My turntable hums as soon as I lower the tonearm

[digitalfrost]

Can somebody explain what causes this and how I can fix it.

As soon as I lower the tonewarm, I have what I think is a 50hz hum. When the arm is up it's not present. I have recorded for you the beginning and the end of a vinyl side, and you can clearly hear it:

Beginning:

7.74 MB file on MEGA

mega.nz

End:

5.39 MB file on MEGA

mega.nz

My phono preamp is battery powered. The batteries are fed via USB 5V, but the amp itself runs on battery power. I connected it single-ended into a Focusrite Scarlett 2i2 to record this.

e: Even weirder:

I if lower the arm, without the turntable spinning and I turn the gain way up, this is what it sounds like:

20.63 MB file on MEGA

mega.nz

WTF?

With the arm up and the gain raised it sounds like this:

4.25 MB file on MEGA

mega.nz

 

[antcollinet]

Can somebody explain what causes this and how I can fix it.

As soon as I lower the tonewarm, I have what I think is a 50hz hum. When the arm is up it's not present. I have recorded for you the beginning and the end of a vinyl side, and you can clearly hear it:

Beginning:

7.74 MB file on MEGA

mega.nz

End:

5.39 MB file on MEGA

mega.nz

My phono preamp is battery powered. The batteries are fed via USB 5V, but the amp itself runs on battery power. I connected it single-ended into a Focusrite Scarlett 2i2 to record this.

I'm gonna state that I think this is actual vibration being picked up by the stylus. It is not electrical noise, because this doesn't care if the arm is up or down.

Most likely motor vibration, or bearings - though an outlier could be acoustic feedback from the speakers.

Try lowering the tone arm with the motor not running.

 

[Philbo King]

You likely have an intermittent wire in the tonearm. (Unless the TT mutes when the needle is up.)

 

[antcollinet]

You likely have an intermittent wire in the tonearm.

It's possible, but it would be a bit of a coincidence that it opens a the precise moment the stylus contacts the record, and connects again at the precise moment it lifts off.

 

[JP]

It's not 50Hz, it's 100Hz plus second and third harmonic. As @antcollinet suggested, lower the stylus on to the record with 1) the motor not running and 2) the turntable unplugged from the mains. This will give you a good indication of what the contributors are.

 

[JP]

Looking at the waveform in Audacity, it looks like a lot of mechanical vibration going on. You've 100Hz, 200Hz, and even 1kHz modulating the signal.

 

[Palmer]

I bought Adele 30, my first new vinyl in a decade - ordered regular black vinyl, but got the clear vinyl and it has a nice 60 Hz hum throughout. Lead in to lead out.
And no, my TT does not hum, how this was cut that way is beyond me. I have about 1600 or so vinyl records and this is the first and only one that does that.

I think JP has answered the question, in any case.

 

[JP]

e: Even weirder:

I if lower the arm, without the turntable spinning and I turn the gain way up, this is what it sounds like:

20.63 MB file on MEGA

mega.nz

WTF?

With the arm up and the gain raised it sounds like this:

4.25 MB file on MEGA

mega.nz

1) If you edit a post like that people won't get an alert so they won't see it - best to add new information in a new post.
2) When doing comparisons like this do not change the gain/recording level. If you do, no reference to anything can be made for comparison. The only thing that can be seen is what frequencies are present and their relative amplitudes to each other within the same recording.

Still, looks like your motor is vibrating like mad.

 

[digitalfrost]

Ok so I figured the following out:

- As soon as I connect either RCAs of the turntable to the preamp, I have the hum
- I've disconnected the turntable completely from power and it still happens
- The preamp was actually connected to a different power outlet, but I've tried connecting it to the same one as the turntable (it shouldn't matter, the motor is separate from the chassis, and the chassis is made of wood) and I've connected the preamp to the same outlet as the PC. Same result. Always the hum. In any case it shouldn't matter since preamp power is delivered by internal batteries.
- Preamp connected to the audio interface without turntable connected is not an issue, it's quiet.
- My turntable does not have a dedicated grounding wire. But if I touch either RCAs negative and the grounding thing of the pre, nothing changes
- If I lower the arm onto the platter, there is an additional repeating thumping noise, like the house is moving or something, I have no idea where it comes from. But If I lower the arm, turntable disconnected, nothing spinning, it's still there and it repeats

 

[Palmer]

You haven't mentioned what kind of turntable it is.

 

[digitalfrost]

Acoustic Solid Wood MPX Midi.

 

[Timcognito]

Check the connections at the cartridge, are the correct and tight. If you touch the stylus in a up position does it happen? Does it happen if yo move the arm up and down away from the platter?

