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Old 9th January 2009, 07:01 PM   #1
Sponkii is offline Sponkii  Denmark
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Default Amplifier for headphones

Hey..

Im thinking of making a small portable headphone amplifier.

voltage source is going to be 2 lithiumbatteries 2X9v.

and i think the chip is going to be either a TL071CP or NE5534P..

wich would you recomend..

the ohm value of the headset's is 32ohm and 50.. the 50oms is a 3.5W... Source is a PC, mobilephone, and Ipod..

but i think that around 1watt of music it JUST fine..

i would like it to be as clear a possible..

any help..

another thing is it possible to parallelle opamps?.. i know that my opamps is around 500mW max.. and at 9v the headphones draws a little under 1 watt.. so two chips per channel or is that rubish, then rather make a transistor optputstage ?..
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Old 9th January 2009, 07:24 PM   #2
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Default Re: Amplifier for headphones

Quote:
Originally posted by Sponkii
voltage source is going to be 2 lithiumbatteries 2X9v.
No such voodoo.

Quote:
Originally posted by Sponkii
but i think that around 1watt of music it JUST fine..
1w through your headphones will leave you permanently deaf, if they don't fry first.

Quote:
Originally posted by Sponkii
...or is that rubish...
Yes, nearly everything you said.





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Old 9th January 2009, 08:26 PM   #3
DcibeL is offline DcibeL  Canada
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Oh my, I recommend some (a lot) more research...

Start by reading datasheets, they include the max output current from which you can calculate power. Speaking of power, any reference you have made to power is completely out to lunch, to say the least.

If you want a good headphone amp, try something like LM4562 and a BUF634. See figure 4 and 5 in the BUF634 datasheet. But please, more research is necessary to understand what you are doing, and to get the most of your project.
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Old 9th January 2009, 09:44 PM   #4
mjf is offline mjf  Austria
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hello.
i think a ne5534(or ne5532) can drive a 600ohm headphone.
with a 30 ohm system perhaps look at lm 386 or something else........
greetings............
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Old 10th January 2009, 08:52 AM   #5
Igla is offline Igla  Slovenia
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I have just build ''cmoy'' pocket headphone amp with OPA2132. I have used another opamp as voltage splitter to get +-4.5V from 9V battery.
It has all the power you need to drive almost any headphones. I also implemented bass boost circuit in the feedback loop with a switch to turn it off or on. It is still prototype but plays sweet with planty of power.
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Old 10th January 2009, 10:46 AM   #6
Igla is offline Igla  Slovenia
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You can easily power your headphone chip amp from two 9V batteries to get +-9V
;look the photo of my first prototype.

1W of power would be too much; you need no more then 50mW for most headphones and you can get this power from OPA 132, OPA134, OPA227 and similar. I think TL071 would be good just to check if the amp is working properly. This chip is a poor performer.
Check this link: http://tangentsoft.net/audio/opamps.html
You will find there all the info of most opamps.

Do some research and type in Google cmoy and cmoy bass boost.
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File Type: jpg cmoy v1_11.jpg (98.3 KB, 728 views)
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Old 10th January 2009, 11:05 AM   #7
AndrewT is offline AndrewT  Scotland
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Hi,
most headphones have a sensitivity between 90dB/mW and 100dB/mW.

If we take the lower sensitivity and apply a 1mW signal the phones will be very loud. I would suggest too loud for average level music.

Apply the normal +20dB overhead for transient peaks, that will give 110dB from just 100mW.
The 100dB phones will require only 10mW to achieve the same targets.

The difficulty is that headphones come in a very wide range of impedances and this makes a universal headphone amplifier more awkward to specify. High enough voltage for 300/600ohm phones.
High enough current for 8/16ohm phones.
But, with either, the design must be low noise, effectively -120dB relative to your required maximum power.
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Old 10th January 2009, 11:22 AM   #8
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Default Re: Amplifier for headphones

Quote:
Originally posted by Sponkii
and i think the chip is going to be either a TL071CP or NE5534P..

wich would you recomend..
If you use the NE5534 look for the audio type, i. e. NE5534A.
Did you check http://www.headwize.com/projects/cmoy2_prj.htm?
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Old 10th January 2009, 05:34 PM   #9
Sponkii is offline Sponkii  Denmark
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no not if it is rechargable.. if rechargable it is 10.8V...

the one watt req, is just to try it out, i sure know that is insane to crank it up to one watt with the headphones on your head..

DcibeL

the equations i have used is for eksampel from wiki for RMS voltage on sine waves.. so it might not be right..
- could you send me a link to a side with better equations?..

Igla
Ill give it a try look ..
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Old 10th January 2009, 09:31 PM   #10
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Quote:
Originally posted by Sponkii
no not if it is rechargable.. if rechargable it is 10.8V
There is no such thing as a single 9V or 10.8V lithium cell (rechargeable or not). To get 10.8V you need three lithium cells in series.
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