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Feedback(?) at loud volume.

TechnicsSL

TechnicsSL

Member
I just set up a new AT LP120 for my son and it sounds fine a lower volumes but when we turn it up We get this loud base feedback through his subwoofer. Everything is set up correctly on the turn table, I took great care to make sure the tonearm was balanced and set correctly for tracking weight and anti skate. Turntable is leveled too. I never had this issue before with my old Technics turntable in the past so I'm not sure what to do to fix the issue. Oh, it does not feedback when only using headphones. Please help!
 
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I would post a video but the phone doesn't really capture it. Not sure why because it is very noticeable by ear.
 

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It's a feedback loop from the sub causing sympathetic vibration in the tonearm and cartridge. The stylus gets 'excited' and transmits it back through the system to the sub again. Do you have a subsonic filter switch on his amp? If not, try adding mass to the stereo stand like dumbell weights or turn down the sub for records. Or relocate the sub away from the rest of the system. The AT doesn't have the built in mass or special anti-resonant base that your Technics does.
 
jimreeves said:
It's a feedback loop from the sub causing sympathetic vibration in the tonearm and cartridge. The stylus gets 'excited' and transmits it back through the system to the sub again. Do you have a subsonic filter switch on his amp? If not, try adding mass to the stereo stand like dumbell weights or turn down the sub for records. The AT doesn't have the built in mass or special anti-resonant base that your Technics does.
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Do you think the rubber feet I have on the equipment stand I built him helps or not? Also, Dust cover on or off makes no difference. I even tried putting rubber pads under the turntable feet and no glory. He doesn't even have the subwoofer turned up that much. Just using it with the base management.
 
TechnicsSL said:
Do you think the rubber feet I have on the equipment stand I built him helps or not? Also, Dust cover on or off makes no difference. I even tried putting rubber pads under the turntable feet and no glory. He doesn't even have the subwoofer turned up that much. Just using it with the base management.
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Not sure what you mean by subsonic filter. He has base management on the Emotive Basx TA2 and we are using it.
 
Sub sonic = bass frequencies below human hearing. They are present in many recordings on records but cancelled with other sources. Phono preamps often have this filter built-in for this purpose. Try listening at high volume without the sub to see if the feedback stops. It could also be caused by room modes reacting with the subwoofer. If you still have feedback without the subwoofer engaged you may need to relocate the turntable.

Or get a phono preamp with a subsonic filter.
 
jimreeves said:
Sub sonic = bass frequencies below human hearing. They are present in many recordings on records but cancelled with other sources. Phono preamps often have this filter built-in for this purpose. Try listening at high volume without the sub to see if the feedback stops. It could also be caused by room modes reacting with the subwoofer. If you still have feedback without the subwoofer engaged you may need to relocate the turntable.

Or get a phono preamp with a subsonic filter.
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The feedback stops when the subwoofer is turned off. So what does this mean?
 
TechnicsSL said:
The feedback stops when the subwoofer is turned off. So what does this mean?
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It means vibrations from the subwoofer are reaching the turntable. Try to put cut tennis balls or something spongy under the subwoofer to stop the vibrations from reaching the floor.
 
I have tried holding the sub in my arms off of the floor to see if the issue disappears and it does not. I have to turn off or lower the volume on the sub to the point that there is no reason to even have a sub to get it to stop. What does everyone think about turntable record weights or clamps?
 
So the vibration is reaching the turntable through the air (probably very loud playback), there is not much you can do other than get turntable designed to withstand it (like the SL1200). You can try keeping the cover off completely (remove it).
 
CrSens said:
So the vibration is reaching the turntable through the air (probably very loud playback), there is not much you can do other than get turntable designed to withstand it (like the SL1200). You can try keeping the cover off completely (remove it).
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I have tried with the cover off.
 
Maybe the rack shelf is picking up vibration from the air, than some industrial strength vibration insulator under the turntable might work.
Like Sylomer SR-11, cut it in four 2.5" squares and place it under the feet, or directly under the plinth if feet are too shaky.
 
TechnicsSL said:
Turntable is leveled too. I never had this issue before with my old Technics turntable in the past so I'm not sure what to do to fix the issue.
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Betcha never heard that horrible music either, never played it that loud from so close, never used a sub and never used a Technics knock off to do all that "magic" - uh? For someone who's handle is "TechnicsSL" you seem to miss the point, which is - that's the difference between a real engineered piece of audio gear, and a cheap Asian knock off. Nothing you can do but turn the volume down on that sub, or isolate that turntable with real Technics feet or some 'spenisve isolation platform.
 
I recall this cheap DJ trick called a 'trampoline' from my clubbing days in 80's NY. These young infamous DJ's used a wooden cradle with criss·crossing office rubber bands, in an intersecting pattern across it, enough to support the weight of an SL-1200 on top. It could take more basses than my ears could.
 
You could try these, if feeding through the stand these will help
Screenshot_20230124-130613.png

It could also be you have the sub turned up too loud, you should only know it's on when you turn it off and notice the low frequencies drop out
 
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tnsilver said:
I recall this cheap DJ trick called a 'trampoline' from my clubbing days in 80's NY. These young infamous DJ's used a wooden cradle with criss·crossing office rubber bands, in an intersecting pattern across it, enough to support the weight of an SL-1200 on top. It could take more basses than my ears could.
Click to expand...

Very ingenious. :thumbsup:

jeff
 
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