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Amp and Digital Volume

post #1 of 7
Thread Starter 

A little bit about my set up first: I am using the Jaycar rebrand of the Brainwavz HM-5 headphones and a Schiit Magni Amp.  

 

Generally, I know that you should keep the digital volume on the computer at 100 and manipulate the physical volume on the amp.  However, this does not leave much movement room on the amp because it very quickly gets to the point where it is not comfortable (Less than a quarter turn).  

 

I've played around with changing the volume on the computer and then turning the volume on the amp higher than "normal" with great success to the sound quality which before almost sounded distorted especially with bass (and I listen primarily to electronic music, which is very sensitive to audio equipment and settings).

 

How high can the amp volume go before it blows the speakers? Is that threshold far above what my ears could handle or do I have to be really careful?

 

Thanks in advance.

post #2 of 7

Your ears should tell you well before the speakers damage.  The amp can clip both on the input or output end.  Most sources supply low voltage to the input which is why we say keep the source volume at 100% and use the amp volume.

 

It is funny how we all have perceptions of where we expect and want the volume knob to be at.  Your issue sounds more like an attenuator step value and not a general volume setting issue.  Each click or degree on the volume knob should be around .5dB for idealizing your volume needs.  Some gear go in 1dB or even 1.5dB increments making harder to achieve the exact volume you want regardless of where the dial is.

 

Here is a quote from Schiit's Site:

 

"And IEMs too?
Yes. Magni’s noise floor is low enough for most of them, though Magni’s gain of 5 (necessary for orthos and high-impedance headphones) might mean you have to use software volume control to get a good range of adjustment on the volume pot."

 

So if you have to adjust your source volume and the audio quality remains the same I see no reason to not do it.

post #3 of 7
Thread Starter 

Thanks a bunch NA Blur!

 

I am really interested in the science behind so I am trying to understand the little snippet you posted from Schiit's site.  Let me tell you what I understood from it and then maybe you can correct me if I'm wrong.

 

The noise floor is the threshold level where you begin to hear noise from the source so you want the noise floor to be low so that you don't hear it even when you turn up the volume on amp.

 

As far as I can tell, gain is just amplitude or signal strength which often times manifests as volume but isn't necessarily the case, especially with different types of headphones which require a specific amount of amplification to drive the wavelengths into the headphones from the source.  

 

So, in my case, because of gain of 5... it means I might not need that much amplification? I'm not really sure how to interpret this. I feel like I'm back in school again and my professor is asking me to explain stuff in class.  :P

post #4 of 7

I think what they are saying is that in most cases you want to keep your source volume high and use the volume knob on your amp, but in some cases it is better to adjust both to achieve the lowest noise while avoiding any clipping.

post #5 of 7

A simplified explanation:

 

Lets say your source outputs 1.5V with the volume set to 100% and has a noise floor at -100 dB. Reducing the volume by 20 dB (output reduced to 0.15V) means that the noise floor is now at -80 dB.

The amp will amplify by its gain (14 dB, so 0.15V will be amped to 0.75V along with the noise) and also add some noise. The noise is now at least at -66 dB.

 

In this example you end up with more noise than you'd get with many onboard audio chips, which typically output a fraction of the 2V (redbook standard) at full volume.


Edited by xnor - 1/20/13 at 2:33pm
post #6 of 7
Quote:
Originally Posted by xnor View Post

A simplified explanation:

 

The amp will amplify by its gain (14 dB, so 0.15V will be amped to 0.75V along with the noise) and also add some noise. The noise is now at least at -66 dB.

 

That is, referenced to 0.15 V, and with the amp volume at 100%. More importantly, there will be at least 75 uV noise voltage on the output that way. With some 600 Ω headphones, that may in fact be acceptable, but with sensitive low impedance ones the noise would become audible. However, given that increasing the digital volume to 100% would result in 7.5 V full scale output, one would normally only want to use this setup with the hardest to drive headphones anyway. Other than to fix channel balance problems (which can be done digitally, too), it is better to set the amp volume such that 100% digital volume (or whatever still works without clipping) gives the maximum loudness one would want to use at all, and then attenuate that with the digital volume control for lower volume. About 10 dB constant (volume independent) noise SPL is likely acceptable, so that gives a peak SPL of maximum 110 dB (ignoring the amp noise) with digital volume control before the noise starts to become an issue.

post #7 of 7
Thread Starter 

Thank you for all the answers guy! 

 

All the technical stuff is a little hard to understand, but I'll look into it. 

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