Voyager
Do not let me borrow your SportaPros
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What is the ideal headphone impeadence? 16 Ohms, 32 Ohms, 50 Ohms, 100 Ohms, 200 Ohms, 300 Ohms, 600 Ohms, >600 Ohms and why?
What is the ideal headphone impeadence?
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Apheared
You call that an amp? THIS is an amp!
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Fix your avatar.
And greater than 600 ohms. Why? Battery life. While it may take a 10V swing to get it sufficiently loud, the battery drain will be less than the quiescent of the amp, and it makes building amps easier; high ohm headphones are less susceptible to tonal changes on an amplifiers Zout.
Although no one makes them anymore, and I doubt you'd ever find any made for a portable above 60 ohm... it's a thought, anyway.
If it's not running off batteries, then it really doesn't matter... you can tailor a design to work with a 1 ohm headphone just fine when the wall juice is endless.
The real nasty is designing something to work with all things... at a given voltage the difference between driving a 16 ohm efficient earbud and a 300 ohm inefficient headphone can be 50dB... more! It's impossible really. It's a matching game. One Zload isn't "better" than the other without a reference point, like the amp that's driving em.
And greater than 600 ohms. Why? Battery life. While it may take a 10V swing to get it sufficiently loud, the battery drain will be less than the quiescent of the amp, and it makes building amps easier; high ohm headphones are less susceptible to tonal changes on an amplifiers Zout.
Although no one makes them anymore, and I doubt you'd ever find any made for a portable above 60 ohm... it's a thought, anyway.
If it's not running off batteries, then it really doesn't matter... you can tailor a design to work with a 1 ohm headphone just fine when the wall juice is endless.
The real nasty is designing something to work with all things... at a given voltage the difference between driving a 16 ohm efficient earbud and a 300 ohm inefficient headphone can be 50dB... more! It's impossible really. It's a matching game. One Zload isn't "better" than the other without a reference point, like the amp that's driving em.
Voyager
Do not let me borrow your SportaPros
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Thanks for the reply Apheared! I promise to get a Grado avatar as soon as I find a pair of Grados I like better than my Senns.
Apheared
You call that an amp? THIS is an amp!
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no, I wasn't commenting on your choice of avatars, but that it shows a missing graphic box.. I don't know what it is so I can't give you any flak. heh.
thomas
Who needs headphones when there's the JVC MX-GT80?
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Quote:
not all of us like to lug around 12 D sized batteries
| While it may take a 10V swing to get it sufficiently loud, the battery drain will be less than the quiescent of the amp, and it makes building amps easier |
not all of us like to lug around 12 D sized batteries
Apheared
You call that an amp? THIS is an amp!
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Uh Thomas, that is/was the point.
If you carried 2 lbs of batteries around for an amp that only drew 12mA at ear-splitting volume, that would be a silly thing. But hey, it'd run for a year w/o changing the cells.
It's only us Grado types that need the stack of cells... 40mA isn't even normal listening level for me, but the voltage to move 40mA thru HD600s would destroy them. Somewhere around half a watt.
But Grados and Apheared... I'm drawing about 90-150mA from the batts normally, so 9Vs are just plain dumb in this case.
If you carried 2 lbs of batteries around for an amp that only drew 12mA at ear-splitting volume, that would be a silly thing. But hey, it'd run for a year w/o changing the cells.
It's only us Grado types that need the stack of cells... 40mA isn't even normal listening level for me, but the voltage to move 40mA thru HD600s would destroy them. Somewhere around half a watt.
But Grados and Apheared... I'm drawing about 90-150mA from the batts normally, so 9Vs are just plain dumb in this case.
thomas
Who needs headphones when there's the JVC MX-GT80?
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keep in mind that is power that's important, not current...
In an ideal amplifier, where the amp can supply infinite amounts of current/voltage, and there is no Iq, then impedence has absolutely no effect on battery life. Low Z phones will draw lots of current and have very little voltage drop, vice versa for high-Z phones... The power drawn is the same regardless of the headphone's impedence... Its SENSITIVITY, in dB@1mW that determines how much power is needed
If you want to factor in the amp's quiescent current, then low-Z headphones actually become more efficient than high-z phones. As you said, a 600ohm headphone will draw less current than the amp's Iq. As a result, the power that is lost due to Iq is very high. If a low Z headphone was used, then a much larger current would be drawn, and Iq will make up a much smaller fraction of the overall power draw. And, in addition, Iq usually goes up with higher voltages, which makes high-z headphones even less efficient...
The reason that 9V's suck for high current amps is because they have very low power densities. THey hold much less power/unit of volume than AA's...
BTW, you're crazy... how the hell do you get 150mA out of a portable amp!!! I'm lucky to draw 50mA out of 4 class A opamps! are you using class A discretes or somthing?
In an ideal amplifier, where the amp can supply infinite amounts of current/voltage, and there is no Iq, then impedence has absolutely no effect on battery life. Low Z phones will draw lots of current and have very little voltage drop, vice versa for high-Z phones... The power drawn is the same regardless of the headphone's impedence... Its SENSITIVITY, in dB@1mW that determines how much power is needed
If you want to factor in the amp's quiescent current, then low-Z headphones actually become more efficient than high-z phones. As you said, a 600ohm headphone will draw less current than the amp's Iq. As a result, the power that is lost due to Iq is very high. If a low Z headphone was used, then a much larger current would be drawn, and Iq will make up a much smaller fraction of the overall power draw. And, in addition, Iq usually goes up with higher voltages, which makes high-z headphones even less efficient...
