I am not familiar with your unit, but the answer is probably yes. One would have to have a schematic or some idea about the circuit design and then test the appropriate components. Do you have a schematic or circuit diagram?
The SubOne has an external controller which I think is where the diffuclty comes in. It consist of the volume, gains, filters and phase selection. Finding the schemetic for this would probably be impossible.
The circuit is likely not much more than power supplies to several op amps with associated caps and resistors. Adjustments are typically made by varying resistances in the circuits with potentiometers and swtichable resistive networks. Not much to troubleshooting these things if you have some skills. The parts are usually very generic and cheap. Labor can be another matter. Even without a schematic you can usually sort it out with pin out diagrams of the active devices.
These kinds of circuits are often so generic that they are not concerned with someone copying the design. Many are little more than implementations of the application examples provided by the maker of the op amps in the unit. Some companies will make the schematics available if you just ask.
You can measure some components in circuit, but it depends on the circuit and what you are trying to measure.
Thanks for all the help Leonard, looks like NHT do publish their schematic on their site. The SubOne however is vintage so it's not there. I just emailed them for a schematic, hopefully they have one. I'll post a reply on the progress.
Cool, I'm reading only on how to read the components, you're correct about not having much components, just resisters and capacitors. I'll test each component to see which part is bad. If all else fails, you'll hear from me.