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Audio newbie in need of some help

post #1 of 12
Thread Starter 

Hi all,

 

I have an Asus Xonar Essence ST with Sennheiser IE80s plugged in, and being the audio newbie that I am, I have a couple of questions. :)

 

Firstly, should I be looking into getting an amp? The sound levels definitely don't need a boost, but I hear that amps are used to improve the quality of the signal? And if so, which ones should I be looking at to compliment my current setup?

And what about a DAC - I hear that some people use them with the Essence, sounds like overkill? 

 

Secondly I have two small issues:

   1. There is a slight hiss on the line. This doesn't increase if when I increase the volume. So far I have been using an old in line volume remote to lower the signal post audio card, which eliminates the hiss, but I am pretty sure (untrained ears) that it is colouring the sound.

   2. The IE80 cable is too short. Currently using the same in line remote as an extension, but same issue with colouring. Do extensions usually colour the sound? 

 

Thanks!

 

- Cebi

post #2 of 12

The IE80s have a rated 16ohm impedance, so they would probably benefit from from an amp. The Xonar ST/STX headphone amp has a low impedance rating of 10 ohm. The general rule is for the headphone output to be at least 1/8 of the headphone impedance for optimal SQ, or in your case, 2 ohms. So you want an amp that's rated down to 2 ohm (or less). 

 

The sensitivity is also very hi on those phones (125db), so not surprising you would hear some hiss. 

post #3 of 12
Thread Starter 
Quote:
Originally Posted by cel4145 View Post

The IE80s have a rated 16ohm impedance, so they would probably benefit from from an amp. The Xonar ST/STX headphone amp has a low impedance rating of 10 ohm. The general rule is for the headphone output to be at least 1/8 of the headphone impedance for optimal SQ, or in your case, 2 ohms. So you want an amp that's rated down to 2 ohm (or less). 

 

The sensitivity is also very hi on those phones (125db), so not surprising you would hear some hiss. 

 

I didn't know any of this, thanks!

 

Can you suggest a 2 ohm amp that would do justice to my setup? And would this fix the hissing issue too?

 

Thanks! :)

post #4 of 12

I don't know a lot about the different amps. But there are two whole forum areas devoted to amps whether you want a desktop or portable one:

 

http://www.head-fi.org/f/5/headphone-amps-full-size

http://www.head-fi.org/f/105/portable-headphone-amps

 

For example, I just ordered a Little Dot I+ hybrid tube amp to go with my STX. It's supposed to work very well with low impedance phones and has that warmer tube sound. That might or might not be a good fit for you. 

 

Might be that the amp will help with the hiss. Not sure. Certainly I know that with other types of amp setups (such as guitar amps), depending how the gain is set, a hiss can be more present or not. Ask the guys in the headphone amp forum that you choose to post in. Some of the amp experts will know. 

post #5 of 12
Thread Starter 

Excellent, I will do that.

 

Thanks very much Cel!

post #6 of 12
Quote:
Originally Posted by Cebi View Post
I didn't know any of this, thanks!

Can you suggest a 2 Ohm amp that would do justice to my setup? And would this fix the hissing issue too?

The Fiio E11 portable headphone amplifier ($65) has an output impedance of around .5-Ohms.

The E11 is battery powered and will not power headphones and recharge at the same time, so ordering the Micca package will give you an extra battery (BL-5B) and a simple AC battery recharger.

You would plug the E11 into the Essence ST's RCA output jack, but you would only have stereo 2-channel audio, fine for music, but no surround sound (from the RCAs)

 

The O2 (Objective 2) portable headphones amplifier ($155) can power headphone while the battery is recharging.

You just leave the O2's recharger adapter plugged into the wall socket, functions like a normal desktop amp.

Connects to the Essence ST's RCA jacks also.

 

Or just buy some new headphones with a 80-Ohm or higher impedance.

post #7 of 12
Quote:
Originally Posted by cel4145 View Post
Might be that the amp will help with the hiss. Not sure. Certainly I know that with other types of amp setups (such as guitar amps), depending how the gain is set, a hiss can be more present or not. Ask the guys in the headphone amp forum that you choose to post in. Some of the amp experts will know. 

 

A good low noise amplifier like the O2 can easily reduce the hiss, and even make it completely inaudible. That is because the Essence ST has fully digital volume and gain controls, so it always produces the maximum amount of noise on its headphone output, and using a very sensitive headphone at low gain and volume reduces the dynamic range. An external amplifier with an analog volume control connected to the line output makes it possible to run the DAC at a high digital volume and maximize the dynamic range.

 

Without an amplifier, the noise can still be reduced if you resample the audio from 44.1 kHz to 48 kHz with e.g. the SoX sample rate converter plugin in foobar2000, assuming that you have not been using 48, 96, or 192 kHz already. Xonar sound cards are noisier at sample rates that are a multiple of 44100 Hz.


Edited by stv014 - 10/30/12 at 4:10am
post #8 of 12
Thread Starter 
Quote:
Originally Posted by PurpleAngel View Post

The Fiio E11 portable headphone amplifier ($65) has an output impedance of around .5-Ohms.