The reason that 9V's suck for high current amps is because they have very low power densities. THey hold much less power/unit of volume than AA's...
BTW, you're crazy... how the hell do you get 150mA out of a portable amp!!! I'm lucky to draw 50mA out of 4 class A opamps! are you using class A discretes or somthing?
Apheared
You call that an amp? THIS is an amp!
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Nope, switching... I just listen extremely loud compared to most everyone else, that's all. 75mW/ch is about my normal volume on Grados.
Yea, goes back to my original reply. Battery LIFE. Efficiency be damned if you got an AC outlet.
Batteries though, current is important. I can stack a bunch of 3V lithium button cells like 4 rolls of lifesavers and get 120V @ 500mAh in a space about as big as a single D cell, which is why I say >600 ohm. If I need 20Vpp to set em on fire, no biggie.
Yea, goes back to my original reply. Battery LIFE. Efficiency be damned if you got an AC outlet.
Batteries though, current is important. I can stack a bunch of 3V lithium button cells like 4 rolls of lifesavers and get 120V @ 500mAh in a space about as big as a single D cell, which is why I say >600 ohm. If I need 20Vpp to set em on fire, no biggie.
mbriant
Headphoneus Supremus
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My MG Head has a toggle switch for low and high impedance. Other amps may have separate jacks for low and high.
What are they doing inside the box to make a difference?
Would it be possible to construct a variable impedance amp that could be stepped to the exact impedance of any phone?
What are they doing inside the box to make a difference?
Would it be possible to construct a variable impedance amp that could be stepped to the exact impedance of any phone?
thomas
Who needs headphones when there's the JVC MX-GT80?
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your amp is talking about output impedence, which is different from what we're talking about... your amp is simply connecting/disconnecting a resistor in serries with the headphone...
We were talking about the impedence of the headphone. generally, low inpedence headphones work better with low output impedences. Some people believe that high output impedece will give a flatter frequency response, while others think that low output impedence is good for all headphones, regardless of the headphone's impedence...
Apheared... no, current means nothing, unless you also consider the voltage... in your example, if you use a low-Z headphone, you'd only need one button cell . with a high-z headphone, you'd need 120 button cells at a time... Obviously, the 120 batteries would last longer than the single cell, but much less than 120X longer, due to the Iq of the amp... So a low-Z headphone is actually more efficient than a high-z headphone...
my amps draw 50mW@18V, which is 1 watt,or $1/ hour of use... i don't see how you can afford any more than that!
We were talking about the impedence of the headphone. generally, low inpedence headphones work better with low output impedences. Some people believe that high output impedece will give a flatter frequency response, while others think that low output impedence is good for all headphones, regardless of the headphone's impedence...
Apheared... no, current means nothing, unless you also consider the voltage... in your example, if you use a low-Z headphone, you'd only need one button cell . with a high-z headphone, you'd need 120 button cells at a time... Obviously, the 120 batteries would last longer than the single cell, but much less than 120X longer, due to the Iq of the amp... So a low-Z headphone is actually more efficient than a high-z headphone...
my amps draw 50mW@18V, which is 1 watt,or $1/ hour of use... i don't see how you can afford any more than that!
Apheared
You call that an amp? THIS is an amp!
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Thomas, we're beating a dead horse... heh it's implied that current means nothing without a voltage.
But I'm low-brow physics... and I know how many HUNDREDS of AA cells I've drained in a year @ 2750mAh driving Grados, compared to the runtime that two 550mAh 9Vs will drive a pair of 600s or 931s... SPL efficiency is a large part of that but it's mostly the current consumption. And the fact that I can tax out any single opamp with Grados because of current, whereas any opamp can send HD600s/DT931s into orbit on 18V rails and 15mA.
Which is what I'm sayin redundantly - 1 cell or 40 cells in series, the mAh is the same... but the *usuable lifetime* is better on the device that consumes the least current, regardless of the voltage.
And I'm really lazy, charging is too much effort when you only get 10 hours or so runtime and use your amp 10 hours a day... but that's a separate issue.
But I'm low-brow physics... and I know how many HUNDREDS of AA cells I've drained in a year @ 2750mAh driving Grados, compared to the runtime that two 550mAh 9Vs will drive a pair of 600s or 931s... SPL efficiency is a large part of that but it's mostly the current consumption. And the fact that I can tax out any single opamp with Grados because of current, whereas any opamp can send HD600s/DT931s into orbit on 18V rails and 15mA.
Which is what I'm sayin redundantly - 1 cell or 40 cells in series, the mAh is the same... but the *usuable lifetime* is better on the device that consumes the least current, regardless of the voltage.
And I'm really lazy, charging is too much effort when you only get 10 hours or so runtime and use your amp 10 hours a day... but that's a separate issue.
Apheared
You call that an amp? THIS is an amp!
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mbriant, uhm, I guess... your Hi/Lo switch controls where the output comes off the output transformer... I guess some individual could make an output transformer from a variac-like transformer... but I don't think it'd sound very good.
audioguru1
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Quote:
this in incorrect, the Mghead uses output trannies, you are switching witch winding you are using. Talked with joeseph lao, apparently the low is for less than 100 and the high is for less than 600.
| Originally posted by thomas your amp is talking about output impedence, which is different from what we're talking about... your amp is simply connecting/disconnecting a resistor in serries with the headphone... |
this in incorrect, the Mghead uses output trannies, you are switching witch winding you are using. Talked with joeseph lao, apparently the low is for less than 100 and the high is for less than 600.
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