Eeek, sorry for the umpteenth question on this...

[Roobubba]

Hi all (again!)

I'm still trying to work out why, at moderate volumes and above on the amp, I get huuuuuge amounts of feedback. I now have the ISP decimator prorackG, but in order to tame the amount of feedback at useful volumes, I have to run a **lot** of supression, and it makes it impossible to play solos, as it kills the notes as I play them!

I've tried it with two different guitars now, as I thought it might be a problem with shielding in my main guitar (which I've since had a go at sorting, too). Miracle Man bridge pickup in an ibanez rg470 guitar. I re-soldered the connections to give me star-grounding, and that has made no difference :(

I've taken the amp to a tech who gave it the all clear (and I specifically mentioned the feedback issues!). It has new tubes in, and sounds lovely, except for the feedback!

Tried new cables, minimum of equipment, 2 guitars, not sure what else to try.

Ahh yes, equipment list:
Peavey 5150-II
Peavey 5150 cab
Zoom G2.1u (with and without!)
Ibanez RG470F/TBL guitar with miracle man bridge pickup, neck and middle pickups lowered miles away from strings as I never use them.
Also tried with Marlin guitar. Horrible, but spare!
Planet waves cables (new)


Any help would be much appreciated!

Roo

[Orkestra]

turn your treble+presence down?

have you tried that?

[MDV]

Knackered cables? Tried new ones?

I've played a ceramic pig in close proximity to a LOUD 5150, straight into the amp, and it was pretty quiet. Certainly nothing unusual.

Failing that, I'd say theres a fault with the amp. No idea what though.

Oh, where are you playing? If its in amongst a lot of other electrical gear that can give you a tonne of noise!

[noodleplugerine]

Are you really sure the amp is in good condition?

You should be getting uncomfortable feedback on a 5150.

[Brow]

Sounds like you could have a knackered valve in the amp somewhere

[TwilightOdyssey]

Sounds like valves are going microphonic.

[Orkestra]

^ Yeah thats the problem I had with my Powerball, i had a set of tubes in there for a year, gigging 3 times a week for that roughly... by the end of the tour my guitar was squeeling at gigs like a stuck pig. it was horrid.
Do you get fizzy, clunking , clicky sounds too?

[Roobubba]

The valves are new (also happened with the old ones), I've tried various cables (I have about 10, and I've tried various permutations).
I also contacted the guy from ISP - he suggested using a cable with no ground in the effects loop for the prorackG - I did that and it made no difference to the feedback.

I've tried cutting the presence and treble, and that helps quite a lot, but not enough for me to play a solo at about 5 on the master volume (and about 7 to 9 on the preamp gain), due to the amount of noise suppression needed just to cut the feedback.

We have a couple of tracks with very tightly controlled guitar (start-stop stuff), and on these I need to turn the noise suppression up so that I don't get a squeal after every note. When I say turn the noise suppression up, I mean about 0db on both channels on the ISP prorackG.

Thanks for the suggestions so far.

I will try swapping around the preamp valves tomorrow, just in case they're microphonic - but it did the same with the old valves (and the new ones sound better by far!) - the new valves are JJs. It gives huge feedback both at home and at the studio. I can't guanrantee that both aren't bad for electromagntic interference,  of course!

Roo

[FELINEGUITARS]

Is this in a practice room ?
Or on stage?

5150s poke out an almost obscene amount of gain and in close proximity or a small enclosed space you can get bad feedback with most guitars.
Its kinda like you have nowhere to run or hide in a smallish rehearsal room

Also try packing some foam into the guitars cavities under the pickups - may help if the air gaps in the guitar are creating a physical resonating feedback

[Roobubba]

practice room. It's about 5 m by 3 m (triangluar shape), so not tiny.
When I turn off the ISP prorack, it's not like there's nowhere to run - it's just completely unbearable - HUUUUUUUUUUUGGEEEE feedback and screaming from the amp at massive volume, which only goes away when I turn the guitar volume down, or turn the noise suppression back on.

Will try the foam trick tomorrow too, and report back!

Cheers, and keep it coming!


Roo

[Roobubba]

OK,

I had the pickup out, and found behind it a spring from the previous pickups which had stuck itself to the miracle man! D'OH! I removed this and chucked some foam into the gaps. I also had a play around with the pre-amp valves. The whole lot sounds really, REALLY nice now - the pickups have actually come to life! There is still a lot of feedback when I crank the master volume (even with the guitar volume on 0, or guitar unplugged), but the decimator is doing a sterling job of taming the beast. I think I'll just have to have some sort of boost for any solo sections (my drummer won't let me play solos anyway :( ), which I can do with my zoom pedal. I am going to try to get the set up recorded so you can all hear what my definition of lovely is! :)

Thanks for all the suggestions. I don't think it's a problem that will ever be fully solved, but for now it's under control (mostly), so that will do!

Cheers,

Roo

[fps_dean]

Try swapping preamp tubes.  You can swap your preamp tubes yourself - they are plug and play so you can do this yourself.  The power amp tubes you can do yourself but you might not want to use it for very long so you don't risk damaging your tubes without getting the amp properly biased.  Despite having new tubes, there are enough cr@p tubes on the market today that new doesn't really mean anything anymore.

[CJ]

bit of a dumb question... but do you mute the strings when you're not playing and/or mute open strings?

[Roobubba]

to answer those two points:

I've already tried mixing up the (all new x6) preamp tubes. They're better than the old tubes. No crackles or pops, and they seem really really nice on the clean channel.

I was there while the amp was serviced and got the gy to talk me through everything. The output transformer ahs one side more efficient than the other. THe 4 matched power tubes mean that I can't balance out the uneven transformer with different pairs of tubes, but that's fine, because it's putting 120W through 4 of them anyway, which is plenty enough power!

OK second point - yes I mute strings. With the decimator, I can get a very nice stopped-muted sound at low to medium volume. At about 5 on the post (and 7 to 9 on the preamp gain), I have to set the noise suppression very high to stop feedback or squeals, but 5 on the post amp volume is HIGH. It's sort of hurt-your-ears-through-ear-plugs territory. I appreciate the comments, and encourage more, just in case I've missed something!

Cheers,

Roo

[Orkestra]

Have you tried taking each tube and putting it up your bum?


THAT REALLY HELPS.
























heheh.








Also, I would see if someone had a Powertube blow on them if they connected the wrong ohm speaker cab too your amp and instead of taking it to a store they just swapped out the tubes without re-biasing and raped your amp.

have you taken it to anyone? Because I suggest you do.