YOU EXPERIENCE HUM WHEN CONNECTION TWO TURNTABLES TO A PREAMP VIA THE LNS

OR

YOU EXPERIENCE HUM WHEN CONNECTION JUST ABOUT ANY DEVICE TO ANOTHER

 

 A few facts about the Low Noise Switch (LNS). There are no connections between L & R shields (grounds) anywhere.  Each input shield only connects to the corresponding internal Source 1 or Source 2 switches. The LNS chassis ground is not connected in any way to any of the input or output shields. This eliminates hum loops that usually occur when trying to use ordinary switches to connect two turntables to a preamp input.

One must connect the appropriate chassis ground of each turntable (Source 1 or Source 2) to the switch box, and run another from the switch box to the preamp being fed by the switchbox.  There are variations that might be tried, such as, connect the chassis of each turntable to the preamp chassis and also the chassis of the switchbox to the earth of the preamp.

On rare occassions,  hum problems can occur.  This can be caused by some turntables being manufactured with its chassis body being connected to one of the output cable's shields.  Some turntables have no separate ground wire connection and work fine with most preamps.  Then again, some preamps may have one input channel shield connected to its chassis.  So, some odd combinations may result in connecting the L & R  shields external to the LNR

 

One solution could be reversing the power line plug polarity of one of the amps or the other, even both. Just pull the plug out turn it round and stick it back in.

A variation of the previous suggestion might be tried if one of the components has a 3 prong plug.  Use a ground lifter on that component and see if it helps.
 

 

 

 

 


When totally baffled, I suggest, trying one turntable at a time to see if one behaves differently to the other.

* Connect one turntable to Source 1.

* Connect Common to the preamp input.

* Connect the turntable ground to the SW ground and connect the SW ground to the preamp ground.

Now, the above electrically represents almost no difference than connecting the turntable directly to the preamp. The only circuit intervention is 4 electrical contacts that connect the L, the R, the LG, and the RG. The earth connection of the turntable directly connects to that of the Preamp. The chassis of the the SW simply surrounds and shields the switches. There is no connection from the SW earth to anything else. There should be no hum. If there is, something is extremely bizarre.  The below LAST RESORT has, so far, produced a good result!


RCA CONNECTOR COMPATIBILITY- YES, THIS HAS HAPPENED!

Nowadays there are often mixtures of English and of Metric connector parts. The simple RCA connectors can sometimes look connected, but are not. To explain. Sometimes, the diameter of the shield connection of an RCA connector may actually be a minute fraction of a mm larger than the ring of the jack into which you are plugging. You will feel normal resistance when pushing it in, but what you are feeling may simply be that of the center post connecting. The shield may actually be held by that center post directly in the middle and the shields are apart by that minute fraction of a mm. The fix is to pull the plug out and squeeze the connector's shield. You may have to use pliers to make that circle a tad oval. Then, when you plug it in, it will definitely make a good ground connection.


A POSSIBLE LAST RESORT MOD FOR SOME SITUATIONS

This simple modification to the circuit board has proven to solve nasty hum problems.  The situation has usually been when one or both of the turntables have the chassis ground connected to one of the signal cables' shield.  Two short insulated wire leads of just about any gauge that is convenient can be used.

 

HOW ABOUT ONE TURNTABLE TO TWO AMPS?

Connects either of any two sources to any one input or any
   one source to either of any two inputs.  Either direction.
 
So, the two inputs become the two outputs, and the one output becomes the one input for the turntable.
 
However in that case, it can get a bit more complicated.  One would hope that both amp chassis are at the same potential.  If the two amps are powered from different power outlets, this may not be true due to how the house wiring was done.  Then in that case, you might experience hum from one or the other or both. 
 
One solution could be reversing the power line plug polarity of one of the amps or the other, even both.  Just pull the plug out turn it round and stick it back in.  
 
Another solution could be running a length of wire (any small gauge) from the chassis of one amp to that of the other.  Often there are ground connectors near the phono inputs.
 
Actually, the first thing I would do would to be connect the turntable to the box and connect one amp.  See how that works.  Hopefully, when you connect the other amp, it would also behave.
 
It won't hurt to try.  The one thing to keep in mind is that all chassis be electrically connect, and that includes that of the box and the turntable.  There is the ground wire from the the  turntable it should go to the box, a wire from the box should go to the chassis ground of one amp, and another wire (you'll have to did up that one (any gauge-no big heavy wire is necessary) from the box to the other amp.