The E11 is battery powered and will not power headphones and recharge at the same time, so ordering the Micca package will give you an extra battery (BL-5B) and a simple AC battery recharger.

You would plug the E11 into the Essence ST's RCA output jack, but you would only have stereo 2-channel audio, fine for music, but no surround sound (from the RCAs)

 

The O2 (Objective 2) portable headphones amplifier ($155) can power headphone while the battery is recharging.

You just leave the O2's recharger adapter plugged into the wall socket, functions like a normal desktop amp.

Connects to the Essence ST's RCA jacks also.

 

Or just buy some new headphones with a 80-Ohm or higher impedance.

 

Why should I connect via RCA?

I will only be listening via headphones or 2 speaker setup, so won't miss surround sound.

Great information, thanks! 

 

Quote:
Originally Posted by stv014 View Post

 

A good low noise amplifier like the O2 can easily reduce the hiss, and even make it completely inaudible. That is because the Essence ST has fully digital volume and gain controls, so it always produces the maximum amount of noise on its headphone output, and using a very sensitive headphone at low gain and volume reduces the dynamic range. An external amplifier with an analog volume control connected to the line output makes it possible to run the DAC at a high digital volume and maximize the dynamic range.

 

Without an amplifier, the noise can still be reduced if you resample the audio from 44.1 kHz to 48 kHz with e.g. the SoX sample rate converter plugin in foobar2000, assuming that you have not been using 48, 96, or 192 kHz already. Xonar sound cards are noisier at sample rates that are a multiple of 44100 Hz.

 

Excellent, thanks for confirming that. So I should be running at maximum digital volume (i.e. set OS volume to full) to maximise the dynamic range, and then lower it to reasonable levels via the amplifier? 

 

It sounds like I should really be getting myself an amplifier, but that workaround is great to know!

 

I see that you have both mentioned the O2, I'm going to go and read up on it now, but is there any particular reason you suggested that over other models?

 

 

Thanks very much, this is really helpful!

post #9 of 12
Quote:
Originally Posted by Cebi View Post

 

Why should I connect via RCA?

I will only be listening via headphones or 2 speaker setup, so won't miss surround sound.

 

I see that you have both mentioned the O2, I'm going to go and read up on it now, but is there any particular reason you suggested that over other models?

I had just assumed you would be connecting the external add-on headphone amplifier to the RCA jacks.

But if you connect an external head amp. to the Essence ST's headphone amp. and it improves the sound quality, cool.

 

The O2's headphone output comes with a very low impedance (,5-Ohm) :), I'm not sure of the headphone output impedance of other desktop (external) headphone amplifiers.

For the price ($155), it's about the best headphone amplifier in it's price range.

post #10 of 12
Quote:

Originally Posted by Cebi View Post

 

Excellent, thanks for confirming that. So I should be running at maximum digital volume (i.e. set OS volume to full) to maximise the dynamic range, and then lower it to reasonable levels via the amplifier? 

 

It is not required to use maximum digital volume, just avoid the combination of too low volume on the PC and high volume/gain on the amplifier, so that the noise stays inaudible. Within reasonable limits, the volume can be controlled on both devices. But it is recommended to set the resolution of the audio output to 24 bits in Windows.

post #11 of 12
Thread Starter 
Quote:
Originally Posted by PurpleAngel View Post

I had just assumed you would be connecting the external add-on headphone amplifier to the RCA jacks.

But if you connect an external head amp. to the Essence ST's headphone amp. and it improves the sound quality, cool.

 

The O2's headphone output comes with a very low impedance (,5-Ohm) :), I'm not sure of the headphone output impedance of other desktop (external) headphone amplifiers.

For the price ($155), it's about the best headphone amplifier in it's price range.

 

It does seem like a great piece of kit. Thanks for suggesting it!

 

Quote:
Originally Posted by stv014 View Post

 

It is not required to use maximum digital volume, just avoid the combination of too low volume on the PC and high volume/gain on the amplifier, so that the noise stays inaudible. Within reasonable limits, the volume can be controlled on both devices. But it is recommended to set the resolution of the audio output to 24 bits in Windows.

 

It sounds like it would be easiest to set OS volume to full, and then control the volume via the amplifier. Any disadvantage to doing so?

 

Setting to 24 bits... is that the Default Format for shared mode?

 

Much thanks.

post #12 of 12
Quote:

Originally Posted by Cebi View Post

 

It sounds like it would be easiest to set OS volume to full, and then control the volume via the amplifier. Any disadvantage to doing so?

 

Normally, there should not be, but there are a few potential issues:

- having to set the analog volume on the amplifier very low sometimes results in audible channel imbalance

- some amplifiers may clip if the input signal is too high (e.g. the FiiO E9 cannot handle the full scale line output of the Xonar ST)

- some DACs can slightly clip the peaks in a complex signal at maximum digital volume

In the case of the O2 and Xonar ST, using a 1x gain should avoid the second problem, and minimize the first (the default 2.5x gain would not clip on AC power either, but it might be too much for an IEM). While the third one can occur on this sound card (see here), it is likely not much of an issue when playing actual music.

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