Digital vs Analog Volume Control

[petak]

Hi,

A complete newbie here with maybe a very stupid question

May I ask if the analog volume controls on chip are actually purely analog or the signal does in fact get converted to digital, processed and then converted back to analog? Like, for example, the new Fiio K5 Pro is said to have "NJRC NW1195a analog volume adjustment chip"- is that the same as a resistor pot just controlled electronically? If it is indeed analog, how come the channel imbalance issues magically disappear? Also, I have an Arcam amp that also has an electronically controlled analog volume control that allows the adjustment steps to be changed - how does that work with an analogue device? Do these analog volume adjustment chips act like resistor pots - attenuating both signal and noise?

Thank you very much,
Peter

 

[kipman725]

in the case of the NJRC NW1195a its just a resistor ladder on a chip and will be put after the DAC, for practical purposes its the same as volume pot but will have better channel matching at high attenuation.

 

[AnalogSteph]

Usually these PGA chips will combine a resistor ladder attenuator with a variable gain stage, opamp being either internal or external. Otherwise their dynamic range tends to be a bit lacking. Going by the specs, this part seems to be doing the same.

Hmm, going by specs this part's dynamic range may actually be exceeding the PGA2320. The datasheet does hint at several typical problem areas... distortion at increasing attenuation (FET switches in series are only ever so linear), integrated opamp distortion performance, and the need for low drive impedance to keep crosstalk low.