Help with Weird Amp Noise

Anxiety Serum

Active member
When I run this pretty hot gain pedal (Catalinbread Dirty Little Secret) into my 18w Vox clone I hear this swirling noise after a while. It goes away immediately after I turn the pedal gain down or off and comes back as I turn it up/on again.

What is this?

Should I be concerned?

Can I still run the pedal or should I stop if I hear that noise?



Trying to upload a video (only 18 seconds) but it says too big for the server.
 

Anxiety Serum

Active member
Is it in a loop?

what else is in the signal chain or describe signal chain
No loop in the amp.

Signal Chain:
Les Paul>MXR 10 Band EQ (not on when this happened)>Gain Pedal>Master Dispatch (not on) into amp.

It's happened before wit just the gain pedal into the amp.

Video Link (turn it up to hear).




The amp builder was quick to respond and noted:

It possibly could be too much gain for the first preamp tube to handle. I’d try swapping that out first. Go from an ecc83 to Ecc81

Or 12au7. Could also be a shielding issue in one of your cables or guitar. Try imputing different cables and guitar also you can try input 2 on the amp. It’s padded 5db (I am already into input 2)

You won’t hurt anything
 

311splawndude

Well-known member
Those sound like good first steps, I was going to say a preamp tube going microphonic could do this too so swapping some tube around is a always a good first step - so long as you keep track of what your changes are. Sounds like it does this despite what else is going on in the chain.
 

griff10672

Well-known member
even if it's off .... does turning any knobs on the Dispatch Master do anything to the noise at all ?? especially the " time " knob

I've had instances where overdrives in front of certain " time based " effects has amplified the clock noise to the point of hearing it even if the pedal is off .....
 

Anxiety Serum

Active member
even if it's off .... does turning any knobs on the Dispatch Master do anything to the noise at all ?? especially the " time " knob

I've had instances where overdrives in front of certain " time based " effects has amplified the clock noise to the point of hearing it even if the pedal is off .....
I'll have to try that. But I think I have run it on its own with no other pedals and gotten the same issue.
 

Anxiety Serum

Active member
It’s instability. You’re driving the first stage grid positive.

Turn the gain down or use a tube with less beta. 12ax7 is a beta of 100. Try a 12AT7 or 12AU7.
Thx. That did go over my head a bit though?


What do you mean by first stage grid positive? And what is Beta in a tube?

Will using a different tube change the amp sound much? I like its base tone and don't want to mess with it much.
 

Anxiety Serum

Active member
So I ran a few test. Plugged straight into the pedal then into the amp. Still has the issue. Changed cables, changed guitars. Still same issue.

Turning guitar volume down even off, same issue. Turning amp gain (volume knob) down, same issue.

The only thing that eliminates the noise is taking the gain on the pedal (labeled Pre-Amp) down (below noon) or turning pedal off.

I can probably still get the tone I want out of pedal at noon or less. Just want to make sure I am not overloading some circuit or overworking my tubes if I do this.
 

Anxiety Serum

Active member
Ran one more test. I used the 9V option instead of the 18V plug for the pedal (it is designed for both). With the 9V option the noise goes away even with maxed out gain. Again with the 18V it goes away if you cut the gain by 50% or more.

The noise is only audible when not playing and you can't hear the amp noise through the speaker or anything.

Just want to make sure I am not harming anything (or ruining the tubes ect.) if I play with 18V and Gain maxed and just ignore the internal amp swirling noise.
 

JackBootedThug

MODERATOR
I had an issue with a one spot pedal power thing years ago. Made a weird sound in the loop of my vh4. Battery power it was gone. Single 9 volt adapter was fine. Plugged in the one spot and boom...noise.
 

Anxiety Serum

Active member
I had an issue with a one spot pedal power thing years ago. Made a weird sound in the loop of my vh4. Battery power it was gone. Single 9 volt adapter was fine. Plugged in the one spot and boom...noise.
Using individual plugs on this. My VH4 pedal and MXR 10 Band EQ come with an 18V plug. So that's what I am using there or a 1Spot solo 9V plug. Seems like its just pushing too much gain into the tubes in the 18V/higher gain setting.

glpg80 said (below), but I didn't fully understand what "stage grid positive" or "beta" meant:

It’s instability. You’re driving the first stage grid positive. Turn the gain down or use a tube with less beta. 12ax7 is a beta of 100. Try a 12AT7 or 12AU7.
 

Anxiety Serum

Active member
I had an issue with a one spot pedal power thing years ago. Made a weird sound in the loop of my vh4. Battery power it was gone. Single 9 volt adapter was fine. Plugged in the one spot and boom...noise.
Well I think you just solved my issue. The 18V Diezel power supply seemed to be causing the noise. When I used the MXR 18V, just like using the 1Spot 9V, there was no noise. Now I only tested this for 15 minutes, but the noise immediately came back when I replugged in the Diezel power supply. So it seems to be the culprit.

The pedal sounds better with an 18V. Now I know just to use a different 18V and not to use the Diezel power supply with it.

Many thanks.
 
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