Crate blue voodoo werid feedback noise not making sense need help

[dixiedevil1369]

I have a Crate blue voodoo its a 2005 to 2007 model checked preamp tubes there good dont have a way to check power tubes yet but this is the problem i'm having when amp is on clean channel theres no feedback of noise of any kind doesnt even hum and plays great as soon as i switch to overdrive channel i get this werid feedback or odd noise it almost sound like a bad jack plate or something to that affect all the time and even when i play on that channel you can still hear it in the background i have unhooked everything form the effects loop and tried it with and without pedal board still only overdrive channel does this. so if anyone can help that would be great.

[Chuck H]

I'm honestly not trying to be a dick, but I cant imagine what bad jack plate feedback sounds like. When you say "jack plate" do you mean like on a guitar or speaker cabinet? Is this feedback or a rattling or vibrating sound and how does it behave when the amp is just idling (both with the guitar turned up and with the guitar turned down) compared to when it's being played?

Chuck

[dixiedevil1369]

hey

weather the guitar is turned up or down doesnt affect it the hum stays at same volume only other way i can descirbe it is as long as there is no cable plugged into input of the amp everything is fine but as soon as i plug in the sound starts , i tried other amp heads ss and tube with same cables and guitar and i dont get this sound

[Chuck H]

+++

Your input jack ground may be loose on the circuit board. That's the first thing to check anyway.

Chuck

[dixiedevil1369]

thought of that but as i said before it only does this when i switch to overdrive does not do this on clean channel so it has to be something else, thanks for the info thou

[Chuck H]

One way to narrow the search for the problem is to remove preamp tubes. Start with the first tube. If the hum persists pull the next one. When you stop the hum you will have narrowed the problem to somewhere behind the gain stage that was amplifying the hum and the gain stage that wasn't the problem. The schem is available at schematicheaven.com

Chuck

[dixiedevil1369]

thanx chuck i will try that tonight

[dixiedevil1369]

ok used preamp tubes from a amp that has just been serviced and doesnt have any problems still got same humming noise but only on distortion channel i did notice that in the humming you can just hear what i can describe as a phaser type sound when i can get sometime i plan to pull chassis out and see if i can see anything touching or burnt looking anything not normal if you read this and think you might know whats casuseing this please leave a comment.

[Chuck H]

I wasn't saying to swap or replace tubes. Just pull them. Start with the first one, if that doesn't stop the hum pull the next one. When you pull a tube and the hum stops you will have narrowed down which part of the circuit we need to look at.

Chuck

[dixiedevil1369]

cant do it that way with this amp chuck if you take 1 preamp tube out it cuts power to rest of amp i did try doing it that way but as soon as you pull tube signal is cut off. i did notice that when on overdrive channel if i unplug cable from input it stops the humming

[Chuck H]

Do you mean that it cuts the filament power??? It's supposed to cut signal power. That's how we narrow what part of the circuit is humming. But it hardly matters now that I know that if you unplug the cable the hum stops.

What happens to the hum when you are using the OD channel (no pedals) and you turn your guitar volume down to 0?

Chuck

[dixiedevil1369]

still bad hum the hum is there with volume on guitar at 0 and amp volume at 0 on overdrive and i did mean it cuts filament power i belive it does this because of the blue voodoo have a circuit board at the preamp stage i have the chassis out now looking for anything werid or out of place when i took it out i heard what sounded like a screw rattling around so i got the flashlight looking around in the amp

[dixiedevil1369]

found the problem it was a screw rattleing around in here just plugged everything back in and everything is back to normal no more hum or anything. thanx very much chuck for being patient and trying to help me,and to everyone else that pitched in and helped thankyou.

[jterrats]

I have the same problem but no screw rattling... do I have the right tubes? I got 8 12Ax7 preamp tubes (groove tubes) and 6 6L6-R power tubes (groove tubes).

The noise stops when i touch the jack plugged into the output speaker (the cable from the output speaker to the cabinet). I know that a tube amp is supposed to have some noise but this "hiss" or "rain noise" can't be ignored.

Will appreciate any help, thanks!

[jterrats]

Another question... when the amp is on the power amp tubes don't glow orange as in the blue voodoo publicity pictures that I've seen. Are they supposed to be orange/red when I'm playing? because you can barerly see an orange light... maybe if I get my power tubes replaced can get rid of the noise...