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Confusion about Amplifiers

post #1 of 12
Thread Starter 

Hello

I have read some about amps. But I actually do not exactly know what they really do. I hear people say they make the sound better etc. And that high impedance headphones need amps to make them perform as expected. I got some questions I would be really happy if anyone could help me out.

1) If I do not need my music to be louder. Do I not need an amp?

2) Why are amps also used for low impedance headphones and custom IEMs?

3) Do amps remove distortion? Is that the whole deal?

Some of these questions sure look stupid for a lot of people here. But I have to start somewhere. I do not undersand all the technical explanations I read places. If someone can explain some how I would be really thankful.

My setup right now: Sansaclip+ , 1964-Ears V3.
I have ordered a DIY CMoy amp. I hope it will be good. I am not even sure if it will be a huge buff to my setup. But I will enjoy to make it anyways.

post #2 of 12
Quote:
Originally Posted by HwangMiHee View Post

Hello

I have read some about amps. But I actually do not exactly know what they really do. I hear people say they make the sound better etc. And that high impedance headphones need amps to make them perform as expected. I got some questions I would be really happy if anyone could help me out.

1) If I do not need my music to be louder. Do I not need an amp?

Louder isn't the only reason to use an amp.  Some devices have very poor headphone amps in them and an external amp can improve the sound quality.  But that's only sometimes, not every time.  So you may or may not need an amp.  Some headphones are less efficient and require more power to drive to an adequate level.  Those would benefit from an amp with more power.

 

Quote:

Originally Posted by HwangMiHee View Post

2) Why are amps also used for low impedance headphones and custom IEMs?

Low impedance headphones are sometimes harder to drive well, and some amps can do the job better than what's built into a player.  However, it's really a combination of output impedance of the driving amp (internal or external), and the impedance curve of the headphones vs frequency.  High output impedance and a radically changing impedance curve is a band combination.

 

Quote:

Originally Posted by HwangMiHee View Post

3) Do amps remove distortion? Is that the whole deal?

No.  Nothing removes distortion.  However, if an internal amp in a player is really bad and has higher distortion, then an external amp may provide a lower distortion result.  May.  Again, this is highly dependent on specifics, there are no rules for every device.  Most of what we hear as distortion in today's music is in the music itself, and there's no removing it.

Quote:
Originally Posted by HwangMiHee View Post

My setup right now: Sansaclip+ , 1964-Ears V3.
I have ordered a DIY CMoy amp. I hope it will be good. I am not even sure if it will be a huge buff to my setup. But I will enjoy to make it anyways.

The Clip + has an excellent internal amp.  The Ears V3 is very sensitive, doesn't need a lot of power at all, the Clip should be just fine.  Many CMoy designs are worse than the Clip.  There are far better headphone amps in the world.  

 

So enjoy the project, but there's very little if any improvement to be had in sound quality.

post #3 of 12
Quote:
Originally Posted by jaddie View Post

No.  Nothing removes distortion.  However, if an internal amp in a player is really bad and has higher distortion, then an external amp may provide a lower distortion result.  May.  Again, this is highly dependent on specifics, there are no rules for every device.  Most of what we hear as distortion in today's music is in the music itself, and there's no removing it.

The Clip + has an excellent internal amp.  The Ears V3 is very sensitive, doesn't need a lot of power at all, the Clip should be just fine.  Many CMoy designs are worse than the Clip.  There are far better headphone amps in the world.  

 

So enjoy the project, but there's very little if any improvement to be had in sound quality.

 

For your 2nd answer, May I know why low impedence IEM is hard to drive as well? as compared to high impedence headphone, low impedence should be much easier to drive, right? but if we put an extra AMP between the source and IEM, then the AMP may (mostly the case) amplify the audio signal, the AMP output impedence now (not the audio source impedece anymore) seves as a competing factor with our IEM impedence, right?

 

I am also confused with AMP sometimes, hope anyone can kindly clear my doubt. Thanks

post #4 of 12
Quote:
Originally Posted by windcloud View Post

 

For your 2nd answer, May I know why low impedence IEM is hard to drive as well? as compared to high impedence headphone, low impedence should be much easier to drive, right? 

No, actually the opposite.  Higher impedances present a lighter load to the amp, lower impedances present a heavier load.  

You can learn more about impedance as an electrical property here.

