Hum in right speaker becomes hum in both speakers when headshell detached - diyAudio
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Old 8th June 2011, 10:32 AM   #1
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Default Hum in right speaker becomes hum in both speakers when headshell detached

Hi



I have an SME 309 tonearm and hum in my right speaker . When i detach my headshell the hum appears in both speakers . Ive cleaned the headshell pins both ends and headshell leads are snug

headshell leads are stock van der hull (they seem undamaged)

Changing the cartridge makes no difference

Ive disconnected all other appliances in house (Tvs , fridges , light dimmers)

My phonocable is XLR. Ive tried different brand phonocables makes no difference

My turntable is belt driven and the motor is away from cartridge . Touching the turntable or tonearm with my hands doesnt alter the hum

Hum in right speaker gets louder as I turn up volume . I live in australia - electricity supply is 10 amps/240 volts .
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Old 8th June 2011, 11:07 AM   #2
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all my gear is solid state
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Old 8th June 2011, 11:10 AM   #3
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Use a multimeter to check the wires running trough the tonearm all the way to the XLR plugs. Seems to me one wire might be interrupted.
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Old 8th June 2011, 11:17 AM   #4
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Is the turntable grounded?
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Old 8th June 2011, 11:42 AM   #5
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Click the image to open in full size.

this is what it looks like - the PSU has a three prong connector - whether the turntable/arm itself is grounded i dont know.

I tried to disassemble the SME tonearm but dont know how to : the cap on front seems very well attached (maybe i need to use more force)

Click the image to open in full size.

Ill buy a multimeter tommorow

i should state that i can hear music through both speakers , despite the Hum on the right

I have the motor/turntable about 60 cm away from my phonostage -moving the turntable further away makes no difference
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Old 8th June 2011, 06:28 PM   #6
oshifis is offline oshifis  Hungary
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Have you done a continuity check?
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Old 8th June 2011, 06:45 PM   #7
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well if u mean checking tonearm leads with multimeter , ill be doing that tommorow

Sorry i havent dont electronics for about 15 years
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Old 18th June 2011, 11:45 AM   #8
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Quote:
Originally Posted by oshifis View Post
Have you done a continuity check?
Ok just finished with my multimeter and i have continuity between red , white , green and blue headshell leads and their corresponding pins on the tonearm DIN plug

ive checked my XLR phonocable and it has continuity for signal and the ground lead ( im assuming everyone is using Pin 2 HOT , pin 3 return Pin 1 shield)


when i tested continuity of the turntable's earth : the ground pin on the DIN plug of the tonearm has continuity with everypart of the turntable Except there is no continuity between DIN ground pin and the actual magnesium shaft of the tonearm (excuse my ignorance of this is normal)
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Old 19th June 2011, 07:23 AM   #9
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The SME arm and headshell are painted magnesium - ive just checked with multimeter...

No continuity between tonearm DIN plug ground pin and tonearm shaft

No continuity between tonearm DIN plug ground pin and tonearm headshell

Perfect continuity between tonearm DIN plug ground pin and headshell screw that secures headshell

i presume this is normal ?

I have no continuity between the cartridge body and the headshell - i presume because the headshell is painted ( i seem to recall a guy in the UK scraping the paint from his headshell to get rid of hum , cant be sure )

Also the transformer on the electricity pole up the road from my house makes the most awful loud buzzing noise . I presume this has nothing to do with my speaker hum

my pre amp , power amp and phonostage all have 3 prong IEC connectors
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Old 19th June 2011, 08:14 AM   #10
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What phono stage is it?

sp
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