Ground loops, galvanic isolation, earthing and mains

RF noise, grounding and power

Answers on this topic

• If the data reaching the DAC is bit perfect, can the source (laptop, phone, streamer, CD transport or network gear) still change the sound?
• Is battery power better than mains, and can I power the M Scaler or Qutest from a power bank?
• Which Chord inputs are galvanically isolated, and which setups short the isolation out?
• Which input sounds best on a Chord DAC (optical, coax, USB or BNC), and why does Rob prefer optical when it is said to have more jitter?
• Why do I hear a buzz or feel a tingle when the charger is connected, and should I earth my unit?
• Will a USB purifier, JitterBug or USB isolator improve my DAVE, TT2 or Hugo?

Everything he said on this topic (263)

One-line summaries in our words, oldest first. Each link opens the original.

• 2014-06-09Watts recounts 1980s mains cable experiments that showed RF noise mattered, leading to a 12-stage RF mains filter, and explains RF-induced noise floor modulation, audible even at -200dB. Head-Fi, Jun 2014
• 2014-06-20Watts says he will test an ADuM-based USB isolator for ground-induced RF noise; it only works to 96 kHz as no 480Mb USB isolator exists. Head-Fi, Jun 2014
• 2014-06-25Watts suggests USB isolation also removes signal-dependent ground noise from the computer, which, unlike RF noise, can change perceived sound stage depth. Head-Fi, Jun 2014
• 2014-09-13Watts says USB isolation gives smoother sound and better depth by blocking correlated ground noise; two USB cables still join grounds; the new QBD has galvanic isolation. Head-Fi, Sep 2014
• 2014-10-01Watts says USB cables change sound through RF noise causing NFM and brightness, while signal-dependent ground currents degrade depth; galvanic isolation addresses both. Head-Fi, Oct 2014
• 2014-10-01Watts says the Olimex breaks Hugo's HD USB negotiation but makes the SD input smoother, and suspects it uses the Analog Devices isolator chip with 2pF coupling. Head-Fi, Oct 2014
• 2014-10-12Watts says his Olimex tests used a noisy Dell, so an iPhone may need no isolation; smoother sound and better depth indicate lower RF and correlated noise. Head-Fi, Oct 2014
• 2014-10-12Watts describes repeated 30-second tests on three tracks, single-blind only for surprises, two months on the new QBD's noise shapers, and avoiding coax transformers. Head-Fi, Oct 2014
• 2014-10-27Watts says RF in Hugo's ground plane causes bright noise floor modulation and zero-crossing currents degrade linearity and depth; the Olimex removes LF currents and matched optical for him. Head-Fi, Oct 2014
• 2014-11-30Watts says he has never experienced or heard of ticking noises, will ask Chord, and suggests the Mac may be creating ground currents. Head-Fi, Nov 2014
• 2015-04-15Watts says Hugo TT differs from Hugo in beefier batteries, better reference supply circuitry that reduces noise floor modulation, and galvanic isolation on USB. article, Apr 2015
• 2015-04-15Watts confirms isolation follows the USB chip, which draws PC power, so Hugo lacks it; laptops cause earth-loop and RF problems phones do not, and isolation removes audible laptop differences. article, Apr 2015
• 2015-06-27Watts says it will work, but because of the galvanic isolation power is drawn from the source, so a charger or powered USB hub may be needed. needs context Head-Fi, Jun 2015
• 2015-10-03Watts says pulse array's constant switching makes it immune to jitter, and USB purifiers are pointless for galvanically isolated Dave, Hugo TT and 2Qute; Hugo's issue is RF noise. Head-Fi, Oct 2015
• 2015-12-20Watts says the unit needs earthing for safety though its PSU is medical grade; he has used it unearthed on travels without sound penalty but agrees that may be hazardous. Head-Fi, Dec 2015
• 2016-01-04Watts explains that source differences heard with Hugo came from RF noise (noise floor modulation heard as brightness) and correlated ground currents degrading depth, which Dave's galvanic isolation removes. Head-Fi, Jan 2016
• 2016-01-11Watts says TT beats Hugo via supercaps lowering PSU impedance, heavier metalwork, USB galvanic isolation and a better flip-flop reference supply that cuts distortion and noise some 4 dB. Head-Fi, Jan 2016
• 2016-01-21Watts says Dave's FPGA has 132 DSP slices plus 34 fabric cores, his DACs reject source jitter equally, and source differences come from RF and correlated noise, removed by isolation. Head-Fi, Jan 2016
• 2016-01-24Watts compares 2 Qute and Hugo: similar on optical or coax, 2 Qute's galvanic isolation helps with a PC on USB, Hugo can feed power amps directly; output stages match. Head-Fi, Jan 2016
• 2016-02-24Watts says his DACs' DPLL removes incoming jitter, so optical's benefit is galvanic isolation reducing noise floor modulation, while USB is also isolated and already clocked by the DAC. Head-Fi, Feb 2016
• 2016-05-13Watts doubts DAVE is sensitive to source RF via the mains and explains how RF intermodulating in analog electronics causes noise floor modulation that sounds harder and brighter. Head-Fi, May 2016
• 2016-06-15Watts says a careful AB test might reveal a small, musically unimportant difference due only to extra earthing, and DAVE won't mind the tiny extra loading. needs context Head-Fi, Jun 2016
• 2016-06-21Watts says DAVE's USB isolation leaves 2 pF coupling, about 79 ohms at 1 GHz, and plans a JitterBug test to find whether laptop RF arrives via mains or USB. Head-Fi, Jun 2016
• 2016-06-27Watts reports a JitterBug lifted DAVE with a mains-powered laptop from 0% to 75% but made no difference on battery, concluding RF couples mainly via USB. Head-Fi, Jun 2016
• 2016-07-18Watts explains how source RF couples into DAVE through the USB isolator's 2 pF capacitance and ground plane, raising noise floor modulation, and why a battery-powered laptop avoids it. Head-Fi, Jul 2016
• 2016-07-18Watts says audibility depends on the DAC: unlikely with DAVE or a battery source, but an SSD may help DACs lacking USB galvanic isolation or PSU RF filtering. needs context Head-Fi, Jul 2016
• 2016-07-19Watts says lifting the ground does not help since the loop then runs through the neutral of the laptop and DAVE supplies, and isolation transformers have high coupling capacitance. Head-Fi, Jul 2016
• 2016-07-20Watts says ground is still connected, a switched ground would add capacitance like the isolator's, and he unplugs the laptop charger for critical listening. needs context Head-Fi, Jul 2016
