Need Advice: Vinyl Hum Issue

I have him before on my old vynil set up. My friend told me to connect the turntable on different outlet .it works.

Have you tried reverting to bare wire connections ? What happens?

Though you take pains to give us all the relevant information, you don’t mention the cartridge. What cartridge?

When I had hum on my turntable it ended up being a grounding issue.  The ground wire from the turntable was not connected properly.

@viridian +1 "Do you have hum, or acoustic feedback? A quick test is to have the turntable off -  not spinning - and put the needle in the groove of a record. Gently tap the plinth while advancing the volume."

Surprised to hear someone else is using my TT hum debug method! LOL 

Maybe this is the time to test if AI is really that intelligent...

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Based on your observations, this is almost certainly a grounding / subsonic issue in the analog (vinyl) chain, not a general system fault. Let’s break it down symptom by symptom and then converge on the most likely causes and fixes.

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What your symptoms tell us

1. Hum only on vinyl

• Rules out power amp, preamp main gain stage, and speakers.

• Points directly to phono stage / turntable grounding / cartridge loop.

2. Hum increases with volume

• Classic ground-related hum, not RF noise or digital hash.

• Confirms it’s entering before the volume control (phono input).

3. Hum disappears when KC62 is disconnected

• This is critical.

• Indicates a ground loop introduced by the subwoofer, most likely via:

  • RCA shield ground

  • Sub’s internal grounding reference

  • Mains earth relationship between sub and main system

4. With sub disconnected & volume > ~10 o’clock

a) Audible vibration / rattling

b) Woofer cones fluctuate excessively

• This is subsonic energy, not audible hum.

• Very common with vinyl:

  • Tonearm/cartridge resonance

  • Record warp

  • Bearing noise

  • Footfall feedback

• Digital stays silent → confirms this is mechanical → electrical, not electronic.

5. Touching RCA plugs does NOT reduce hum

• Suggests:

  • Signal ground is intact

  • The issue is not an open shield

  • More likely a ground potential difference between components

6. Tonearm ground not yet tested

• This is a key missing datapoint.

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What’s really happening (most likely scenario)

You have two separate but related issues:

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Issue A — Ground loop involving the KC62

• Vinyl chain is extremely sensitive to ground reference

• Adding the KC62 introduces a second ground path

• Result: hum only when sub is connected

This is very common with:

• Subs with grounded power supplies

• Systems where phono ground, preamp ground, and sub ground don’t share the same reference

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Issue B — No subsonic filtering

• Your system is passing very low-frequency energy (<20 Hz) from vinyl

• This causes:

  • Woofer pumping

  • Cabinet vibration

  • Rattling at higher volume

• The KC62 normally masks this by absorbing LF energy

• When disconnected, your mains show it clearly

This is not a defect — it’s physics.

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High-probability fixes (in order)

1️⃣ Test tonearm grounding (important)

• Touch the tonearm or headshell while the hum is present

  • If hum decreases → tonearm ground issue

  • If hum increases → reversed ground reference somewhere

If your turntable has a separate ground wire:

• Ensure it is connected only to the phono preamp ground post

• Do NOT ground it to chassis or wall earth

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2️⃣ Break the subwoofer ground loop

Try one change at a time:

• Power the KC62 from the same outlet / power strip as the rest of the system

• If already shared:

  • Use a cheater plug (temporarily, for testing only) on the sub

    • If hum disappears → confirmed ground loop

• Alternatively:

  • Insert a ground-loop isolator on the sub RCA input

  • Or use a balanced/high-level input if available (KC62 supports speaker-level)

⚠️ The fact that touching RCAs does nothing strongly suggests this is not a shielding problem but a loop.

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3️⃣ Engage or add subsonic filtering

This addresses the woofer pumping and rattling:

• Check if your phono stage has:

  • Subsonic filter

  • Rumple filter

  • 20 Hz high-pass

• If not:

  • An external subsonic filter (18–20 Hz, 12–24 dB/oct) will dramatically help

  • Especially important with:

    • Modern high-excursion woofers

    • Rigid cabinets

    • Sensitive cartridges

This will not affect musical bass, only garbage energy.

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4️⃣ Check cartridge / tonearm resonance

If the pumping is extreme:

• Cartridge compliance may be mismatched to tonearm mass

• Resonance likely sitting in the 6–9 Hz range

• That energy goes straight to your woofers

This again explains:

• Vinyl-only issue

• Digital silence

• Excessive cone motion

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What this is NOT

• ❌ Bad DAC

• ❌ Bad amp

• ❌ Bad speakers

• ❌ Bad subwoofer

• ❌ Faulty RCA cables (very unlikely)

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Summary diagnosis

You are hearing a combination of a KC62-induced ground loop on the phono chain and unfiltered subsonic vinyl energy.

Both are common, solvable, and consistent with every symptom you described.