[jarthel]

as title.

the stepped attenuator is using Dale RN55/60 resistors. the chip-based pot is using pga2310.

thank you

 

[ericj]

Varies. Read the datasheet.

 

[jarthel]

Quote:

Originally Posted by ericj /img/forum/go_quote.gif Varies. Read the datasheet.

I probably was unclear.

I meant any sonic pros/cons between a chip-based attenuator vs a stepped attenuator.

ps. I have the datasheet of the PGA2310 in front of me. What should I be looking for?

 

[balou]

I don't think that there any SQ wise pros - the digital circuitry in the chip will add noise to the attenuator, the only question is, how well can the chip manufacturer damp the noise.

I just had a glance at the datasheet. the chip contains internal opamps. The stepped attenuator will be clearly the better alternative. it would be especially bad if the opamp adds a certain sound signature to the signal.
Output voltage noise of the opamp is also fairly high - double that of a NE5534 opamp.

I for one would only use this chip if there are very very good reasons why a stepped attenuator wouldn't work. or a normal pot. I like to keep things simple, and a digital circuit with yet more opamps in it isn't really what I'd consider simple. YMMV of course

 

[jarthel]

Quote:

Originally Posted by balou /img/forum/go_quote.gif Output voltage noise of the opamp is also fairly high - double that of a NE5534 opamp.

where did you see this? can you point it out? thank you

 

[balou]

I'm sorry - I misread it, only the output noise is stated in the PGA2310 datasheet, not the input voltage noise. which doesn't make me more confident in this chip.

 

[d0td0t]

I'll go with more discreet component too.. maintain e signal better then chip base.

 

[amb]

While I personally would use passive SA or high quality pots in my builds, chip-based digital attenuators do have a few advantages. One of which is lower stereo crosstalk. Pots and stepped attenuators add significant impedance at low to medium volume settings, which makes it susceptible to stereo crosstalk due to capacitive coupling. It may also pick up noise interference if the wiring from the pot to the amp is not directly on the amp board. Such problems are virtually absent in digital attenuators. Channel matching is also potentially superior in a digital attenuator, even when compared to a SA with precision resistors. Digital attenuators with micro-controller could also be made to provide cool features like remote control or attenuation display, etc.

I guess I'm playing devil's advocate here, but neither solution is perfect and each has its pros and cons.

For an all-discrete, reference quality amp like a β22, inserting a volume control with internal opamps just seems like the wrong thing to do. However, in a lesser amp, a digital attenuator might be compelling in its own way.

 

[Cauhtemoc]

Quote:

Originally Posted by amb While I personally would use passive SA or high quality pots in my builds, chip-based digital attenuators do have a few advantages. One of which is lower stereo crosstalk. Pots and stepped attenuators add significant impedance at low to medium volume settings, which makes it susceptible to stereo crosstalk due to capacitive coupling. It may also pick up noise interference if the wiring from the pot to the amp is not directly on the amp board. Such problems are virtually absent in digital attenuators. Channel matching is also potentially superior in a digital attenuator, even when compared to a SA with precision resistors. Digital attenuators with micro-controller could also be made to provide cool features like remote control or attenuation display, etc. I guess I'm playing devil's advocate here, but neither solution is perfect and each has its pros and cons. For an all-discrete, reference quality amp like a β22, inserting a volume control with internal opamps just seems like the wrong thing to do. However, in a lesser amp, a digital attenuator might be compelling in its own way.

A chip-based volume control such as the PGA2310 is not digital. You connect it after the DAC, it is nothing more than a digitally controlled stepped attenuator. Because of the way they are constructed, they are also often noisier than a proper discrete attenuator.

A true digital stepped attenuator connects via the I2S signal before the DAC. I'm assuming this is for an amplifier however, in which case this is not possible.

 

[luvdunhill]

why not try a relay-based volume control? seems to be the best of both worlds, according to amb's critique.