Feedback

[kedo]

Although I have spent my life playing bass guitar, I was trained on the double bass and now that I am a bit older, have acquired a Stentor Elysia with a double Shadow pick up, and am working with a trio playing mainly jazz. My amplification is the Markbass CMD 121p (Little Mark II combo) with the 121 New York extension.

I have never played an amplified double bass until recently and have been plagued by feedback. On sunday, the gig was ruined for me as I had to keep of the top string as It occurs entirely between the open G up to about D where the notes boom and oscillate. I have tried dialling out the offending frequency on the Markbass, and the only way I can control it is to lower the volume or completely cut low bass and curtail the mid. The resulting sound is rather thin and toppy. I have experimented with a bass graphic equaliser, but still can't solve the problem.

Maybe the problem is that I am expecting the thing to behave like a bass guitar.

Can any of you experienced guys offer any help, otherwise I may have to resort to a solid DB.

Thanks

[thisnameistaken]

Try using a dedicated DB preamp before your amp like the Fishman Platinum Pro. The pre will have some feedback-fighting features you won't see on a bass guitar head.

[Bilbo]

Fishman Platinum Pro is exactly what you need - there are other brands etc but that is the industry standard and will do the job.

[fatback]

As said above. Also, speaker placement really matters. You might find raising the speaker up a foot or so, or angling it up, helps a lot.

Ordinary EQ won't do much, but the notch filter on a db preamp will. You can test your bass, find the worst frequencies, dial them into the notch filter and stick with that setting.

[Jezyorkshire]

you also need a phase switch as open g upwards sounds like a phase issue, lower you need highpass filter, both these are on the fishman pro platt bass pre, thet come up used for sale

[kedo]

Thanks for all of that. I've tried a few things sing posting:
1. By detaching the extension speaker, feedback on the G string is less. body of the sound suffers a bit, but maybe I don't need it for UDB.
2. Flattening all the controls on the Markbass including the VLE and VPF (all anti-clockwise) helps a lot and leaves me with a neutral uncoloured sound which I quite like although there is still a lot of bright string noise. Louder volumes still induce feedback on the upper string.
3. Sitting the amp up on a cushion off the floor as suggested by fatback (thanks) and angling it back also helps. Maybe the vibrations causing feedback are transmitted through the wooden suspended floor into the endpin and then onto the Shadow.
4. Detaching the sensor from the Shadow from the treble side. This reduces feedback but reduces the output to the amp and leaves a very unbalanced sound.

I think you're correct jezyorkshire. The sound I am getting oscillates like an old fashioned amp with very slow reverb. In and out.

Would like to try the Fishman though. Would you do all the shaping from the equaliser and flatten the amp controls?

Thanks everybody.

Edited March 4, 2014 by kedo

[Jezyorkshire]

yes keep amp eq flat and do it all from outboard pre, dont do what i did with my markbass amp and go into the effects return, use the front input, you will get phase problems if you are loud hence the need for a phase switch and a high pass filter is essential

[kedo]

Thanks Jezyorkshire.

You recommend the jack socket on the front of the amp? What about the three-pin balanced input? Thanks for your advice.

[Jezyorkshire]

aye front input works best with pre amp as buffer, havent tried the 3pin, though thats usually for a mic?