OT: Portable headphone amplifier

plasmavideo wrote on 8/18/2006, 12:15 PM

We have a need for some type of small, preferably battery operated, headphone "booster". We need to amplify the output of some laptop computers that we use for editing in the field. The level coming from the computer headphone jack is not loud enough for ambient high noise conditions in our ENG trucks.It would need to have 1/8 inch input and outputs and a level adjustment. I've seen that type of device before at Radio Shack, but I can't find them anymore.

Do any of you know a source for a device like this? I've found a personal audio monitor from Rolls, which includes a mic input and is intended for "sing-along" to a line input, but I'm hoping there is something more appropriate. I've also found a number of headphone amps with multiple headphone outputs, but these are all AC powered. Ideally, a small battery operated amp would be the ticket, so that editing can be done just about anywhere, either in or out of the trucks.

Thanks.

Tom

Comments

johnmeyer wrote on 8/18/2006, 1:27 PM

Others may have an idea where to get an amplifier. If they don't have a good suggestion, another solution is to get headphones that are more sensitive. There is a HUGE difference in volume between different headseats. Also, obviously, those with enclosed earphones can also make a big difference when dealing with ambient noise, and are probably a good idea with or without the amp boost.

This product from Radio Shack might also provide a solution:

Siig® USB SoundWave 7.1 Audio Adapter

[Edit]

This device turned up all over the place when I did a Froogle search:

Boostaroo

farss wrote on 8/18/2006, 1:53 PM

John's suggestion re getting more sensitive cans is a good one. We use the ones sold on eBay under the Takstar name. Well over 10dB more sensitive than the 7506 from Sony and way cheaper, almost disposeable.
We also have the Rolls unit, works very well and it's loud. Also great for boom operators.
Bob.

plasmavideo wrote on 8/19/2006, 6:20 AM

Thanks for the suggestions. The boosteroo looks like the device RadioShack used to sell. I had "googled" and looked at that, but the one supplier I checked with said it's not available anymore - however as you said, John, it's everywhere on the internet! Looking at the specs it says: :"output 40 mW per channel". I'm not sure how much the laptops put out, but I can easily check with my test gear. That might not be any more than we already have

The Siig USB device looks intriguing. I'm not sure that it would offer any more output than the onboard sound chip, but for the price it's worth experimenting with. Honestly, I hadn't even given USB a thought! We are using Grass Valley NewsEdit configured laptops and I would need to see if USB audio would work in the GV configuration.

Yeah, we are using the Sony 7506 (and one of their other similar models) - one of my favorite earphones. I'll look into the ones you mentioned, Bob.

I also had a brainstorm last night that maybe a better idea than blasting their eardrums with more sound is to try a pair of the active noise cancelling earphones, as ambient noise is the real problem. Maybe I can find a pair of those that's also more sensitive than the Sonys and kill two stones with one bird.

riredale wrote on 8/19/2006, 11:41 PM

I've been casually looking for an in-line headphone booster to use with a portable DVD player that I sometimes take on flights. The ambient background noise makes certain commercial DVDs almost impossible to hear properly, given their aggressive use of Dialog Normalization.

There are several such units on display at the local Fry's Electronics store. Typically they use a couple of AA cells and are long and thin. The cost about $30, which is why I haven't bought one yet.

craftech wrote on 8/20/2006, 4:24 PM

Actually they are quite simple to build. You might want to try building a simple CMoy amp using Tangent's directions. An Altoids tin makes a nice shielded project box for the amp. If you run into a problem there is lots of help available on the Head-Fi DIY Forum.

John

busterkeaton wrote on 8/20/2006, 4:34 PM

You don't necessarily need noise cancellation, if you have headphones that block ambient noise.

Check out the Sennheisher HD280's
http://www.headphone.com/products/headphones/sealed-and-noise-canceling/sennheiser-hd-280-pro.php
These block a lot of noise and are low impedance meaning you can drive them easily from a laptop or an ipod.

Correct me if I'm wrong, but I believe noise cancellation works best on predictable background noise, ie jet engines, AC vents, etc. Something where the noise is consistent. But say something like traffic noise with horns honking, engines revving and brakes screeching wouldn't get blocked out because the headphones can keep up with short random noises.

craftech wrote on 8/20/2006, 8:44 PM

and are low impedance meaning you can drive them easily from a laptop or an ipod.
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Still no comparison to a headphone amp. They make a noticeable difference in the sound using any headphone.
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Correct me if I'm wrong, but I believe noise cancellation works best on predictable background noise, ie jet engines, AC vents, etc.
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Noise cancellation works by using a small microphone to pick up the noise and then electronics to phase cancel the sound. Works best with a constant frequency. That means it will do little or nothing to block out traffic noises, people talking, or even crickets. Low pressure waves are a problem as is electromagnetic interference from things like mobile phones. Sometimes they generate their OWN noise because of the microphone.
A homebuilt headphone amp is an ideal solution.

John

riredale wrote on 8/20/2006, 10:04 PM

Actually, I think it might be most accurate to say that active noise cancellation works best over a certain frequency range, typically centered on about 1KHz. I remember a few years back when I flew a light plane a lot I tried out a pair of Lightspeed headphones. They relied on high frequency noise elimination entirely through passive means, i.e. the liquid ear seals and the plastic shell. But lower frequency outside noise could be sampled, inverted, and then added back to the signal going to the transducers in order to minimize it. I think the inability of active noise cancellation at higher frequencies had much to do with trying to model a typical ear canal and ear shape; what might have worked great for one user would be horrible for another. Fortunately for piston-engine pilots, the primary noise generation was the splats of air against the windscreen from the prop, which just happened to be at about 1KHz for a two-blade prop (I think; it's been a while). So active noise cancellation worked well in this instance.

These days when I fly commercial I don't rely on active noise reduction at all any more--I use the $60 Shure in-the-ear transducers with the expanding foam tips. Absolutely wonderful. I would gladly sit next to a screaming infant if it meant extra legroom--that's how effective these things are.