Determining the Source of Noise when TT is On

I can use a hand.  I have a scratchy noise coming out of my left front speaker whenever I have my TT on.  The sound is on without the TT turning.  The noise started about a month ago long after I had installed the component parts.  The TT is grounded.  I have a relatively new phono pre-amp MP 1100 with balanced cables going to a 5 yo MX 121 a/v control.  When I disconnect the left cable from the back of the phono pre-amp the noise stops.  Q: how can I determine if the defect is in the phono pre-amp or the a/v controler?  

Showing 2 responses by oldhvymec

Doesn't the MX121 have a Phono out.. It's a Mcintosh too. My MX120, and MX150, both had Phono out.. Pretty sure a MX121 has it ..
Every Mac pre I have has at least one and  the old valve units have 2. C11,20,22,C2500,MX110 all had 2, MM and MC phono out. 
MX120, 150 have one..But no way to set the gain..C2500 I can.

Just a thought..

I am sure you mean Phono input on the MX150 or MX120.
From Turntable to phono input on MX

Yes thank you.. gray9hound. That would be a tough one.
I need to pay attention..LOL Tape out (loop) 

MX121 has a place for a balanced input also, noise cancellation cable. Some people use balanced. I don't think phono carts are balanced so
I can't see a reason, unless it is the cable  I'm not an expert on LP stuff, but I've made a few TTs and arms.

Your not a battery powered guy, floating everything, ground,pos,ect..?

Mac pres have Phono in, most have MM and MC, C2500 the MC gain is adjustable, via menu option. 

happy hunting