audio technica lp120xusb problem help pls

[onnik]

What could it be that turns the turntable into a... microphone. if I turn up the music a little more, there is a hum, the speakers are 1.50 m away, could it be from the intgrated preamplifier i use line.
here is video

 

[BillK]

That's the way a phonograph works; the cartridge amplifies any vibration, whether from the record groove or coming in from the outside by pounding on the plinth.

 

[onnik]

for me this is not normal, 40 years ago when I had a turntable it was not like this, maybe if I buy an amplifier with a phono input it will be better, now I use aux and Sony shake x30d, or to change moving magnet to moving coil cartridge.

 

[BillK]

It is, though.

Rapping on the plinth is a standard test of mine and virtually any turntable will do the same except for suspended turntables (spring suspension) or massive tables weighing over 100 lbs.

 

[onnik]

Yes true, my old turntable was nothing special, you may not have seen such a miracle of technology, and it was on a spring suspension, but it sounded great at the time on audio cassettes

 

[mtemur]

Tapping plinth, that’s not the way of testing a turntable’s isolation. You should tap the stand where turntable sits and if you hear feedback from speakers then you have an isolation problem. Tapping plinth is one of the mistakes most people do. Plinth is directly connected to bearing, platter and most importantly tonearm. That’s how a plinth should be, directly connected. The job of isolation is to decouple plinth from the stand and the room.

 

[onnik]

You can't hear it just when I tap on the turntable, you can hear boom boom even when I walk on the ground, and if I turn it up a little more, it starts boooooo from the speakers, the same as if you bring a microphone to the speaker but with low frequency, it becomes microphony.
It is possible that the built-in preamplifier of the turntable is wrong, the turntable is not new, it is second hand but it looks like new, it is 2 years old, I hope that if I get an amplifier with a phono inpu to turn off the turntable's preamplifier, this will go away, also the power with which the device plays is about 10% of the real one, if it is 100 watts I hear it as 10 watts and there is no bass, it plays like a regular TV.

 

[BillK]

Tapping plinth, that’s not the way of testing a turntable’s isolation. You should tap the stand where turntable sits and if you hear feedback from speakers then you have an isolation problem. Tapping plinth is one of the mistakes most people do. Plinth is directly connected to bearing, platter and most importantly tonearm. That’s how a plinth should be, directly connected. The job of isolation is to decouple plinth from the stand and the room.

Actually, it's both.

Tapping on the table shouldn't be heard, but IMHO, neither should tapping on the plinth.

Both allow room vibrations to make it back into the cartridge and phono stage.

Many turntable manufacturers address the former, a surprising number do not address the latter.

One of the big advantages of vacuum hold-down is you can tap on the LP itself and it will not be heard through the cartridge; AFAIK only vacuum hold-down gives that advantage.

I've raised the query before that some say vacuum hold-down makes the record sound "dead," but I wonder if that's because people have grown used to the additional "feedback" caused due to resonance in the vinyl itself being added to playback rather than just what is being picked up by the stylus; I personally have no idea but like the idea that you could use a hammer to pound on the table, the plinth, the platter or the record itself and the only sound making it into the stylus is what's in the grooves.