Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › SS amp for low impedance headphones <250£
New Posts  All Forums:Forum Nav:

SS amp for low impedance headphones <250£ - Page 2

post #16 of 25
6/17/09 at 4:20pm
Quote:
Originally Posted by Edoardo View Post
Seems to much for easy to drive phones
"Easy to drive" usually refers to voltage. Low impedance headphones require little voltage to be driven but lots of current to be driven well.
Reply
post #17 of 25
6/17/09 at 4:42pm
Thread Starter 
Quote:
Originally Posted by koto-in View Post
"Easy to drive" usually refers to voltage. Low impedance headphones require little voltage to be driven but lots of current to be driven well.
wait, when it comes to technical things I always mess up. I thought that "easy to drive" was a matter of Ampere, and not Volta... Can anybody explain this?
Reply
post #18 of 25
6/17/09 at 5:24pm
Edoardo, if you are looking for an amp (mainly SS) you should look for THD(+N)% (usually less than 0.5% is good enough, and most amps have less than that) and output impedance.

For example if your HPs have an impedance of 50 Ohms it is better if you look for an amp that has an output impedance <=50 Ohms. The amplifier can have an impedance of 100 Ohms, but that might make the output volume be too loud.

You basically need to avoid getting some amplifier that will have an output impedance much higher than the HPs you are going to use it with, and not excessive voltage output. So that you can control the volume easily without bursting your ear drums.
Reply
post #19 of 25
6/18/09 at 4:49am
Quote:
Originally Posted by Edoardo View Post
wait, when it comes to technical things I always mess up. I thought that "easy to drive" was a matter of Ampere, and not Volta... Can anybody explain this?
V/r=I and I*V=W

Putting these together we get W=V*(V/r). Assuming we want the headphone to see 200mW of power:

If a 32 ohm low impedance headphone is used, the voltage required is only 2.5V but the current draw is 79mA.

With a 300 ohm high impedance headphone, the voltage required is 7.7V but the current draw is only 26mA.

Low impedance headphones work well with the typical 3V output of portable devices because they are "easy to drive." You just need to keep changing the batteries. The current available in most portable devices is limited to extend battery life however, thus reducing the power available to the headphones.

If a 300 ohm high impedance headphone is used with the 3V output of a portable device, only 30mW of power will be available to drive the headphones and therefore they are "difficult to drive."

Portable amps are always a compromise between portability, battery life and power output. Desktop amps can typically offer sufficient voltage and current to drive all headphones well.
Reply
post #20 of 25
6/18/09 at 2:28pm
Quote:
Originally Posted by koto-in View Post
V/r=I and I*V=W

Putting these together we get W=V*(V/r). Assuming we want the headphone to see 200mW of power:

If a 32 ohm low impedance headphone is used, the voltage required is only 2.5V but the current draw is 79mA.

With a 300 ohm high impedance headphone, the voltage required is 7.7V but the current draw is only 26mA.

Low impedance headphones work well with the typical 3V output of portable devices because they are "easy to drive." You just need to keep changing the batteries. The current available in most portable devices is limited to extend battery life however, thus reducing the power available to the headphones.

If a 300 ohm high impedance headphone is used with the 3V output of a portable device, only 30mW of power will be available to drive the headphones and therefore they are "difficult to drive."

Portable amps are always a compromise between portability, battery life and power output. Desktop amps can typically offer sufficient voltage and current to drive all headphones well.



Excelent explanation.... Mind if I save this for other Threads?
Reply
post #21 of 25
6/18/09 at 6:23pm
Quote:
Originally Posted by boomy3555 View Post
Excelent explanation.... Mind if I save this for other Threads?
Spread the love.
Reply
post #22 of 25
6/18/09 at 7:44pm
Quote:
Originally Posted by Bullseye View Post
Edoardo, if you are looking for an amp (mainly SS) you should look for THD(+N)% (usually less than 0.5% is good enough, and most amps have less than that) and output impedance.

For example if your HPs have an impedance of 50 Ohms it is better if you look for an amp that has an output impedance <=50 Ohms. The amplifier can have an impedance of 100 Ohms, but that might make the output volume be too loud.

You basically need to avoid getting some amplifier that will have an output impedance much higher than the HPs you are going to use it with, and not excessive voltage output. So that you can control the volume easily without bursting your ear drums.
Those are not particularly good guidelines on what to look for. You don't need to worry about THD(+N), because no amp on the market, especially a solid state amp, is going to have anywhere near .5%. For example, the readings of THD+N on my CK2 III are .024%. You don't need to worry about distortion.

On top of that, your advice about output impedance is correct, as far as the info that you want output impedance to be less than your headphones impedance, but the results of a mismatch are nothing like you described. An impedance mismatch makes the amp/phone coupling more efficient and you lose some of the power that the amp is delivering. This will not increase the volume of your phones in any way. You should lose volume. Impedance mismatch also gives you a less-controlled midbass and makes phones become somewhat boomy. The only time you really need to worry about impedance mismatch is with low Z phones and OTL tube amps. Other wise, the output impedance will be very low with SS amps.
Reply
post #23 of 25
6/19/09 at 7:37am
^Well, was hoping someone would correct what I had said. I just wrote it on a rush, so couldn't be too precise... Should have left it for later...

So yeah, I knew it was not correct information what i have written, but as othe memeber had answered correctly I decided to leave it like that. Thnks for the comment ^^
Reply
post #24 of 25
6/22/09 at 10:32am
Thread Starter 
Hi guys, thanks for all the knowledge shared with me.

Just wanted to let you know I've chosen the new Corda Swing: sober design, high power, gain-switch and crossfeed filter.
Looks just perfect for me.

Thank you all!
Reply
post #25 of 25
6/22/09 at 11:53am
Quote:
Originally Posted by Edoardo View Post
Hi guys, thanks for all the knowledge shared with me.

Just wanted to let you know I've chosen the new Corda Swing: sober design, high power, gain-switch and crossfeed filter.
Looks just perfect for me.

Thank you all!
Congratulations! Drop a line on the Swing thread after you've had a chance to spend some time with it.
Reply
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Headphone Amps (full-size)
Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › SS amp for low impedance headphones <250£