Crate V5 squeal

[Tele-Dave]

What would cause my V5 to squeal when I reach in to grab the EL84?

Amp also has a lot of hum at max vol. Are they all like this?

That is how I found that it squeals then I reached for the tube. Starts when you get your fingers about 1/2 inch from tube, and gets pretty serious when you wrap your fingers around it. Is this normal?

 

[Tarin]

Being the V5 my first tube amp, i read the owners manual start to finish and it caught my attention that a tube (don't remember wich one) had certain "microphone" properties if tapped... or something.
So i made the test, unscrew the chasis and turned on my amp.
tapped here and there but nop... no squeal.

 

[Tele-Dave]

Being the V5 my first tube amp, i read the owners manual start to finish and it caught my attention that a tube (don't remember wich one) had certain "microphone" properties if tapped... or something.
So i made the test, unscrew the chasis and turned on my amp.
tapped here and there but nop... no squeal.

Hi there again Tarin,

It's not the tapping, try wraping your fingers around the tube, the power tube, the big one, like your going to pull the tube, and see if your amp squeals. Volume was up a little more than half way when I did this, but it does this at all volumes.

I'm just curious if this is normal.

 

[Plank_Spanker]

Tele-Dave,

I don't want to come across as pompous and offend you but...................


Why are you grabbing the tube with the amp powered up? If you suspect the tube is microphonic, the best way is to check is to tap the tube with the erasor end of a pencil. But a hum at max volume is generally not caused by microphonic tubes.

Don't grab the tube and it won't squeal......:beer:

As for your hum at max volume, that's normal for some amps....unless it's totally obnoxious and over rides the sound of the amp.

 

[Tele-Dave]

Why are you grabbing the tube with the amp powered up?

Don't grab the tube and it won't squealQUOTE]

If it was a circuit oscilation, might be felt as a slight vibe in tube. Not talking whatsoever about microphonics.

But, is it normal for squeal when you touch tube??? Never had that happen with any other amp.

If touching tube will cause me harm, then all amps would not be safe for release to public. Glass is the best electrical insulator.

 

[Plank_Spanker]

I don't know. I've never tried it. I've had no need to handle the tubes when the amp is on.

Just a guess, but you might be forming a resonant cavity with your hands near the tube, hence the feedback.

I wouldn't worry about it at all if the amp behaves itself when you're not touching the tubes.

 

[tunghaichuan]

If touching tube will cause me harm, then all amps would not be safe for release to public. Glass is the best electrical insulator.

But glass is an excellent conductor of heat. Running the tube in Class A like the Crate does produces a lot of heat very quickly. Be careful not to burn yourself on it.

Given that this is a PCB-based amp, it could be a flaky solder joint. You might try the "shotgun" approach and reflow the solder joints on the power tube socket.

tung

 

[Tele-Dave]

Just a guess, but you might be forming a resonant cavity with your hands near the tube, hence the feedback.

I wouldn't worry about it ................

Resonant cavity??? isn't that like a black hole???

Yea, just trying to eliminate reasons for hum.

Thnx for come-back.

 

[Plank_Spanker]

Amp also has a lot of hum at max vol.

This statement leads me to believe that this is normal operations. We're talking dimed out here. That will certainly bring any line hum right to your ears.

 

[markb]

Resonant cavity??? isn't that like a black hole???

Yea, just trying to eliminate reasons for hum.

Thnx for come-back.

Try cupping your hand over a microphone on the edge of feedback for an illustration of the "resonant cavity" effect. I've seen this so many times. Mic starts to howl, singer puts hand up, howl increases exponentially. The correct response is to step back.

As for electrical safety in tube amps. Well, yes they're compliant but I wouldn't go sticking my hands in the back of a live amp even with the PSU tucked away in the chassis. Better safe than sorry.
For your amp, it wouldn't hurt to try a few different tubes. My Pro Junior hummed like mad when I tried a set of Ruby Tubes. There's just the two in the V5, right?