[Plecto]

Hi. I'm constructing a headphone amplifier that's supposed to drive any pair of headphones, but I'm not sure of how powerful I actually need it to be. I'm currently getting about at least 1W output up to about 150Ohms which is enough to blow most headphone, but what about headphone with a higher impedance? Are there some really power hungry headphone with an impedance of up to 600Ohms? I don't want the amplifier to be the bottle neck regardless of what types of headphones that are plugged into it.

 

[davidsh]

  Hi. I'm constructing a headphone amplifier that's supposed to drive any pair of headphones, but I'm not sure of how powerful I actually need it to be. I'm currently getting about at least 1W output up to about 150Ohms which is enough to blow most headphone, but what about headphone with a higher impedance? Are there some really power hungry headphone with an impedance of up to 600Ohms? I don't want the amplifier to be the bottle neck regardless of what types of headphones that are plugged into it.

Well, there are no commonly used very insensitive high impedance headphones, so I suppose 1 watt at 150 ohm would drive just about all high impedance headphones out there except maybe a few vintage ones.
 
The problem would more be low impedance planars like the HE-6. We are talking 5 watts 50 ohm here..

 

[Plecto]

Lower impedance's isn't a problem, my amp can deliver close to 8W into 50Ohms. I'm glad to hear that there aren't many high impedance headphones that require the same kind of power

 

[davidsh]

  Lower impedance's isn't a problem, my amp can deliver close to 8W into 50Ohms. I'm glad to hear that there aren't many high impedance headphones that require the same kind of power

Well, I suppose it could drive HE-6 and akg k1000 then 

 
 
Of course your amp can't drive electrostats, though.

 

[Plecto]

Electrostats? What type of headphones are those?

 

[Koolpep]

  Electrostats? What type of headphones are those?

 
http://www.kenrockwell.com/audio/stax/electrostatic.htm

 

[davidsh]

Yeah, electrostats is a hole different type of headphone. If you ever want to do some DIY in headphones I'd recommend stats because they are fairly simple to make if you got the tools and they can sound as good as some of the best headphones around.

 

[Plecto]

I can't find what makes these so difficult to drive though. Do they have a very high impedance or are they just very inefficient?

 

[davidsh]

  I can't find what makes these so difficult to drive though. Do they have a very high impedance or are they just very inefficient?

You got it all wrong. Very, very high impedance, but that's not the issue. They work almost purely by voltage swing, we are talking about amps that should be able to deliver 400+ vrms to drive them properly.
 
They work from the electrostatic principle, like electric fields, not magnetic fields. So you charge up the diaphragm with enough voltage generating 200-1000 volts of static electric charge, then you sandwhich it between 2 plates (stators), through which you pass the electrical sound signals usually amplified with a gain of some 55-60dB.

 

[Plecto]

I see. So there are special types of high voltage amplifiers meant for these headsets?

 

[davidsh]

  I see. So there are special types of high voltage amplifiers meant for these headsets?

Yes, I have myself been thinking about a solution involving an output transformer design tapping high voltage on the tube side for electrostats and having the headphone and/or speakers on the down-transformed side as you usually would do it, but I simply don't have anywhere near the knowledge to make something like that from scratch if it even makes sense in the first place.
 
There are also adaptors for electrostats, using transformers to amplify the signal from a speaker amp. One example is the woo wee, but Stax made many of those back in the days.

 

[kramer5150]

This thread might be useful for you.  Not sure how accurate the data is however.
 
http://www.head-fi.org/t/668238/headphones-sensitivity-impedance-required-v-i-p-amplifier-gain