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Persistent Buzzing When Stylus Makes Contact - Need Help Troubleshooting!

JP said:
The manual doesn't mention an auto-standby mode, but as they're active with an internal DSP it's not unusual for a DSP to auto-mute if it thinks there is no input signal. If you've an ADC, likely the easiest way to test this is to record from the line out of the phono pre and see if the noise level changes at all. If it doesn't, then it's something with the monitors. Or maybe Mackie support can tell you.

It's not extraordinarily difficult to get a vinyl signal chain to be pretty quiet, but I don't think it's achievable with what you have, and near field is going to add to that challenge. If your recording is at/near full volume on the Mackie's then I probably wouldn't find the level of noise you're getting to be odd. The only odd part is that it cuts in and out.
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I can also trigger it by turning the switch on and off for the ceiling fan, same thing, a short temporary buzzing, that's with the tonearm parked and not touching anything. Just a bunch of strange stuff. Going to do my best to just enjoy my records at this point. None of my gear is top tier either, can't expect too much from it
 
JP said:
Turn the volume up - it's there plain as day, and it cuts in and out which is the odd part. I put markers at the top of the spectrum plot below to show these events. My guess is the signal is right on the cusp of an auto-standby/mute circuit.

View attachment 3441177
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I listened again, only louder. You're right, there's a buzz which starts when the stylus touches the record. However, it stops without the stylus being lifted. Then it starts again and continues (briefly) without the stylus in contact.
Yes, it sounds like a nose gate is cutting in and out, but I looked at the manual for the active speakers and found no mention of an auto mute or noise gate function.
All very odd.
 
djchaseb said:
The tonearm is grounded, and the table is grounded through the left RCA output with a piggy back adapter U-Turn sent me that plugs directly into the outlet ground.
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Just to mention, "grounded" is a bit of an ambiguous term. A turntable doesn't need a connection to mains earth to be noise-free (or as noise-free as possible). Maybe removing that connection might help.
 
rothwellaudio said:
Just to mention, "grounded" is a bit of an ambiguous term. A turntable doesn't need a connection to mains earth to be noise-free (or as noise-free as possible). Maybe removing that connection might help.
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The buzz is slightly more quiet with a ground connected. I tried several different ways, most quiet was preamp to wall outlet.

Outlet_.jpg
 
djchaseb said:
I can also trigger it by turning the switch on and off for the ceiling fan, same thing, a short temporary buzzing, that's with the tonearm parked and not touching anything. Just a bunch of strange stuff. Going to do my best to just enjoy my records at this point. None of my gear is top tier either, can't expect too much from it
Click to expand...

That makes sense if the Mackie's are muting and the signal is dancing right around the threshold - any bit of noise that's picked up by the phono stage could make them un-mute. I'm 99% sure this is what's going on.

The U-Turn has an improperly engineered ground using one channel's signal return (shield) as the chassis ground. Most engineered phono stages have the signal ground isolated from the chassis at the input to keep noise from entering the most sensitive area of the circuit, and the U-Turn is doing its absolute best to put all the noise right there. Their ground adapter can help a little, but will never correct the fundamental mistake.
 
JP said:
That makes sense if the Mackie's are muting and the signal is dancing right around the threshold - any bit of noise that's picked up by the phono stage could make them un-mute. I'm 99% sure this is what's going on.

The U-Turn has an improperly engineered ground using one channel's signal return (shield) as the chassis ground. Most engineered phono stages have the signal ground isolated from the chassis at the input to keep noise from entering the most sensitive area of the circuit, and the U-Turn is doing its absolute best to put all the noise right there. Their ground adapter can help a little, but will never correct the fundamental mistake.
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Any recommendations on correcting this?
 
Why?
Actually - yes, the feature is (mildly speaking) questionable, but it won't interfere considering the level of your other equipment.
 
djchaseb said:
Any recommendations on correcting this?
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In principal you want the cart signal hot and cold to go directly to the phono stage inputs, and the chassis ground (all the metal bits) of the turntable and arm to connect to the phono stage ground lug. What would need to be changed on a U-Turn table to do that specifically I couldn't tell you.

I'd also caution that you're peeling on onion - if the arm shielding, phono stage, etc. aren't engineered for low noise, then those will set the floor for what you can attain. That's not to say that you need to spend oodles of cash to get there; an economic phono stage can be engineered for low noise just like any other. I can't advice on yours as I've no experience with it.
 
Oh! My bad!
I thought you were asking about the auto-muting.

The grounding scheme is indeed very important - regardless of the equipment quality level. Exact instructions could be possible only with the device schematics.
 
catBot said:
Oh! My bad!
I thought you were asking about the auto-muting.

The grounding scheme is indeed very important - regardless of the equipment quality level. Exact instructions could be possible only with the device schematics.
Click to expand...

The u-turn has a PCB with a jumper that sends the tonearm ground to the left rca, I believe I can remove the jumper and send the ground directly out. I did try that already and it didn't make any difference, I'm going to try and rewire the tonearm with some nicer shielded cables. That's my last attempt to remedy or at least quiet things down a bit more.
 
Grounding issues can drive you crazy. Each device needs a single solid path to a star ground. Multiple ground paths or weak ground paths will cause these issues. Earth ground isn't necessary, depending on the gear.
 
djchaseb said:
I'm going to try and rewire the tonearm with some nicer shielded cables.
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Be careful with shielded cables:
  1. within the tonearm their higher mass and lower flexibility will affect the tonearm's movement freedom
  2. shielded cables usually have high capacitance - that will affect the resonance frequency with the cartridge coils' inductance
I'd check if the tonearm has its own ground wire beginning near the cartridge shell, connecting all the metal parts on both sides of the pivot bearings. This wire should be the fifth, counting from the four wires connected to the cartridge contacts.
Again, without the schematics and decent "exploded" view of TT's construction - it is difficult to give any meaningful advises.
 
The tonearm does indeed have it's own ground wire and it is near the headshell end of the tonearm tubing. That black wire's pcb pad had continuity with the blue cartridge wire's pcb pad which also had continuity with the left rca outer shield. I didn't think that was correct so I moved the blue wire over to the green cartridge wire's pad. I'm going to lift the ground from the tonearm pad to the left outer shield this weekend and run my own ground wire off that pad.
 
Hmmm...
I guess - you have worsened the grounding scheme by shorting the left and right channels' grounds (the "blue" and "green" pads).
Make the "black" wire all the way to the preamp's shielding, let all four cartridge's wires go to the RCAs - the "hot" wires to the central pins. the "cold" wires - to the outer barrels.
The signals' grounds should connect only to the preamp's ground inside its' (preamp's) shield/case/box.
 
catBot said:
Hmmm...
I guess - you have worsened the grounding scheme by shorting the left and right channels' grounds (the "blue" and "green" pads).
Make the "black" wire all the way to the preamp's shielding, let all four cartridge's wires go the RCAs - the "hot" wires to the central pins. the "cold" wires - to the outer barrels.
Click to expand...

Thanks! I will do that!
 
removed the jumper that sent ground to left rca shield. I now have a dedicated ground wire from the table to the preamp. The buzz was still there, I then grounded the preamp to the wall outlet and the buzzing is virtually gone. I have to have my ears right up to the speakers to hear it with the monitors at max volume. Pretty sure I’m at the noise floor for my setup now. Happy with the way things turned out, and the setup sounds good enough for my ears. Thanks to everyone for the suggestions!

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