• 2016-07-23Watts says another galvanic isolator won't help DAVE, a JitterBug gets to 99.75%, and isolated USB now edges optical in detail and flow because its clock comes from DAVE. Head-Fi, Jul 2016
• 2016-07-24Watts says fully isolating DAVE from a USB source needs the source free of earth and mains cables, so he uses portable hard disks, and wireless should be fine. Head-Fi, Jul 2016
• 2016-07-25Watts says his hard disk is bus-powered from the laptop, so it travels to planes and hotels and keeps ground isolated when the laptop charger is unplugged. Head-Fi, Jul 2016
• 2016-08-10Watts says player differences depend on DAC isolation, OS and program; Chord's Windows driver resends errored packets, and with DAVE on a battery laptop he expects no differences. Head-Fi, Aug 2016
• 2016-08-10Watts confirms that 2Qute, Hugo TT and DAVE share the same USB decoder and galvanic isolation. Head-Fi, Aug 2016
• 2016-08-28Watts says DAVE's USB 5 V is isolated, and battery-laptop or USB-vs-optical differences are tiny; optical gives full RF isolation, USB slightly better timing from DAVE's clock. Head-Fi, Aug 2016
• 2016-10-05Watts blames SMPS leakage switching currents in the ground upsetting an amp with poor common mode rejection, avoidable by earthing Hugo via the coax input or using battery mode. Head-Fi, Oct 2016
• 2016-10-05Watts calls the idea not bad and recalls a friend whose custom audio-only ground spike improved his system. Head-Fi, Oct 2016
• 2016-10-28Watts says Chord's new remote works like the old one, and expects reversing the Schuko plug to make no difference as DAVE is transformer coupled; warmer would mean less RF. Head-Fi, Oct 2016
• 2016-11-01Watts says Blu Mk2's optical output reaches only 176.4 kHz, so 705.6 kHz reaches DAVE via dual BNC, whose outputs are RF isolated with optional full galvanic isolation. Head-Fi, Nov 2016
• 2016-12-08Watts confirms it is grounded via a wire to the aluminum chassis block, with each spacer connecting the chassis to the PCB ground planes. Head-Fi, Dec 2016
• 2016-12-18Watts says ASIO and WASAPI are both bit perfect; DAVE shows no difference via isolation and battery laptop, yet ASIO sounds slightly better on Mojo, likely from less processor noise. Head-Fi, Dec 2016
• 2017-01-09Watts says WTA processing is identical from 44.1 to 384 kHz, explains mounting the FPGA core switching regulator underneath to limit ground-plane noise, and Blu Mk2 needing 12A. Head-Fi, Jan 2017
• 2017-01-09Watts says the bi-directional USB port carries any rate at 32 bits each way and is galvanically isolated, as are the BNC outputs, and isolation makes the biggest difference. needs context Head-Fi, Jan 2017
• 2017-01-10Watts says Hugo 2's USB is not galvanically isolated because the USB chip would drain mobile source batteries, but RF filtering and isolation on USB power and ground are improved. Head-Fi, Jan 2017
• 2017-02-28Watts heard almost no optical versus USB difference on Hugo 2 with a mains laptop and headphones, crediting RF-filtered USB ground and VBUS, separate input supplies and 144 dB crosstalk. Head-Fi, Feb 2017
• 2017-02-28Watts says USB galvanic isolation may help when driving a power amp depending on source noise, and charging makes no measured and no reliably audible difference. Head-Fi, Feb 2017
• 2017-03-04Watts explains that headphones keep source noise common mode, while a grounded power amp drives ground-loop currents through Hugo 2's ground plane, now limited by a USB RF ground filter. Head-Fi, Mar 2017
• 2017-03-04Watts says a laptop off the mains and connected only to the DAC forms no ground or power loops, so it is perfectly isolated. Head-Fi, Mar 2017
• 2017-03-04Watts tells a poster they should be fine because the ground loop does not include the source, adding that results may vary. needs context Head-Fi, Mar 2017
• 2017-03-05Watts cautions one laptop test proves little: Hugo 1 improved enormously with isolation from a Dell PC, while galvanic isolation on production Blu 2 with DAVE gives a substantial improvement. Head-Fi, Mar 2017
• 2017-03-05Watts says the isolation is at the dual BNC outputs, and USB input isolation has no effect so long as the DAC is isolated. needs context Head-Fi, Mar 2017
• 2017-03-15Watts says further isolating USB would have no effect, since optical and USB sounded the same with a high-spec laptop and headphones, though other sources may differ. Head-Fi, Mar 2017
• 2017-03-16Watts says his test used the short supplied USB cable and a 10-pound optical cable, and galvanic isolation would not help there, though results vary with source and power amps. Head-Fi, Mar 2017
• 2017-03-16Watts explains that an earthed power amp lets source currents loop through Hugo 2's ground plane, while optical, galvanic isolation or battery sources prevent this. Head-Fi, Mar 2017
• 2017-04-06Watts reports a USB ground-loop test slightly truncated depth and added brightness; isolation seems unnecessary for headphones, and Hugo 2 is 5 to 10 times less sensitive than Hugo 1. Head-Fi, Apr 2017
• 2017-04-06Watts reports no consistent grounded versus ungrounded difference with a battery laptop, but turning crossfeed on (max blue) more than doubled perceived depth. Head-Fi, Apr 2017
• 2017-04-07Watts says his MSI laptop tests suggest no galvanic isolation is needed on battery power, and even on mains the change is not large. Head-Fi, Apr 2017
• 2017-04-10Watts says the device is galvanically isolated only at low frequencies, as its grounds are joined by capacitors, so for sound quality it should be treated as not isolated. needs context Head-Fi, Apr 2017
• 2017-05-08Watts says the M scaler is 0.234 dB louder (-2.766 dB insertion loss, +3 dB volume) and its 10 A signal-dependent FPGA ground current forces a separate, isolated box. Head-Fi, May 2017
• 2017-05-17Watts could not reliably hear optical versus USB on headphones with a mains laptop, but heard differences with a power-amp ground loop; brighter sound means more noise floor modulation. Head-Fi, May 2017
• 2017-06-08Watts says galvanic isolation mattered greatly on Hugo 1, but Hugo 2's RF filtering and supply isolation (over 144 dB separation) cut its benefit tenfold; he suggests listening to USB versus optical to test sensitivity. Head-Fi, Jun 2017
• 2017-07-17Watts says USB and optical sounded identical on Hugo 2 only with headphones and one MSI laptop; grounding the analog output made a difference, though the gap is greatly reduced. Head-Fi, Jul 2017
• 2017-08-10Watts asks a poster what makes them think the Benchmark DAC2 is properly isolated. Head-Fi, Aug 2017
