amp for AKG Q701

IMHO, it will be able to generate approximately 117dB SPL into those headphones, and will easily be loud enough. This is just going by the raw specs though.

The maths: 11Vp-p = 11/2/sqrt(2) = 3.89V RMS.

Sensitivity of the headphones: 105dB/V

Gain in dB at maximum output of the amp with respect to reference:  =20*log(3.89) = 11.8dB

Resulting SPL at maximum output: SPL at 1V RMS + gain = 105 + 11.8 = 116.8db SPL. 

Also, the amp appears to have quite a high maximum gain setting, and should cater well for low output devices, such as portable devices. 

For example, the gain required for a 0.5V RMS portable device to reach maximum output is: 20*log(3.89/0.5) = 17.8dB, which matches nicely with the maximum gain of the amp, which is 18dB. 

The amp has good specs - on paper.

Greg.

Note that there are no power specs that I can see for the amp. So, I don't know whether it can reach 11 volts peak-peak with your headphones.

Also missing is the output impedance of the amp.

So, the actual level achievable with your headphones may be less than the ideal maximum I calculated. It is very hard to say without more comprehensive specs. 

Greg.

The E7's probably going to be to weak on its own and the E9 isn't portable.  The E9's output impedance is probably too high as well.  It does have plenty of power though.

If saving some money is an acceptable trade for a bulkier amp, more power, and no extra features like crossfeed or tone control the Objective2 is a good choice.  Its hard to beat the Arrow's form factor and extra features though.

Quote:

Originally Posted by maverickronin 
The E9's output impedance is probably too high as well.  It does have plenty of power though.

 

Looking at the impedance vs frequency plot here: http://www.headphone.com/headphones/akg-q701-quincy-jones.php  (specs tab), my gut feel is that the affect of the output impedance of the E9 would be extremely subtle. I think the recommendation is at least an 8:1 ratio of headphone impedance to output impedance, and yes, the E9 would not quite meet that at 6:1, but the impedance doesn't seem to vary all that much with frequency.  It appears that the largest deviation is 100 ohms at 20kHz, and doing the maths, there would be a tiny boost in level of about 0.5dB, and there isn't typically much happening up at 20kHz anyway.  I know the damping factor affects the sound in other ways other than simple frequency response though, but do you think it will be noticable?

With the E7, you have a portable amp with a very low output impedance, which could be used with very low impedance IEMs, for example. It looks like a versatile combination. (but no, the E9 is not portable)

I was thinking more along the lines of damping factor and not the FR variation but you're right that the damping ratio isn't too bad.

I think the worst thing I've seen about the E9 is that in a test, it had a channel imbalance of 1.8dB, which seems a bit high, but not terrible.

Quote:

Originally Posted by MaxNorway 

I've decided to go ahead with buying the arrow. The E7 is allot cheaper, but i dont want to carry around a brick in my pocket. Sadly I cant give you any feedback on the sound when I get it other than if it improves the headset sound or not, being my first amp I wont have anything to compare it with.

 

Thanks for your help, really first class!

-Max Lauritz

take a look here 

http://www.head-fi.org/t/574116/delivery-of-headstage-arrow-he-4g

some of us are waiting more than 7 months