Role of pre-amp in my set-up

[Sonic Defender]

I am posting in this forum as I know it is typically a fairly busy forum here. I am embarrassed to admit this, but I really don't know about the relationship between using my Asgard 2 as a preamp out (with headphones plugged into it) and my NAD M3 integrated. As my NAD  doesn't have a headphone section I decided to get a headphone amp and prior to that decision I was looking at a dedicated pre-amp. Here is where the heart of my ignorance is revealed. Would there be any reason to use the Asgard as a pre-amp with the NAD to drive my headphones (NAD HP50s) or am I just as well to use the Asgard and forget it?
 
I do not well understand the relationship between the pre and power amp in terms of what provides what to the finished product. I understand that the final sonic characteristics I will hear will be the analogue output stage of the pre-amp, so knowing that what aspects of the sound quality would the power amp effect? Cheers.

 

[ProtegeManiac]

A preamp circuit basically controls the signal strength thus controlling the overall system volume (vis a vis output power of the amp and the efficiency of the speaker). When we say integrated amplifier, that means it integrates both a preamp and a poweramp circuit in the same box. A headphone amplifier is essentially a integrated design, but it's not like you'd find a pure headphone power amp, but regardless of whether they were designed for speakers or headphones, some integrated amps may have some option of integrating other components. The Asgard has a preamp output from its potentiometer (ie what's behind that knob in front), while the M3 has both outputs from its preamp section as well as inputs directly into its amp section (that bypasses its preamp). See that grey bar? That's a jumper connecting the preamp to the power amp - it's not wired internally.
 

 
 
In your system you could do this a number of ways since both amps have preamps, however I suggest that you just no longer use the Asgard2's preamp. Why? Your integrated amp has a "Rec" output, which is a bypass output. Every input in the preamp if selected will go out through there, and in older amps, will do so even if the amplifier is not powered on (you'll have to run it like this to confirm how the M3 works), without going through the actual circuits in the M3. You hook up this Rec output to the inputs on the Asgard, and any sources in your system will play through the headphones.
 
The Asgard2's preamp is really more useful for example if you're using a pure power amplifier for the speakers, or if you have an all-desktop system and you're using powered monitors which have volume controls on the cabinets (for pro models, they'd be in the rear, and on on each speaker), so you can have within arm's reach.

 

[Sonic Defender]

Thank you very much for the detailed explanation, greatly appreciated. Two related questions if I might. First, I assume that the gain is controlled via the Asgard's potentiometer, and finally, if I was to implement things as you are suggesting is there any potential sound quality advantage to doing so as opposed to simply just using the Asgard as a stand-alone amplifier? I do not need to use the M3 per say as now I have some RCA from my DAC going to the Asgard. As you would expect, if there is a sound quality gain by using the Asgard I would certainly do so. Thank you again for your input, cheers.

 

[ProtegeManiac]

  ...I assume that the gain is controlled via the Asgard's potentiometer...

 
Not the gain, but the volume on the headphones. If the Asgard's potentiometer also controls the volume on the speakers, that means it's set-up in the way that I mentioned but recommend against.
 

  ...finally, if I was to implement things as you are suggesting is there any potential sound quality advantage to doing so as opposed to simply just using the Asgard as a stand-alone amplifier? I do not need to use the M3 per say as now I have some RCA from my DAC going to the Asgard. As you would expect, if there is a sound quality gain by using the Asgard I would certainly do so. Thank you again for your input, cheers.
 

 
You mean just the Asgard and the DAC? I only suggested using the M3's Rec output because your original post was essentially asking about how to integrate the Asgard into an existing system with the M3 in it, so I assumed you were putting the the headphone system in the same room as the DAC and using the source/s. If you are using a DAC that is not the source for the M3, or if your DAC for example has two sets of outputs (ie Unbalanced RCA for the Asgard, Balanced XLR for the M3) then there really is no need to hook up the Asgard to the M3 in any way.
 
As for there being any SQ gains in totally separating the Asgard (and the whole headphone system), there won't be any. In (typical money-driven audiophile) theory using the REC out means you might, for example, use some $5,000 cable to hook up the source/DAC to the M3, then another $5,000 cable to hook up the Asgard to the M3's rec output, leaves you with the factory copper PCB between those two $5,000 cables and thus "SQ degradation" in that part of the chain. Personally, if there is any difference in sound, it's more likely because the cables are EQ-ing the sound rather than the preamp swticher causing degradation and mishandling the signal, and either way if you actually have some practical purpose for using the two amps as such (like getting any source to easily go through either amp) this will outweigh any minute (and likely hallucinated) audio quality differences from having the preamp switcher in the chain or not. If your DAC has two sets of outputs feeding both amps then all the better, since this eliminates the need for routing the signal as such.

 

[Sonic Defender]

Thanks, it sounds like I can just continue using the Asgard as I have been doing. My DAC (Gungnir) does have various outputs and I am going balanced to the M3 and unbalanced RCA to the Asgard so all is well. I shouldn't be as ignorant on this front as I am, but that is how we learn. Thanks again for the input, much appreciated.