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Avoiding Feedback While Pushing Amp
Old 23rd January 2016
Gear Head

Avoiding Feedback While Pushing Amp

Hello all,

I am the proud owner of a Sunn O))) alpha 115 amplifier head. I disconnected it from the original speaker it came with (it was originally a combo). Now I am experiencing some problems when pairing it with new speakers. I hear a loud "yell"-like feedback coming from any new speaker I add whenever I go past about 10 o'clock on the gain knob. Don't get me wrong, I generally love feedback, but I don't like what I am hearing.

I realize feedback is not abnormal considering high levels of distortion, but the feedback "yell" I hear sounds very different from anything I have ever heard in recording. Plus, gain knob at just past 10 o'clock is not exactly what I would call a high gain setting.

Perhaps it has something to do with my connection. I do not have a dedicated 1/4'' female jack on the amp head, other than the headphone jack, so I have been connecting wires from female connectors inside the chassis either a 1/4'' plug going to the speaker
2. directly to the new speaker.

The ports inside my amp look like this:

Does anyone have any ideas how I could limit this feedback?
Old 23rd January 2016
Registered User
I would be more worried about your hearing ... gain is gain, and feedback is caused by the acoustic vibration moving your guitar strings. (Or maybe you have a bad tube that has gone microphonic?). I don't know what guitar and pickup you have - hollow body guitars are more prone to feedback. This is why many high gain players went to solid body guitars, and some had their pickups filled with epoxy to stop them feeding back ...

Ifr this is studio use - put the head in the control room and play in the control room.
Old 23rd January 2016
Gear Head

Thanks for your response, Kiwi!

I'm sure it is the speaker. I have played the head and listened using the headphone output - no such feedback occurs.

The guitar is solid body. I use Epiphone 650R Humbucker and Epiphone 700T Humbuckers. Like I said, gain is only pushed up just past 10, 11 max and I hear it real loud. It's not screechy and metallic like I usually hear feedback in heavy metal recordings. It has a certain softness and roundness to it without actually sounding distorted. Also, I'm not even playing when I hear it. So it seems like the feedback "yell" is a direct result of the amp and the speaker combination. Not sure if I have heard it without the guitar attached, so the humbuckers could be playing a role since they are simply hooked up to the system.

Also - I'm realizing my level knob might be up pretty high when I experience the feedback. Say past 1.

The amp is solid state, btw.
Old 23rd January 2016
Registered User
A speaker is part of the feedback loop, so if it has a different resonant frequency or higher efficiency it can be a factor - but it's not likely to be the problem. Unless the noise is not feedback at all, and more of a cabinet rattle ...?

From your description, it sounds like more of a low frequency feedback. What eq settings are you using? Probably the bass maxed out for a bass heavy sound? Also - your room is probably boosting certain low frequencies ... if you understand about room acoustics you can work out your room nodes ... basically, the distances between walls, floors and ceilings create a boost at those particular wavelengths, which tend to be bass frequencies ...

You could get an eq that would put a notch at the problem frequencies - that could help. You might want more control than a typical graphic eq.

But basically - i think you are playing too loud (be careful about damaging your hearing) and too bass heavy. If you like heavy guitar sounds, in most cases the bass is coming from a bass guitar that does not need a lot of gain. And electric guitars can sound just as heavy with a lot less gain than you think you need ...

Most guitar amps are designed for filling halls, competing with drummers and bass amps etc. They are usually way too much for a small room.

Then again ... some top players struggled with unwanted feedback and needed to glue their pickups with epoxy. Brian May (Queen) uses very highly saturated tones, and his Red Special guitar is designed with this in mind ...

So you aren't alone with having problems with unwanted feedback ... but I think there is a lot you could do to prevent it.
Old 23rd January 2016
Registered User
BTW - on checking the article about the Red Special - it mentions that Brian May designed the guitar specifically for feedback, which might seem to contradict what I was suggesting. The thing is - he uses a LOT of gain, and the feedback that he wants is that musical, higher pitched, intentional feedback. The epoxy is to stop out of control unwanted feedback, which sounds more like what you are getting. Click on the link about 'microphonics' ....

Controlled feedback is a very cool thing - but uncontrolled is not.
Old 23rd January 2016
Gear Head

I see your point. You offer some good food for thought...
Old 23rd January 2016
Gear Head
phaezusa's Avatar

Try a different guitar with a normal Dimarzio or SD pickup. Sounds like unpotted pickup feedback.
Old 3 weeks ago
Here for the gear

Is there any way you could take a picture of how the rocker switch is hooked up? I can not figure out how to hook mine back up.
Old 3 weeks ago
Originally Posted by hfdz0 View Post
Thanks for your response, Kiwi!

I'm sure it is the speaker. I have played the head and listened using the headphone output - no such feedback occurs.

OF COURSE listening through the phones jack won't produce feedback. In order to get feedback the energy from your speakers has to be able to physically vibrate some part of the guitar or amplifier. It can be your strings, the coil in your pickup, or a part inside the amp. In solid state amps it's often a bad solder connection, but occasionally you run into a part like a capacitor or resistor that has developed a bad joint where the lead enters the component.

If turning down the volume of the guitar doesn't help try taking the amp head off the speaker cabinet so there's no direct physical connection.
Old 2 weeks ago
Here for the gear

Could you possibly post a photo of the power switch from inside the head? I’m having trouble hooking mine back up after changing it out. I should have taken a picture myself.
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