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Humming noise just after pressing play


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I've got an SLJ-33 Technics turntable. This is a Linear track, in very good condition. 

 

When I connect it to my amp, and select phono on the amp, there's no noise. However, when I press play, and the needle goes down, I start to hear the humming noise just before the record starts to play. The louder I have my speakers, the more I can hear the humming

 

I purchased a Galvanic Isolation Filter from Jaycar, which removed a whistling noise from a Yamaha amp to a jukebox I have, but has the opposite effect when I use it on my Technics system. I actually get the humming noise at all times when the Amp is set to Phono on the technics system, rather than just after selecting play on the turntable when I don't use the Isolation Filter. 

 

 https://www.jaycar.com.au/galvanic-isolation-filter/p/AA3075

 

Any thoughts on what it could be? I've changed RCA cables and connected the ground (turn table has a ground wire) with no results.  It is an American, so I use a step down transformer, that's the only odd thing about my setup that I can think of (the transformer itself is silent, but no clue what kind of effect that has on my turntable output. 

 

Any advice? 

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Could it be cartridge picking up the hum from the motor as it drops closer?

Is there any hum with the stylus on the record without the platter turning?

When my Linn was converted to DC the motor was moved 90° to ensure that didn't happen.

Edited by GregWormald
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7 hours ago, MM86 said:

The louder I have my speakers, the more I can hear the humming

 

Are you referring to a 50 Hz hum from mains noise pickup, or motor vibration,  or is it perhaps low frequency feedback from having the speakers to close to the turntable or just too loud?

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7 hours ago, GregWormald said:

Could it be cartridge picking up the hum from the motor as it drops closer?

Is there any hum with the stylus on the record without the platter turning?

When my Linn was converted to DC the motor was moved 90° to ensure that didn't happen.

 

I wish I could tell, but it's one of these linear tracker turn tables, so I can't physically drop the stylus to see. 

 

There's a play button, and it automatically plays the record. My options are tracks 1-8, 'cueing', stop and play. 

 

The Stylus is attached to the top lid, so you can't really play with it much. 

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1 hour ago, aussievintage said:

 

Are you referring to a 50 Hz hum from mains noise pickup, or motor vibration,  or is it perhaps low frequency feedback from having the speakers to close to the turntable or just too loud?

 

Not sure, but on the my EQ, when i check out the spectrum analyzer, that specific noise shows up as a small vibration at the 16KHZ bar.

 

I don't think my turn table is to close to the turn table, as I have them on a separate shelf below. I'll see if i can get a photo and post.

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Stupid question:  is your ground wire attached?   Most of the technics turntables have a mute switch that disengages the entire audio circuit if the system isn't playing, you won't hear any ground hum until the turntable is trying to play something.

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4 hours ago, Old Man Rubber said:

Stupid question:  is your ground wire attached?   Most of the technics turntables have a mute switch that disengages the entire audio circuit if the system isn't playing, you won't hear any ground hum until the turntable is trying to play something.

 

There's a ground wire coming out of the the back of the turntable, I've connected that to the ground on the amp. No idea if it's working.

 

I didn't realise it, but according to the manual, the ground wire is removable to the turntable (i thought it was inbuilt). I'll try plugging it in/out tonight and see if that works  

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1 minute ago, aussievintage said:

That's a high pitched whistle.  :)  Did you mean 16Hz - if so, I'll bet it resonance / feedback.

Yep, prob 16Hz, I can't read my EQ properly because it's up on a high shelf.

 

If it's feedback, I wonder why the Isolation Filter didn't fix it. It worked well on my Yamaha system. 

 

Just tried taking the ground in/out (it seemed to be installed correctly) and no effect on reinstalling it.

 

Any advice on dealing with resonance/feedback? Is it caused by the stepdown transformer potentially?  

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1 minute ago, MM86 said:

Any advice on dealing with resonance/feedback? Is it caused by the stepdown transformer potentially?  

 

No,  it's purely sound energy from the speakers, reaching the turntable, causing the record surface and tonearm to vibrate and transmitting that sound back into the system via the stylus and cartridge.   

