[ericj]

Someone's got a few NOS Pioneer JB-21's on ebay:

http://cgi.ebay.com/ws/eBayISAPI.dll...m=260162936107

This is a box that lets you hook up your headphones to the speaker jacks on your favorite speaker amp.

This little box was designed for pioneer's "high polymer membrane" piezoelectric headphones but should work for any 'phones - as long as you are very careful with the volume knob.

It probably contains voltage dropping resistors and likely overvoltage protection as well, but, can't say for sure.

Since the Pioneer piezos are a capacitative load they're not as easily damaged as moving coil headphones, and their power handling limitation is literally documented as "30 volts".

If it doesn't, it's certainly a good place to start if you're someone like me who's been meaning to build such a box.

Hook this puppy up to your old Rotel arc welder and never again think twice before telling someone "Yes, my headphone amp has enough power".

 

[Fitz]

The "power" of a headphone amplifier has nothing to do with anything like its voltage swing, current delivery, or slew rate, but rather in how much prestige it has and how expensive it looks. So I don't think this will do anything about having "enough power" 'round these parts.

Both of my speaker amps have the headphone jacks tied to the speaker outputs... one with series resistors, the other with a proper voltage divider (but it still colours the sound slightly on some of my phones). They do make pretty good amps for high impedance phones though.

 

[JadeEast]

Thanks for the heads up.
I've been meaning to make one as well but I've always ended up with a mess of resistors and alligator clips that have done the job but looked like crap.

 

[Ruckus]

Fitz!!

Is that Lain with a guitar in your avatar?

 

[Fitz]

Why yes it is.

 

[Fing]

Is there a possibility of frying your headphones doing this, or is it all sorted in that 'junction box'?

 

[facelvega]

as ericj implies up above, we don't really know what's inside this box, namely whether there are resistors or overvoltage protection, but since the box is meant to drive Pioneer's old piezos, I'm guessing even if it's got them it could potentially fry your headphones. It's a common sense thing, though; start low and don't go up to excruciating volume, and you're just as safe as with any other amp. Just don't accidentally flip the volume of a big amp up to full while the headphones are plugged in-- but you probably don't want to do that even if there is voltage protection.