Digital volume control vs analog volume control

[Ropeburn]

Please can you escribe your methodology for blinding and setting levels to be within 0.01V of eachother.

It's worth adding that preamplifiers do have some strengths: well designed ones do have good, high impedance input buffers and good low impedance output buffers which can be beneficial in some use-cases. But of course they also contribute noise and distortion as well as potentially band-limiting.

I'm pretty sure you could measure some degradation on my cheap as dirt passive volume controller, mainly using it for input switching and volume control for any non-DAC source, there must be something. However, I don't hear a thing. Good enough, easily.

 

[dansan69]

As a curiosity - my integrated amp (a Lyngdorf TDAI-2170) which is essentially a power DAC (PWM), does most of the volume control by adjusting the supply rails of the amp, only below a certain level does digital regulation kick in

 

[Scytales]

As an curiosity - my integrated amp (a Lyngdorf TDAI-2170) which is essentially a power DAC (PWM), does most of the volume control by adjusting the supply rails of the amp, only below a certain level does digital regulation kick in

This technique is not unique to this Lyngdorf and there have been other designs to control the volume by changing an analogue quantity under the command of a digital signal.

For instance, in the 1990s Sony, has designed the volume control of its SDP-EP9ES processor around a current to voltage converter chip in which the master current source was made variable under the control of a D/A converter that took the output of the volume control knob coder to generate a DC voltage. I very much suspect that the built-in volume control of the Burr Brown PCM1738 and PCM179x DAC family works the same way or a very similar method.

That is to say that a digitally controlled volume control has not necessarily to be entirely digital in the sense that it computes the input data to scale their values prior to D/A conversion; it can be a mixed design that is actually more of an analogue volume control than a digital volume control.

 

[Roland68]

As an curiosity - my integrated amp (a Lyngdorf TDAI-2170) which is essentially a power DAC (PWM), does most of the volume control by adjusting the supply rails of the amp, only below a certain level does digital regulation kick in

This technique is not unique to this Lyngdorf and there have been other designs to control the volume by changing an analogue quantity under the command of a digital signal.

For instance, in the 1990s Sony, has designed the volume control of its SDP-EP9ES processor around a current to voltage converter chip in which the master current source was made variable under the control of a D/A converter that took the output of the volume control knob coder to generate a DC voltage. I very much suspect that the built-in volume control of the Burr Brown PCM1738 and PCM179x DAC family works the same way or a very similar method.

That is to say that a digitally controlled volume control has not necessarily to be entirely digital in the sense that it computes the input data to scale their values prior to D/A conversion; it can be a mixed design that is actually more of an analogue volume control than a digital volume control.

The Axign chips likely offer the best volume control. Since this control only modifies the step size/height in the PWM signal, it should be the most loss-free method.

 

[dansan69]

The Axign chips likely offer the best volume control. Since this control only modifies the step size/height in the PWM signal, it should be the most loss-free method.

Adjusting the rails on a PWM (or class D) amplifier will amount to this

 

[olds1959special]

Revisiting this thread. I have a very good pre-amp (Topping A70 Pro) and I have tried connected my DAC with short high quality balanced cables, but the sound is so much better going straight from the DAC. It's a night and day difference.

I think it's important to add the volume range is totally usable. I can listen at low volumes at about 15, and very loud levels at 70, and never have to go higher. The sound is better around 25 and higher, but I'm pretty sure that has nothing to do with bit loss or the noise floor of the DAC.