Why do I hear a buzz or feel a tingle when the charger is connected, and should I earth my unit?
Short answer
Watts says the tingle is a small leakage current from the mains power supply of a unit that is not earthed, and calls it safe on the Hugo M Scaler and TT 2 Head-Fi, Jun 2019Head-Fi, Jun 2020. His statements about Dave differ: in 2015 he wrote that Dave needs earthing for safety and that unearthed use may be hazardous Head-Fi, Dec 2015, while in 2018 he called the tingle on an unearthed Dave "perfectly safe" Head-Fi, May 2018. On TT 2 he said the same current can flow through a sensitive IEM and your body to ground and cause hum, and that earthing the unit or battery power fixes it Head-Fi, Apr 2020Head-Fi, Aug 2019. Where to attach the ground differs by product. On Dave he later said it is connected to mains earth (2019) and, in 2022, that its supply is inside the metal chassis, "so has to be earthed" Head-Fi, Apr 2019Head-Fi, Apr 2022.
Practical answer. Rob Watts attributes the tingle, and in some setups an audible buzz or hum, to a small mains leakage current from the power supply of a unit that is not earthed. He calls the tingle safe on the Hugo M Scaler and TT 2 Head-Fi, Jun 2019Head-Fi, Jun 2020. For Dave he said both that it needs earthing for safety (2015) and that the tingle is "perfectly safe" (2018); see the Dave entry below Head-Fi, Dec 2015Head-Fi, May 2018. His usual fix is a single low-impedance connection to ground, or battery power Head-Fi, Apr 2019Head-Fi, Apr 2020Head-Fi, Aug 2019.
Why it happens
- Tingle (Hugo 2 thread, January 2018): touching an anodized surface mostly isolates you from the PSU leakage, so voltage builds up, then discharges through your finger when it touches a lower-impedance part of the chassis Head-Fi, Jan 2018.
- Size: "of the order of 10's of uA" for power supplies in general (Hugo 2 thread, April 2019); 100uA for the TT 2 supply (2020) Head-Fi, Apr 2019Head-Fi, Apr 2020Head-Fi, Jun 2020.
- Buzz in IEMs (TT 2, 2020): the 100uA flows out of the supply, through the IEM and your body to ground, making a small voltage the IEM turns into hum; it is "only really an issue with sensitive IEMs" Head-Fi, Apr 2020Head-Fi, Jun 2020.
- Where you live: in June 2020 he said that in the UK, where neutral is connected to ground locally, you won't get a tingle, and that it is more noticeable in countries without a ground; his worst case was Indonesia on 317V Head-Fi, Jun 2020. In August 2021 he suggested an electrician check neutral-to-ground voltage Head-Fi, Aug 2021.
What to do, by product
- Hugo 2: earthing stops the hum (April 2019) Head-Fi, Apr 2019. In February 2020 he told an owner whose IEM buzzed with an unearthed charger that connecting USB had earthed the charger; to use optical instead, earth Hugo 2 via the coax input ground, RCA phono outputs or spare headphone socket ground Head-Fi, Feb 2020. Coax and the analog outputs connect directly to the ground plane, so use whichever is convenient (May 2019) Head-Fi, May 2019.
- Hugo TT 2: USB grounding won't work because TT 2's USB is galvanically isolated; use XLR pin 1, the phono ground, BNC input grounds, DX output grounds or a chassis screw (April 2020) Head-Fi, Apr 2020. Battery power or lower-impedance IEM cables also help (August 2019) Head-Fi, Aug 2019. In April 2022 he said TT 2's double-insulated supply means it doesn't need earthing Head-Fi, Apr 2022.
- Hugo M Scaler: in June 2019 he called the tingle "entirely safe", removable by grounding a BNC input or the BNC output ground, and said TT 2 is the same Head-Fi, Jun 2019. In June 2020 he added that ideally the ground is away from the DAC Head-Fi, Jun 2020. In August 2021, with Dave, he suggested a ground far from Dave, battery power, or a high-value resistor to ground, as the leakage is only 100uA Head-Fi, Aug 2021.
- Qutest: ground the BNC inputs or RCA outputs, use an earthed USB power supply, wrap a wire around a chassis bolt, or ground the amp (August 2020) Head-Fi, Aug 2020. In December 2018, for Qutest with M Scaler, he said the power amps needed grounding, as both are isolated from ground Head-Fi, Dec 2018.
- Original Hugo: in October 2016, for an amp with poor common-mode rejection, earth Hugo via the coax input or use battery mode Head-Fi, Oct 2016.
- Dave: in December 2015 he said it needs earthing for safety and agreed unearthed use may be hazardous, though he had used it unearthed on his travels Head-Fi, Dec 2015. In May 2018 he called the tingle on Dave's anodized chassis "perfectly safe" because the supply is medical grade with low leakage, and said he gets it only in some hotels in Japan or the USA without earthing Head-Fi, May 2018Head-Fi, May 2018. These two statements pull against each other, and the posts cited do not reconcile them; the 2018 post is about the tingle and does not retract the 2015 earthing advice. In 2019 he confirmed Dave is connected to mains earth, and in 2022 said it is earthed because its supply is inside the metal chassis, so it "has to be earthed" Head-Fi, Apr 2019Head-Fi, Apr 2022.
Sound-quality trade-off he mentions
- Choice of supply: in November 2018 he said the M Scaler supply is not grounded "for very good reason": grounding creates earth loops but stops the tingle, and a grounded supply would almost certainly sound worse Head-Fi, Nov 2018. In November 2020 he said the TT 2 supply he chose measured like a battery and happened to be unearthed, with the 100uA tingle as the downside Head-Fi, Nov 2020.
