Should I get an attenuator for MBP and headphones?

[Josh83]

Hey everybody

 

I noticed this low noizy crackling when plugging my iPod headphones into my Macbook Pro already long time ago, and after some searching I found that this has to do with the impedance, which seems to have to do with the amount of power that is delivered to the headphones, and if the headphones doesn't need this much power, then the mentioned crackling is being heard. Is this right?

 

Well, I'm planning to buy some good headphones soon to produce using Logic while traveling, but I fear that this crackling will be distracting. So I wonder what I can do? Buy headphones that need all the power supplied by the Macbook Pro? How do I tell that from the headphones' specifications?

 

To be specific: I'm thinking about getting an AKG K 240 MK II:

http://www.akg.com/site/products/powerslave,id,1063,pid,1063,nodeid,2,_country,EN,_language,EN.html

 

On another website I stumbled upon an "attenuator" which should reduce the impedance so low powered headphones can be used with the Macbook Pro too:

 

http://www.amazon.com/gp/product/B00029U0X6?ie=UTF8&force-full-site=1

http://store.shure.com/store/shure/en_US/pd/productID.104210500

 

But then I wonder whether this will have a negative impact on the sound quality, e.g. by clipping certain levels (such as drums/cymbals)?

 

Thanks a lot for your help,

Josh

[fader8]

I noticed this low noizy crackling when plugging my iPod headphones into my Macbook Pro already long time ago, and after some searching I found that this has to do with the impedance, which seems to have to do with the amount of power that is delivered to the headphones, and if the headphones doesn't need this much power, then the mentioned crackling is being heard. Is this right?

No.

 

On another website I stumbled upon an "attenuator" which should reduce the impedance so low powered headphones can be used with the Macbook Pro

Attenuators don't change the line impedance, they just reduce the voltage level.

 

As for the K240's, the Macbook headphone outputs are usually around 20 ohms output impedance. The K240's are usually about 50 ohms as a load impedance. This is good. The source impedance should always be smaller than the load. That's why you can plug that 20 ohm headphone output into a 1000 or 10,000 ohm line level input and it still works OK.

[Josh83]

Thanks for your reply.

 

So what exactly is the impedance, and what did I misunderstand?

 

Attenuators don't change the line impedance, they just reduce the voltage level.

 

As for the K240's, the Macbook headphone outputs are usually around 20 ohms output impedance. The K240's are usually about 50 ohms as a load impedance. This is good. The source impedance should always be smaller than the load. That's why you can plug that 20 ohm headphone output into a 1000 or 10,000 ohm line level input and it still works OK.

 

Thanks for this useful information. So why do my iPod headphones (and pretty every other headphone I connected) have this noizy background? Because their load is smaller (<20 ohms) than the Macbook Pro's output?

 

Thanks a lot for your very useful reply.

[fader8]

So what exactly is the impedance, and what did I misunderstand?

Got some time? Here's a primer:

http://www.opamp-electronics.com/tutorials/ac_theory.htm

So why do my iPod headphones (and pretty every other headphone I connected) have this noizy background?

Because there's something wrong with that output,

[Eriksimon]

 

So what exactly is the impedance?

 

http://europe.beyerdynamic.com/service/faqs/kopfhoerer.html#fo547

[Josh83]

So why do my iPod headphones (and pretty every other headphone I connected) have this noizy background?

Because there's something wrong with that output,

 

Oh really?? So I'm owning a defective MBP since the very first day and wasn't aware of this fact? Would Apple repair this, if it still was under warranty?

[fader8]

Would Apple repair this, if it still was under warranty?

I don't see why they wouldn't.

 

http://europe.beyerdynamic.com/service/faqs/kopfhoerer.html#fo547

Wow. There's actually quite a bit of "misinformation" at that link. Written by a marketing guy, no doubt.

[Andyreww]

So what exactly is the impedance, and what did I misunderstand?

Got some time? Here's a primer:

http://www.opamp-electronics.com/tutorials/ac_theory.htm

So why do my iPod headphones (and pretty every other headphone I connected) have this noizy background?

Because there's something wrong with that output,

 

It's been a long time since I did R,L,C networks...thanks for bring the memories back

[Eriksimon]

I don't see why they wouldn't.

 

http://europe.beyerdynamic.com/service/faqs/kopfhoerer.html#fo547

Wow. There's actually quite a bit of "misinformation" at that link. Written by a marketing guy, no doubt.

 

I'ld be grateful if you could point them out, for my knowledge of electric and/or electronic engineering is sketchy, at best.

The provided explanation (thinner wire, higher resistance, more accurate signal representation because of less inertia (mass) of the coil) well, seemed plausible to me, but I certainly don't want to spread any misinformation.