Volume Attenuation and low volume listening

[Ricky64]

Hi;
I don't have very good understanding of methods of volume attenuation, and their effects on sound. I understand that some digital attenuation schemes result in loss of information, but I am more interested in the effects on dynamics and sound quality at lower levels. Do analog volume attenuators do a better job of this than digital? Are certain schemes of analog volume control objectively better than others? Outside of loudness curves and psychoacoustics, is there any more to this?
rh

 

[ecwl]

Hi;
I don't have very good understanding of methods of volume attenuation, and their effects on sound. I understand that some digital attenuation schemes result in loss of information, but I am more interested in the effects on dynamics and sound quality at lower levels.

To me, when we do digital attenuation, mathematically, there should be no sonic issues theoretically, assuming appropriately accurate math is done and proper dithering or noise shaping is introduced.
But in reality, most DACs struggle a little with small signal linearity and accuracy. So by attenuating the volume digitally. You’re using the smaller and smaller signal range of the DAC to accurately create the original analog waveform. I think that’s why many DACs digital volume attenuation, although sounding very transparent, may not sound as good as feeding the DAC at full volume into an analog attenuator.
Of course an analog volume attenuator or preamp can also add euphoric distortion you might like. So lots of factors at play here.

 

[analogsa]

analog volume attenuators do a better job of this than digital?

Not imho. Well implemented digital attenuation sounds more transparent to me than even a premium resistive attenuator with just two resistors per position. Definitely less euphonic though.

Which doesn't mean I find a direct connection between dac and power amp desirable. A preamp is still essential musically, only without an analogue attenuator.

 

[Tuckers]

I agree that digital attenuation can be very good, I've used it a lot, though I now use active preamps. However, in my system which is highly efficient, digital attenuation starts at 30db and can go as low as 50db. This much attenuation can definitely impact the sound in almost all systems. Though mostly in subtle detail, not in impact or dynamics. The best digital attenuation I've heard is the Leedh. But again, I prefer an active preamp (especially with a resistor network) as it doesn't matter how much attenuation I apply, it does not affect the sound.

However, transformer-based passive preamps might be the best of the passive world, as the increased resistance of the lower volume taps usually boosts the lower frequency a bit, acting a bit like a loudness control. Many low volume listeners find that this is a great solution.

 

[audiobomber]

Hi;
I don't have very good understanding of methods of volume attenuation, and their effects on sound. I understand that some digital attenuation schemes result in loss of information, but I am more interested in the effects on dynamics and sound quality at lower levels. Do analog volume attenuators do a better job of this than digital? Are certain schemes of analog volume control objectively better than others? Outside of loudness curves and psychoacoustics, is there any more to this?
rh

Digital level control works by shedding bits. Each bit represents 6dB of headroom, which means a 32-bit machine, as most are currently, theoretically has a range of 32x6 = 192dB, but audio gear cannot resolve that much dynamic range. Some very high quality gear can resolve 22 bits (132dB). With a 24 bit file via USB, you could drop the level to (32-24)x6 = -48dB and still replay all 24 bits.CD can resolve 16x6 = 96dB. When playing a CD, you could drop the level to (32-16)x6 = -96dB before impacting the sound.

IME, a preamp needs to be state of the art to out-resolve a high quality DAC/preamp. Simply having digital volume control capability on a DAC does not guarantee success however. The DAC needs a good analogue section to properly drive an amp directly.

 

[Kingrex]

I think a bigger piece of what needs to be considered is the amp and speaker relationship. As the volume goes up, the voltage and current to the drivers also go up. There is a sweet spot when the amp is giving what the speaker needs. When your well below that level, your starving the speaker and the drivers can not perform at their peak level.

There is also room interaction. At low volume your bass will act quite different in the room.

 

[analogsa]

Digital level control works by shedding bits

Even the earliest Sabre chips did attenuation using 48 bit maths. How many bits do you expect shedded this way?

 

[analogsa]

Looks like some responses to the thread do not discuss digital vs analogue attenuation but whether an active pre should be used vs a direct connection to amp. Not the same.

 

[ecwl]

Perhaps people misunderstood what I meant when I said “most DACs struggle a little with small signal linearity and accuracy”
Here’s a measurement of a fairly decent DAC
https://www.audiosciencereview.com/forum/index.php?threads/weiss-dac205-dac-review.50402/

You can see that despite “excellent” linearity, the line is not flat between -120dB to -100dB signals. So while the mathematics of digital volume attenuation can always be perfect, DACs are physical objects with voltage fluctuations in the delta-sigma modulation that are not precise. So if you need to attenuate by -30dB or -50dB, you’re relying on the accuracy of the -120dB to -100dB signals for accurate analog waveform reconstruction.

This is why in some instances, running a DAC at full volume and then using analog volume attenuation is better because you are no longer relying on the accuracy of these -120dB signals to reproduce the analog waveform as you‘re using the more linear parts of the DAC to generate the analog waveform and then you’re using the analog volume attenuation to lower the volume.