[Rob S.]

This could be a "lab" topic so feel free to move it if necessary.

I've just setup a Koetsu rosewood cartridge (demo from a generous AC'er) on my VPI classic TT.  I now have a rather loud hum coming from my left speaker- there's really no hiding it with music.  As the volume goes up so does the hum.   By switching my input on my preamp to cd the hum goes away, so it's only in the TT/cartridge/ phono section.  The hum continues w/ different input jacks on the back of the preamp.  And all preamp inputs work fine with my digital source.

I've swapped out cables, swapped out my vista phono preamp for another demo vista phono pre and the problem continues.

I then disconnected the 4 cartridge hookup wires and swapped the left +,-  for the right +,- and the hum then resumes in the right speaker.   The previous cartridge (similar Low output MC Benz glider) had no problems.  What does this mean and how do I get rid of the hum?

TIA,

Rob s.

[Ericus Rex]

The VPI Classic has the motor in the front left corner which makes it susceptible to hum.  The only way I know to get rid of the hum is to change to another cartridge...sorry.

[Rob S.]

Interesting....so the VPI motor doesn't like the Koetsu cartidge.  I wonder what's different about the Benz glider LO cartridge that doesn't seem to interfere with the motor?  housing to the cartridge?

Rob

[doug s.]

the fact that the noise goes from one channel to the other when you switch wires indicates a problem likely unrelated to possible compatibility issues between a koetsu and a vpi.  you have a wiring issue - it's either the cartridge itself, or the tonearm wiring.  something isn't getting properly grounded...

doug s.

[Sonny]

the fact that the noise goes from one channel to the other when you switch wires indicates a problem likely unrelated to possible compatibility issues between a koetsu and a vpi.  you have a wiring issue - it's either the cartridge itself, or the tonearm wiring.  something isn't getting properly grounded...

doug s.

Yep, what Doug said!

[Ericus Rex]

Or maybe what Doug and Sonny said 

[1ZIP]

FYI:

I had just mounted a a Shure cart. to a TD 160 arm and had a 60hz problem on both channels but stronger on one of them.  I don't know how much time I spent swapping outlets, cables. etc. and nothing did any good.  Then a couple of days ago I looked in the box the cart. came in and found a small, very thin, clear piece of plastic.     I remounted the cart with the plastic piece between the cart. and shell and bingo....dead quiet?    Instructions....who needs stinking instructions! 

[Rob S.]

Does anyone with a Koetsu cartridge have some sort of shim between it and the arm/head?  No instructions in the Koetsu box.

Rob S.

[Uptown Audio]

This could be a "lab" topic so feel free to move it if necessary.

I've just setup a Koetsu rosewood cartridge (demo from a generous AC'er) on my VPI classic TT.  I now have a rather loud hum coming from my left speaker- there's really no hiding it with music.  As the volume goes up so does the hum.   By switching my input on my preamp to cd the hum goes away, so it's only in the TT/cartridge/ phono section.  The hum continues w/ different input jacks on the back of the preamp.  And all preamp inputs work fine with my digital source.

I've swapped out cables, swapped out my vista phono preamp for another demo vista phono pre and the problem continues.

I then disconnected the 4 cartridge hookup wires and swapped the left +,-  for the right +,- and the hum then resumes in the right speaker.   The previous cartridge (similar Low output MC Benz glider) had no problems.  What does this mean and how do I get rid of the hum?

TIA,

Rob s.

Check the condition and fit of the connections at the cartridge clips and cartridge. They should be fairly clean and relatively snug.

If the problem isn't there, then it is likely at the tonearm wire junction box where you connect external cables. Either way, it's a tonearm wiring problem.
-Bill

[Wayner]

Try a heavy piece of paper. Sounds  like you do have a ground loop between the VPI ground and the cartridge. Did you ever take the VPI gound wire off of your preamp?

Wayner

[toobluvr]

I now have a rather loud hum coming from my left speaker- there's really no hiding it with music.

I then disconnected the 4 cartridge hookup wires and swapped the left +,-  for the right +,- and the hum then resumes in the right speaker.   The

If above is true, it is definitely not a tonearm wiring issue!     

(1) Hum occurs in both channels when hooked up to L cart outputs,
and
(2) there is no hum when either channel is connected to R cart outputs.

The hum occurs specifically with the L cartridge outputs, therefore the problem is inside the cartridge itself, on the L side.

As Barretta used to say...."you can take dat to da bank!"

 

[Rob S.]

thanks for the input guys,  i'm putting back in the Benz cartidge now.

one more question on grounding:  I have a grounding screw on the TT near the rca outputs.  Haven't used it yet, how important is it to have it grounded?  Where would the wire go, and what kind of wire do I use?

Rob

[Wayner]

Well, there is your problem. The chassis/arm of the turntable needs to be grounded to the phono preamp or preamp. Please connect ground wire between the 2 and hum will go away.

Wayner

[doug s.]

Well, there is your problem. The chassis/arm of the turntable needs to be grounded to the phono preamp or preamp. Please connect ground wire between the 2 and hum will go away.

Wayner

yes, you should at least try this before abandoning trying the koetsu.  and, a non-metallic shim between the koetsu and the tonearm may also be worth trying.

doug s.

[Rob S.]

ok, grounded the TT to the phono pre.  Hum still there.

Rob S.

[toobluvr]

ok, grounded the TT to the phono pre.  Hum still there.

Rob S.

There is some problem inside the cartridge itself.
Read my last note.  Everything you have done...all the diagnostics and all the evidence .....points to it.

Try to put cartridge into a different setup, I bet L channel hums there as well.

[Wayner]

I only ask the questions in order to determine problem. Now if you are a little skilled, you could try connecting the left and right (-) together. This may also cure your problems. These 2 wires are usually connected together in the phono preamp anyway.

Wayner

[Uptown Audio]

I now have a rather loud hum coming from my left speaker- there's really no hiding it with music.

I then disconnected the 4 cartridge hookup wires and swapped the left +,-  for the right +,- and the hum then resumes in the right speaker.   The

If above is true, it is definitely not a tonearm wiring issue!     

(1) Hum occurs in both channels when hooked up to L cart outputs,
and
(2) there is no hum when either channel is connected to R cart outputs.

The hum occurs specifically with the L cartridge outputs, therefore the problem is inside the cartridge itself, on the L side.

As Barretta used to say...."you can take dat to da bank!"

 

Ah!, good catch!
If the hum switched channels when he switched the leads at the cartridge, then it points to the cartridge itself. Otherwise, it would have remained in the same channel. When the OP said "resumed" I lost track of him starting with the hum in the other channel.

That said, getting a factory new cartridge with a defect is not a common experience. If the cartridge clips are making good contact with both pins on the troubling channel, and they do not have intermittant breaks, then the cartridge may have a broken lead internally.
-Bill

[Ericus Rex]

What was the outcome to this problem?

[dangerbird]

I'm betting that the cartridge is the culprit--please keep us posted as to the outcome. Good luck,,hope you get it cured.