• 2017-08-10Watts notes Benchmark's website omits galvanic isolation, disputes that Hugo 1 sounds different, praises its musicality with archive recordings, and says 1960s Decca sounds real via Blu 2 and DAVE. Head-Fi, Aug 2017
• 2017-10-02Watts says he hears no difference between USB cables on DAVE, optical versus USB is minute, and a battery source via DAVE's isolated USB isolates better than mains-powered optical. Head-Fi, Oct 2017
• 2017-10-13Watts says others listen only after something enormous, recalling 1980s solid versus stranded mains cables on a preamp with 220 dB of supply rejection, which he had his girlfriend blind-test. miceblue425 53:06
• 2017-10-20Watts says the 200T FPGA draws 10 A processing versus 2 A idle, so it sits in a galvanically isolated Blu 2 rather than DAVE, keeping DAVE's ground plane clean. Hifistatement 0
• 2017-10-20Watts says an external scaler reduces ground-plane noise through galvanic isolation, and that how the isolation and power supply were implemented made a substantial change to sound quality. Hifistatement 55
• 2017-12-02Watts says a ferrite does not change the cable's signal impedance; it raises common-mode ground impedance, improving GHz isolation into DAVE's ground plane without affecting bandwidth. Head-Fi, Dec 2017
• 2017-12-02Watts says he heard no optical vs USB difference on Hugo 2 from his laptop with headphones, a small one with grounded outputs, and credits improved USB RF filtering. Head-Fi, Dec 2017
• 2018-01-10Watts says get Hugo 2 for headphones as any external amp degrades transparency; with headphones USB sounded like optical, so isolation matters only with mains-powered amps. Head-Fi, Jan 2018
• 2018-01-11Watts says his listening tests showed no change from ferrites on USB cables, though sources differ, and battery operation should avoid ground loops and RF pick-up. Head-Fi, Jan 2018
• 2018-01-11Watts says a USB cable with ferrites made no change for him, and external RF only matters with a ground loop, so battery operation avoids it. Head-Fi, Jan 2018
• 2018-01-11Watts says airborne RF is unlikely to induce ground-plane currents in DAVE's thick aluminum chassis, and without ground current there is no pick-up by the analog electronics. Head-Fi, Jan 2018
• 2018-01-11Watts now attributes USB's slight brightness on DAVE to RF through ground loops and the isolators' 2 pF, not timing, since Hugo 2 USB sounds like optical. Head-Fi, Jan 2018
• 2018-01-25Watts says the tingle comes from an unearthed system discharging PSU leakage current through the finger, and earthing the system will stop it and probably the hum. Head-Fi, Jan 2018
• 2018-02-23Watts says a separate, galvanically isolated M Scaler keeps that noise out of Dave, isolation took two prototypes, another M Scaler is in progress, and timing recovery reaches 16-bit accuracy. MajorHiFi 20:49
• 2018-02-24Watts says the poster's situation 1 technically forms a mains ground loop but he heard no change with the charger connected; Blu 2's isolated BNC outputs remove the problem. needs context Head-Fi, Feb 2018
• 2018-02-24Watts heard a difference grounding the output phonos with USB versus optical, but none with the supplied PSU, likely because RF filtering on the charging input removed the loop. Head-Fi, Feb 2018
• 2018-02-24Watts says plugging units into one power strip only reduces ground loop area and low-frequency magnetic hum pick-up; with effective isolation there are no ground loops even via the mains. Head-Fi, Feb 2018
• 2018-02-27Watts says the FPGA draws 10 or 12A at 1V, a 12W peak; the M scaler draws about 15W from mains, well isolated and RF filtered, as on Blu 2 and Dave. Head-Fi, Feb 2018
• 2018-03-08Watts says a proper mains RF filter needs Y capacitors, giving more leakage but a warmer sound, and that DAVE is relatively immune to mains quality. Head-Fi, Mar 2018
• 2018-03-08Watts says it is not an issue if the PSU has effective RF filtering and the galvanic isolation works at GHz frequencies, but these effects are extremely sensitive. needs context Head-Fi, Mar 2018
• 2018-03-17Watts describes DAVE's development: individual RF filtering of digital sections, care over ground-plane return currents and layout, two ground planes, and Chord's patience over time and prototypes. Head-Fi, Mar 2018
• 2018-04-08Watts says his MSI laptop PSU is grounded with many ground loops; DAVE with a battery laptop sounds better, but only by careful AB listening. Head-Fi, Apr 2018
• 2018-04-29Watts says he uses stock mains cables, heard no difference adding 300 MHz ferrites on the mains input, and DAVE has extensive supply RF filtering and regulation. Head-Fi, Apr 2018
• 2018-05-17Watts says all mains-powered DAC/amps have isolation, USB sounds very close to optical, he is amazed 2Qute can drive a loudspeaker, and he explains his single-stage output amplifier. Head-Fi, May 2018
• 2018-05-21Watts says the tingle from touching unearthed gear is leakage current discharging through imperfectly isolated anodizing, and it is safe because Dave's PSU is a low-leakage medical grade supply. Head-Fi, May 2018
• 2018-05-22Watts says only anodized surfaces such as Dave's chassis tingle, and he gets it only in hotels without earthing, from the leakage of his whole mobile rig. Head-Fi, May 2018
• 2018-06-15Watts says his Poweradd Pilot Pro2 has noisy internal regulators, but what matters is no mains RF; it made no difference on Hugo 2 and prevents ground loops and leakage. Head-Fi, Jun 2018
• 2018-07-17Watts agrees the goal is reducing ground currents, which that filter cannot touch as ground is unfiltered; only ferrites reduce Blu 2 and Dave RF common-mode ground currents. Head-Fi, Jul 2018
• 2018-07-18Watts says extra shielding will not help; ferrites, like BNC galvanic isolation, raise the RF coupling impedance between Blu 2 and Dave grounds, with the worst problem around 2GHz. Head-Fi, Jul 2018
• 2018-07-21Watts says improved isolation on the BNC output drivers removes the need for ferrites, which in listening tests made it sound slightly worse; the code is identical. c w 30:37
• 2018-07-26Watts reports no difference, says Blu 2 avoided problems he had with the Hugo M Scaler, and never needed USB isolation since the noise comes from the FPGA. needs context Head-Fi, Jul 2018
• 2018-07-29Watts says optical and USB sound the same on Hugo 2 with headphones but differ once grounded; coax lacks galvanic isolation, so RF raises noise floor modulation and sounds brighter. Head-Fi, Jul 2018
• 2018-07-29Watts says the supplied PSU is doubly insulated with no ground; a grounded PSU caused ground-loop problems measured with the Audio Precision, and the filter module is identical. Head-Fi, Jul 2018
