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post #2116 of 2247

Question for you gentlemen:

 

I decided to try out the Optical connection between my NFB 12.1 and iMac. In USB mode, I could change the volume on my iMac, but with Optical that's not the case anymore.

Is my iMac's internal DAC still being bypassed in Optical mode like it was in USB?

 

The two connections definitely sound a bit different, and I can turn the volume up much higher in USB mode for some reason.

post #2117 of 2247
Quote:
Originally Posted by anoxy View Post

Question for you gentlemen:

 

I decided to try out the Optical connection between my NFB 12.1 and iMac. In USB mode, I could change the volume on my iMac, but with Optical that's not the case anymore.

Is my iMac's internal DAC still being bypassed in Optical mode like it was in USB?

 

The two connections definitely sound a bit different, and I can turn the volume up much higher in USB mode for some reason.

 

I don't know about macs, but optical and coax SPDIF signals output from a computer have to pass trough a sound card first. With USB, the NFB-12 acts as a stand-alone external sound card. When you use SPDIF, be it optical or electrical, you are really using your computer's audio card. The audio signal is processed by the card and sent over the digital out. It bypasses the DAC, but the signal is still re-encoded by the CODEC chip.

 

You probably have problems with "master volume" configuration. Again, I have no experience with macs, but in Linux the master volume does nothing to the SPDIF output. The master volume only change the "front stereo" output, which is the DAC of the sound card, to which my laptop's speakers are connected. I can't even change the volume of the SPDIF output. I can only mute it. You may want to go study your computer's audio setup. There's probably something there that you can tweak. I'm guessing the SPDIF volume isn't at 100%, if such a thing is possible on macs. Just keep in mind that the optical out is part of the imac's sound card, and so configuration to the sound card will affect the optical out.

 

I personally use SPDIF for functional reasons. I don't leave my NFB-12 on all the time, and Linux doesn't like that. I get flooded with messages asking me what to do every time I turn the DAC on and off, and often the transition doesn't work and I have to relog for KDE to switch. It's also a pain, see impossible, to use two DACs at the same time. With SPDIF, I can have two different streams at the same time, independent of each others. For example, I can have a music player streaming bit-perfect trough SPDIF while simultaneously watching a youtube video trough my laptop's speakers. Very handy.

post #2118 of 2247

Thanks for the info. So there is no way to actually bypass the soundcard? I thought that was the entire point of buying an external DAC?

 

This is what it says when I use USB with my NFB 12.1:

post #2119 of 2247

Does anyone else occasionally hear crackling sounds when using USB connection? Usually when I minimize/maximize windows or switch programs. SPDIF doesn't have this problem although when I first connected the device with coaxial cable I could hear some static sounds when the music/sound was not playing AND frequency in Windows was set to 44.1khz. 48khz and higher solved this problem. But since optical connection works perfectly without any of these issues I'm using that at the moment.

 

Luckily USB and SPDIF sound exactly the same to my ears.

 

Great unit btw smily_headphones1.gif PRO 900 and Denon D7000 with this thing is bass head heaven basshead.gif

 

Another thing is that those Filter and OS switches make absolutely zero changes to the sound. Everything sounds the same.

post #2120 of 2247

Filters are rather subtle, but you should be hearing different OS settings.

post #2121 of 2247

Do I have to resample to higher than 44100hz in foobar before I can use the OS switches?


Edited by silverbox - 10/2/12 at 3:45am
post #2122 of 2247

No. 44,1KHz is OK.

 

Try listening to whole decently recorded album on one setting and then listen again the same album on other setting. Quick switching just confuses you. I would tell you what to listen for when changing OS levels, but that would subconsciously bias your listening sessions.

post #2123 of 2247

Thanks, I'll listen to it some more.

post #2124 of 2247
Quote:
Originally Posted by KimLaroux View Post

 

I don't know about macs, but optical and coax SPDIF signals output from a computer have to pass trough a sound card first. With USB, the NFB-12 acts as a stand-alone external sound card. When you use SPDIF, be it optical or electrical, you are really using your computer's audio card. The audio signal is processed by the card and sent over the digital out. It bypasses the DAC, but the signal is still re-encoded by the CODEC chip.

 

Quote:
Originally Posted by anoxy View Post

Thanks for the info. So there is no way to actually bypass the soundcard? I thought that was the entire point of buying an external DAC?

 

This is what it says when I use USB with my NFB 12.1:

Well actually the audio isn't decoded to analog just digitally transmitted through the sp/dif interface so you're not actually using the the DAC part of your soundcard, just the sp/dif transmitter


Edited by Disharmonic - 10/2/12 at 11:40am
post #2125 of 2247

So is that the optimal configuration to use with my iMac? Also, should I have it switched to DAC or Headphone? The headphones work in both modes...

post #2126 of 2247
Quote:
Originally Posted by anoxy View Post

Question for you gentlemen:

 

I decided to try out the Optical connection between my NFB 12.1 and iMac. In USB mode, I could change the volume on my iMac, but with Optical that's not the case anymore.

