Grounding Issue with ADC Linear Tracking Turntable (connected to Fosi Audio Box X2)

I

iKokomo

Enthusiast
I just got an ADC LT 32 Linear Tracking Turntable from a thrift store super cheap.

I replaced the belt and stylus, however, whenever I hook this up to the amp, there is a humming sound in the speakers. I have attached the ground to the amp, and it cuts the sound in half, but it is still fairly loud.

I know it is the turntable because whenever I unplug the turntable from the amp, the humming goes away.

Unfortunately, the cables are "permanently" attached to the record player.

I was wondering how to fix this weird issue?

I have a video attached to this post.

 
TLS Guy

TLS Guy

Seriously, I have no life.
I just got an ADC LT 32 Linear Tracking Turntable from a thrift store super cheap.

I replaced the belt and stylus, however, whenever I hook this up to the amp, there is a humming sound in the speakers. I have attached the ground to the amp, and it cuts the sound in half, but it is still fairly loud.

I know it is the turntable because whenever I unplug the turntable from the amp, the humming goes away.

Unfortunately, the cables are "permanently" attached to the record player.

I was wondering how to fix this weird issue?

I have a video attached to this post.

Usually these problems are caused by ground loops, which are resistances between grounds. Hum issues are common with turntables.

My first question would be:- what is the Fosi Audio Box 2 connected to? The next question is is there a grounding connection on whatever the Fosi 2 is connected to?

If yes, then run a ground wire between the ground connector of the Fosi and the unit it is connected to.

If that fails then I suspect there is an internal grounding fault in that turntable.
 
highfigh

highfigh

Audioholic Slumlord
I just got an ADC LT 32 Linear Tracking Turntable from a thrift store super cheap.

I replaced the belt and stylus, however, whenever I hook this up to the amp, there is a humming sound in the speakers. I have attached the ground to the amp, and it cuts the sound in half, but it is still fairly loud.

I know it is the turntable because whenever I unplug the turntable from the amp, the humming goes away.

Unfortunately, the cables are "permanently" attached to the record player.

I was wondering how to fix this weird issue?

I have a video attached to this post.

Look at the plug on the turntable's power cord- if the metal tangs are the same and one isn't wider, turn the volume down, unplug it and try it again- if the hum stops, it means the chassis was connected to the hot wire, so you should mark the plug or the metal tang, it to show that it's the hot connection.

Also, if you haven't disconnected the ground wire from the turntable, try that and it may stop humming.

Remove the small screw behind the cartridge and remove the cartridge, inspect the pins and clean them if you see any haze that prevents them from being shiny, then reinstall it. This is pretty old and connections oxidize, so it's possible that the hum is caused by a connection that isn't clean.

The audio cable may not be removable, but some of these have RCA plugs inside with a strain relief retainer where it passes into the base- you might want to secure the tonearm and remove the bottom, check for RCA ends and unplug them or rotate them in the jacks- that should clean them enough to improve the connections.
 
Last edited:
I

iKokomo

Enthusiast
Hmmm, ok so update! :)

So I took it apart and it seems that whenever I touch the tonearm or the wires that run from the tonearm into the circuit board on the inside, the humming intensifies a lot.

The humming still occurs if I do not have it plugged in, so I do not think it is a power supply issue.
 
TLS Guy

TLS Guy

Seriously, I have no life.
Hmmm, ok so update! :)

So I took it apart and it seems that whenever I touch the tonearm or the wires that run from the tonearm into the circuit board on the inside, the humming intensifies a lot.

The humming still occurs if I do not have it plugged in, so I do not think it is a power supply issue.
In that case the chassis is probably not grounded.

Got out your multimeter, and check that there is zero resistance between the chassis, tone arm and the grounding lead that goes to the grounding connector on the preamp. If there is any resistance, then bond the PU arm, and the turntable chassis with stout wire.

Now check that there is zero resistance from the cartridge grounds to the outside of the RCA connectors.

If both those have zero resistance then there should be no hum.
 
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