• 2018-07-29Watts says optical is warmer and smoother from complete galvanic isolation, USB comes close, and coax cannot take RF filtering without degrading lock. Head-Fi, Jul 2018
• 2018-07-29Watts says optical is perfect galvanic isolation with near-zero coupling capacitance, while every electrical digital connection carries ground RF noise that isolation coupling capacitance passes at GHz frequencies. Head-Fi, Jul 2018
• 2018-07-31Watts says it is largely immune; RF corrupting other devices is the issue, so he plugs TT2 and the source in on opposite sides of the room. Head-Fi, Jul 2018
• 2018-08-05Watts advises against powering the DAC and laptop together, since it shorts the USB galvanic isolation; source and DAC grounds must stay isolated. Head-Fi, Aug 2018
• 2018-08-26Watts says power banks beat mains on RF noise (10 MHz to 10 GHz), linear supplies lack RF filtering, RF causes audible noise floor modulation, and batteries avoid ground loops. Head-Fi, Aug 2018
• 2018-09-18Watts says the M scaler PSU came from TT2 testing, grounded C13 PSUs caused ground loops, quality SMPS beat linears, the Chord driver works, and auto low-power mode exists. Head-Fi, Sep 2018
• 2018-10-17Watts says battery power sounds the same in his system, YMMV, but battery banks are the best supply, better than linear, with no leakage currents or RF noise. Head-Fi, Oct 2018
• 2018-11-22Watts says the M scaler PSU is deliberately ungrounded to avoid earth loops, grounded PSUs sound brighter, overvoltage failures void warranty, and 15 V is the maximum input. Head-Fi, Nov 2018
• 2018-11-26Watts says using optical requires disconnecting other sources, otherwise the isolation is shorted via the BNC ground or galvanic isolation coupling capacitance. Head-Fi, Nov 2018
• 2018-11-26Watts says BNC directly couples grounds so it matters most to remove; listeners may hear no difference between inputs, but should disconnect during listening tests. Head-Fi, Nov 2018
• 2018-11-30Watts says capacitive loads are fine, earthing it to TT2 sounds like a good idea, and the phono outputs disconnect only when a headphone jack is inserted. needs context Head-Fi, Nov 2018
• 2018-11-30Watts says the dual BNC outputs are isolated from the other outputs, so noise from other DACs should not upset DAVE, and the optical output is fully isolated. Head-Fi, Nov 2018
• 2018-12-12Watts says every circuit point has RF decoupling, with quad-layer ground planes, a digital PLL eliminates source jitter, and TT2's noise floor is minus 178 dB with zero measurable NFM. Pursuit Perfect System 34:53
• 2018-12-13Watts explains 2 GHz ground-plane noise crossing the BNC isolation's 5pF; clip-on ferrites help Blu 2 but degrade the Hugo M Scaler, solid-core help slightly, cables beyond 2m don't. Head-Fi, Dec 2018
• 2018-12-16Watts advises against replacing TT2's supplied PSU, saying he hears no change when it is pulled for 10 seconds and an earthed supply would likely degrade sound. Head-Fi, Dec 2018
• 2018-12-16Watts says he has never seen an M scaler EMC issue, finds it odd since red is low power, and suggests repositioning, earthing via a BNC input, and moving cables. Head-Fi, Dec 2018
• 2018-12-19Watts says the poster needs to earth Qutest, really the power amps, since Qutest and the M scaler are both isolated from ground. Head-Fi, Dec 2018
• 2019-01-29Watts says both, since both have galvanic isolation on their BNC outputs. needs context Head-Fi, Jan 2019
• 2019-02-22Watts says TT2 and M Scaler USB inputs are galvanically isolated, drawing about 250 mW from the source, which may drain a phone about 15% faster. Head-Fi, Feb 2019
• 2019-02-24Watts explains that noise harms sound via ground-plane current causing RF intermodulation and noise floor modulation; optical avoids it unless mains-powered sources form an electrical loop. Head-Fi, Feb 2019
• 2019-02-27Watts says all his galvanically isolated designs power the USB decoder from VBUS, isolating it so the DAC sees only I2S data without decoding noise. Head-Fi, Feb 2019
• 2019-03-11Watts says Qutest isolates USB with RF digital isolators of 2 pF coupling plus GHz filtering, not transformers, so added USB devices raise system RF noise rather than improve isolation. Head-Fi, Mar 2019
• 2019-03-12Watts explains how a mains-powered USB reclocker creates intersecting ground loops that defeat Qutest's isolation, and weighs an M Scaler against removing an external amp, advising a dealer trial. Head-Fi, Mar 2019
• 2019-03-16Watts says USB VBUS powers the decoder on the isolator's source side, so only ground loops let sources matter, and added source complexity can sound like improvement while degrading timbre. Head-Fi, Mar 2019
• 2019-03-16Watts says one earthed component on each side of Qutest is fine, because problems need current flowing through a Qutest output loop intersected by a source loop. Head-Fi, Mar 2019
• 2019-03-17Watts says Qutest's supplied PSU is ungrounded, and SMPS have low coupling capacitance and RF filters linear supplies lack; a USB battery pack removes mains coupling, with tiny differences. Head-Fi, Mar 2019
• 2019-04-17Watts says ferrites on BNC cables raise common mode impedance, unlike a single-wire RF-to-heat device whose mechanism he doubts; he offers to test one. Head-Fi, Apr 2019
• 2019-04-19Watts says chip ferrites in the coax ground corrupted data, but USB tolerates ground ferrites as differential signaling, which is why the M Scaler is isolated on the transmit side. Head-Fi, Apr 2019
• 2019-04-21Watts says pin 1 of TT2's XLR must connect to pin 1 on the amp, or large common-mode differences could damage the amp. Head-Fi, Apr 2019
• 2019-04-21Watts says DAVE is connected to mains earth, ground boxes have the whiff of snake oil, and buyers should do careful AB tests before buying. Head-Fi, Apr 2019
• 2019-04-25Watts says PSU leakage current of tens of uA can flow through the listener and headphones causing hum and tingling, and earthing Hugo 2 stops it. Head-Fi, Apr 2019
• 2019-05-16Watts says the coax and analog output grounds connect directly to the ground plane, so either can be used, while USB ground goes via a ferrite bead. Head-Fi, May 2019
• 2019-05-17Watts says the ferrite bead has no significant effect at audio frequencies but reduces RF currents, which may or may not improve sound quality. needs context Head-Fi, May 2019
• 2019-06-29Watts says it is due to PSU leakage, entirely safe, and removable by grounding a BNC input or the single BNC output ground; TT2 behaves the same. needs context Head-Fi, Jun 2019
