Feedback

Jimmyk68

hi all, I’m new to this forum but really looking for a bit of advice. I have a 2004 Gibson USA standard. Love the tones and playability of this guitar, but whenever I turn up the volume above no 6. I get horrendous feedback. I took the guitar to a technician and he played it and checked the wiring and said it was all as it should be, no problems. I use a black star 100 watt valve amp and cab, but seem to get feedback through other amps I’ve tried. I can’t seem to find what the cause is! Any advice much appreciated. Thanks in advance. Jimmy

Jimmyk68

Forgot to mention it’s a Gibson Sg. 

OilCityPickups

Is it howl or microphonic squeal? Are the pickups stock or have they been changed? The standard, covered Gibson humbuckers are normally very well potted and with the covers well fixed. 

ICBM

How close are you to the amp? (Amp, not speakers.) Direct electromagnetic coupling from the amp's output transformer to the pickups will cause feedback if you're very close to it. If it's that the only solution is to move further away - or use a solid-state amp.

Jimmyk68

They’re standard Gibson humbuckers. I move away from the amp, but it doesn’t seem to make much difference. Could it be a valve in the amp?

octatonic

Make a small video showing your amp and guitar settings and demonstrate the problem.

Funkfingers

TheGuitarWeasel said:

the covers

Good call. Poorly fitted metal covers can contribute to feedback issues. 

Do the pickups have metal covers or are the bobbins of the humbuckers exposed? More importantly, have they always been this way? 

Jimmyk68 said:

... guitar ... technician ... checked the wiring and said it was all as it should be, no problems.

Has anybody inspected the undersides of the two humbuckers? (As in, unfastening the four mounting surround screws, gently lifting the pickup out of the guitar and eyeballing the metal plate for identifying clues.) 

If your guitar was purchased pre-owned, it is possible that a previous owner installed non-original pickups. That could mean either cheap, nasty fakes or upmarket "historically accurate" replicas of vintage Gibson items.

In the latter case, the "historical accuracy" may have been taken to the extent of wax potting the copper coils but not the air gap between the pickup and its cover. In this example, the squealing through high gain amplification is also "historically accurate". Thus, the guitar tech's assessment would be correct, if unhelpful.

Marshall_stax

Jimmyk68 said:

They’re standard Gibson humbuckers. I move away from the amp, but it doesn’t seem to make much difference. Could it be a valve in the amp?

Unlikely to be the amp but just to rule this out, are you seeing the problem with any other guitars?

Jimmyk68

No issues with my other guitars, just the Sg. I’ll check the underside of the pick ups tonight.

OilCityPickups

Funkfingers said:

TheGuitarWeasel said:

the covers

Good call. Poorly fitted metal covers can contribute to feedback issues. 

Do the pickups have metal covers or are the bobbins of the humbuckers exposed? More importantly, have they always been this way? 

Jimmyk68 said:

... guitar ... technician ... checked the wiring and said it was all as it should be, no problems.

Has anybody inspected the undersides of the two humbuckers? (As in, unfastening the four mounting surround screws, gently lifting the pickup out of the guitar and eyeballing the metal plate for identifying clues.) 

If your guitar was purchased pre-owned, it is possible that a previous owner installed non-original pickups. That could mean either cheap, nasty fakes or upmarket "historically accurate" replicas of vintage Gibson items.

In the latter case, the "historical accuracy" may have been taken to the extent of wax potting the copper coils but not the air gap between the pickup and its cover. In this example, the squealing through high gain amplification is also "historically accurate". Thus, the guitar tech's assessment would be correct, if unhelpful.

Covers vibrating against the bobbin tops is the commonest cause of microphonic squeal. Often people retrofit covers to uncovered buckers not realising that they need to be potted on as well as just soldered. Loose magnets are common too ... tightening the four base bobbin screws can help that ... but don't overtighten as you'll strip the threads in the soft plastic bobbins. Loose screw poles are common on 'unpotted boutique PAF' pickups that don't use threaded baseplates (as the original PAF had). Occasionally I've come across a loose pole slug causing the issue ... but that's very rare. Basically anything that can move and vibrate on or in the pickup can cause squeal.

ESBlonde

One test to see if it's the covers is to squeeze a bit of card between the cover and the mounting ring as a temporary thing. This might be enough damping to assertain if the covers are in fact the problem. It won't solve the problem but may increase the threshold at which feedback starts. Alternativly just pushing a finger against the 'in use' pickup cover while it sqeals might give an indication.

Funkfingers

Jimmyk68 said:

No issues with my other guitars, just the Sg. I’ll check the underside of the pickups tonight.

My comments earlier about pickup surrounds only apply to an SG with the small pickguard. For the larger "batwing" pickguard, the strings and bridge have to come off first. 

The stock humbuckers should have Gibson USA embossed into their baseplates and twelve polepiece screw holes. (Gibson uses a one-size-fits-all baseplate for the 490/498/496/500 pickups.) If you find anything other than this, please post photographs of your pickups and, maybe, the controls wiring too.

Jimmyk68

Thanks for all the advice, seems the pick up covers were the problem after all.