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Update on VPI Prime noise issues

Hi everyone,

Thanks for the advice you all shared on my previous questions about my VPI Prime noise issues.  As an update, the motor noise has quieted down significantly with about 50 hours of play time, so I'm happy to report that the motor noise is no longer a problem.  

However, I am still struggling with the hum that comes from the tonearm wire that connects to the junction box.  I'm using shielded phono cables (Silnote), but apparently the unipivot tonearm is not grounded.  I measured the volume of the hum by turning the volume all the way up on the preamp (Van Alstine Fet Valve) with no record playing.   Obviously I would never listen to anything with the volume pot wide open, but the hum itself measures 75db, which seems excessive to me.  I've tried grounding the tonearm, but that hasn't made any difference.  Even if I'm listening at moderate volumes I'm sure that the noise floor is higher than optimal and that I'm missing out on some low level details.  The dealer suggested trying another pair of phono cables, which I will probably do soon (don't have any on hand).  

My system is the Prime > Manley Chinook > Alstine Fet Valve Pre > Alstine Fet Valve 600R > KEF LS50.

Any more thoughts would be more than welcome.  And Happy Thanksgiving to all.
Best, Scott
smrex13
raymonda
847 posts
 
The 3d arm is made of non conductive material, right?  So, it does not need to be grounded.

smrex13 OP
423 posts
 
I believe it's made of some type of epoxy compound.  I think the issue is the wire that runs from the arm to the junction box - if I move it around the hum will change a bit.  If I put my fingers on the connector the hum will dissipate quite a bit.
stringreen's avatar
stringreen
5,112 posts
 
My 3D arm is absolutely dead silent...no hum at all  - even wide open.  I would therefore think its not the arm that is the problem.  Call VPI and get their suggestion.
smrex13 OP
423 posts
 
Did some troubleshooting this morning and found out the following:

1.  System is dead quiet with a CD player plugged in a volume control wide open.

2.  Put in passive preamp and still got the hum.

3.  Used the headphone output of the preamp and got the hum.

So, by process of elimination it's something before the preamp.  And if I lift the unipivot arm off the point it rests on the hum becomes deafening to the point that I was afraid I had blown a tweeter.  

Anyway, I'm going to enjoy the football games today and then get back to troubleshooting. Posted a question on the VPI forum, too.  

Happy Thanksgiving,Scott  


mb1audio
151 posts
 
" And if I lift the unipivot arm off the point it rests on the hum becomes deafening to the point that I was afraid I had blown a tweeter. "

Try a lower gain setting on your phono preamp. Also, check the wiring at the headshell. Make sure all 4 wires are secure, on the right pins and not touching each other. 

I would also check the din connector for anything unusual, along with all the wires to make sure they're not damaged/exposed.

" I'm using shielded phono cables (Silnote), but apparently the unipivot tonearm is not grounded."

You don't need to use phono cables. Regular IC' are fine.
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