To summarize:
A.
paolo, you plug your bass into your DI, and your DI into the PA
and the Rumble.
2. You want to stop using the Rumble while still using the PA.
2.a. You don't want to turn down the Rumble's volume (or power it off) first.
2.¢. So, you unplug the instrument cable to the Rumble.
2.¢.# You see this as the most
convenient way to accomplish this.
2.¢.@ You
prefer this method.
2.¢.% Doing this makes a big, loud noise in the PA.
2.¢.& Why?
2.¢.&.i. Why does it do this?
2.¢.&.i.π Maybe the short of unplugging the amp Input is traveling backwards through the DI to the PA?
2.¢.&.i.π.∆. Maybe something is wrong with the DI?
2.¢.&.ii. Why do you prefer this if the noise is annoying?
2.¢.&.iii. Why not turn down the Volume or turn off the amp to avoid the noise?
2.¢.&.iv. Why is convenience more important than preventing noise.
2.¢.&.v. Why not use the Rumble's XLR Out instead of the external DI?
2.¢.&.v.¿. You could plug something into the Headphone jack to mute the amp while still going through the PA.
III. Most Rumblers here suggest muting the Rumble before pulling the plug.
III.e. Turn the Drive & Level knobs fully counterclockwise.
III.f. Use the Overdrive button (or a footswitch) to mute, or un-mute, the Rumble.
.
2.¢.&.i.π Maybe the short of unplugging the amp Input is traveling backwards through the DI to the PA?
Yes, but I don't understand why...
2.¢.&.i.π.∆. Maybe something is wrong with the DI?
Yes it what I'm thinking, but I bought the DI one month ago... But it's possible it has a problem
2.¢.&.iii. Why not turn down the Volume or turn off the amp to avoid the noise?
Yes, I can use other methods, but there is still something not working correctly and I would like to understand why
2.¢.&.v. Why not use the Rumble's XLR Out instead of the external DI?
Because the amp DI is post eq and gain, and I want to change the amp levels without changing the signal that go to PA
2.¢.&.v.¿. You could plug something into the Headphone jack to mute the amp while still going through the PA.
III.f. Use the Overdrive button (or a footswitch) to mute, or un-mute, the Rumble.
Ok, thank you for your advice!