[royewest]

Here's a basic question that I'm hoping someone will have some insight into. I'm looking for theory here -- I know that in the end I will do what my ears like best, but perhaps there are adjustments I'd make to my gear if the theory were persuasive.

I have a DAC with control over the "volume" of its line out connection.

I have a headphone amp with a volume knob.

If I set the DAC to maximum "volume", I have barely any wiggle room on the headphone amp volume knob before it's way too loud. But if I turn down the volume on the DAC, don't I risk degrading the signal (I assume anything lower than max means putting resistors in the path).

Here's a real-world example: I have effectively no room to play with on my Bottlehead S.E.X. headhpone amp if I turn my Lavry DA10's "volume" to maximum (=line level?). I've settled by keeping the Lavry at a middle volume (33/56ths), so about one-third to one-half turn on the amp's volume knob is a decent volume.

I have noticed that on some other amps I've built, the lowest 10 or 20 degrees of volume have minor audio problems -- slight imbalances in L/R volume, etc. They all seem to like to run with the volume at least 45 degrees up from zero. This is not so noticible on the S.E.X. amp, but still...

Thanks in advance for any insight into this.

 

[ninjapixie]

I had this problem using the outputs of my Cambridge 840c cd player to my little Arietta. With the volume set to zero on the Arietta, I could still measure the sound from my HD580s at about 65db! Plugging the 840c into my studio monitors I could barely turn the volume on the monitors up at all.

When I use my cd player as a DAC I controlled the volume through Foobar which worked well but apparently you lose quality that way.

I found a passive volume controller (Nano Patch) which helps fix this problem as I can run the volume full on Foobar, and turn the amp up on my monitors and use the Nano Patch to control the volume.

The sound quality is pretty transparent, but the channel balance isn't exact (about 0.5-2 db off on one channel) through my monitors. Barely noticeable, but just the fact that I know they're not equal is kinda annoying. Could be a power issue as each of the monitors have their own power source and I can't measure any difference on my heaphones.

I've read about using a preamp as volume control but the decent ones are much more expensive then the Nanopatch which goes for about $50.

 

[amb]

It depends on how the DAC's volume control is implemented. If it does it in the digital domain (i.e., by reducing the digital audio data stream's amplitude), then you'd lose bit-resolution at anything less than full-scale "max volume". If the volume control is via a regular pot, then it's essentially equivalent to the amp's volume control. That said, if there are two analog volume controls at two different stages of the audio chain, it would be best to maximize the setting of the first one and use the second one to do most of the controlling. This will give the best S/N ratio. But the overload margins of all the different stages must be taken into consideration to avoid possible clipping. If setting the DAC volume to max and it's too loud when the amp's volume pot is set low, then the amp has too much gain.