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[raider]

Hi, I am trying to understand why the sound from my integrated amplifier when paired with a DAC is much louder (about 100% louder) than when paired with a sound card via the RCA input?

Soundcard = Asus Xonar U7
DAC = Maverick Audio D1+
Amp = Rotel 06SE

Is this anything to do with the RCA voltage line out between the Asus and the DAC?

Thanks

[mwillems]

It's not at all uncommon for DACs to have a hotter (louder) line-level output than PC soundcards.  I couldn't find a spec sheet with the electrical specs of the Mav D1, so I can't confirm that's the case, but it wouldn't be surprising.

The Asus has a max line-level output of 1 VRMS; many DACs use the "pro-audio" line levels with significantly higher outputs.  For example, my Stenberg UR824 puts out about 6.2 VRMS.  That's a difference of about 16 decibels which perceptually would sound about two and a half times as loud.  And that's not uncommon, there are many DACs with "high-level" outputs like that.

Other things can also affect perceptual loudness.  For example, all other things being equal, distortion tends to make sound seem louder (although the effect is usually not so pronounced that it seems twice as loud), so that may be part of the story (that's a tube DAC, right?).

But my money is on different line-level outputs.

[raider]

Thanks mwillems for that explanation. Yes. The Mav is a tube DAC.

What I am trying to achieve here (and you have previously steered me in the right direction) is to use the Xonar U7 to connect its front right/left channel to my integrated Rotel amp. I have recently bought a used Pro-Ject Amp Box mono (at a cheap cost) and my intention is to pair that with my centre speaker. Currently I am running that centre speaker using a cheapo Chinese class D amp.

I find that with the RCA outputs of the xonar, the integrated Rotel amp need to be adjusted up to 12oclock mark and slightly more when I am watching a movie. I have never turned up the Rotel this high before when I am using it with the Mav DAC for playing back music and the high volume setting on the rotel kinda concerned me....at least a little....because I am using the ZoneSwitch function on JRiver to switch the output....i.e. when it is a music, the HTPC output the sound through the Mav and if it is a movie, output the sound though the Asus.

Are there any ways I can "equalize" the Rotel integrated amp when using the Mav and Xonar?  I am worried I will one day blew the speakers or something if I don't do something...

Any thoughts?

thanks

[mwillems]

Thanks mwillems for that explanation. Yes. The Mav is a tube DAC.

What I am trying to achieve here (and you have previously steered me in the right direction) is to use the Xonar U7 to connect its front right/left channel to my integrated Rotel amp. I have recently bought a used Pro-Ject Amp Box mono (at a cheap cost) and my intention is to pair that with my centre speaker. Currently I am running that centre speaker using a cheapo Chinese class D amp.

I find that with the RCA outputs of the xonar, the integrated Rotel amp need to be adjusted up to 12oclock mark and slightly more when I am watching a movie. I have never turned up the Rotel this high before when I am using it with the Mav DAC for playing back music and the high volume setting on the rotel kinda concerned me....at least a little....because I am using the ZoneSwitch function on JRiver to switch the output....i.e. when it is a music, the HTPC output the sound through the Mav and if it is a movie, output the sound though the Asus.

Are there any ways I can "equalize" the Rotel integrated amp when using the Mav and Xonar?  I am worried I will one day blew the speakers or something if I don't do something...

Any thoughts?

thanks

The easiest solution (by far) is to put a passive in-line attenuator in between the Mav and the amp, like these: http://www.amazon.com/Harrison-Labs-Line-Level-Attenuator/dp/B0006N41AG/ref=pd_sim_e_1?ie=UTF8&refRID=1MQ0EAX4M41RH9772SSV

Parts express also sells them and a few other manufacturers, and they make XLR and TRS versions as well.  They make them with different amounts of attenuation (6dB, 12 dB, etc).  Based on your "twice as loud" statement, you probably want to find one with 10 or 12 dB of attenuation (a 10dB difference in volume sounds perceptually twice as loud). 

[raider]

Many thanks mwillems again. Didn't even know such things existed.  Will this cause the sound quality from the mav to degrade?  Would it not be better to get a device to boost the line out from the asus to match the mav or something?

[mwillems]

Many thanks mwillems again. Didn't even know such things existed.  Will this cause the sound quality from the mav to degrade? 

Not meaningfully so if well-designed.  A well designed passive attenuator is basically just resistors of a specific value in a specific configuration.  All electronic components introduce some limited amount of noise (even resistors), but the amount of noise introduced is so miniscule that you most likely couldn't measure it (virtually all measuring equipment has a higher noise floor than the distortion I'm talking about).  It certainly won't introduce anything like the distortion that the tubes in the DAC introduce.  It will be quieter, and volume has a way of tricking people (louder music sounds better perceptually), but if you dial it back to the old volume settings, there should be no difference.

Would it not be better to get a device to boost the line out from the asus to match the mav or something?

That would require an amplifier of some kind, and, unlike the passive attenuators, that will definitely introduce measurable distortion into the audio signal.  Better designed amplifiers will introduce less distortion, but better designed amplifiers are expensive, and you're already running the signal to an amplifier that you probably spent a pretty penny on. 

So I'd go for the $20 passive attenuators that will effectively leave the signal untouched, instead of investing serious cash in some kind of line-level step up amplifier that will necessarily introduce actual measurable distortion into the line, unless you reallly need more volume.

[raider]

Thanks for that clear explanation! I understand now. Will get that attenuator you mentioned. Now off to eBay

[raider]

Just an update, it appears my maverick audio d1 has a hidden jumper within the unit and when those jumpers are set in the correct position, the DAC's volume control now works to control the line out volume...so now I am able to set the volume of the speakers whether it is from the Mav or from the Asus, to be roughly about the same. No need to buy a line attenuator yet. So I am happy how this turns out. Cheers