• 2019-07-06Watts says a battery-powered optical-to-coax adaptor is no worry, but a mains-powered one can create ground loops, raising RF noise and making the sound brighter. Head-Fi, Jul 2019
• 2019-08-21Watts says IEM hum on TT2 is cured by earthing it, battery power, breaking the body path, or lower impedance IEM cables, as PSU leakage current causes ground voltage drops. Head-Fi, Aug 2019
• 2019-10-16Watts says ground-plane currents cause noise floor modulation, battery Hugo 2 into headphones showed no optical-USB difference, and his M scaler's dual galvanic isolation makes source noise a non-issue. Head-Fi, Oct 2019
• 2019-11-17Watts says linear PSUs will sound worse than the supplied PSU on mains, batteries give complete isolation, and the handbook's toroidal note is generic, not an M scaler problem. Head-Fi, Nov 2019
• 2019-11-27Watts explains 2 GHz loop currents through the DAC ground plane, why clip-on ferrites stopped helping after his M scaler treatments, and why linear PSUs degrade sound. Head-Fi, Nov 2019
• 2019-11-27Watts says he uses solid-core ferrite cables at home but not when traveling with Hugo 2, TT2 or DAVE, and notes a battery-powered Hugo 2 avoids ground loops. Head-Fi, Nov 2019
• 2019-12-05Watts says the USB input needs source VBUS to power the decoder chip on the isolator's source side, so decoding noise cannot affect the DAC. Head-Fi, Dec 2019
• 2020-01-18Watts explains how a mains-powered USB-to-optical converter can create RF ground-current loops a DAC may intersect, advises keeping sources simple, and notes Ethernet isolation still has capacitive coupling. Head-Fi, Jan 2020
• 2020-01-20Watts explains isolating output-stage supply currents, shown in TT2's distortion plot, says delay follows tap length and oversampling, describes the M scaler's asymmetric video filter, and heard no USB-optical difference. Head-Fi, Jan 2020
• 2020-02-21Watts says a buzz in IEMs came from a non-earthed charger's leakage current, and earthing Hugo 2 via coax, RCA or spare headphone ground fixes it on optical. Head-Fi, Feb 2020
• 2020-04-01Watts says 55 kHz PSU noise is irrelevant to the M scaler; 2 pF isolation coupling at 2 GHz matters, the ungrounded supplied SMPS helps, and linear PSUs worsen it. Head-Fi, Apr 2020
• 2020-04-01Watts says he chose TT2's SMPS as the only one matching a battery's measured HF performance; being ungrounded raises 2 GHz loop impedance, slightly helping the M scaler too. Head-Fi, Apr 2020
• 2020-04-06Watts says TT2 hum with sensitive IEMs comes from 100uA PSU leakage and is fixed by grounding via XLR pin 1, phono, BNC or DX grounds, not isolated USB. Head-Fi, Apr 2020
• 2020-04-09Watts says USB decoding and galvanic isolation work down to 3.3v VBUS, and the gain from better-than-16-bit over 13-bit timing varies by listener, but he needs the M scaler. Head-Fi, Apr 2020
• 2020-04-10Watts says Chord desktop DACs and the M scaler need 5v VBUS to power USB galvanic isolation, and portable DACs need VBUS on as a USB-connected flag. Head-Fi, Apr 2020
• 2020-05-01Watts doubts the JitterBug will help, since it stopped making a difference once he treated USB grounds with ferrites, and the M scaler has ferrites and galvanic isolation. Head-Fi, May 2020
• 2020-05-04Watts says the JitterBug helped Hugo 1, suspects USB treatments add brightening RF, heard no USB-optical difference on M scaler or ungrounded Hugo 2, and enjoys Tangerine Dream box sets. Head-Fi, May 2020
• 2020-05-07Watts says a car battery is the best PSU but a power bank suffices, TT2 gains nothing, and a battery helps the M scaler by removing 2GHz ground return currents. Head-Fi, May 2020
• 2020-05-25Watts says 13.2V works with M scaler and TT2 on separate supplies, TT2 is supply-insensitive, and a battery on the M scaler removes the ground loop into the DAC. Head-Fi, May 2020
• 2020-05-27Watts says certified USB cables work at any length, he heard no difference among them, doubts audiophile cables, and found longer BNC cables better through reduced ground loop currents. Head-Fi, May 2020
• 2020-06-05Watts says the tingle is a safe 100 uA PSU leakage depending on local mains wiring, and grounding the chassis or a BNC input, away from the DAC, cures it. Head-Fi, Jun 2020
• 2020-06-24Watts says TT2's USB isolation rules out a USB ground loop, ferrites handle 2 pF coupling at 2 GHz, and IEM hum is PSU leakage fixed by grounding TT2. Head-Fi, Jun 2020
• 2020-07-06Watts says linear PSUs add mains hum, vibration, magnetic fields and coupling; TT2's chosen SMPS showed no noise degradation in a 96kHz bandwidth, is unearthed, and matched a battery. Head-Fi, Jul 2020
• 2020-07-24Watts says conventional phase shift seems unimportant but phase varying with time or amplitude is audible, defends sinc ringing for bandlimited signals, and discusses SMPS design and USB isolation. Head-Fi, Jul 2020
• 2020-08-03Watts says PSU leakage current causes the amp issue, which a battery avoids; earth Qutest via BNC, RCA, an earthed USB PSU or a chassis bolt, or earth the amp. Head-Fi, Aug 2020
• 2020-08-10Watts says 2 m BNC cables beat 1 m, solid-core 2 GHz ferrites help most, clip-on ferrites hurt with the M Scaler, and battery power breaks its ground loop. Head-Fi, Aug 2020
• 2020-08-11Watts explains that longer BNC cables or solid-core ferrites raise the RF impedance of the ground path from M Scaler to DAC, reducing circulating ground currents into the DAC. Head-Fi, Aug 2020
• 2020-08-13Watts estimates 2 m over 1 m BNC gives 25-33% of the ferrite gain, explains the ground loop, recommends Wave, and says other audiophile USB and BNC cables match or degrade certified ones. Head-Fi, Aug 2020
• 2020-08-13Watts says the best source injects least RF noise into the DAC ground; a battery phone is lowest noise; the USB decoder sits on the isolation's source side. Head-Fi, Aug 2020
• 2020-08-17Watts says the BNC inputs on the DACs are not galvanically isolated, which is no problem with an M scaler because its BNC outputs are isolated. Head-Fi, Aug 2020
• 2020-08-23Watts explains optical injects far less RF noise than USB because the receiver has no processing, ferrites on optical made no difference, and it blocks source ground currents. Head-Fi, Aug 2020
• 2020-09-07Watts advises running the M Scaler from the 12 V battery and not worrying about TT2, since breaking the current path once suffices; keep the battery isolated from ground. Head-Fi, Sep 2020
