[MaxNorway]

Hi, I`ve been looking at portable amps for my q701 and want some oppinions from you guys. I am now mostly leaning towards the Headstage Arrow 12HE 4G.
 
It sais it will handle headsets and soundsystems up to 600 ohms, and since the akg website states that the headsets imput impendance is 62 ohms I figured they would work. (Im not sure if 11 volts from the amp is enough though, need some help here)
 
In addition im planning on buying an USB DAC cable from the same company for the amp so i can use the same amp for my computer for the time being.
 
 
Basically what i want to know is this:

• Will the amp be strong enough for my headset, please explain
• Is this amp a good match for the headset?
• Is the USB DAC from Headphonia any good? (planning on using it for a macbook)

 

---

 
 
Specification sheet - Q 701 (English)

1. http://uk.akg.com/tl_files/catalog//AKG/AKG/Spec%20sheet/Quincy/Q701/Specification%20Sheet%20-%20Q%20701%20%28English%29.pdf

 
Arrow 12HE 4G info site

1. http://www.headstage.com/The-Arrow-Amp/Headstage-Arrow-12HE-4G::10144.html?XTCsid=a2af9fc94110e9f2ddc432792927bacf

 
Headstage USB DAC

1. http://www.headstage.com/USB-DAC-Cable/USB-DAC-Cable-with-35mm-Mini-Plug-75cm-30::10134.html?XTCsid=a2af9fc94110e9f2ddc432792927bacf

 

[skip129]

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.

 

[skip129]

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.

 

[MaxNorway]

Mind = blown

I think i just learned more from you and wikipedia in 10 min than i have learned in school the last month. electronic engineering is cool!

Anyways, will come back tomorrow when im not actually writing while sleeping.

 

[MaxNorway]

Sorry it took so long, I had to fight of an ice bear attack with my thumb and an ice pick after striking oil again!
 
Now the choice is really between the proven and cheap fiio E7 (+maybe E9?), or the arrow with the good reviews. If somebody knows somebody who has tried the arrow with k701 / q701 / k702, I'd be really happy if you could ask them what they thought.

 

[maverickronin]

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.

 

[skip129]

Quote:

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)

 

[maverickronin]

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.

 

[skip129]

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.

 

[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

 

[heart banger-97]

Quote:

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

 

[MaxNorway]

I have faith he will sort everything out. Hell, lets help the little guy out!

 

[colon]

As much as I like the q701s (just got a pair) they don't seem that portable to me, but would still like to hear your opinion on the amp you got. I would like to drive these to see if they are worth getting an amp for.

 

[MaxNorway]

I can give you an opinion, but since i dont have a reference I doubt it will be worth anything. I'll be ordering the amp soon and im looking forward to trying it