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[rabidgerry]

Ok guy's after a 2 months of heavy gigging and re-arranging my rehearsal room setup and thinking the problem was that.........................I got the squeals.

No I wanna know how do I find out what exactly the problem is??


So I aint changed live guitar in a while, could it be this?  Do I need to repot the pickup?

Bare in mind this feedback has only just happened say the last few weeks but was particularly bad after some heavy traveling last week.

Or is it my rockmaster which has been on the road taking all the bumps?

oR my GT5 fx unit which seems to now have a slightly temperamental input that will squeal if not in correct?

I need to neutralize this issue fast as I've more shows next week.

I personally always jump to the guitar is the issue, but I dunno with this particular problem, the pick has been potted already and nothing has changed.  Even got sponge under the pickup.

My own gut feeling is it might be the preamp (may be the tubes???) or the GT5 and it's annoying input that needs replaced I guess.  However I cannot be sure, I just know the squeally annoying shit was not there before, I had not feedback for at least a year using my current setup and of course noise reduction in the chain after the preamp.

If its a cable?  How can I tell which one needs replaced?  DAM I hate feedback.

[vansinn]

I would bet on either pickups not potted well enough, or tubes going bad or incorrectly supported against vibrations.
You've stated pickups were potted not too long ago, so it would stand to reason this might not be the reason.

Romulan Logic dictates to me that if only one guitar has this feedback issue, that guitar is likely having a problem.
If feedback occurs with other guitars, it must be the gear.

Checking and replacing tubes is inherently easier than re-re-potting pickups.
So, start checking whether only one or all guitars creates feedback, then check/replace tubes - especially long-plate tubes, which from comments on the web are the most prone to feedback.
I don't think cables will cause such, but c'mon, you have tried different cables, haven't you?


Joke: Tried the old telephone smash trick?
Lift up the telephone and smack it hard onto the table's edge.
If it still works, it's a good phone.
If the squeal is gone, it was the phone, so maybe go buy a new one before the squeal returns.
If the squeal is still there it is indeed the phone, so go buy a new one.
If it doesn't work after this, and the squeel is gone, it was likely the phone, so go buy a new one..

[Dante]

I have read that tube will become harmonic after a while and it is usually described as a squeal. As van says, it would be far easier to swap tubes than to do other things...try that first. My second guess would be the GT5's input jack.

When I was getting all noisy with my Classic recently, I assumed it was the preamp, only to find it was a combination of a bad cord and a dead battery still sitting in my tuner pedal (the tuner powers all the other pedals, so it was sending noise everywhere). Try isolating the problem until it's gone, then you'll know which piece of gear it is.

Take the GT5 out of the chain. If the squeal is gone, that's the culprit. Like van says, if it's just one guitar, there's the problem. Take the preamp out of the equation and just use the GT5 to see if the squeal disappears. Try the rig without your pedals (as I did) to see if the problem lies in that pedal board chain or one of those tiny patch cables.

Best of luck, let us know what you find

[rabidgerry]

Thanks guys, that's good advice and stuff I should know better about to be honest.  I guess I just got desperate and panicy and sometimes in that state we just need that voice to point you in the right direction!

Ok I'll do that, may be try another guitar first.  I always leap to blame the pickup even though the dimarzio in my axe was factory potted, then I potted it again as I feel I do a better job.

Second try the tubes.  They are old and been in since I bought the unit over a year ago so who knows how old they are.  Also been travelled a lot recently and taken a lot of bumps on the road and general travel/onstage/offstage manoeuvring.

also depending on how things go....

Third I shall take the GT5 out of the equation (although this is providing my noise reduction) and just play through preamp and power amp. 

Fourth play through GT5 in a similar setup only using the on-board preamp.

Ok shall try these things before I start re-potting anything!

[vansinn]

Weeeel.. you got feedback, asked for feedback, and feedback is what you got..

When in stressful panic, always put on the old BOC "Method To The Madness"..
Or sit yourself in a painful position and say five times "Om, namu, guru dev namu", and ask your spiritual helpers for advice

[Systematic Chaos]

Been there RG...

I remember one of my RGs (no pun intended) turned squealy, real annoying high-pitch feedback in the bridge position on high-gain. Drove me nuts! I could rule out my racked gear pretty fast as it happened only with that specific guitar.
First thing that came to my mind then was the humbucker, so I sent it back to DiMarzio for re-potting and trouble-shooting (they do that for free, you just have to pay the postage to the US).
Pickup came back, soldered it back in...the feedback was still there.
I then swapped out the complete electronics (2 pots,, switch, jack, wiring) for new ones - still feedback. In the end it turned out it was the mounting ring.....

If you say that them toobz in your preamp are fairly old, swap them for new one (or at least some that you know aren´t microphonic) and take it on from there, step by step and item by item (Guitar->preamp->poweramp), adding one piece of your "normal signal chain" at a time (even cables) until you find the culprit!

   

[Dante]

Goddamn, it's good to have SC back

[Harley Hexxe]

Microphonic tube squeal is fairly easy to determine, even without a tube tester, (fortunately I have one).
  If the noise is happening, just thump the top of your rack case mildly with the side of your fist, and you'll hear the tube respond to that if it's the culprit. This usually happens when the mu is higher through the 1st side than it is on the 2nd side.

  Another thing that caused that with me once was a short in a pot connection. Just a stray strand of wire from one solder connection to another post was enough to cause a high pitched squeal in a high gain setting.

    Just my two cents.

      Harley

[rabidgerry]

Hey SC mailed ya man 

SC, how was the ring microphonic?  Rattling?  How could I determine this?  I have actually heard of others with a similar mounting ring issue before so I'm curious.

