Guitar head squealing at moderate volumes

[soccerman58]

Hi
This is our first foray into tube amps and my first post. I bought my son a B-52 AT100 tube head. It was and is very well reviewed and compared favorably to Marshalls and Mesas and Peavey 6505s.

He plays metal which means he is fairly loud (has a half-stack) but no more so than the other guitarist who has a Line 6 modeling amp. He is getting terrible squeal coming out of this. It came with Chinese 12AX7 pre tubes (4 preamp, a loop driver tube, a phase splitter and a tube driver for the reverb (12AT7).

We were sent a set of ElectroHarmonics by the factory, but they were no improvement at all. They aklso sent a new quad of Sovtek 5881s which I put in, but I have not rebiased as I don't know how (am scared to actually).

He has tried it with 4 guitars: an LTD with active EMG81, two Schecter, an Epiphone with fake PAF and a Kramer with quad rails and they are all just as bad. I can hear them practicing downstairs and I'm just about to throw the &%#^@&# thing out the window!

I have a few questions for the experts among you:

What is causing the feedback noise...tubes, pickups, both, something else?

There are at least 3 identifiable frequencies that appear regularly, so I don't even think an EQ would really help, and anyway, you don't see SLash or Kirk Hammet having a problem with squealing and having to use equalizers. I've even tried a Behringer feedback destroyer and a Rocktron Hush with no luck

What can I do?

I am not replacing 7 preamp tubes and a 6l6 quad at about 160 bucks for JJs just on the off chance it might go away, but I would consider buying one or two preamp tubes to start off with. 2 JJs is 20 bucks, fair enough. But which tubes are the likely offender(s) please? There are 4 in the pre unlike a Marshall, so I am not sure how they are working, although 1 and 2 are shielded, so maybe start there?

ALL reviews, really without exception, from all kinds of guitarists rate this amp very highly indeed. NOBODY that I have read (and I have read a lot!) has said this is a squealing pig that should be trashed.

Thanks
Phil

[Rick Erickson]

you don't see SLash or Kirk Hammet having a problem with squealing and having to use equalizers.

No - they pay technicians to maintain their rigs. Did you buy this amp from a local store? Is it new? A local store can usually help you with problems of this nature and should be expected to at least diagnose it for free if you recently purchased it from them. If the amp is new then you should seek a warranty repair center. Failing all that, you need to determine if the amp is the problem or if it might be in the cables, effects, guitars etc.. First thing to do is turn the guitar's volume control down and see if the squealing continues or goes away. If the squealing continues then it's probably an amp problem. If it goes away then it's either in the guitar pickups-lack of shielding or potting, or possibly a bad cable, or even an effect pedal that is acting microphonic. You didn't mention any floor effect pedals but I thought I would include them in the diagnosis. Unfortunately I'm no Edgar Cayce and the only way I could begin to tell you if the amp is as good as it's hype is if it came into my shop. Before you spend $150.00 on tubes I recommend having a good local guitar amp tech look it over and then consider following his recomendations. It may not be tubes at all - it could be a loose wire or a microphonic coupling capacitor, internal oscillation or who knows what.

RE

[Satamax]

And if you trace it down to the amp being the bad part, check this http://www.geofex.com/ampdbug/ampdebug.htm

Bye.

Max.

[soccerman58]

Hi

It doesn't do it with the guitar turned down. Nor does it do it if I unplug the guitar and pass the jack close to the front of the amp. Interestingly, it will do it if I unplug the cord and wave the jack in front of the speaker cabinet.

We can get two types of feedback. Depending on which tube I have in #1 we can generate a solid, powerful howl at one of two frequencies. The "microphone" style squealing of piercing, shifting frequencies usually only comes if he is either playing or waiting to play and is muting the strings out with the left hand. The only way he can get rid of it is to wave the guitar around or stand on one leg or something.

If I tap all the tubes, the only one that makes any noise is #1. I get a clanking noise out of it when I tap it, and I have tried two tubes there, both from B-52. Maybe there is something wrong in or around the socket?

