[mmd8x28]

I just got myself some new headphones, Koss Pro4AAT, and they are 250 ohm, 10Hz-25KHz, but I have to crank the EF2 up to the max to get it loud enough to be enjoyable.  Usually with my IEM's all it needs is a 12 o' clock position...
 
Anyway to get more "juice" out of this amp?  My Onkyo amp powers these headphones with major ease.

 

[mrarroyo]

Is your source volume down? Does your source put out 2 Vrms as many sources do?

 

[Zombie_X]

Those PRO4AAT's don't have a high sensitivity at all. They need a lot of voltage to get loud as they are very difficult to amp properly. They need gobs of juice!!

 

[mmd8x28]

Quote:

Is your source volume down? Does your source put out 2 Vrms as many sources do?

The source is definitely up all the way..  I'm using the built in DAC, and I tried the Mac Pro's output, which is slightly louder, but hardly that much.

 

[mrarroyo]

Ok, do not laugh! What is the position on the EF2 which selects source.

 

[mmd8x28]

Quote:

Ok, do not laugh! What is the position on the EF2 which selects source.

USB, or Line In, whichever source I use...
 
Like I originally said, my IEM's are nice and very loud..  It's only these Koss that are tough to drive on this amp..  My Onkyo receiver has no problem driving them however.

 

[Zombie_X]

Like I said it's because they aren't very sensitive either. They need more power than what the amp can put out.  But don't fret! There are other alternatives out there!
 
Quote:

USB, or Line In, whichever source I use...
 
Like I originally said, my IEM's are nice and very loud..  It's only these Koss that are tough to drive on this amp..  My Onkyo receiver has no problem driving them however.

 

[mmd8x28]

What other alternative?  Sounds foolish a $200 headphone amp can't drive $99 headphones.
 
Quote:

Like I said it's because they aren't very sensitive either. They need more power than what the amp can put out.  But don't fret! There are other alternatives out there!
 

 

 

[Zombie_X]

Well the EF2 is a hybrid which specializes in outputting current rather than voltage. The PRO4AAT is not that sensitive and also has a higher ohm rating as well which means it will need a lot more power than what the EF2 can provide. Don't get me wrong, the EF2 is a great amp for sure, it's just that the PRO4AAT's require more power than what the amp could provide. The EF2, being a hybrid amp, is better for low impedance headphone like Grado's or Denon's.
 
I didn't mean to sound like I was pushing anything before, but just wanted to you to know that the EF2 wouldn't be able to drive them, but there were cheaper alternatives out there.

 

[mmd8x28]

The head-direct site states the EF2 can drive 32-300 ohms...
 
Still, hybrid or not, cost wise it should still be able to drive it..  (Considering the parts in the EF2 definitely don't equal $200, FAR less, single digits).

 

[Zombie_X]

I get what you are saying about it. How loud do you listen though? 
 
Also I hope nothing I have said has angered you. I'm just trying to help you get the most out of the PRO4AAT's.

 

[mmd8x28]

No anger..  Kinda hard to explain how loud I enjoy them, but if I had to try, I enjoy them at concert levels..  I can get close enough, but the volume is already at max..  On movies, forget it, not even close to being loud enough..  (I hate it when movies are so quiet then get loud).
 
Quote:

I get what you are saying about it. How loud do you listen though? 
 
Also I hope nothing I have said has angered you. I'm just trying to help you get the most out of the PRO4AAT's.

 

[Zombie_X]

OK, but don't listen too loud!!
 
Also I have the knack of wording stuff the wrong way and it makes people kinda mad. I just wanted to "cover my bases" to say.
 
Quote:

No anger..  Kinda hard to explain how loud I enjoy them, but if I had to try, I enjoy them at concert levels..  I can get close enough, but the volume is already at max..  On movies, forget it, not even close to being loud enough..  (I hate it when movies are so quiet then get loud).
 

 

[mrarroyo]

I just attempted to use a USB DAC with my iMac and realized the volume out of iTunes can affect the sound out, so you may wish to check your player. Since you already have the unit and it is free after turning the EF2 off pull and reset the two tubes to see if you can hear any changes. Note: If the pins look dirty you may spend some time w/ alcohol and a brush cleaning them. Good luck.

 

[mmd8x28]

As I said, other headphones are fine..  So I'm not wasting my time fiddling with tubes..  ALL software have everything up as high as it goes..  ALL other headphones are loud..  It was only these.