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Old 22nd August 2012, 12:27 AM   #1
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Default Want to build Unusual high powered battery powered headphone amp (and equalizer)

I want to build a kind of unusual battery powered headphone amp.

The design parameters are:
Significantly more power than a normal headphone amp
(by maybe 10 or 20 db)
(for 10 to 100 ohm or so headphones)

to be powered by 4 AA rechargables if this can be a high enough voltage source to achieve this power level.
(If not, then perhaps 4 AA with a voltage booster to ~12 volts -- to avoid carrying around TOO much weight in batteries)
(even if 4 AAs straight works, the ability to tolerate also being run by a 14.4 volt source as an alternate would be nice but not required)
but in any case, a single ended supply ...

CHEAP CHEAP CHEAP

Easy, minimum component count (chip amp with minimal required support components)

(optional but desired would be the ability to add some active eq ... my mp3 player has NO eq, and some would be nice to have)

Why do I want to do this ...
I work in an industrial area, (under the flight path of an airport no less) and I want to play my mp3 player while taking a walk at lunch.
Needless to say there is a LOT of ambient noise.
Think airplanes flying overhead every 3-5 minutes, trucks galore, jackhammers, surface grinders etc ....

I have found a solution that works surprisingly well is to insert foam earplugs
(about 30-35db attenuation) and then turn the mp3 player WAY up.
The earplugs are not flat, but attenuate treble more than midrange, but it's possible to re-equalize the mp3s to compensate, which sounds quite natural ...

But the MP3 player just cannot get nearly enough volume to be anywhere near satisfying without being driven into hard clipping.

(the average power available when driven this hard seems to be ok though already ... (i.e. when driven hard enough that the peaks are distorting quite badly, the "average" level is just barely loud enough to be acceptable, )
(I suspect the re-equalisation contributes to this as well, since the extreme high end is boosted by up to 18 db)

I realize that doing this risks blowing my headphones ... (but not my ears since they are protected by the 30 db attenuation of the earplugs ...)

As mentioned before, re-equalization is required... I can do this via re-equalizing the source mp3s, but if I can find some eq circuits to do this, it would be nice to not have to make special MP3s just for this.
I would know how to do the eq using opamps, but they generally are run off of double ended supplies, so some hints as to doing eq using op amps that work well on a 5 volt single rail supply would be nice too.

so which chips amps (and which opamps for eq) would be best for this project
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Old 2nd September 2012, 07:44 PM   #2
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Try to use in-ear headphones and wear some ear muffs against the enviromental noise.
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Old 3rd September 2012, 05:29 AM   #3
qusp is offline qusp  Australia
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just use decent in ear monitors, these can produce ~26db passive attenuation
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Old 5th September 2012, 01:25 PM   #4
jcx is online now jcx  United States
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Default no need to build anything

well sealing iem, DAP with digital eq - be sure to listen a safe level - do not turn up to overcome environmental noise if you value your hearing

HeadWize - Article: Preventing Hearing Damage When Listening With Headphones (A HeadWize Headphone Guide)

passive or active supra aural sound attenuting noise canceling headphone or ear muff over the iem for extreme attenuation

but any headphone, iem will cause some mechanical "microphonics" if you're walking
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Old 10th September 2012, 02:41 AM   #5
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Quote:
Originally Posted by franzm View Post
Try to use in-ear headphones and wear some ear muffs against the enviromental noise.
I've tried various in-ear headphones and none of them seem to fit my ears and be comfortable.

and while the in ear headphones offer some attenuation, none of them attenuate the environmental noise NEARLY as much as the foam earplugs.

The solution of the foam plugs and fairly good headphones (Sennheiser PX 100-II) works GREAT, but just isn't quite loud enough ...
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Old 10th September 2012, 03:17 AM   #6
kevinkr is offline kevinkr  United States
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I have a pair of the slightly older PX-100 and have found that they have extremely poor isolation of environmental noise - I use mine at the gym and work and can hear all of the exercise machines, loud local conversations, not to mention the huge fan at the other end of the gym - my iPod is powerful enough to overcome the ambient noise at some risk to my hearing.

I'd recommend getting a pair of headphones with better isolation or even a pair of noise cancelling headphones rather than trying to build a high power headphone amplifier which might fry your headphones under the described conditions.
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