[robrob]

  I've read the bulk of this thread and I finally have a clear picture in my head of the different options.
 
My question is this: Why are the headpone outputs of integrated amps not already set up this way?  If it is so cheap and sounds so good, what is it that makes manufacturers do something different?
 
I opened up my arcam alpha 10 to take a look at the headpone socket, and all I see are 4 resistors.  Am I really doing anything different that what is already done inside the case by using the speakers taps?
 
The arcam alpha 10 is 100+ wpc in 8 ohms, can anyone guess as to how much attenuation I will need when driving a pair of audeze lcd-2?  Would it be safe to hook them up without?
 
(Additional none related query below)
 
 
Something that has been bugging me is that when people talk about the power requirements of headpones, they talk about the amount of power required to make a certain headphone reach a certain db.  Is this an average figure taken accross all frequencies, because I thought lower frequencies required more power? 
 
When somebody says x amount of power will produce y db output on these headphones, then in theory, could that not be true for the lower frequencies?
 
The reason I ask here is I wonder if this could be the reason that driving headphones from powerful speaker amps produces favourable results.
 
Cheers,
Andy

 
Hey Andy,
 
Built-in amplifier headphone jacks are usually over attenuated and drop the power to the headphone jack too much. This may be due to liability issues with damaged headphones or hearing. The resistors in your arcam alpha probably over attenuate. You could replace the built-in resistors to get the amount of attenuation you want.
 
You can safely connect your headphones to the speaker taps but slowly raise the volume so you don't overpower the headphones. As long as you don't have noise floor (hiss) or volume control issues you don't need a resistor network with a solid state amp (tube amps tend to be more sensitive to speaker load).
 
For 100watts per channel I would recommend about 24db of attenuation.

 

[davidsh]

Something that has been bugging me is that when people talk about the power requirements of headpones, they talk about the amount of power required to make a certain headphone reach a certain db.  Is this an average figure taken accross all frequencies, because I thought lower frequencies required more power? 

When somebody says x amount of power will produce y db output on these headphones, then in theory, could that not be true for the lower frequencies?

The reason I ask here is I wonder if this could be the reason that driving headphones from powerful speaker amps produces favourable results.

Cheers,
Andy

Sensitivity is usually measured relative to 1000 Hz. It will definitely vary across frequencies, and the variation depends on the headphone's impedance curve. As far as I know, many headphones have an impedance peak somewhere in the bass frequencies due to driver resonance, so that peak would require more power. 

It's the opposite, impedance tend to increase in the bass, meaning it requires less power.
Bass in lots of music tend to be fairly 'loud' compared to other sounds and instrument, but bass doesn't require more power per se, at least to reach a certain dB.

 

[hpandy]

Thanks for the answers guys.
 
I've noticed that when I eq the bass significantly, music volume decreases when bass notes are present in a piece, and then increases when they are not.   Empirical evidence suggests that from an amplifiers perspective, bass frequencies are harder to drive.  I would like to see this represented in numbers.
 
I'm considering selling my DAC and one or two of my amps and buying a budget-mid cost receiver to function as an all in one headphone amp/dac.  Can anyone recommend any brands for relivable dac performance in receivers?

 

[robrob]

Somebody made some recommendations on receivers with DACs in the "Speaker amps for headphones" thread. There are some pretty sweet receivers out at pretty killer prices.

 

[themad]

Still no word from brunk?

 

[DaemonSire]

  Still no word from brunk?

 
Nope

 

[kothganesh]

Nope

Same here. I hope he is ok and that he is so busy making the Robinette boxes that he does not have the time to respond now.

 

[d1sturb3d]

will the new he-560 responds the same way when paired with the mini-x? hopefully it will..

 

[rocksteady65]

Same here. I hope he is ok and that he is so busy making the Robinette boxes that he does not have the time to respond now.

Yes, let's hope that is the case...

 

[Miraculous]

Hell if I'm sifting through 233 pages to find if someone asked this already, but let me try to ask a question.
I have an O2/ODAC combo, but it has no coaxial out. I would rather not buy another DAC to use with the A-100. Would a 3.5mm to coaxial from the headphone out of my O2/ODAC be a realistic way to connect the two? I want to get into orthos, but my current amp doesn't come close to the recommended wattage for pretty much any of them.

 

[hpandy]

You would be passing the analogue signal through two amplification stages if I understand you correctly.  I persoanlly would not spend money on good headphones and then do something like that.

 

[DaemonSire]

  Hell if I'm sifting through 233 pages to find if someone asked this already, but let me try to ask a question.
I have an O2/ODAC combo, but it has no coaxial out. I would rather not buy another DAC to use with the A-100. Would a 3.5mm to coaxial from the headphone out of my O2/ODAC be a realistic way to connect the two? I want to get into orthos, but my current amp doesn't come close to the recommended wattage for pretty much any of them.

 
Does your O2/ODAC combo have a Line-Out or just the Headphone out?
 
And you say coaxial...what exactly do you mean by that?  You need to feed the A-100 an analog signal via 2 RCA's (Red and White cable).
 
A direct dac-out or line-out would be the best way to pass the signal to the amp, skipping the internal amp in the O2 (and avoiding dual amping).  But going from the 3.5mm to dual RCA would still work.  You would essentially be using the O2 in a sort of 'pre-amp' fashion where the volume would be controlled by both the O2 and A-100.
 
I'm doing something similar at the moment where I have the Line-Out on my Matrix M-Stage going to the input on the A-100.  I just set the A-100 to about 9 o'clock on the pot and control the volume via the M-Stage.  Works well.  As I mentioned, a Line-Out would be better than the headphone out if it is a possibility.

 

[IwasDerp]

 
Use in line resistors for attenuation and you wont have any noise.

So I was looking at BTG's custom adapter maker and he has a 499 Ohm resistor. I guess that would work but I am not sure how much wattage it's resisting. How much would the output decrease from around the 12-13W at 38 Ohms (I think that's how much it's outputting) which I am currently getting?

http://btg-audio.com/webstore.htm#ecwid:category=3351504&mode=product&product=14641214

 

[davidsh]

That is 23 dB if I am not mistaken.
Calculated like (38 ohm + 499)/ 38 to find out with which factor the voltage drops. Then it is fairly easy to figure out how much the power drops relative to full voltage (no resistor in path) using the formula P = U^2/R
Then convert to dB.
It's a mere 65 mW through he-500 by the way, assuming the emo puts out the same voltage as when pushing 13 watts in 38 ohm.

 

[IwasDerp]

That is 23 dB if I am not mistaken.
Calculated like (38 ohm + 499)/ 38 to find out with which factor the voltage drops. Then it is fairly easy to figure out how much the power drops relative to full voltage (no resistor in path) using the formula P = U^2/R
Then convert to dB.
It's a mere 65 mW through he-500 by the way, assuming the emo puts out the same voltage as when pushing 13 watts in 38 ohm.

Ah ok, thanks for this. I decided not to do buy the adapter for now. I'll live with a bit of noise floor since I don't notice it at all when I am listening to music at my normal listening volume. I just don't have that kind of money right now.