Harley, I have a feeling it's not the tubes you know, and I think your test will prove that also.  I kinda know what tube feedback sounds like as well.  I'll try the test though.  I think if I bash my MFX pedal I'll get the feedback, and that leads me to believe that it's this input jack that has gone bad.  I really need a good few hours to sit down and have a look at everything.  If it's the input I will swap it out.  Possibly using the same kind of method used in the ADA MP1 input jack mod, where an actual guitar (switchcraft jack) is used in place of the original closed style.  I did the input mod before on my first MP1 so I could apply the same kind of logic

ie wires from the PCB to the actual switchcraft jack.

The jack is my gut feeling, does this seem like a likely candidate to anyone else?  Example moving the cable about which causes the jack to move around in the input can sometimes cause crazy squealing feedback, however surely if stationary this would be no longer an issue?  I dunno.

[Harley Hexxe]

RG,

    I didn't think it would be one of the valves, but threw that out there just in case. I've heard of faulty input or even output jacks causing something like that from time to time, but never experienced it myself. I suppose it's possible with some of the more complex jacks that have multiple connections that serve different functions at the same time.
   Just like the old Engineer's motto: "The more you overhaul the plumbing, the easier it is to stop up the drains!"

        Harley

[rabidgerry]

Actually the  valves in the preamp in question (Peavey Rockmaster) rest on like a foam bedding so I actualy fail to see how any vibrations during travel would gradually make them microphonic.  They are due a change none the less.  I've new ones lined up.

Any good ways I could check see if it was the pickup? 

I would love to know for sure if it was the MFX input, I'm gonna mod it out regardless.  I've 45mins to lay on Saturday, hopefully I get a look at before then.

[vansinn]

Actually the  valves in the preamp in question (Peavey Rockmaster) rest on like a foam bedding so I actualy fail to see how any vibrations during travel would gradually make them microphonic.

Foam certainly helps; however, if the tube is going bad and micro, it can do this noneless - you know, sound waves, creating vibrations, do get into the box anyways..

Any good ways I could check see if it was the pickup? 

If a pickups is really badly potted, it'll often go microphonic just by standing in some specific angles in front of the amp.
If the potting is ok and it's the mount causing it, you might be able to clamp down on the squealing simply by clamping the pick or it's mount ring with your fingers. Just find a position relative to your amp that'll cause it to squeal, and then finger the puppie

[Harley Hexxe]

Actually the  valves in the preamp in question (Peavey Rockmaster) rest on like a foam bedding so I actualy fail to see how any vibrations during travel would gradually make them microphonic.  They are due a change none the less.  I've new ones lined up.

   As Sinn said above; foam helps. But if a valve is going microphonic, a good rap on top of the case will send enough vibration to it to make it react. It will be very noticeable. Still, from your description, I don't believe it's a valve.

    Harley

[rabidgerry]

Badly potted pickup you say?  Hmmmmmm I left in the wax a few hours, I'd be confident it was potted well.  I never know what to do with when I'm done though so I lay it upside down.

The feedback does happen in random places, but pretty much in front of the amp.  Moving the guitar to certain angles doesn't really help.  Bare in mind I can silence it when I stop playing, but that's the noise reduction eventually getting on top of it.

Despite the few various possibilities here, one thing I will do is definitely replace the input jack as I said it will howl and let no signal at all through if it moves a little when I'm moving around and the guitar cable is moving with me or if it's not in correctly.

I need advice however on something.

Do I:

A, replace the input jack with the exact same kind
B, Do I replace the input with say a better kind or more durable kind

I have the theory of doing something a little like the input mod for the MP1 where I hard wire another type of input socket to the PCB (and I would do this because obviously a different type will not match the solder points on the PCB).

If I do this what kind of input should I use?

see attached photos to see the kind that are original

[rabidgerry]

Anyways, so I figured out the extra feedback I was getting 

Stupidly when testing my rack out at home I had played around with settings and of course one of those was the output level of my preamp.  Which mean the signal going back into my GT5 was louder than normal and of course causing feedback that I couldn't control.  So that was sorted.  I still think I need to fix the input jack on the GT5 however.

In an experiment I did what I mentioned a few posts ago,  I did my own input jack mod.

So it turned out successful, and this was on my GT5 I keep on the studio (not the same one that is used live).  I dismantled the unit, removed the main PCB, unsoldered the input, removed it, then soldered wires from the points on the PCB to the matching points on the new jack.  The type of jack I used was a this:

http://www.technobotsonline.com/6.35mm-1-4-switched-stereo-pcb-jack-socket-with-optional-breakout-board.html

It mounted to the chassis providing more stability and fit perfectly allowing the pcb to mount in original position without any clash for space.  Anyways, I soldered it up, fitted the jack (very good tight fitting socket BTW), screwed the pcb back into the chassis, then fitted the top half of the chassis back with the bottom, turned the unit on and tested.  All good!    I got a great new jack and a no noisey scratchy input.

Time to test with my MP1.  Connected everything up, turned it all on............................oh wait a minute?  What's that noise?

Started getting this horrendous noise from something.  Sounded ground related.  First thing I did, took the MP1 out of the loop to my GT5 and played the GT5 by itself.  No noise, tried a multitude of settings on the GT5, no noise!

Tried the 3TM in the loop instead of the stock MP1....................no weird noise! Tried the Peavey Rockmaster in the loop, no weird noise. So I succeeded with the GT5 mod for sure!  I am %100 certain, but now it seems my MP1 has an issue that literally has just occurred for no apparent reason.  I was using it literally right up until the other day and now this problem has occurred!  I'll start a new thread and record this noise for you all.  Hopefully I can get it fixed!