[Sambones]

Long story short, I tried a 12v power supply with my Headroom Total Airhead, and it started smoking. I didn't really listen to it much before then on batteries, but it now works fine, but gets extremely hot. There's a spot on the bottom, right between the rear feet, where the plastic casing is melted, and another much smaller one near the front foot and the 1st headphone socket. I can get pics tomorrow.

For kicks and giggles, here's the long story: I just bought a headroom Total airhead off someone here for $50, and it worked fine. Now, I read somewhere that you can drive an AKG K240 with one, using a 12v power adapter. I see that some sextetts are going for $60 to $80 on that auction site.....so 10 minutes later I've got a 12v PSU with the end clipped off and replaced by a socket that fits, and smoke pouring out of the airhead--er, pouring may be a bit dramatic.

So, beating myself up for doing that all today, I figured I'd pick up some new batteries as a last-ditch "I'm not an idiot" check. So, I put em in, and I've only got the left channel, and that's heavily clipping. It's still playing while I swap it out for my IEM's (cheap headset deally from Newegg.com), and I have the same problem. I kept them on for a bit, I guess to punish myself, when a couple minutes later it clears up quite suddenly!

So, I'm still listening, and the airhead is right under my arm, and getting quite hot. It's only using 4 AAA batteries, just like normal, and I don't see smoke, but those batteries are friggin' hot, and I smell something burning.

So, anyone have any ideas what would do that? Did I damage it with my power-adapter? Does it normally get real hot, and the extra juice and time just make it melt some plastic?

 

[jamato8]

Is this for real?

Sit back, look at what you have written and I bet you will come up with the answer to your question.

 

[chaosfayt]

yea the plastic melting is normal, its supposed to melt, that is why its called a liquid-state amplifier . In fact some users have reported that once all the plastic melts and they keep the total airhead in a bottle it really sounds great!

 

[Pageygeeza]

Sarcasm a-plenty.

 

[Sambones]

Yeah, I noticed the sarcasm. But, seriously, does running 3 volts over spec (admittedly, that is 33%) cause that much havoc?

 

[StevieDvd]

Quote:

Originally Posted by Sambones /img/forum/go_quote.gif Yeah, I noticed the sarcasm. But, seriously, does running 3 volts over spec (admittedly, that is 33%) cause that much havoc?

4 AAA batteries would be 4 x 1.5v. So that's 6v (100%) over spec is it not!!

 

[OPTiK]

You also have to pay attention to current.

 

[Tyll Hertsens]

I got a fire hose you can take a drink from if you'd like.



C'mon dude, manual or some dumb@ss on the internet, who ya gonna believe?

 

[qusp]

^^ what he said, voltage is only half the energy rating, amperage is what you really have to watch and you can bet your wall adapter has FAR MORE current than the 4 x AAA

most likely you have cooked the regulator and caps at the very least
LOL yeah it does sound much more liquid when its melted.

 

[n_maher]

The Airhead manual actually states that you can use anywhere from a 5 to 12VDC power supply provided that it has a rating greater than or equal to 200mA and the appropriate plug. I'm guessing that the power adapter used was putting out a lot more than 12VDC.

 

[Tyll Hertsens]

My bad then, Nate. Sorry Sambones.

But yeah, if it says 12V on an unregulated supply, it's prolly putting out more like 15-16V unless it's loaded down.

 

[n_maher]

Quote:

Originally Posted by Tyll Hertsens /img/forum/go_quote.gif My bad then, Nate. Sorry Sambones. But yeah, if it says 12V on an unregulated supply, it's prolly putting out more like 15-16V unless it's loaded down.

I've had 12VDC supplies put out over 18VDC when lightly loaded so it's very much a game of give and take and the bottom line is that if you don't know what you're doing you should probably ask before just blindly plugging something in.

 

[bdr529]

Quote:

Originally Posted by qusp /img/forum/go_quote.gif ^^ what he said, voltage is only half the energy rating, amperage is what you really have to watch and you can bet your wall adapter has FAR MORE current than the 4 x AAA most likely you have cooked the regulator and caps at the very least LOL yeah it does sound much more liquid when its melted.

Not really in this case, there would only be a problem if the rated current was too low. The current value you see on the wallwart is the maximum it can handle before getting all wacky on you and goes out of spec.

 

[n_maher]

Quote:

Originally Posted by bdr529 /img/forum/go_quote.gif Not really in this case, there would only be a problem if the rated current was too low. The current value you see on the wallwart is the maximum it can handle before getting all wacky on you and goes out of spec.

I think you're making a big assumption, which is that the supply is regulated and most wallwarts are not. For unregulated supplies the voltage given is usually the expected voltage output under full load. While you should never exceed the current rating it is highly likely that if you under-load the supply you will see significantly more voltage on the output.

Example: if you have two "12VDC" wallwarts and one has a current rating of .2A and the other a rating of 1A and you load both with the same .2A load you'll likely get close to 12V out of the first and several volts more out of the second. Whether or not your device can handle this overhead is impossible to guess without more information.

 

[bdr529]

Yeah, that makes more sense with what happened here.