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help !!! some questions about adding 75 Ohm quality resistors to porta pro - Page 2

post #16 of 22
1/24/11 at 12:25pm

People buy amps specifically for low impedance headphones because not everyone likes the way headphones sound with resistors. Even headphones that perform well with the resistors show a point of diminishing returns or too much of a good thing when adding more. An amp like the crack already has a bit of output impedance (about 60ohms If memory serves) BUT has difficulties driving a low impedance load.

 

Crack+HD600/650 was a realllly nice pair. 

 

Im not sure which way Id go between the DT770/D2000. I think that the D2000 has a slight edge for sound, but it dosnt isolate very much at all. 

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post #17 of 22
1/24/11 at 1:40pm

Does the "style" of the D2000 vary much vs the Beyers? I want something that fills a different niche than my Senns and the Sextett (Sextett hasn't arrived yet though, so no impressions yet).

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post #18 of 22
1/25/11 at 8:09am

I would normally recommend "whatever resistors you happen to have handy" but this usually comes with a reply of "what would be better"?

A 100 to 250 ohm dual linear pot would be better so you can tune the sound to your preferences, but since 75 is the number written in the bible by the lord 75 is what it is. Texas components bulk foil vishay resistors are well regarded.


 

Wow those things are expensive resistors. I guess that would be the ultimate impedance adapter. ;-)

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post #19 of 22
1/25/11 at 8:12pm

well guys, how does adding a resistor affect the sound in general?

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post #20 of 22
1/25/11 at 8:17pm

From Meier Audio

 

If your headphone sounds sharp and aggressive, you might consider increasing the effective output impedance of your headphone jacket. The simplest method is to place an adapter between headphone jack and headphone as shown in the figure. The adapter has a resistor placed in series with each audio-channel of the headphone. The effective output impedance is the sum of the output impedance of the jacket and the value of the resistor

(Ro + Ra).

Note: The value of the resistor should not be higher than 3 till 4 times the impedance of the headphone drivers. Further increases do hardly effect sound.

 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 

 
 

 

 If your headphone sounds dark and muddy and is driven by an amplifier or receiver, you might try to decrease the effective output impedance. This also can be done by an adapter, but this time the resistors (with value Ra) are placed in parallel with the audio-channels of the headphone. The effective output impedance of the combination of headphone jacket and adapter becomes (without proof)

Ro * Ra / (Ro + Ra).

The value of the resistor should be 0.1 .. 1 times the impedance of the headphone drivers to have a noticable effect. However, be aware that with very low values of Ra your amplifier has to deliver a much higher current signal to obtain the same sound pressure. This might have some adverse effects on sound quality by itself. Also be aware that the resistors should be able to dissipate enough heat!
 

 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
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post #21 of 22
1/26/11 at 8:35am
Thread Starter 


 

Quote:
Originally Posted by RuiCanela View Post

From Meier Audio

 

If your headphone sounds sharp and aggressive, you might consider increasing the effective output impedance of your headphone jacket. The simplest method is to place an adapter between headphone jack and headphone as shown in the figure. The adapter has a resistor placed in series with each audio-channel of the headphone. The effective output impedance is the sum of the output impedance of the jacket and the value of the resistor

(Ro + Ra).

Note: The value of the resistor should not be higher than 3 till 4 times the impedance of the headphone drivers. Further increases do hardly effect sound.

 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 

 
 

 

 If your headphone sounds dark and muddy and is driven by an amplifier or receiver, you might try to decrease the effective output impedance. This also can be done by an adapter, but this time the resistors (with value Ra) are placed in parallel with the audio-channels of the headphone. The effective output impedance of the combination of headphone jacket and adapter becomes (without proof)

Ro * Ra / (Ro + Ra).

The value of the resistor should be 0.1 .. 1 times the impedance of the headphone drivers to have a noticable effect. However, be aware that with very low values of Ra your amplifier has to deliver a much higher current signal to obtain the same sound pressure. This might have some adverse effects on sound quality by itself. Also be aware that the resistors should be able to dissipate enough heat!
 

 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 


but for 1 driver, there re 2 wires out + and - label, which one is considered the signal wire to be added resistors ??

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post #22 of 22
1/26/11 at 9:07am
Quote:
Originally Posted by khanhhoa1912 View Post


 

Quote:
Originally Posted by RuiCanela View Post

From Meier Audio

 

If your headphone sounds sharp and aggressive, you might consider increasing the effective output impedance of your headphone jacket. The simplest method is to place an adapter between headphone jack and headphone as shown in the figure. The adapter has a resistor placed in series with each audio-channel of the headphone. The effective output impedance is the sum of the output impedance of the jacket and the value of the resistor

(Ro + Ra).

Note: The value of the resistor should not be higher than 3 till 4 times the impedance of the headphone drivers. Further increases do hardly effect sound.

 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 

 
 

 

 If your headphone sounds dark and muddy and is driven by an amplifier or receiver, you might try to decrease the effective output impedance. This also can be done by an adapter, but this time the resistors (with value Ra) are placed in parallel with the audio-channels of the headphone. The effective output impedance of the combination of headphone jacket and adapter becomes (without proof)

Ro * Ra / (Ro + Ra).

The value of the resistor should be 0.1 .. 1 times the impedance of the headphone drivers to have a noticable effect. However, be aware that with very low values of Ra your amplifier has to deliver a much higher current signal to obtain the same sound pressure. This might have some adverse effects on sound quality by itself. Also be aware that the resistors should be able to dissipate enough heat!
 

 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 


but for 1 driver, there re 2 wires out + and - label, which one is considered the signal wire to be added resistors ??


It dosnt matter which side of the driver the resistors are placed on. 

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