impedance phones. It competes quite well with other amps in this price range too. As a matter of fact, it actually controls the bass on my UE11pro customs very well.
Edited by HeadphoneAddict - 1/26/12 at 10:37pm
post #1199 of 1318

Hmm - you could be right about it being a hybrid (output stage via opamp?)

 

You haven't had issues with the gain either? With high sensitivity and low impedance phones I can barely turn the volume knob before it's too loud. rarely can I get past the channel imbalance mark on mine (which isn't much). It's a bit better from the USB since I can digitally turn things down, but using the CD/Line in, this is nearly unusable. 

 

Edit:

Right you are - the tubes are the input stage, not output. I stand corrected. I will maintain that I have not found it a good combination with the IEMs I tried, or low impedance/high sensitivity headphones. 


Edited by liamstrain - 1/26/12 at 11:02pm
post #1200 of 1318
Thread Starter 
Quote:
Originally Posted by liamstrain View Post

Hmm - you could be right about it being a hybrid (output stage via opamp?)

 

You haven't had issues with the gain either? With high sensitivity and low impedance phones I can barely turn the volume knob before it's too loud. rarely can I get past the channel imbalance mark on mine (which isn't much). It's a bit better from the USB since I can digitally turn things down, but using the CD/Line in, this is nearly unusable. 

 

Edit:

Right you are - the tubes are the input stage, not output. I stand corrected. I will maintain that I have not found it a good combination with the IEMs I tried, or low impedance/high sensitivity headphones. 


Yeah, there's always gonna be some headphone that doesn't work well with some amp. As for the RCA inputs being too loud, it depends on the source's output voltage, and what I recall trying with the EF2 are the Pico DAC-only, iBasso D10 and D4, andNuforce uDAC's which weren't too loud.
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