• 2020-09-08Watts says battery isolation works if capacitance to ground is low, as with his PowerAdd bank; power-up order causes no damage, but TT2 should be last on, first off. Head-Fi, Sep 2020
• 2020-09-09Watts calculates a battery on a desk has about 0.1 pF to ground, 796 ohms at 2 GHz; a Poweradd battery on the M Scaler nearly eliminates BNC cable differences. Head-Fi, Sep 2020
• 2020-09-09Watts says any non-conductive surface, or an unearthed steel rack, will do for the battery; the key is breaking the connection to mains earth. Head-Fi, Sep 2020
• 2020-09-10Watts says plugging Dave straight into the wall is fine, mains-cable ferrites made no audible change, and he habitually puts DACs on a separate socket, untested on Dave. Head-Fi, Sep 2020
• 2020-10-10Watts sees no point in USB clocks since TT2's isolation follows the USB decoder, says added source devices raise RF noise, and lists laptops and a phone as his sources. Head-Fi, Oct 2020
• 2020-11-26Watts says he checked the schematics for Chord: TT1 does have galvanic isolation on the HD USB input, the same circuit as TT2 and DAVE. Head-Fi, Nov 2020
• 2020-11-27Watts says TT2's unearthed PSU was chosen for the best measurements and battery-like sound; full isolation attenuates ground loop currents, at the cost of a 100uA leakage tingle. Head-Fi, Nov 2020
• 2021-03-19Watts says optical cannot pass source ground-plane noise, mains ground loops are mostly theoretical, and suggests a phone with a bit-perfect app as a reference source. Head-Fi, Mar 2021
• 2021-03-20Watts says an optical-only DAC has about 0.1pF to ground, while HMS to TT2 has about 2pF through the BNC isolators, fixed by battery-feeding HMS or solid-core 2GHz ferrites. Head-Fi, Mar 2021
• 2021-03-20Watts says earth voltage matters only when the source drives current across the DAC ground plane, whose impedance creates voltage drops that the analog stages turn into noise floor modulation. Head-Fi, Mar 2021
• 2021-03-22Watts attributes differences between CD players into Dave over optical to mains RF noise and ground loops, and says bit-perfect source differences come from jitter, RF noise or signal-correlated noise. Head-Fi, Mar 2021
• 2021-03-31Watts says CD player differences may be RF pickup via power amps, 2GHz ferrites or cutting loops fix M scaler to TT2 noise, notes a migraine; ADC work continues. Head-Fi, Mar 2021
• 2021-03-31Watts says the single BNC output on the M scaler is not galvanically isolated. Head-Fi, Mar 2021
• 2021-04-01Watts says disconnecting the M scaler charger avoids the source-M scaler-Dave loop, CD players inject RF into mains, and changing Dave's PSU invalidates the warranty. Head-Fi, Apr 2021
• 2021-04-06Watts says volume colors mean the same voltage across DAVE, TT2, Hugo 2 and Mojo (blue is 1.0V RMS), and all desktop DACs have galvanically isolated USB. Head-Fi, Apr 2021
• 2021-05-31Watts says Hugo 2's USB sensitivity depends on mains loops, advises optical and avoiding DDCs in mains systems, and explains RF-induced noise floor modulation as brightness. Head-Fi, May 2021
• 2021-08-19Watts says Opto-DX isolates fully only with batteries on both sides, and calls his volume truncation noise-shapers subjectively lossless but not bit perfect, a claim he is researching. Head-Fi, Aug 2021
• 2021-08-29Watts recommends a 768kHz ADC, plans pulse array ADC tests, favors digital volume over analog, and says grounding via Dave shorts its isolation; ground elsewhere, battery-power, or use a resistor. Head-Fi, Aug 2021
• 2021-08-30Watts says PSU leakage current is mostly 100Hz and inaudible, Xilinx lead times are 55 weeks, and more FPGA space would mainly benefit WTA2 and filters up to 104MHz. Head-Fi, Aug 2021
• 2021-10-13Watts advises certified USB cables over DIY, says audiophile cables can add RF brightness, explains ground-plane RF currents and Mojo's ferrites, and suggests an optical test. Head-Fi, Oct 2021
• 2021-10-18Watts covers phone RF loops with Mojo, USB cable dressing, 2G buzz, Netflix audio, USB galvanic isolators in desktop DACs and M Scaler, and why brighter cables mean more noise. Head-Fi, Oct 2021
• 2021-12-21Watts says the ADC will be free of mains hum but he cannot answer for the microphones. Head-Fi, Dec 2021
• 2022-02-05Watts explains Mojo 2's USB-ground ferrites, when external filters might help (optical is best), how crossfeed mimics loudspeaker listening, and reduced 2G buzz. Head-Fi, Feb 2022
• 2022-02-12Watts says SMPS tones do not cause NFM unlike random RF, recalls switching regulators beating linear in Hugo, and prefers power banks for isolation from RF ground currents. Head-Fi, Feb 2022
• 2022-02-13Watts says battery power on the M Scaler removed his need for ferrited BNC cables, and Wave cables removed the need for batteries, both cutting GHz ground currents into DAVE. Head-Fi, Feb 2022
• 2022-02-21Watts says putting the source and M scaler on one battery keeps source RF from the DAC; the M scaler's USB isolation exists only to cut noise reaching the DAC. Head-Fi, Feb 2022
• 2022-02-26Watts says a working powered speaker will not damage TT2, but its ground connection could carry RF currents that brighten headphone listening, so try switching it on and off. Head-Fi, Feb 2022
• 2022-03-19Watts says optical is best but USB can sound identical; with portable sources it does not matter, but earthed, USB sounds brighter, hence isolated USB on desktop DACs. MFG Audio Reviews 56:15
• 2022-03-19Watts says Mojo and Hugo 2 lack galvanic isolation and that galvanic isolation in general is about 99% effective; optical helps with noisy servers, and his MSI desktop sounds much better on optical. MFG Audio Reviews 56:58
• 2022-03-28Watts details SPDIF word clock extraction and his frequency-locked DPLL on a 104.25MHz clock, and says USB can match optical but RF leaks through the 2pF isolation. Head-Fi, Mar 2022
• 2022-04-12Watts says DAVE is earthed because its PSU is inside the chassis, TT2's double-insulated supply needs no earth, and earthing is moot since GHz noise is the main problem. Head-Fi, Apr 2022
• 2022-04-26Watts advises high gain into a power amp, keeping units on Wave cables apart to avoid capacitive coupling and cable ends touching, and says TT2 tolerates running warm continuously. Head-Fi, Apr 2022
• 2022-05-28Watts attributes a 1 kHz measurement artifact to APx555 ground currents over USB, discusses ground loops and optical as reference, and gives settings for noise floor modulation tests. Head-Fi, May 2022
• 2022-06-27Watts says pure DSD and R2R DACs are fundamentally limited, DAVE's noise shaper is not capped at 17th order, the HF filter sits after WTA2, and car batteries are ideal. Head-Fi, Jun 2022