 

  • Place the turntable away from the speakers, or behind them (unless rear ported)
  • Reduce any cavities in the turntable plinth (a box plinth can resonate) and take any cover off
  • Alter room, add sound absorbing stuff, remove reflections etc
  • Turn the sound down

 

 

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3 hours ago, aussievintage said:

 

No,  it's purely sound energy from the speakers, reaching the turntable, causing the record surface and tonearm to vibrate and transmitting that sound back into the system via the stylus and cartridge.   

 

  • Place the turntable away from the speakers, or behind them (unless rear ported)
  • Reduce any cavities in the turntable plinth (a box plinth can resonate) and take any cover off
  • Alter room, add sound absorbing stuff, remove reflections etc
  • Turn the sound down

 

 

 

What would you advise to move around with this setup? 

 

IMG_20201030_101856605.jpg

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Is the turntable sitting on some sets of drawers?  If so remove them, and put the turntable on the shelf,  possibly with some isolating rubber under it, feet, pods, etc.

 

Take the lid off the turntable, or try it with and without the lid raised while playing - see which is better.

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In my experience, the sort of low hum (like mains sound) that gets louder when you turn up the volume tends to be a grounding issue. The failure could be the grounding inside the TT, the ground on the tonearm itself, the ground8ng cable or the connection on the amp side. Have you tested the detachable grounding wire for continuity?

Also, what happens if you run a ground from the back of the tonearm to the amp directly (as opposed to using the ground plug on the separate cable)

IIRC this is one of those linear TT’s where the tonearm assembly is part of the lid.

The reason why it isn’t humming before you hit play is that these tables have a mute circuit that only switches off once the stylus is on the record, and mutes the signal again when it lifts off...many of the auto tables had this feature, like the old B&O 4000 series.

Have you tried a different TT? That would at least tell you if the hum is the grounding on the amp side or the TT end?
Also, check to see what happens to the noise if you move/wiggle the ground cable around a bit while it’s humming as it could be badly shielded and it’s picking up interference from another power cable?

 

linear TT’s are fiddly, so if you don’t find a simple answer, best to let a tech take a look at it for you.

 

best of luck finding a fix - it can be so frustrating sometimes!

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21 hours ago, aussievintage said:

Is the turntable sitting on some sets of drawers?  If so remove them, and put the turntable on the shelf,  possibly with some isolating rubber under it, feet, pods, etc.

 

 

Good advice. I'll try that on the weekend

Edited by MM86
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12 hours ago, RNWau said:

In my experience, the sort of low hum (like mains sound) that gets louder when you turn up the volume tends to be a grounding issue. The failure could be the grounding inside the TT, the ground on the tonearm itself, the ground8ng cable or the connection on the amp side. Have you tested the detachable grounding wire for continuity?

Also, what happens if you run a ground from the back of the tonearm to the amp directly (as opposed to using the ground plug on the separate cable)

IIRC this is one of those linear TT’s where the tonearm assembly is part of the lid.

The reason why it isn’t humming before you hit play is that these tables have a mute circuit that only switches off once the stylus is on the record, and mutes the signal again when it lifts off...many of the auto tables had this feature, like the old B&O 4000 series.

Have you tried a different TT? That would at least tell you if the hum is the grounding on the amp side or the TT end?
Also, check to see what happens to the noise if you move/wiggle the ground cable around a bit while it’s humming as it could be badly shielded and it’s picking up interference from another power cable?

 

linear TT’s are fiddly, so if you don’t find a simple answer, best to let a tech take a look at it for you.

 

best of luck finding a fix - it can be so frustrating sometimes!

 

Yep, the tone arm is connected to the lid, so hard to tell what's happening. I haven't tested the ground wire, but that sounds like a good idea.

 

Nothing happens when I wiggle the ground cable during play, but  when I touch the ends of the ground cable, I can hear some disturbance. 

 

I have newish turn table (cheap one off ebay) that works perfectly fine. It has an amp built into it, will anything go wrong if I plug that into the photo input on my stereo? 

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32 minutes ago, MM86 said:

I have newish turn table (cheap one off ebay) that works perfectly fine. It has an amp built into it, will anything go wrong if I plug that into the photo input on my stereo? 

 

The built in amp means the ebay turntable is putting out a line level signal. Don't plug it into the phono stage on your amp. You could safely put it into the Aux/Line/Tape inputs and it should work perfectly. 

 

If the ebay turntable has an option to disconnect the internal preamp, then you could run it with the preamp switched off into your phono stage.

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