[saitoki]

Hi all...

I am just considering whether having a class-A headphone amp is really useful when used with a cellphone's headphone out....

while I am aware of the advantages of a Class-A headphone amp... would it matter if the cellphone's headphone output isnt class-A? I mean... lets say (for argument's sake).... my headphone output on my phone is class-B... and I use a class-A headphone amp with it... doesnt that nullify the benefits of the class-A amp since the signal it receives from the phone is already 'distorted' by the class-B?

So... unless the class-A amp has some way of correcting that 'distortion'... the class-A aspect of the amp becomes negated?

Cheers,
Silas

 

[ProtegeManiac]

I am just considering whether having a class-A headphone amp is really useful when used with a cellphone's headphone out....

while I am aware of the advantages of a Class-A headphone amp... would it matter if the cellphone's headphone output isnt class-A? I mean... lets say (for argument's sake).... my headphone output on my phone is class-B... and I use a class-A headphone amp with it... doesnt that nullify the benefits of the class-A amp since the signal it receives from the phone is already 'distorted' by the class-B?

So... unless the class-A amp has some way of correcting that 'distortion'... the class-A aspect of the amp becomes negated?

Personally, it doesn't matter if the amp is Class A or A/B. If you're using the headphone output you're dealing with some noise and distortion (just that it's not from, say, an impedance mismatch with a low impedance IEM) that will be part of the signal that the next amp will amplify. Keep the output low to prevent that, and the voltage of the signal going to the amp might be too low you'd get to the second amp's limit trying to compensate for a weak input signal (though some portable amps were designed for low voltage inputs).

Why not just use USB OTG to a desktop Class A amp driving a headphone that actually needs more power, and just pick a very easy to drive IEM (at least 100dB/1mW, preferably higher; plus impedance roughly between 24ohms and 120ohms) to use on the go?

 

[saitoki]

Personally, it doesn't matter if the amp is Class A or A/B. If you're using the headphone output you're dealing with some noise and distortion (just that it's not from, say, an impedance mismatch with a low impedance IEM) that will be part of the signal that the next amp will amplify. Keep the output low to prevent that, and the voltage of the signal going to the amp might be too low you'd get to the second amp's limit trying to compensate for a weak input signal (though some portable amps were designed for low voltage inputs).

Why not just use USB OTG to a desktop Class A amp driving a headphone that actually needs more power, and just pick a very easy to drive IEM (at least 100dB/1mW, preferably higher; plus impedance roughly between 24ohms and 120ohms) to use on the go?

I totally get the noise and distortion you are talking about.. but I know that already... I am interested specifically in the kind of distortion a class B amp may introduce due to the potential delay when switching biases/cycles/push pull (not sure about the terminology) as described in my question.... which would make a class-A amp after it redundant....

 

[ProtegeManiac]

I totally get the noise and distortion you are talking about.. but I know that already... I am interested specifically in the kind of distortion a class B amp may introduce due to the potential delay when switching biases/cycles/push pull (not sure about the terminology) as described in my question.... which would make a class-A amp after it redundant....

Whatever distortion is present given a high impedance load like the input stage of an amp (vs a different and complex impedance load like headphone drivers) will be amplified by the next amp. it doesn't matter what topology the second amp is, if that distortion is in the signal it receives it will be amplified. At best a Class A amp that isn't clipping isn't going to make it worse.

 

[saitoki]

Whatever distortion is present given a high impedance load like the input stage of an amp (vs a different and complex impedance load like headphone drivers) will be amplified by the next amp. it doesn't matter what topology the second amp is, if that distortion is in the signal it receives it will be amplified. At best a Class A amp that isn't clipping isn't going to make it worse.

Yep... that's what I thought as well... just wanted to confirm my suspicions.... thanks a lot man