• 2022-06-28Watts says every Chord desktop DAC since DAVE has galvanic isolation with the USB decoder source-side, and battery-powered Mojo 2 or Hugo 2 with headphones won't need it. Head-Fi, Jun 2022
• 2022-08-19Watts says the scaler is galvanically isolated and separate from the DAC so that the gigahertz noise is, he hopes, removed by the isolation. needs context AVstore 30:36
• 2022-08-19Watts says he prefers optical into the M Scaler; USB can match it or sound harder, brighter and flatter; BNC is technically worst, lacking galvanic isolation. AVstore 41:06
• 2022-08-19Watts says he knows the interviewer uses the DX and does not know whether it has galvanic isolation built in. needs context AVstore 41:52
• 2022-08-19Watts says the M Scaler's BNC outputs have a galvanic isolator, giving near-optical standard, but about three picofarads (first said two) is tens of ohms at gigahertz, so he also added ferrites and filters. AVstore 42:06
• 2022-08-19Watts says to use optical as the reference since it is perfectly galvanically isolated, and its slightly higher jitter than BNC does not matter with Chord DACs. AVstore 42:56
• 2022-09-07Watts confirms TT2 needs 5V on the USB cable because its galvanic isolator is powered from the USB +5V. Head-Fi, Sep 2022
• 2022-10-04Watts says all wired connections must be removed from the source when using optical, and a USB-to-optical converter should need no external supply; the Douk Audio U2 looks worth trying. Head-Fi, Oct 2022
• 2022-10-12Watts says the discrete conversion components are fed from a different power supply and the digital components are completely isolated. Upscale Audio 2:30
• 2022-12-21Watts says the effect is barely measurable near the FFT noise floor and unheard by others, suggesting the Feliks amp picks up display multiplexing noise through grounding or RF. needs context Head-Fi, Dec 2022
• 2023-01-06Watts says with a Poweradd powerbank and optical on the M Scaler, quality BNC sounded like Wave Stream, since no ground currents can reach the DAC's ground plane. Head-Fi, Jan 2023
• 2023-01-08Watts says only an optical source plus battery on the M Scaler guarantees noise-free operation, as mains units leak noise even via optical; the Choral M Scaler addresses this. Head-Fi, Jan 2023
• 2023-01-11Watts says star earthing is useless for RF noise and cannot be used for SPDIF, which needs a controlled 75 ohm return, causing lost lock or thumps. Head-Fi, Jan 2023
• 2023-01-12Watts says star earthing's 2uH is 25,000 ohms at 2 GHz; adaptors are fine but long cables should be 75 ohm, and his short 50 ohm cables never drop out. Head-Fi, Jan 2023
• 2023-02-04Watts says on planes, about 300 hours a year, he uses his phone with 1 TB of music by USB into a battery DAC, giving perfect isolation. Dusty Audio 1:06:27
• 2023-02-04Watts says his 800 W desktop's USB sounded significantly worse than optical into the M Scaler; optical is the reference because no current flows into the DAC. Dusty Audio 1:07:51
• 2023-02-05Watts says separate I2S clock lines bring no benefit and three cables add ground noise; he always prefers optical, with galvanically isolated BNC from the M Scaler nearly matching it. Soundnews 48:58
• 2023-02-05Watts says isolated BNC is not quite as good as optical; non-isolated BNC is much worse; USB follows, isolated on TT2 and DAVE; optical is the primary reference input. Soundnews 49:45
• 2023-03-01Watts says the M Scaler needs no warm-up, Hugo 2's in-flight change was ear pressure, describes flying with his battery rig and thermal trip, and says battery plus optical isolates. Head-Fi, Mar 2023
• 2023-03-01Watts says 2pF across the M Scaler's USB and BNC isolation gives about 80 ohms at 2 GHz, letting current reach DAVE's ground plane; optical may beat USB, source depending. Head-Fi, Mar 2023
• 2023-03-02Watts says scalers are separate units to keep FPGA noise from the DAC, as the Hugo M Scaler injects 12A of noisy current into its ground plane. Head-Fi, Mar 2023
• 2023-03-26Watts says DAVE measures better than any DAC he has seen, yet others using an APx555 differ; one manufacturer's terrible TT2 and M Scaler results came from ground loops. Eric's Hi-Fi 25:47
• 2023-03-26Watts says the manufacturer rebuilt his lab and it then measured perfectly; the APx555 is very sensitive to grounding and laptops, so he sets his lab up carefully. Eric's Hi-Fi 26:36
• 2023-06-18Watts says an isolated power bank or Wave cables break the M Scaler's GHz ground loop, longer standard BNC sounds better via common mode inductance, and Krisdonia sounded worse. Head-Fi, Jun 2023
• 2023-06-18Watts says TT2 is fine on its supplied PSU, a power bank made no difference, and earthing is largely irrelevant at RF once mains connects everything via transformer winding capacitance. Head-Fi, Jun 2023
• 2023-11-21Watts doubts grounding boxes, says star grounding is useless for RF, and that good ground sounds warmer while bright, artificially transparent sound means more RF noise. Head-Fi, Nov 2023
• 2024-02-15Watts says NFM sounds etched and brighter but degrades focus, the DPLL handles source PSU noise via optical, and battery plus optical on the M Scaler removes the ground loop. Head-Fi, Feb 2024
• 2024-02-22Watts says galvanic isolation fails at GHz via capacitance, optical breaks the link, and an LPS on TT2 would be a downgrade that sounds etched due to no RF filtering. Head-Fi, Feb 2024
• 2024-03-01Watts says the new PSUs must stay independent, as their high impedance from 1MHz to 10GHz blocks RF currents that shared supplies would couple between scalers and DACs. Head-Fi, Mar 2024
• 2024-03-20Watts recounts that solid-core mains cables sounded warmer, darker and smoother than stranded, puzzling given three 70 dB regulator stages and op-amps with 140 dB power supply rejection. MFG Audio Reviews 5:50
• 2024-03-20Watts explains that power supply rejection applied only in the audio band, so he concluded RF noise was changing the sound and began developing a complex RF mains filter. MFG Audio Reviews 6:40
• 2024-03-20Watts describes cascading ever-smaller LC filters from 100 kHz to hundreds of MHz; with the filter perfected, solid-core and stranded mains cables sounded identical, so the difference was RF. MFG Audio Reviews 7:30
• 2024-03-20Watts says a digital cable's RF characteristics, especially if not impedance matched, change RF noise, and RF current through the DAC ground plane to the mains creates small voltage drops. MFG Audio Reviews 17:23
