Weird awful feedback

[daniel_pt]

Hello everyone.

I'm having a really weird and annoying feedback that I'm not being able to understand why!

My amp is a Bugera 333XL and I'm only getting that said feedback with two situations. 1rst is if I unplug any guitar and there's the cable only connected to the amp (should it even feedback without the guitar!?!?) or if I'm using my LTD EC-1000 with passive Seymour Duncans, specially if neck pick up is selected (SD Jazz). It's like a really bad squeal, very different from a growing feedback sounds like. Can it be a grounding issue?
If I switch the bridge pickup, the feedback goes a bit more normaler.

IF I play with any of the other guitars using EMGs, nothing of this happens. Just the normal feedback when the amp is too loud or I'm near the speakers...

I really can't understand why the amp or guitar is doing this... :|

If someone has any tip, I'd be much appreciated.

[Jon Snell]

With the 333, it has extremely high gain to get a realy dirty sound. (Some like it, can't think why, sounds awful). If you plug a guitar lead in with no guitar on the end, the open loop gain is sufficient to make the pre amps go unstable and produce a howling noise.
Some guitars can do the same on this amp. Turn the gain down a bit and that should cure your dilema.

[pdf64]

Maybe you’ve got the amp set up for a lot of gain? If so, try turning it down a bit.

I don’t see how 1 is a problem?

Regarding 2 the pickup squeal, that’s also normal; apply enough gain and anything will become microphonic.
Have you got metal covers on those pickups? If so, try removing them. Or wax potting the pickups with the covers on.
I think Seymour Duncan might only pot the coil assembly, with any covers being an option that’s fitted after the potting. Which leaves them free to vibrate and so can result in this issue.

[daniel_pt]

Maybe you’ve got the amp set up for a lot of gain? If so, try turning it down a bit.

I don’t see how 1 is a problem?

Regarding 2 the pickup squeal, that’s also normal; apply enough gain and anything will become microphonic.
Have you got metal covers on those pickups? If so, try removing them. Or wax potting the pickups with the covers on.
I think Seymour Duncan might only pot the coil assembly, with any covers being an option that’s fitted after the potting. Which leaves them free to vibrate and so can result in this issue.

The 1 is not a problem, but I don't remember ever having feedback with the crunch or lead channels selected, removing the cable from the guitar and the amp immediately producing feedback.

The amp gain is set the same for this guitar and the ones with EMG... I just find really weird, why the EMG don't this immediate feedback and the SD Jazz, which has a lot less gain, does!

[Helmholtz]

I think the difference is in PU impedance.
Active PUs have low output impedance and an amp input terminated by a low impedance is much less sensitive to unwanted EM coupling and interference.

Does increasing the distance between guitar and amp help?

[g1]

Remove the cable at the amp end, not the guitar end. All amps will squeal if an open cord is connected and the volume is up high enough.

[pdf64]

… why the EMG don't this immediate feedback and the SD Jazz, which has a lot less gain, does!

So do the SD Jazz pickups have metal covers?

[daniel_pt]

I think the difference is in PU impedance.
Active PUs have low output impedance and an amp input terminated by a low impedance is much less sensitive to unwanted EM coupling and interference.

Does increasing the distance between guitar and amp help?

No, oddly no... As soon as I stop playing and remove my hands from the strings, an immediate high pitched feedback starts. Doesn't matter my location... I even hide myself behind a door to see if anything changed, but no!

So do the SD Jazz pickups have metal covers?

No, no metal covers on both pickups.

Can a bad pickup generate feedback?

Because the bridge pickup, another Seymour Duncan (the custom 5) doesn't behave the same way. It also produces feedback, but in a normal way and less (way less) high pitched.

I have another Jazz stored in my old guitar parts. I'm even tempted to swap both SD Jazz PUps to see if there's any change.

[Helmholtz]

You could test my impedance theory by inserting a pedal with a buffered output between guitar and amp.

[daniel_pt]

I don't know very well if i understand what a buffered output is, but as i don't use pedals, I'll connect the guitar to the Head Rush MX5 and then to the amp and see what happens

[Helmholtz]

What is a MX5?

[Jon Snell]

MX5 is a digital looper. There may be the issue.
Check it guitar, amp, speaker, dry and no effects..
Nothing in between.

[daniel_pt]

MX5 is a digital looper. There may be the issue.
Check it guitar, amp, speaker, dry and no effects..
Nothing in between.

That's what I'm doing... guitar - amp - speaker. No effects at all. I'm reducing my variables at the maximum.

Helmholtz the MX5 is a digital effect processor. I have it connected to the fx loop, but I'm not using it during this process.

I think I'll record the feedback noise I'm getting from this guitar and maybe you'll see how weird it is.

By words, the best I can describe it is, it sounds the same as if i had only the cable connected to the amp input.

[Helmholtz]

Can you stop the squeal be somewhat rolling back your guitar volume or tone control?

[daniel_pt]

Yes, if i cut the volume it stops... it's definitely coming from the guitar and the neck pick-up. The bridge pick-up has a different behavior (a normal one) surely it feedbacks, but not crazily