You computer feeds USB into your DAC then RCA or XLR ICs feed into your amp.
Your CD player should feed a digital output directly into your DAC.
This is assuming you have the H190 without streamer.
If my laptop connects to the external DAC via USB, external DAC connects to H190 via XLR, how do I know which DAC is bypassed?
The signal from laptop to external DAC via USB is digital. The signal from external DAC to H190 via XLR is analog. Therefore the external DAC is performing the digital-to-analog conversion, and the DAC in the H190 is bypassed. USB is digital, XLR is analog.
Should the volume control on my laptop become bypassed?
Assuming you have the external DAC selected as the output device, then yes–the volume control (and DAC) in your laptop will be bypassed.
Also, I have an old Cayin CDT 15 that has an SS as well as a tube output stage. How do I know if the DAC in the CD player is being bypassed?
Depends on which output you are using. If you are using a digital output the DAC in the CD player is bypassed. If using an analog output the DAC in the CD player is not bypassed.
Would the using the optical outputs bypass the internal DAC?
Yes, as optical is a digital output.
Would bypassing the CD player DAC negate the option for switching between tube and SS output stages?
Yes, as these are analog outputs.
I forgot to mention that some components will take an analog signal and convert it back to digital only to convert to analog using its internal DAC. I have no idea if the H190 does this.
@hleeid So you can use an external DAC without problem but you will need to use the internal DAC for streaming or buy another streaming device and put it's digital output into the external DAC. There is no digital out on the H190. You could use the H190 as a pre-amp and buy a power amp too.