[seaninbrisbane]

Hi there.
 
I am hoping someone might be able to guide me in the right direction.  I've been trying to find information on connecting a pair of headphones to my Copland CTA305 preamp, which I use with a set of active speakers.  Rather than buy a dedicated headphone amp with its own volume control, I was wondering if there was such a thing as a 'headphone power amp'?  I love the sound of my tube preamp and would like to hear it through headphones.  I realise that I could just add a regular headphone amp to the 'tape-out', but would appreciate any other suggestions.  I will be looking to buy Audeze LCD2 headphones with whatever solution.
 
Thanks in advance,
 
Sean

 

[jaddie]

Any amp designed to drive headphones will have a volume control, sorry.  But that's not really a problem.  What you want is a headphone amp with a gain of 1 (low gain), find the sweet spot on the volume control of your Copland and adjust the headphone amp for your average listening level there.  Then don't touch the headphone amp volume control.   

 

[uchihaitachi]

Quote:

Hi there.
 
I am hoping someone might be able to guide me in the right direction.  I've been trying to find information on connecting a pair of headphones to my Copland CTA305 preamp, which I use with a set of active speakers.  Rather than buy a dedicated headphone amp with its own volume control, I was wondering if there was such a thing as a 'headphone power amp'?  I love the sound of my tube preamp and would like to hear it through headphones.  I realise that I could just add a regular headphone amp to the 'tape-out', but would appreciate any other suggestions.  I will be looking to buy Audeze LCD2 headphones with whatever solution.
 
Thanks in advance,
 
Sean

You can use power amps with headphones, via a DIY method, I have tried it before and it works. http://sound.westhost.com/project100.htm
 
But why would you want to? 

 

[jaddie]

Quote:

You can use power amps with headphones, via a DIY method, I have tried it before and it works. http://sound.westhost.com/project100.htm
 
But why would you want to? 

The DIY solution significantly raises the source impedance by more than 100X over a good headphone amp.  It will get you sound, perhaps at the right level, but not a great solution.

 

[uchihaitachi]

Quote:

The DIY solution significantly raises the source impedance by more than 100X over a good headphone amp.  It will get you sound, perhaps at the right level, but not a great solution.

+1

 

[seaninbrisbane]

Quote:

You can use power amps with headphones, via a DIY method, I have tried it before and it works. http://sound.westhost.com/project100.htm
 
But why would you want to? 

Thanks for your reply - I'm not considering using a power amp designed for speakers, I wanted to know if there was a power amp specifically designed for headphones.

 

[jaddie]

The reason you won't find a headphone power amp is that the typical headphone amp application is between a portable player's line output (usually and preferably without volume control) and headphones.  There are millions of users that need this.  That means there needs to be a volume control somewhere in the chain, and it's easiest to put it in the headphone amp.  There's a performance advantage that way too.  That doesn't mean it won't work for you though.  You simply adjust the headphone amp volume control for best level when your preamp is adjusted for best level too. 
 
Your situation is not unique, but makes up a very small percentage of the market, which is why you don't find a headphone power amp only.

 

[seaninbrisbane]

That makes perfect sense - thank you. I always assumed that the head amp would be connected to the tape out of my preamp, but I suppose that means that I would need to have the preamp powered on to listen to the head amp.  I think I'll be considering a more conventional setup.  Thanks again.

 

[seaninbrisbane]

Just a thought - I have a Copland power amp (CTA520, 125wpc) that I'm not using at the moment.  Would this be suitable to power low efficiency headphones?  What type of adapter would I need?  Thanks again.

 

[jaddie]

125wpc is roughly 1000x more power than is needed.  Power amps generally have at least 15dB of voltage gain, usually more, which is also too much.  The typical adapter is a resistive pad using two resistors per channel.  The Grado solution is here, but looking at the circuit, the result will still probably be too much volume for some headphones.  The loss shown is 20dB.  Change the 20 ohm resistors to 100 ohm, and they don't need to be 2W, 1 watt would be fine, the result is 34dB of loss.  What you need depends on the amp gain and headphone sensitivity.
 
A commercial adapter (which would be a much better solution, but not a good functionrice ratio) is here.
 
This is really a DIY project, if you're up to it.  You can buy the resistors and wire something up for very little cost, and use your biggie-sized amp.  Or buy a real headphone amp.
 
 
 
edit: fixed resistor and gain figures.