The controls are set fairly high with the channel gain on 6, the post gain on about 7 and master volume on 7+. According to some users on Harmony Central, at those settings we should be blowing the roof off, and it really isn't that loud at all. I mean, you can't have a fireside chat, but it's really only at the point where you are actually generating some tone out of it. I'm an old fart who shouts at kids on the lawn, but this volume level doesn't bother me, FWIW and one of the guys I talked to said at that volume it setting it should be hard to be in the same room with it.

We have tried several guitars with this from an active LTD Viper with EMG81, two Schecters, one with 81s an inexpensive Epiphone SG with PAF clones and a Kramer with Quad Rails. All are about as bad, except the more expensive of the Schecters with the 81, which is a little better behaved. All are mahogany bodied
Thanks
Phil

[Ray Ivers]

Phil,

Just to add to the excellent suggestions Rick and Max made - if you haven't tried this already, can you put the amp in one room and the cab in another, to acoustically isolate them? If that 'fixes' it, then the amp could possibly be moved off the cab and placed elsewhere in the practice space, mounted on rubber feet or isolation dampers, chassis bolts loosened slightly, etc. If it still squeals, it's almost certainly an internal electronic oscillation of some sort, and most likely non-user-serviceable.

Ray

[Jag]

What about pedals?

Is he using any? If so, what type and what are the approx settings. How many pedals does he have on at one time. Is there an effects loop built into the amp? What, if any,effects are patched into the loop?

Your problem could be coming from a number of places but, considering the apparent low volume, I'm wondering about effects/effects loop usage.

[Regis]

"Interestingly, it will do it if I unplug the cord and wave the jack in front of the speaker cabinet."

Huh? Oh, you mean if you unplug the cord from the guitar and wave it infront of the cab? Yeah, that would make noise.

Try swapping out that tube that makes noise when you tap it.

Now, I don't want to hurt anybodys feelings, but this needs to be said. If this is you and your son's first foray into a high gain tube amp, you need to realize it takes a modicum of ability and skill to be able to handle an amp like this. Even a vintage amp like a plexi takes some getting used to when cranked. Feedback and squealing is part of the package, even when everything is functioning correctly. In a high gain amp with multiple tube stages cascading into each other it's like trying to tame a bucking bronco. I just refurbished an old Kay tube amp from the sixties and when I crank it with a tube screamer it feeds back like crazy, however I know how to work an amp like this because I've been doing it for years.

Does your son know anyone that has experiance with high gain amps? Maybe they could help with setting up the tone and gain stages and cut down on the feedback. Even then it will take some practice to get used to it.

That being said, all the tech advice posted in this thread is good and should be considered, starting with making sure you don't have a microphonic preamp tube.

good luck,

regis

[mocklah]

hi Phil,
i believe Regis is on the right track w/ his hi-gain theory.
i've been playing ultra hi-gain hardcore punk and thrash metal since '83.
i used to have to stomp a switch on and off for all the stops in the songs. some guys are quick enough turn the volume up and down for the breaks 'n' stuff.

but that was before i discovered the wonderful NOISE GATE and all of its offspring. i've tried 'em all, and my favorite is THE DECIMATOR.

buy your son the decimator and his chops will sound nice and tight.

you can get em new for about $120 on ebay.

read reviews here: http://www.harmony-central.com/Effec...Reducer-1.html

[David Schwab]

Have you tried a different patch cord? It either sounds like a microphonic cable or way too much gain to me.

Are you using a real speaker cable for the speaker, and not a shielded cable?

[seeley]

Hi there. I think Regis is on it too. I recently helped out a young guy who'd bought a Laney 100 head and being a young metaller thought the only way was to have the gain fully cranked. The noise and feedback woes he suffered were horrendous to the extent his old man got onto the manufacturer and the shop before contacting me. The old rule of thumb that gain and master should be somewhere around the same number on the dial is worth following