[peck1234]

 
Currently using my AX-497 for my headphone DAC.  Would I benefit from a dediacted headphone amp?
How much power does my receiver put out at say
 
 

1. @ 30 Ohm
2.  @ 120 Ohm
3. @ 300 Ohm
4.  @ 600 Ohm

 
 
Here's the spec of my receiver, I don't know if I reading this correctly, but basically its claiming 300mv @ 680 ohms.  (which kicks the crap out of any basic headphone amp)
 
So my 300 dollar recieiver is better than a http://www.nuforce.com/hp/products/iconhdp/index.php? 

 

[wuwhere]

You can't unless you measure it at those different impedance. Its like asking how much horsepower does my engine put out at 500, 1000, 1500, etc... rpm.

 

[peck1234]

Quote:

You can't unless you measure it at those different impedance. Its like asking how much horsepower does my engine put out at 500, 1000, 1500, etc... rpm.

Understood, I am however reading the 300mv @ 680 ohms correctly though? 

 

[wuwhere]

Quote:

Understood, I am however reading the 300mv @ 680 ohms correctly though? 

Yes, which is about 1mW.

 

[stv014]

Quote:

Yes, which is about 1mW.

It does not look right, even an iPod can output more than 0.3 V. Perhaps it should be read as 0.3 V into a 8 Ohm load, through 680 Ohm output impedance ? That means that the maximum unloaded output voltage is 25.8 V. Assuming that these are RMS voltages, and that the headphone output is simply fed from the speaker output through 680 Ohm resistors (an unfortunately common solution), this agrees with the specification of 85 W maximum power with 8 Ohm loudspeakers (25.8^2/8 is 83.205).
If the above is true, the receiver has plenty enough power (~240 mW) for any currently available 600 Ohm dynamic headphone, although the 680 Ohm output impedance is rather high.
 

 

[peck1234]

 
 

 
headphone output is simply fed from the speaker output through 680 Ohm resistors (an unfortunately common solution

Why unfortunate? 
 
Also how did you get  (~240 mW)
 
Thanks for the help!

 

[stv014]

Quote:

Why unfortunate? 

A very high output impedance audibly changes the sound of many headphones, often making the bass response worse (although increased in overall quantity, thus many people actually prefer the change). Here is a more detailed explanation. Using dropping resistors is basically the cheapest way to implement a headphone output in power amplifiers.
 
What headphones are you driving with the AX-497, by the way ?
 

 

[peck1234]

As of now, just a ATH-M50, so in terms of sound quality I would still benefit from a dedicated headphone amp? 

 

[stv014]

Quote:

As of now, just a ATH-M50, so in terms of sound quality I would still benefit from a dedicated headphone amp? 

 
The ATH-M50 is not very sensitive to changes in the output impedance, so it probably would not make a "night and day" difference. With some others, like the HD598, it would be quite audible.