- Earthing the unit: in May 2020 he heard a difference when Hugo 2 was grounded, "consistent with ground loops" as it is not galvanically isolated Head-Fi, May 2020. In August 2021 he said grounding an M Scaler via Dave is not best for sound, and the next day, naming no product, called the leakage current he had modeled "not audibly important" Head-Fi, Aug 2021Head-Fi, Aug 2021.
- Largely moot: in April 2022 (Dave and TT 2) he called earthing "probably a moot point" for sound; in June 2023, on TT 2, he said that once mains is connected it is "largely irrelevant" Head-Fi, Apr 2022Head-Fi, Jun 2023.
Gaps: there is nothing from him on this tingle or hum with Mojo, Mojo 2 or Poly; his February 2022 Mojo 2 buzz comment concerns 2G phone (GSM) pickup Head-Fi, Feb 2022.
Quotes
“the 100uA of earth leakage current from the PSU flows through the IEM via your body to ground”2020-04-06 Head-Fi, Apr 2020
“So earth your system, the tingling will certainly go away and probably the hum.”2018-01-25 Head-Fi, Jan 2018
“it's entirely safe and is not a problem. But you can remove it by grounding either one of the BNC inputs ground, or the single BNC output ground.”2019-06-29 Head-Fi, Jun 2019
“The issue is leakage current from the PSU to ground, which is 100uA, so it's at a safe low level.”2020-06-05 Head-Fi, Jun 2020
Dated positions
| When | Products | Position |
|---|---|---|
| 2015-12 | DAVE | Dave needs earthing for safety and he agreed unearthed use may be hazardous; its supply is medical grade, and he had used it unearthed on his travels, judged from the sound quality point of view only. Head-Fi, Dec 2015 |
| 2016-10 | Hugo (original) | Switching currents from the SMPS in the ground can upset an amp with poor common-mode rejection; earth Hugo through the coax input or run it on battery. Head-Fi, Oct 2016 |
| 2018-01 to 2018-05 | Hugo 2, DAVE | The tingle on anodized surfaces is leakage current from an unearthed system; earthing removes it and probably the hum, and on Dave he called it perfectly safe because of the medical-grade, low-leakage supply (he had said in 2015 that Dave needs earthing for safety). Head-Fi, Dec 2015Head-Fi, Jan 2018Head-Fi, May 2018Head-Fi, May 2018 |
| 2018-11 to 2018-12 | Hugo M Scaler, Qutest | The M Scaler supply is deliberately not grounded, and a grounded supply would almost certainly sound worse; replying to an owner with Qutest and M Scaler, he said the power amps needed grounding as both units are isolated from ground. Head-Fi, Nov 2018Head-Fi, Dec 2018 |
| 2019-04 to 2020-02 | Hugo 2 | Leakage of tens of uA can flow through headphones and your body and cause hum; earthing Hugo 2 stops it, including through the coax, RCA output or spare headphone socket grounds. Head-Fi, Apr 2019Head-Fi, Feb 2020Head-Fi, May 2019 |
| 2019-06 to 2020-06 | Hugo M Scaler, Hugo TT2 | The tingle is PSU leakage, safe, and removed by grounding a BNC input, BNC output or chassis, ideally away from the DAC; in June 2020 he put the leakage at 100uA. Head-Fi, Jun 2019Head-Fi, Jun 2020 |
| 2019-08 to 2020-11 | Hugo TT2 | For an IEM buzz on TT 2: earth it (not through USB, which is isolated), use battery power, break the body conduction path or use lower-impedance IEM cables; the supply's leakage tingle is the downside of the chosen supply. Head-Fi, Aug 2019Head-Fi, Apr 2020Head-Fi, Jun 2020Head-Fi, Nov 2020 |
| 2020-05 | Hugo 2 | He could hear a difference when Hugo 2 was grounded, consistent with ground loops, as Hugo 2 is not galvanically isolated. Head-Fi, May 2020 |
| 2020-08 | Qutest | Ground the BNC inputs or RCA outputs, use an earthed USB supply, use a chassis bolt, or ground the amp. Head-Fi, Aug 2020 |
| 2021-08 | Hugo M Scaler, DAVE | Leakage varies by country; grounding solves it, but grounding an M Scaler via Dave is not best for sound; use a distant ground, battery, or a high-value resistor. The next day he called the leakage current he had modeled not audibly important. Head-Fi, Aug 2021Head-Fi, Aug 2021 |
| 2019-04 to 2023-06 | Hugo TT2, DAVE, Hugo M Scaler | Dave is connected to mains earth (2019) and, because its supply is inside the metal chassis, "has to be earthed" (2022); TT 2 uses a double-insulated supply and doesn't need earthing; for sound, earthing is probably moot (2022) or largely irrelevant once mains is connected (2023, TT 2). Head-Fi, Apr 2019Head-Fi, Apr 2022Head-Fi, Jun 2023 |
Caveats and open points
- All evidence is Head-Fi forum posts; no transcript figures are used.
- Several Head-Fi dates are estimated from post ID (Head-Fi, Aug 2019, Head-Fi, Apr 2020, Head-Fi, Jun 2020, Head-Fi, Nov 2020).
- Replies are to individual setups, so the product a post applies to is taken from the thread and the post text.
- He gave the Indonesian mains voltage as 310V (2019) and 317v (2020), and Bali as 316v RMS (2021, Head-Fi, Aug 2021).
- Searches for Mojo, Mojo 2 and Poly found no post on this leakage tingle or hum; Mojo 2 buzz comments concern 2G GSM pickup.
Topics: Ground loops, galvanic isolation, earthing and mains, Driving headphones and IEMs