Ready to rumble...

[johnnyreece]

Not in a good way. A few years ago, I cobbled together a Rocket from an old Crate VC 50. I reused the original transformers and pots from that amp. Sometimes, after it's warmed up, I get a rumbling sound, whether there's an instrument plugged in or not. That's a new one for me. The volume knob does increase the volume of the rumble. any thoughts on what this might be? If I ever need a thunder sound effect, I have it covered. I've rolled different tubes (pre and power). I've removed the VVR circuit I had installed, as that was the cause of a separate (I think) oscillation issue. I appreciate any input!

[Structo]

The only time I have gotten weird noises it was tube related.

So if you are sure the tubes are good then check grounds.

Also check filter caps.

[Stevem]

Start pulling out preamp tubes until it stops, when it does then you likely have bad plate load resistors in that stage, or in stages more up stream from there.

[johnnyreece]

Thanks, guys! I'll double-check the tube situation, and pull preamp stage by stage. I was so disgusted that I left the amp at my friend's garage last night, so it may be a day or so before I can test anything out, but I'll be sure to report back.

[R.G.]

The only time I have gotten weird noises it was tube related.

+1.

The *first* step in debugging a tube amp is to sub in known-good tubes.

There is a reason that they're in sockets.

[johnnyreece]

The only time I have gotten weird noises it was tube related.

+1.

The *first* step in debugging a tube amp is to sub in known-good tubes.

There is a reason that they're in sockets.

This looks familiar. I did sub in other (I thought) known good tubes. I've made mistakes before, though. If it's that easy, I should be able to report back quickly.