• 2024-03-20Watts says ground planes have finite impedance at GHz, so RF current creates voltage drops that cause intermodulation and noise floor modulation; this current flows in a mains-source-DAC loop. MFG Audio Reviews 18:03
• 2024-03-20Watts says current needs a loop to flow; ferrites on connections reduce it by raising impedance, and fully battery-operated setups prevent it entirely. MFG Audio Reviews 18:51
• 2024-03-20Watts says a low-power processor reduces correlated RF noise, so a mobile phone can be the best source: battery operation stops current flow and low power means little GHz noise. MFG Audio Reviews 22:11
• 2024-03-20Watts says a low-power battery source removes both correlated and random RF noise, giving better depth and a warmer sound, and that optical, reputedly worst, is best because coupling capacitance is zero. MFG Audio Reviews 22:54
• 2024-03-20Watts says with optical everything is done by light, so there is no coupling capacitance. MFG Audio Reviews 23:41
• 2024-03-20Watts says DC on the mains makes toroidal transformers buzz badly, recalling that his toroidal transformer supplier attributed intermittent buzzing to DC offsets. MFG Audio Reviews 57:28
• 2024-03-20Watts says fiber over USB could help but he is not fully convinced because such links often carry power down the cable. MFG Audio Reviews 58:32
• 2024-03-20Watts says it is fine as long as grounds and power supply are not physically connected; a fiber link whose cable also carries electrical connection gives no benefit. MFG Audio Reviews 58:48
• 2024-03-20Watts says USB-to-optical converters powered from the USB port work perfectly well, but ones with separate supplies risk mains loops between a computer and a mains-powered product. MFG Audio Reviews 59:13
• 2024-03-20Watts says a DAC that intersects a mains loop sees its voltage and suffers, while a converter powered from the source makes a single connection with no local loops. MFG Audio Reviews 59:58
• 2024-03-20Watts says in every listening test they sound the same because current causes the problem; without current there are no ground-plane voltage drops, and perfect ground planes are impossible. MFG Audio Reviews 1:00:30
• 2024-05-10Watts says this must be isolated from that and from the rest of the base to stop currents flowing in a loop, using two cascaded RF filters of a couple hundred components each. Reactcore 23
• 2024-05-16Watts says 200-plus-component RF filters at Quartet's input and supply output keep RF out of Quartet and DAVE; stopping circulating currents makes BNC cable quality irrelevant. ConvinceMeAudio 2:12
• 2024-05-16Watts says this isolation gives much better sound quality, and that isolation through the RF filters is fundamentally crucial. ConvinceMeAudio 2:55
• 2024-05-16Watts says optical would require changing the DAC and fails anyway with DAVE and scaler both on mains, so he kept dual BNC and contained the noise inside the product. ConvinceMeAudio 10:19
• 2024-05-16Watts says the noise does not leak into the mains, so it sounds like battery power and BNC cables matter less than with the Hugo M Scaler. ConvinceMeAudio 10:47
• 2024-05-16Watts says the BNC drivers are improved: the Hugo M Scaler had one stage of galvanic isolation, while this has three, each with built-in RF filters. ConvinceMeAudio 11:00
• 2024-05-16Watts says the two outputs are not isolated from each other, sharing a supply and ground, but both are isolated so each DAC is isolated from the scaler. ConvinceMeAudio 14:42
• 2024-05-16Watts says this isolates Quartet (phrase partly garbled), giving much better sound quality and less need to worry about BNC connections. The Speaker Shack 5:00
• 2024-05-17Watts says separating it reduces processing noise and isolates Quartet from the DAC: RF filters in the supply and Quartet's input stage make it behave like a battery. AVstore 1:38
• 2024-06-18Watts says Quartet links over BNC like the M Scaler but has three FPGA isolation stages to its one, making it less sensitive to BNC cables. article, Jun 2024
• 2024-07-12Watts says the M Scaler was noticeably sensitive to BNC cables (ferrites helped) and sources, from current injected into the DAC despite galvanic isolation; a battery power bank solves it. HIFICLUB 45:42
• 2024-07-12Watts says he developed a supply with special RF filters giving battery-like isolation, reducing sensitivity to BNC cables and sources, and raises why he does not build a network player. HIFICLUB 46:35
• 2024-07-12Watts rejects criticism that audible source differences mean the M Scaler is badly designed: it passes EMC and has galvanic isolation; Quartet is isolated further. HIFICLUB 48:49
• 2024-07-18Watts says 1M taps gave 16-bit accuracy but any timing error is perceptible, describes the isolated 75 ohm coax output, and says flight-ready Quartet needs better FPGAs. Head-Fi, Jul 2024
• 2024-08-12Watts says inputs differ only through source RF noise: optical is the reference, USB has ground ferrites, and coax is most sensitive, hence galvanic isolation on the Hugo M Scaler. Head-Fi, Aug 2024
• 2026-03-17Watts says speaker or interconnect cables, but at CanJam he was talking about mains cables. ecoustics 53:46
• 2026-03-17Watts says a solid-core mains cable sounded better than a stranded one. ecoustics 54:00
• 2026-03-17Watts says in the mid-1980s he dismissed the claim, since his preamp had cascaded regulators and about 300 dB of supply rejection, but tried it one afternoon. ecoustics 54:06
• 2026-03-17Watts says he immediately heard the solid-core mains cable sound smoother and warmer, and asked his girlfriend to listen to each and say what differed. ecoustics 54:51
• 2026-03-17Watts says she heard it as warmer; the preamp rejected poorly above 10 MHz, so he suspected RF, as stranded wire creates more RF noise than solid core. ecoustics 55:38
• 2026-03-17Watts says with the finished RF filter, solid-core and stranded mains cables sounded identical, proving RF noise caused the difference. ecoustics 57:16
• 2026-03-17Watts says the digital processing is bit perfect, but DACs are analog devices, and trouble starts when supply noise gets into the ground plane or supplies feeding analog parts. ecoustics 1:06:37
• 2026-03-17Watts says noise enters electromagnetically or through supply and ground; a USB link forms a mains ground loop between computer and DAC, sending gigahertz RF currents into the ground plane. ecoustics 1:07:21
• 2026-10-02Watts says forum reports of USB sources sounding different led to galvanic isolation on DAVE, the first product with it, still at 768 kHz. HiFi Buys 2:23:47