 

How hard or easy a headphone is to drive is more complex than just the impedance, though.  The impedance is the load presented to the amp.  If the impedance is low, but the headphones sensitivity is high, they will still play loudly.  But impedance is sometimes not constant over the entire audio spectrum, dipping lower at some frequencies, higher at others.  If the amp has a high output impedance, and the headphones have a wildly variable impedance, the result will be a significant change in frequency response.  The equivalent circuit is a voltage divider with one element being frequency dependent. The problem is reduced or eliminated with a low impedance output amp.  

Quote:

Originally Posted by windcloud View Post

 

but if we put an extra AMP between the source and IEM, then the AMP may (mostly the case) amplify the audio signal, the AMP output impedence now (not the audio source impedece anymore) seves as a competing factor with our IEM impedence, right?

 

I am also confused with AMP sometimes, hope anyone can kindly clear my doubt. Thanks

Yes, the amplifier acts as buffer between the source and the headphones.  Amplifiers all have high input impedances, so a source is lightly loaded by them.  A good amp has a low source (output) impedance, and should be capable of driving any headphone load.  However, some amp designs are not done well, and the results are no better, in fact somewhat worse, than if the headphones were connected directly to the source.

 

Like I said before, your Clip has a very low source impedance, better than some amps, likely better than most common Cmoy designs that employ integrated circuit amplifiers never intended to drive 16 ohm loads.  The only reason they sort of work is that most low impedance headphones are also high sensitivity and don't need much power.  When headphones combine low impedance with low sensitivity, they become hard to drive well.  Apparently, some people must think some IEMs fit that category, though can't find any evidence.  Most IEMs are quite sensitive, requiring very little power for high volumes, and many are fairly high impedance too.  Can't imagine they'd be hard to drive, or would ever require an amp at all. 

post #5 of 12
Quote:
Originally Posted by jaddie View Post

No, actually the opposite.  Higher impedances present a lighter load to the amp, lower impedances present a heavier load.  

You can learn more about impedance as an electrical property here.

 

How hard or easy a headphone is to drive is more complex than just the impedance, though.  The impedance is the load presented to the amp.  If the impedance is low, but the headphones sensitivity is high, they will still play loudly.  But impedance is sometimes not constant over the entire audio spectrum, dipping lower at some frequencies, higher at others.  If the amp has a high output impedance, and the headphones have a wildly variable impedance, the result will be a significant change in frequency response.  The equivalent circuit is a voltage divider with one element being frequency dependent. The problem is reduced or eliminated with a low impedance output amp.  

Yes, the amplifier acts as buffer between the source and the headphones.  Amplifiers all have high input impedances, so a source is lightly loaded by them.  A good amp has a low source (output) impedance, and should be capable of driving any headphone load.  However, some amp designs are not done well, and the results are no better, in fact somewhat worse, than if the headphones were connected directly to the source.

 

Like I said before, your Clip has a very low source impedance, better than some amps, likely better than most common Cmoy designs that employ integrated circuit amplifiers never intended to drive 16 ohm loads.  The only reason they sort of work is that most low impedance headphones are also high sensitivity and don't need much power.  When headphones combine low impedance with low sensitivity, they become hard to drive well.  Apparently, some people must think some IEMs fit that category, though can't find any evidence.  Most IEMs are quite sensitive, requiring very little power for high volumes, and many are fairly high impedance too.  Can't imagine they'd be hard to drive, or would ever require an amp at all. 

Thanks for the answer, it really helps. 

post #6 of 12
Thread Starter 
Thank you for our replies. It really helped me understand a lot more. This was exactly what I was looking for.

Do you think the cmoy was a bad idea to add to my setup? (1964-V3 + Sansaclip+)

How do you explain sensitivity with combination of different levels of impedance?
post #7 of 12

The CMoy is unnecessary, and may not even be as good as the Clip by itself.  You'll have fund building it though.

