Help Please - Rhythmic Sub Oscillation Issue - T560

[TCLTDC]

Hello everyone,

I just wanted to ask if anyone has experienced something similar and whether you think I might be heading in the right direction please?

I’ve recently set up another lathe, and while I’m generally happy with the audio quality, I’ve run into a frustrating issue, there’s a rhythmic sub note that seems to follow a consistent pattern. It’s fairly quiet, but when turned up, it becomes quite prominent and can be disruptive / noticeable during quiet parts of music.

Initially, I noticed some slight movement in the platter on my 1210MK2, so I had both the platter and spindle replaced. That seemed to improve things a little, but the issue still persists (it still very slightly pulls over still).

Here’s an audio recording (I have LP the audio to hear better) and short video of the platter (after the replacement spindle and platter) :

https://www.swisstransfer.com/d/47e7a7db-0ad2-4ed8-a774-f90c5f88c3d7

I’ve checked Alignment to centre, Groove depth (stable, no fluctuation), no vibration through anything in the room, moved pipe around, pretty all my go to things to no joy and now I'm going bit bonkers!

This rhythmic movement or pull in the platter, I’m starting to think this might be causing mechanically induced lateral modulation that the dashpot can’t compensate for (unlike vertical modulation). Makes me suspect it’s something specific to this deck.

Does it sound like I’m on the right track here?

Could a very slight platter instability or drag be causing this kind of rhythmic sub note?

Been cutting a fair few years so can generally tweak my way out the stress zone but this has got me! really appreciate your time if you’ve read this far.

Thanks!

[Dub Studio]

It's unlikely to be mechanically induced, because it's exactly 50hz... it seems to be mechanically modulated by the platter, but that is probably not the cause.

What lathe are you using? What speed is the disc rotating? What is the mains frequency in your country? Is the amp switched on or off during the test? What air pump are you using? Where is the pump located? Is it mechanically isolated from the lathe? Are there any PSUs connected to or close to the lathe?

I would check the air pump, to make sure its not coming into contact with the lathe... the wave form is lateral and vertical, which seems to indicate that the whole lathe is vibrating on more than one degree of freedom. AKA shaking around all over the place. This is the sort of movement you would expect from something vibrating against the body of the lathe.

If it were mechanically induced (by the suspension for example) you would expect one degree of freedom (probably vertical) and the chances of it hitting 50hz so constantly would be very slim.

[Dub Studio]

PS The "oil whirl" in the spindle is not something you can completely get rid of, but if you add some of the correct oil to the bearing it might help. You should also invest in a better platter to go on top of the 1210 platter (something with 3 x adjustable feet) so you can keep the disc flat, which would greatly reduce the mechanical modulation.

[TCLTDC]

Thanks for the reply!

> It's unlikely to be mechanically induced, because it's exactly 50Hz... it seems to be mechanically modulated by the platter, but that is probably not the cause.

Yeah, it's always the same @ 50Hz.

What lathe are you using?

T560

What speed is the disc rotating?

45 RPM

What is the mains frequency in your country?

UK – 50Hz

Is the amp switched on or off during the test?

Tested both – seems the same.

What air pump are you using?

Vacuum pump

Where is the pump located?

In a cupboard, isolated away and on a platform to dampen.

Is it mechanically isolated from the lathe? Are there any PSUs connected to or close to the lathe?

Only PSU is the power converter for the overhead motor, and I have it away from the rack on its own. Perhaps I could try moving that further away.

I would check the air pump to make sure it's not coming into contact with the lathe... The waveform is lateral and vertical, which seems to indicate that the whole lathe is vibrating on more than one degree of freedom — a.k.a. shaking around all over the place. This is the sort of movement you would expect from something vibrating against the body of the lathe.

So today I fitted a shelf and moved the swarf pot away from where it was before, which was not on the lathe but to the side (not touching the chassis but suspended).

If it were mechanically induced (by the suspension, for example), you would expect one degree of freedom (probably vertical), and the chances of it hitting 50Hz so constantly would be very slim.

I have also noticed that on this machine (maybe / maybe not relevant), the velocity patterns are not symmetrical as they are on my other machine (even though timing is okay comparing source & cut recording). They are skewed and lean over to one side. I wondered if this could be a further indication of electrical interference?

I did a test this evening and it was better, but the issue came back randomly throughout the cut (still quiet). I cut with no amp and tried holding the swarf jar to see if that would make it go away — no change (was chuffed until it popped up again).

I am going to try isolating some bits and test moving plugs around. I do think moving the swarf pot has helped with the rumble, so overall that area seems quieter, but the 50Hz is still there.

Thanks!

[TCLTDC]

Hello everyone,

I just wanted to ask if anyone has experienced something similar and whether you think I might be heading in the right direction please?

I’ve recently set up another lathe, and while I’m generally happy with the audio quality, I’ve run into a frustrating issue, there’s a rhythmic sub note that seems to follow a consistent pattern. It’s fairly quiet, but when turned up, it becomes quite prominent and can be disruptive / noticeable during quiet parts of music.

