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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => DJ Forum => Topic started by: John Chiara on February 02, 2015, 05:34:06 pm

Title: All possible turntable feedback fixes.
Post by: John Chiara on February 02, 2015, 05:34:06 pm
Sorry, search didn't give me enough. Friend has a basic 2 table DJ setup...mixer and 2 QSC K12's.
He is getting lower freq feedback. Table shoukd be in a foam bottom case.
Thanks.
Title: Re: All possible turntable feedback fixes.
Post by: Cailen Waddell on February 02, 2015, 05:38:23 pm
Well, on one show coffin was on top of a twin mattress.  That worked great.


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Title: Re: All possible turntable feedback fixes.
Post by: Richard Turner on February 07, 2015, 02:35:57 pm
Sorry, search didn't give me enough. Friend has a basic 2 table DJ setup...mixer and 2 QSC K12's.
He is getting lower freq feedback. Table shoukd be in a foam bottom case.
Thanks.

http://www.juno.co.uk/products/free-float-deck-stabilizers-black/254042-01/

I've seen anything and everything, suspending tt rig from chains or rubber strap or rigid suspension, concrete block for the table

at a certain point you will get that LF howl feedback no matter what you do if the booth isnt isolated from playback sources.
Title: Re: All possible turntable feedback fixes.
Post by: Tim Padrick on February 12, 2015, 02:08:18 am
Some of the big euro festivals are using turntable on yoga mat on 1" concrete paver on yoga mat.  Others are using isolators made from 2" tall pieces of 3" or 4" plastic pipe with wide rubber bands crisscrossed over them.
Title: Re: All possible turntable feedback fixes.
Post by: Rob Spence on February 12, 2015, 11:19:39 pm
Low freq feedback from a pair of K12s? Really?
Something else is going on...

Where are the speakers relative to the turntables?


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Title: Re: All possible turntable feedback fixes.
Post by: Chris Lave on February 24, 2015, 08:35:30 pm
Sorry, search didn't give me enough. Friend has a basic 2 table DJ setup...mixer and 2 QSC K12's.
He is getting lower freq feedback. Table shoukd be in a foam bottom case.
Thanks.

I agree with others' assertions, sounds like something else is going on to get feedback from two K12s, unless proximity wise they are really close.  I’ve been spinning since 1985 and in the old days my needles did feedback on occasion depending on a few things:

*Speakers facing me (line of sight with turntables), usually caused by subs (120 -70 Hz)
*Turning up the channel gain too high
*Anything that absorbed the frequency, such as wooden floors, stages, and tables without something to dampen the transfer of energy (i.e. carpet and/or rubber or plastic feet for table or stage)

Notably, the phenomena are rare nowadays since the control vinyl most DJs use on turntables is a “noisemap control tone” which doesn’t produce low frequencies.  Also, I DJed last week with an EAW LA 118 less than 5 feet away from my TTs with no issues.  Below are a few possible solutions or viewed another way, causes of hum:

*Make sure ground wire from TT is screwed into the mixer’s ground screw
*Some TTs don’t require ground wires with ceramic cartridges, try using a different input on the mixer (i.e. tape/cd)
*Check the needle’s headshell and cartridge wires, typically 4 wires, should have tight connections
*Make sure needle cartridge is screwed into tonearm firmly
*Clean dust from needle and vinyl
*Replace needle or cartridge
*Make sure none of the RCA plugs and wires are damaged, bad plugs and other internal TT connections will pickup hums
*Lastly, evaluate your environment (location of DJ setup, speakers, tables, flooring, etc.), cut frequency that's feeding back

Hope this helps[/list]
Title: Re: All possible turntable feedback fixes.
Post by: Scott Holtzman on February 24, 2015, 10:55:32 pm
    I agree with others' assertions, sounds like something else is going on to get feedback from two K12s, unless proximity wise they are really close.  I’ve been spinning since 1985 and in the old days my needles did feedback on occasion depending on a few things:

    *Speakers facing me (line of sight with turntables), usually caused by subs (120 -70 Hz)
    *Turning up the channel gain too high
    *Anything that absorbed the frequency, such as wooden floors, stages, and tables without something to dampen the transfer of energy (i.e. carpet and/or rubber or plastic feet for table or stage)

    Notably, the phenomena are rare nowadays since the control vinyl most DJs use on turntables is a “noisemap control tone” which doesn’t produce low frequencies.  Also, I DJed last week with an EAW LA 118 less than 5 feet away from my TTs with no issues.  Below are a few possible solutions or viewed another way, causes of hum:

    *Make sure ground wire from TT is screwed into the mixer’s ground screw
    *Some TTs don’t require ground wires with ceramic cartridges, try using a different input on the mixer (i.e. tape/cd)
    *Check the needle’s headshell and cartridge wires, typically 4 wires, should have tight connections
    *Make sure needle cartridge is screwed into tonearm firmly
    *Clean dust from needle and vinyl
    *Replace needle or cartridge
    *Make sure none of the RCA plugs and wires are damaged, bad plugs and other internal TT connections will pickup hums
    *Lastly, evaluate your environment (location of DJ setup, speakers, tables, flooring, etc.), cut frequency that's feeding back

    Hope this helps

Like a microphone feeding back you should be able to "ring out" the config and equalize out the offending frequency.