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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?  
normantaylor
normantaylor OP
51 posts
 
Stereo5
I would not know how to check for a cable problem.  I have wiggled connections and it did not make a difference.

petg60
Yes, the MC 1100 phono pre-amp has tubes.  I'll give that a try.  I will also switch the cables to rule that out.  Thank you.  
atmasphere's avatar
atmasphere
11,564 posts
 
When I disconnect the left cable from the back of the phono pre-amp the noise stops.
If this is the case, swap this cable with the one for the right channel. Does the problem move? If yes, the electronics are off the hook- and investigating the cable itself is a good idea. There are other kinds of defects that have nothing to do with the connectors.

To sort out if its the cable, swap it left for right at the turntable end. Do not swap at the preamp end. Does the problem move? If no=> its the cable if yes=> its in the turntable.
normantaylor OP
51 posts
 
Excellent guidance.  Thank you!

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oldhvymec
5,101 posts
 
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..

Regards
grey9hound
1,112 posts
 
I am sure you mean Phono input on the MX150 or MX120.
From Turntable to phono input on MX
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