Using resistor at output to reduce volume of headphone

wwenze · 16th September 2009, 03:54 AM

Another question to ask the experienced...

I'm looking a way to reduce the volume output to the headphones (32-ohms and lower) without changing the gain of the amp.

I've seen adding resistors in series as some sort of impedance adaptor to make earphones sound better in some more fanatical forums.

But my primary concern is that, voice coils are inductors, and inductors have varying impedance depending on frequency, I'm guessing that impedance of a resistor is more or less the same at varying frequencies. That would mean the voltage will be divided differently at different frequencies, giving it some kind of strange equalization effect that may be thought of as "better sound" in other forums?

Would I be better of with this resistor or should I stick with lowering the volume digitally at the source?

rdf · 16th September 2009, 04:07 AM

Depends. What are you using for a headphone amp? I use a second hand Rotel RA-820AX integrated picked up cheap. The speaker out feeds an 8 ohm resistor in series with 1 ohm, the latter to ground. The headphones are across the 1 ohm resistor. The amp is happy with the load, the headphones see an almost purely resistive 1 ohm drive impedance from DC to well up into the RF range, the divider knocks down the amp's noise almost 20 dB while still allowing deafening volumes.

sandyK · 16th September 2009, 06:03 AM

wwenze

A few helpful references.This time, not from a more "fanatical" forum.

SandyK

http://www.stereophile.com/features/808head/index2.html

http://www.epanorama.net/circuits/he...ttenuator.html

http://sound.westhost.com/project70.htm

rdf · 16th September 2009, 07:40 AM

wwenze, before over-complicating things consider if there's anything 'fanatical' about understanding what happens to the frequency response of the headphones shown here when driven by 120 ohms. Checking with the manufacturer if your headphones are designed to the IEC 61938 spec is advisable before choosing an approach.

wwenze · 16th September 2009, 09:28 AM

Thanks, those impedance measurements sure answered my questions.

My headphone is a Alessandro MS-1, which I presume to be similar to Grado in terms of construction.

"Minor bun engine made benny lava"

sandyK · 10:22 AM

wwenze
The AKG K701 can sound "edgy" with some amplifiers.
The attachment may help complete the overall picture.
SandyK

16th September 2009, 03:54 AM	#1
wwenze diyAudio Member Join Date: Mar 2008	Using resistor at output to reduce volume of headphone Another question to ask the experienced... I'm looking a way to reduce the volume output to the headphones (32-ohms and lower) without changing the gain of the amp. I've seen adding resistors in series as some sort of impedance adaptor to make earphones sound better in some more fanatical forums. But my primary concern is that, voice coils are inductors, and inductors have varying impedance depending on frequency, I'm guessing that impedance of a resistor is more or less the same at varying frequencies. That would mean the voltage will be divided differently at different frequencies, giving it some kind of strange equalization effect that may be thought of as "better sound" in other forums? Would I be better of with this resistor or should I stick with lowering the volume digitally at the source?

16th September 2009, 04:07 AM	#2
rdf diyAudio Member Join Date: Jun 2004 Location: the thermionic past	Depends. What are you using for a headphone amp? I use a second hand Rotel RA-820AX integrated picked up cheap. The speaker out feeds an 8 ohm resistor in series with 1 ohm, the latter to ground. The headphones are across the 1 ohm resistor. The amp is happy with the load, the headphones see an almost purely resistive 1 ohm drive impedance from DC to well up into the RF range, the divider knocks down the amp's noise almost 20 dB while still allowing deafening volumes. __________________ Ears aren't microphones.

16th September 2009, 06:03 AM	#3
sandyK diyAudio Member Join Date: Apr 2007 Location: Sydney	Using resistor at output ro reduce volume of headphone. wwenze A few helpful references.This time, not from a more "fanatical" forum. SandyK http://www.stereophile.com/features/808head/index2.html http://www.epanorama.net/circuits/he...ttenuator.html http://sound.westhost.com/project70.htm

16th September 2009, 10:16 AM	#6
sandyK diyAudio Member Join Date: Apr 2007 Location: Sydney	Using resistor at output to reduce volume of headphones. wwenze The AKG K701 can sound "edgy" with some amplifiers. The attachment may help complete the overall picture. SandyK Last edited by sandyK; 16th September 2009 at 10:22 AM.

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16th September 2009, 09:28 AM	#5
wwenze diyAudio Member Join Date: Mar 2008	Thanks, those impedance measurements sure answered my questions. My headphone is a Alessandro MS-1, which I presume to be similar to Grado in terms of construction. "Minor bun engine made benny lava"

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