Initially, I noticed some slight movement in the platter on my 1210MK2, so I had both the platter and spindle replaced. That seemed to improve things a little, but the issue still persists (it still very slightly pulls over still).

Here’s an audio recording (I have LP the audio to hear better) and short video of the platter (after the replacement spindle and platter) :

https://www.swisstransfer.com/d/47e7a7db-0ad2-4ed8-a774-f90c5f88c3d7

I’ve checked Alignment to centre, Groove depth (stable, no fluctuation), no vibration through anything in the room, moved pipe around, pretty all my go to things to no joy and now I'm going bit bonkers!

This rhythmic movement or pull in the platter, I’m starting to think this might be causing mechanically induced lateral modulation that the dashpot can’t compensate for (unlike vertical modulation). Makes me suspect it’s something specific to this deck.

Does it sound like I’m on the right track here?

Could a very slight platter instability or drag be causing this kind of rhythmic sub note?

Been cutting a fair few years so can generally tweak my way out the stress zone but this has got me! really appreciate your time if you’ve read this far.

Thanks!

PS The "oil whirl" in the spindle is not something you can completely get rid of, but if you add some of the correct oil to the bearing it might help. You should also invest in a better platter to go on top of the 1210 platter (something with 3 x adjustable feet) so you can keep the disc flat, which would greatly reduce the mechanical modulation.

P.S been testing a lot and have now done some further recordings

Previously, I mentioned that the issue was present regardless of the amp being on or off, but I now believe it's sporadic rather than consistent as today was different.

I’ve done a test cut on a 10" at 45 RPM — first with the amp on, then stopped and cut again on the same side with the amp off. There’s a significant difference in the 35–65 Hz range between the two.

Recordings : https://www.swisstransfer.com/d/42535f4a-423c-40eb-ac1f-ab6052013de1

For analysis, I’ve isolated 35–65 Hz and applied a +20 dB gain to make the sub-frequency content more audible. Based on the results — and your suggestion — I agree this appears to be a solid tone, and the flatness of the platter likely influences the rhythmic pattern, which initially led me to think it was mechanically induced.

I’ll be sending the amp back for inspection on Monday under warranty so they can test further and hopefully they can give me an answer.

Thanks!

[Dub Studio]

As far as I can see, there are 3 ways it could be getting in: 1) through the amp (and any equipment connected to it) 2) through a solid object connected to the amp 3) through the air

You could check the amp by connecting it to a speaker large enough to push 50hz.

Does the amp PSU hum? Is there a fan on the amp?

The PSU that comes with the lathe hums like crazy, keep it away.

What sort of pump are you using? Could the vibration be travelling down the pipe somehow?

Is the lathe well isolated from the floor?

[TCLTDC]

As far as I can see, there are 3 ways it could be getting in: 1) through the amp (and any equipment connected to it) 2) through a solid object connected to the amp 3) through the air

You could check the amp by connecting it to a speaker large enough to push 50hz.

Does the amp PSU hum? Is there a fan on the amp?

The PSU that comes with the lathe hums like crazy, keep it away.

What sort of pump are you using? Could the vibration be travelling down the pipe somehow?

Is the lathe well isolated from the floor?

Still fighting it unfortunately, the amp was checked under warranty and they found no faults with it.

I do not have a big speaker I could run it to unfortunately, I have gone from speakon to female line adapters into some smaller speakers and then out of them into a headphone pre amp and the heavy 50hz was not there.. but the speakers could be filtering out down there im not sure. If it was in fact not there that would mean it is happening between the amp and the head again making me think mechanical but it is exactly 50hz and never changes..

Im using a vaccum pump and I changed to a much longer hose and vibration is pretty minimal and it is well isolated.
⁶
The amp does have a fan but it's very quiet, the PSU for the lathe is on its own and out the way.

I have tried unplugging as much as I can to make the chain as simple as possible and it won't go, any further suggestions are much appreciated!

[Dub Studio]

One thing at a time... I can't work out if you are saying the noise is from the amp or not.

Does the noise go away completely when you switch the amp off?

If yes, where is the amp located? Is it possible the fan is causing mechanical vibration of the lathe? Amp fans are usually intermittent as they only come on when the amp gets hot.

If no, forget the amp, it's not that.

[TCLTDC]

I think I've fixed it! I stripped my racks down, removed the amp, and have now isolated it to the side of everything. No more hum!

It must have been a low-level ground loop going through the actual chassis of the rack, probably why going down the plug route was not doing anything. I have ordered some isolator m6 screw pads and will add stuff back in once they arrive, my room is now like a music equipment shop with everything separated but at least, I hope, that is the end of that headache ha!

Thanks for the help!

[MEGAMIKE]

hi
I had these issues before

when you put it all back make sure the amp is about 20 cm away from all the other stuff ,assuming you have the setup in rack mount form ..

also get some dinsync plugs like midi plug but 3 prong male into the t560 female ,so you can listen to your head through speakers

[TCLTDC]

Noted, thank you.

The dinsync plugs - never thought of that.. great !

Thanks all for the help