 

[JP]

Ok so I figured the following out:

- As soon as I connect either RCAs of the turntable to the preamp, I have the hum NOT NECESSARILY UNUSUAL
- I've disconnected the turntable completely from power and it still happens OK
- The preamp was actually connected to a different power outlet, but I've tried connecting it to the same one as the turntable (it shouldn't matter, the motor is separate from the chassis, and the chassis is made of wood) and I've connected the preamp to the same outlet as the PC. Same result. Always the hum. In any case it shouldn't matter since preamp power is delivered by internal batteries.
- Preamp connected to the audio interface without turntable connected is not an issue, it's quiet. NORMAL
- My turntable does not have a dedicated grounding wire. But if I touch either RCAs negative and the grounding thing of the pre, nothing changes WARRANTS RESEARCH
- If I lower the arm onto the platter, there is an additional repeating thumping noise, like the house is moving or something, I have no idea where it comes from. But If I lower the arm, turntable disconnected, nothing spinning, it's still there and it repeats

Comments above. If a manufacture doesn't list a single spec...

The cartridge is going to pick up noise including some mains hum, so that's not necessarily unusual. If the grounding is correct, what you get with the cartridge in the air would be your best-case scenario.

All the metal bits should be grounded at a single point, and that point should be connected to the ground lug on your phono stage. A small number of manufacturers like to achieve this chassis ground through one of the interconnect shields. This is not optimal as most phono stages do not bond the input RCA shields to the chassis in order to prevent noise from being injected in to the most sensitive part of the circuit. Using the interconnect shield as the chassis ground for the turntable does just this.

Cartridges are basically seismic transducers, so they'll pick up all kinds of stuff.

 

[DVDdoug]

Cartridges are basically seismic transducers, so they'll pick up all kinds of stuff.

And electro-magnetic pick-ups! They are shielded, but some electro-magnetic radiation can get through. And there is 50 or 60Hz radiation all around. Even more around transformers and AC motors.

But I agree, if it's happening only when the stylus touches record it's mechanical. And if it's happening when the motor isn't running we can't blame the turntable motor. It's possible that vibration is getting-through the feet/base of the turntable. Do you have wood floors? Maybe it's vibration from your refrigerator or something like that.

 

[Palmer]

Hum without the cart touching the record is one problem, rumble (plus hum, I suppose) when playing a record is another.

Short of having someone more knowledgeable come to your house to diagnose the issues, I would try and get a single wire and connect one end to the ground of your phono preamp, and touch the other end to the base of the arm.

If the table indeed has rumble issues, I would contact the seller and if you bought it from a retail shop have them figure it out.
It is not an inexpensive table and there should be a warranty on it.

There is of course a possibility that your cartridge is defect. Again, that would be an issue for the place you bought it from.

Grounding issues are a difficult subject, and without being present in your environment I think it is hard to remotely diagnose what exactly is going on.

It is unfortunate that you are experiencing these problems with a significant investment in this set-up.

I would venture that most of the more knowledgeable vinyl enthusiasts here have gone through quite a lot of different turntables and cartridges,
and have the luxury of being able to swap out components when troubleshooting.

I would PM someone who you are comfortable with, and see if you can get a zoom call going.

 

[Timcognito]

If possible go to the panel and turn off everything and check to rule out RFI. If its still there it is mechanical or a problem with wires, connectors, preamp or cartridge. Borrow another preamp or take yours to a friends house or dealer. Was it okay and did this just start? What is humming describe what else is in the circuit? Unplug just one side L or R on everything and check

 

[Heinrich]

Can somebody explain what causes this and how I can fix it.

Alas, I can't download the files. Anyway, as somebody mentioned already, some (better) platters mute the signal when the tonearm is up for good reason. If you wipe the needle, e/g for cleaning, in the tonearm's "up" position, does it transfer to the amp? This should be checked first.

Second we could analyze where the hum comes from. RFI with or w/o grounding problem, or mechanical.

 

[AaronJ]

And electro-magnetic pick-ups! They are shielded, but some electro-magnetic radiation can get through. And there is 50 or 60Hz radiation all around. Even more around transformers and AC motors.

But I agree, if it's happening only when the stylus touches record it's mechanical. And if it's happening when the motor isn't running we can't blame the turntable motor. It's possible that vibration is getting-through the feet/base of the turntable. Do you have wood floors? Maybe it's vibration from your refrigerator or something like that.

I suspect it may be mechanical.

At one time I had my setup with a subwoofer in the corner of a room with wooden floors, and the turntable on a rack next to it. The subwoofer has its natural 60Hz inaudible hiss from the listening position, but when I lowered the tonearm it would create a feedback loop that would cause the sub to rumble quite loud. It would shake the entire room if it was tucked all the way into the corner, moving it out several inches lowered the rumble to a drone. This wouldn't necessarily happen if a record was playing, only if the stylus was lowered down onto the record without spinning. I fixed the problem entirely by moving the sub from the corner. Not saying that the OP has a similar issue with speakers, but it's anecdotal evidence of the stylus picking up 60Hz hum

 

[Palmer]

So, it has been a while - have you been able to solve the problem(s)? I for one would hope you did. Don't leave the thread hanging...

 

[digitalfrost]

I did not touch the turntable since. Strangely enough the problems are gone at the moment. I did not change anything. This is on one hand disappointing since I don't know the root cause, on the other hand I'm happy that it works again.

Here is a recording of the turntable without anything playing, as you can see the spectrum is clean:

And here is with the needle down: