Hi everyone,
I am pretty new to this, but I'm trying to build a headphone amp and I have a few questions.
I'm using the PCM1794A with an I/V conversion stage, flowing into an AB amp output stage. All of the PCM1794A reference designs I've seen set the gain of the I/V converters such that they generate a higher Vrms (~4.5Vrms) than the outputs of most of the headphone amp designs I've seen, which generally spec 1.2Vrms or less as output voltage swing.
I've also read Small Signal Audio Design, which states in the very beginning to avoid amplifying then attenuating. Yet, the same book cites higher operating voltages as generally accommodating better SNR.
Put simply, I am struggling to define the output specs for the IV stage and the input specs for the AB amp stage. I would prefer to design the DAC and the AB amp stage in a modular way.
So my questions are as follows
- First, am I thinking about this correctly?
- How dependent should the output stage be on this IV stage and vice versa?
- Is it just plain old OK to attenuate with a preamp here?
- Is there anything I should do or read to get a better grasp on this?
Thank you for your help!
I am pretty new to this, but I'm trying to build a headphone amp and I have a few questions.
I'm using the PCM1794A with an I/V conversion stage, flowing into an AB amp output stage. All of the PCM1794A reference designs I've seen set the gain of the I/V converters such that they generate a higher Vrms (~4.5Vrms) than the outputs of most of the headphone amp designs I've seen, which generally spec 1.2Vrms or less as output voltage swing.
I've also read Small Signal Audio Design, which states in the very beginning to avoid amplifying then attenuating. Yet, the same book cites higher operating voltages as generally accommodating better SNR.
Put simply, I am struggling to define the output specs for the IV stage and the input specs for the AB amp stage. I would prefer to design the DAC and the AB amp stage in a modular way.
So my questions are as follows
- First, am I thinking about this correctly?
- How dependent should the output stage be on this IV stage and vice versa?
- Is it just plain old OK to attenuate with a preamp here?
- Is there anything I should do or read to get a better grasp on this?
Thank you for your help!
The data-sheet shows a 2Vrms design.
Yes, it does attenuate.
When a signal path has ALREADY jacked the level more than you need, yes, just pad it back down.
