It sounds like you are describing the normal noise on the repeats that is present at long delay times, which is inherent with the PT2399. Is it there when you have the delay time at noon or lower?... or to put it another way, is it more pronounced with longer delay times?
The very faint hum type sound I described is really only present when there are no repeats happening so it sounds like we are likely talking about two different things.
The VFE designs usually push the boundaries of some components, sometimes to an extreme. The PT2399 associated noise is allowed in the design of the Blueprint in order to push the delay time to an extreme for that chip. I'm not sure if the Mobius Strip is designed for longer delay times, or if it has different filtering, so the nosie may not be present there for that reason
The very faint hum type sound I described is really only present when there are no repeats happening so it sounds like we are likely talking about two different things.
The VFE designs usually push the boundaries of some components, sometimes to an extreme. The PT2399 associated noise is allowed in the design of the Blueprint in order to push the delay time to an extreme for that chip. I'm not sure if the Mobius Strip is designed for longer delay times, or if it has different filtering, so the nosie may not be present there for that reason