 

Sensitivity is the sound pressure level  (SPL) produced with a given amount of power.   For your Ears V3 specifications from the manufacturer:

•  Impedance: 16 Ohms @1kHz  --- Note that they specific impedance at a frequency, which may mean it's different at other frequencies.  
•  Sensitivity:  119 dB SPL/mW, 1 kHz  --- That means if you provide them with 1 milliwatt at 1KHz, they will produce a sound pressure level of 119dB...VERY loud!  These phones would never need an amp to be loud.  Just about anything can provide 1 milliwatt to 16 ohms. That's 1/1000 of a watt, and around 1/10 of a volt.  You'll NEVER listen that loud, that would damage your hearing.  Your typical listening will be below 85dB SPL which is about .0000004 watts max, and well below that on average.
•  Frequency Response:  12-17kHz --- What's missing is a level variance tolerance, so we have to assume they are just able to produce an audible result over that range, it's not a qualitative figure.   A good FR spec would include the allowable variation, like + or - 3dB.  It's hard to do with headphones because the desired response would not measure flat, so they would also have to state the target curve.  It gets complicated, so they just don't bother.
•  Noise Isolation: -26dB  --- This is how much reduction in ambient noise they provide.  It's also a curve, though, not a single figure.  When specified like this, it's usually at 1KHz, and is worse at other frequencies.   Typical ear plugs are in the 29dB to 32dB range, so these phones are good, not great.  But there are many that are much worse.

post #8 of 12
Thread Starter 
Quote:
Originally Posted by jaddie View Post

The CMoy is unnecessary, and may not even be as good as the Clip by itself.  You'll have fund building it though.

 

Sensitivity is the sound pressure level  (SPL) produced with a given amount of power.   For your Ears V3 specifications from the manufacturer:

•  Impedance: 16 Ohms @1kHz  --- Note that they specific impedance at a frequency, which may mean it's different at other frequencies.  
•  Sensitivity:  119 dB SPL/mW, 1 kHz  --- That means if you provide them with 1 milliwatt at 1KHz, they will produce a sound pressure level of 119dB...VERY loud!  These phones would never need an amp to be loud.  Just about anything can provide 1 milliwatt to 16 ohms. That's 1/1000 of a watt, and around 1/10 of a volt.  You'll NEVER listen that loud, that would damage your hearing.  Your typical listening will be below 85dB SPL which is about .0000004 watts max, and well below that on average.
•  Frequency Response:  12-17kHz --- What's missing is a level variance tolerance, so we have to assume they are just able to produce an audible result over that range, it's not a qualitative figure.   A good FR spec would include the allowable variation, like + or - 3dB.  It's hard to do with headphones because the desired response would not measure flat, so they would also have to state the target curve.  It gets complicated, so they just don't bother.
•  Noise Isolation: -26dB  --- This is how much reduction in ambient noise they provide.  It's also a curve, though, not a single figure.  When specified like this, it's usually at 1KHz, and is worse at other frequencies.   Typical ear plugs are in the 29dB to 32dB range, so these phones are good, not great.  But there are many that are much worse.


Thanks a lot. You replied exactly what I wanted.
Speaking of that my earphones are good but not great. Do you mean their sound isolation is good or that the overall is good? Could you show me an example of great sound isolating custom IEM and or great custom IEMs?

post #9 of 12

"Good" was just a reference to isolation.  Note that in practice, it depends a lot on ear canal shape, how it's fitting, how good the mold was for a custom, design of venting and other acoustic considerations.

 

InnerFidelity does some noise isolation measurements (and properly, so there it shows the level at different frequencies).  It's the upper-right graph.

 

An with high isolation (Etymotic ER4P):

http://www.innerfidelity.com/images/EtymoticER4PT.pdf

 

An IEM with relatively low isolation (Brainwavz M2):

http://www.innerfidelity.com/images/BrainwavzM2.pdf

 

But those are universal-fit IEMs.  I don't know if anybody bothers fitting a custom to a dummy ear, and if that would be a valid comparison anyway.  Usually the deeper the fit and more elastic and form-fitting the materials are, the more isolation you get.


Edited by mikeaj - 4/20/13 at 5:51pm
post #10 of 12

sorry for the off topic, but do any of you know the output impedance of the jds labs cmoy bb? on their site it just says "impedance of the opamp", and the opa2227 data sheet is just a long long mess of data, but i couldnt see any output impedance rating.

post #11 of 12

For cmoybb v2.3, it will be around 0.6ohm. I don't expect this number to different by much with newer or older version.

post #12 of 12
Quote:
Originally Posted by ClieOS View Post

For cmoybb v2.3, it will be around 0.6ohm. I don't expect this number to different by much with newer or older version.

awesome. thank you very much!

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