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Increased Impedance/Resistance = Low Volume

post #1 of 17
Thread Starter 

Hey, i use 32 ohm sennheiser hd407 and creative x-fi go pro sound card. (i dont know the soundcard's impedance, if you find it i'd be very grateful)

I was having buzzing at bass, so i decided to make a 100 ohm adapter cable. It worked to fix the buzz, but cut the volume down like %50. So, is there any way to increase volume, besides amplifiers?

If i make a 50 ohm cable instead of 100 ohm, will it work too with the equipment which i said up there?


Edited by NAeternal - 7/15/12 at 8:06am
post #2 of 17

Are you listening at a fairly high volume?

You may be running out of power?

The 50 ohm resistor will still decrease the volume somewhat.

post #3 of 17
Thread Starter 

Can you compare 50 ohm and 100 ohm adapter cable, (assuming 50 ohm will fix the buzzing too) at volume base

post #4 of 17
Thread Starter 

Well, looks like noone responses, i will try to build 50 ohm adapter cable tomorrow and share the results.

post #5 of 17

Sorry man, if you really want to increase the volume (assuming you need more power) you need to buy an amp.

 

Is your X-Fi a little USB key with a headphone jack?


Edited by Chris J - 7/15/12 at 5:20pm
post #6 of 17
Thread Starter 

yes it is, but without the resistance imported, the volume level is great. (i mean the direct connection with headphone's jack, sound card's output)

it is just the addition of the resistance (100 ohm), cut down the volume like %50. 

i was wondering, if i'd use 50 ohm resistance cable, instead of 100. would it be still the same? if not how much volume gain i'd get, compared to 100 ohm ones.

edit: well, i find out there are no 50 ohm resistors, so let's say 47 ohm or 56 ohm. doesn't matter actually, you got the idea.


Edited by NAeternal - 7/16/12 at 1:57am
post #7 of 17

Yes, with 47 or 56 ohm you will loose a lot of volume.

post #8 of 17

(Voltage Squared)/Resistance = Power.  An impedance of 132 ohms will receive about 24% as much power.  That's about -6.2 decibels (65% perceived volume).  To achieve a perceived 50% volume, 10 decibels must be lost, which would require a cable with 288 ohms (10x the resistance, or 1/10th power).  A 50 ohm cable will put you at -4dB (76% perceived volume).


Edited by iZMXi - 7/16/12 at 4:26am
post #9 of 17
Thread Starter 

Well, iZMXi that was the answer which i needed, thank you so much.

So, is there any solution to boost the volume up, besides amps cause they are kind of expensive in my country

Another question

would a fiio e5 (in example) make the perceived volume up from %65 to like %90 or something?

post #10 of 17
Quote:
Originally Posted by iZMXi View Post

(Voltage Squared)/Resistance = Power.  An impedance of 132 ohms will receive about 24% as much power.  That's about -6.2 decibels (65% perceived volume).

 

That is not entirely correct, since it is the power into the headphones that matters, the rest just heats the resistor. Therefore, the real volume reduction is 20 * log10(32 / 132) = -12.3 dB.

post #11 of 17
Thread Starter 

Well, that means 4.5 db difference between 47 ohm and 100 ohm resistor, still not that good?

Actually my headphone vol is good @ %100, but it is the feeling of "i can't increase the volume more" that bothers me.

Lets hope 79 ohm (-7,84954226 db) is gonna be enough for me, and still fix the buzzing ofc. 

one last question for me and the people that want an enlightenment for this matter

my current resistor is 100 ohm 11 watt, if it was 100 ohm 2 watt, would be there volume increase (more power to the headphones)?


Edited by NAeternal - 7/16/12 at 2:18pm
post #12 of 17

No way.

They are both still 100 ohm resistors. Sorry!

In your case, it is the resistor's value that is of significance. Not the resistor's power rating (it's Watt rating).

Headphone amps usually only output a few thousandths of a Watt,  i.e. much less than one Watt.

 

If you can't increase the volume any more with zero resistance, adding more resistance will only make things worse.

 

Sounds like you need an amp.

post #13 of 17
Thread Starter 

Well, i bought a 47 ohm 2 watt resistor today

Removed the 100 ohm one and imported 47 one, it means -7.8 db decrease in volume. [20*log10(32/79)]

So i added +7.8 db from soundcard driver's equalizer. Same volume output as the zero resistance, with no distortion. Fixed the buzzing at the bass problem that happens with zero resistance too. 

Win!


Edited by NAeternal - 7/17/12 at 9:15am
post #14 of 17

well you will get distortion, maybe you just cant hear it, or havent come across any tunes yet that are hot enough that your increase in level digitally clips the onboard amps input. your USB thingo is limited to the voltage USB can supply, which is a rather paltry 5v

post #15 of 17
Thread Starter 

Well, yes there is a distortion. So only thing left is buying an amp.

But i think it wont worth for a 50 $ usb soudcard.


Edited by NAeternal - 7/17/12 at 1:03pm
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