Can a certain amp cause feedback?

barend · #1 11-06-2009, 03:20 AM

Last week I had a rehearsal with my Aguilar AG500 amp and Eden 210 XT cabinet in combination with a Full Circle pickup. My double bass was feedbacking really much.
Each time I let go my fingers of the neck it started feedbacking. Even when everyone was quiet and I didn't play.

This week I had a rehearsal with the same group in the same room but now I used a big Hughes en Kettner head and 410 cabinet that always is standing in that rehearsal room.
This time I had no feedback at all!

What can it be? All the same equipment and same setting only a different amp and cab.

PB+J · #2 11-06-2009, 05:43 AM

Could be any number of things--the two amp rigs have different eq profiles, for one thing. One is bound to be emphasizing a different frequency range than the other. One may be louder at the same setting, or it may be louder within a given frequency range that sets your bass off. It might be the speaker placement or the type of cab.

Was the feedback higher pitched? or a low howl? Try turning down whichever knob seems closest to the pitch of the feedback

barend · #3 11-06-2009, 07:06 AM

I had the EQ flat on both amps and the same volume (not terribly loud, just a fusion trio). I did the (same) EQ-ing with the Platinum Pro preamp.

It was high and low pitched feedback. Hard to control.

dar512 · #4 11-06-2009, 02:01 PM

Having all knobs set straight up does not necessarily mean that the output is flat.

fdeck has a document on his web site of finding out which settings got the flattest output on an amp of his. The settings were not the 12 o'clock positions.

Marc Piane · #5 11-06-2009, 02:07 PM

Yes, yes, and yes. Could also be the phase was reversed. Did you try taming it with the phase switch on the Platinum?

Jaromir · #6 11-06-2009, 03:13 PM

Quote:

Originally Posted by fingers

Yes, yes, and yes. Could also be the phase was reversed. Did you try taming it with the phase switch on the Platinum?

I agree totally! The most important thing is the basic sound of the amp. If it's double bass friendly (whatever that is) there will be only little problems with feedback. On the other hand - if the basic sound is not friendly, than you need to mess with EQ, notch, phase etc. etc. to just get close to the double bass friendly sound of the other amp.
Recently, I made exactly this experience with two Markbass combos: CMD 121P and Mark Acoustic 12. To my surprise, CMD was the acoustic bass fiendly one.

barend · #7 11-06-2009, 04:45 PM

Quote:

Originally Posted by fingers

Yes, yes, and yes. Could also be the phase was reversed. Did you try taming it with the phase switch on the Platinum?

yes, I tried everything. Canceling the high pitched feedback resulted in a low pitched feedback and visa versa.
What I want to know is why with one amp I get feedback and with other one zero feedback.

You would expect te get less feedback from the Aguilar since it is a much better amp in evry aspect than the H&K. Also I would expect to have less feedback from a 210 cab then a 410 cab.

The 210 cab has a horn (tweeter). Can the cause more feedback? I have the horn setting in the middle.

Marc Piane · #8 11-06-2009, 05:22 PM

Quote:

Originally Posted by barend

The 210 cab has a horn (tweeter). Can the cause more feedback? I have the horn setting in the middle.

yes. There's your high end feedback right there.

Les Fret · #9 12-05-2009, 09:11 AM

Can feedback be killed by putting some foam or whatever in the f-holes?
will it help a lot or will it only slightly reduce the feedback?

Ric Vice · #10 12-05-2009, 04:35 PM

Quote:

Originally Posted by Les Fret

Can feedback be killed by putting some foam or whatever in the f-holes?
will it help a lot or will it only slightly reduce the feedback?

Les,
I'd try any other technique than that, because it compromises the sound of your instrument. IMHO it's not a good solution at all.

Ric

Les Fret · #11 12-05-2009, 04:58 PM

What technique do mean?

and does covering the f-holes help to kill the feedback? I have seen rockabilly bassplayers covering the f-holes sometimes.
I am only talking about covering the f-holes in a live or rehearsal situation, not permanently.

kurt · #12 12-05-2009, 11:15 PM

Putting foam in will help. More so with low end feedback. I usually use it as a last resort, and that's usually when it's in a live setting with a loud country band in rock clubs. Did you try muting the tailpiece and afterlengths of the strings? Maybe the 2x10 is feeding back because it's lower to the ground thus less audible so you have to turn it up more? Try raising it up on a chair or something. I also find that sometimes if the amp is on the floor it can cause certain resonant frequencies in the floor making the bass sound uneven.

barend · #13 12-06-2009, 04:36 AM

In the mean time I have tried many things. Different amps (also amps specially designed for DB) different speakers. Nothing helped.
As soon as I turn the amps volume up it starts feedbacking. It spoils all my playing fun.

So Les Frets suggestion might not be so bad. I have to ty that.

@ Kurt: How do mute the tailpiece and afterlenghts of the strings?

Can it also be that a certain bass responds more to feedback than others?

kurt · #14 12-08-2009, 10:59 AM

Quote:

Originally Posted by barend

@ Kurt: How do mute the tailpiece and afterlenghts of the strings?

Can it also be that a certain bass responds more to feedback than others?

Certain basses do feedback more. My plywood bass feeds back less than my carved top.

To mute the tailpiece, stuff some foam or a piece of cloth in between the tailpiece and top down at the bottom of the bass. To mute the afterlengths, wrap some velcro, rubber tube or band, or short piece of leather around the strings between the bridge and tailpiece. For a detailed discussion on the subject, do a search for feedback.

hofner · #15 12-08-2009, 11:29 PM

What are your settings for the "mediums" eq ?
I often got feedback with the medium frequencies, whatever the amp.
I play on a genz benz shuttle 3.0 + TC electronic 21O, and don't have any feedback even when i play rockabilly sessions with horn for the slap sound. But if i raise too muche the mediums settings, feedback starts.

barend · #16 12-09-2009, 05:55 AM

by medium EQ I meant flat EQ (no cut or boost). I have tried many EQ configurations but it didn't improve.

I am thinking about trying this Biesele magnetic pickup for loud situations: http://www.biesele.org/pickups/

I think they only can be ordered bij the Diesele website? Are there any European distributors for this pickup? I am not sure if I want to buy it though because it is quite expensive. It is a bit of a gamble because I never heard or tried one before. If I don't like it it is a lot of waysted money.

Is it completely feedback proof? and does the pickup conflict with your bow because of the way it is positioned? (I play a lot of classical too so I don't want anything that limits the bow in any way).