Is my iMac's internal DAC still being bypassed in Optical mode like it was in USB?

 

The two connections definitely sound a bit different, and I can turn the volume up much higher in USB mode for some reason.


For best sound quality you should never use the volume on your computer anyway, just keep it at max.  All volumes in your path should be at the unity or max level except the one (and it has to be an analog one) that you are actually using.

 

Yes, the line outs on the back of your -12 are the DAC out and it skips the headphone amp.  Note, every DAC in the world has an amp built into it to get it to line level and the RCA out's on the back are at line level.  Otherwise you'd be creating big problems with the next amp and your headphones and your ears.

 

You are not really using your sound card using optical, you just need someplace to convert the signal to optical (or coax) (aka spdif) and that is usually on the sound card.  You are not using the sound card as a sound card or as a DAC so don't worry about that.

post #2127 of 2247
Quote:
Originally Posted by silverbox View Post

Does anyone else occasionally hear crackling sounds when using USB connection? Usually when I minimize/maximize windows or switch programs. SPDIF doesn't have this problem although when I first connected the device with coaxial cable I could hear some static sounds when the music/sound was not playing AND frequency in Windows was set to 44.1khz. 48khz and higher solved this problem. But since optical connection works perfectly without any of these issues I'm using that at the moment.

 

 

That's probably the same reason I never use USB myself.  Besides it always seeming to be too much trouble and you can simple plug in coax and never have to worry about any setting or anything happening on you computer.  But anyway, that is probably usb noise from the usb bus which is very busy depending on how many usb components you have going at any one time.  You can try to use a different usb port (they may not all be the same and they may be using different connections to your motherboard.  You can also make sure youre using a proper usb cable.  I'm not talking any fancy or pricey crap just make sure its a certified usb 2.0 cable which could cost $6 - this is as apposed to usb printer cables or very low end free cables you may have.  This made a difference for me but I admit I was using a usb powered DAC at the time (which the -12 is not) so that could have been the difference.  This whole issue is also why some people have separete media center computers with nothing running on them so nothing interferes with playing music.

post #2128 of 2247
Quote:
Originally Posted by tme110 View Post


For best sound quality you should never use the volume on your computer anyway, just keep it at max.  All volumes in your path should be at the unity or max level except the one (and it has to be an analog one) that you are actually using.

 

Yes, the line outs on the back of your -12 are the DAC out and it skips the headphone amp.  Note, every DAC in the world has an amp built into it to get it to line level and the RCA out's on the back are at line level.  Otherwise you'd be creating big problems with the next amp and your headphones and your ears.

 

You are not really using your sound card using optical, you just need someplace to convert the signal to optical (or coax) (aka spdif) and that is usually on the sound card.  You are not using the sound card as a sound card or as a DAC so don't worry about that.

 

As I stated many times before, the line out of the NFB-12 do not bypass the amplifier. There is no difference between the 1/4 jack at the front and the RCA at the back. The NFB-12 has a relay that switches between these two outputs, but the signal comes from the amplifier either ways. You could use a TRS cable into the front jack to connect the unit to another amp, and it would be the same thing as the "variable" option using the RCA.

 

And indeed, this is not a bad thing but a necessity, as you stated. To "skip" the headphone amp, they'd have to build a second amplifier between the DAC and the RCA, or use op-amps. This would simply be silly to do.

post #2129 of 2247

I guess I just don't buy it then.  I have the -12 too and you're trying to tell me that the RCA outs on it put out 3.5 watts like the headout does?  It is a proper line out signal like any other DAC.
 

post #2130 of 2247
Quote:
Originally Posted by tme110 View Post

I guess I just don't buy it then.  I have the -12 too and you're trying to tell me that the RCA outs on it put out 3.5 watts like the headout does?  It is a proper line out signal like any other DAC.
 

 

It can output 3.5w, but that doesn't mean it forces 3.5w into the line out. You cannot force a load to use power, the load uses the power it needs. If you look at the NFB-12's specs, you'll notice that the output power depends on the impedance of the load:

 

3500mW into 25 ohm 
1800mW into 50 ohm
900mW into 100 ohm
300mW into 300 ohm
150mW into 600 ohm
 
If you extrapolate this data, into a 100 Kohm, which is a normal input impedance for an amplifier, you get 0.9 mW of power. But these are maximum values, with the volume to the max.

 

On "fixed", the output voltage is 2.25V RMS. Into a 100 Kohm load, 2.25V will demand 0.05 mW of power.

 

A "proper" line out in consumer audio is ~ 0.3 V RMS, but some Hi-Fi and Pro-audio equipment can go as high as 2 V. So I wouldn't call the NFB-12's line out "proper". I personally prefer louder line levels, as this often translate into better signal to noise ratio. And since the NFB-12's output can be adjusted with the volume knob, you can tune it for anything between 0 and 5V. I seem to remember someone in this thread who measured the signal out of the NFB-12 and concluded that the distortion lowered as the volume was raised, which is another good reason for higher line level signals.

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