headphone amp questions

[hendriko]

hey hey
i got a couple of questions about these, each of them building up on the previous so...here we go

1. how many (tube) watts would you need for a tube amp to not blow your ears out but still be able to rock out?
2. could you make a battery powered tube headphone amp?
3. is it possible to wire a small speaker to that amp and still make pre and poweramp available for headphones

cheers, and thanks!

[rockgardenlove]

1-Like...quarter watt?
2-Not really.  Heaters draw alotta current.
3-Sure.

IMO a tube headphone amp totally isn't worth it.  Just build a Ruby or so.

[hendriko]

yea i kinda figured that....was just some idea i had - would have been awesome if it worked but i didn't expect it:P

cheers

[Pushtone]

Center of the universe for DIY headphone amps.

See CMoy amp projects although there are other topologies.

http://www.headwize.com/projects/


This link has some cool discussions as well but more commercial product oriented
http://www.head-fi.org/

[Pushtone]

Google found a CMoy tutorial


http://tangentsoft.net/audio/cmoy-tutorial/

[Mark Hammer]

Required power will depend on the headphone efficiency.  Headphones are like speakers in that some will give lots of loudness with less power, and others need even more power to achieve even modest listening levels.  You will find a wide variety of stereo power-amp chips intended for headphone amplification in everything from old Walkman tape players to discman and MP3 players.  Some of these go as low as a paltry 50mw on a pair of AAA's into a 4ohm load, and some are intended to pump out a half-watt or more on 12v or more.  In many respects you need to start your quest by identifying what headphones you plan on using, finding out what their efficiency is, and selecting the amp around that.  You should also build in some sort of protection against excessive listening levels.  Rocking out is one thing, damaging your hearing by rocking out quite another.  Something as seemingly benign as 50mw into efficient headphones applying their energy at close distance to your eardrums is a lot more dangerous than you might think, if you are used to playing through 100W stacks.  Kinda like the difference between a 22 calibre bullet aimed at your head from 20ft and a 44-calibre bullet aimed at your head from a mile away.  The .44 slug might sound like the more deadly but all flying things lose momentum and energy over distance, and sound is no different.

I dispute the notion that a tube amp could not be run off batteries, since there are those Vox Cool-Tube things, and all manner of low-voltage tubes that would surely deliver some reasonable lifespan on an octet of D-cells.  The bigger question is whether that lifespan is too confining in some way, and whether the quality of headphone and program material you plan on using justifies going to the trouble of using tubes.  Cheap headphones, and distorted guitars are not going to sound THAT much better with low-voltage tubes doing the work.  If it was acoustic music and electrostatic headphones...maybe.

As for question 3, it is always possible to wire up a variety of simultaneously available "taps" for the signal.  You tend not to see them in practice because they are usually mutually exclusive in how people use them (why have line out, speakers and headphone all at once?).  However, arranging for plugs inserted at point X to cancel the signal reaching downstream is always possible.