Add-on tweaks and modifications

RF noise, grounding and power

Answers on this topic

• Does source jitter matter with a Chord DAC, and would a reclocker, external clock or USB-to-SPDIF converter help?
• Why does Rob use a digital DC servo instead of coupling capacitors, and is there anything worth modding?
• Will a USB purifier, JitterBug or USB isolator improve my DAVE, TT2 or Hugo?

Everything he said on this topic (48)

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

• 2014-06-09Watts says USB affects sound via jitter and RF noise; Hugo solves jitter internally, add-on USB units add RF noise though isolation may help. Head-Fi, Jun 2014
• 2014-06-19Watts says he is about to test USB isolators, aims for Hugo to work with any bit-perfect source, uses regular USB cables in his office and optical at home. 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
• 2014-06-24Watts reports the 33-pound Olimex USB-ISO on Hugo's SD USB input (44.1/48 kHz only) gives better depth, focus and separation, consistent with better RF isolation. Head-Fi, Jun 2014
• 2014-10-01Watts says he also uses the Olimex with the short stock Chord USB cable and regrets no high data rate version exists. 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
• 2014-10-25Watts gauges an improvement by how long it stays noticeable, from one day to over three months, rates the Olimex isolator a one-week change, and calls Hugo's break-in mental adaptation. Head-Fi, Oct 2014
• 2014-10-26Watts says the Olimex isolator works only with the SD USB input, not at all on the HD USB input, and only up to 48 kHz. 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
• 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
• 2016-01-23Watts says the Remedy re-clocker is a chip sample rate converter to 96k, and such SRCs add distortion, noise floor modulation and timing damage, a bad idea with his DACs. Head-Fi, Jan 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
• 2016-07-23Watts 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
• 2016-12-21Watts says the Remedy's cheap TI SRC chip is not bit perfect, adds distortion, noise and timing errors, and is possibly the fastest way to destroy Mojo or Dave's sound. Head-Fi, Dec 2016
• 2017-02-28Watts says USB needs VBUS 5V connected, but it is heavily RF filtered and only a flag to the FPGA, so feeding a clean 5V line is pointless. Head-Fi, Feb 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
• 2017-05-17Watts says re-timing has no benefit for any source, but RF levels can matter; the Remedy would sound worse or no different in his system, so spend on music instead. Head-Fi, May 2017
• 2017-06-13Watts says Hugo 2 re-clocks via its DPLL locked to the master clock, eliminating source jitter, shown by USB sounding the same as optical, so re-clockers are pointless. Head-Fi, Jun 2017
• 2018-03-26Watts says he cannot hear the charger connected on headphones, USB tweaks only add RF noise and brightness, and Chord dealers can supply replacement batteries. Head-Fi, Mar 2018
• 2018-09-03Watts says certified USB cables sound the same, but one audiophile cable, servers and reclockers sounded brighter with poorer depth from RF noise; a battery bit perfect source is ideal. Head-Fi, Sep 2018
• 2018-09-06Watts says Blu 2 uses USB VBUS only as an RF-filtered logic flag, so removing it just disables the USB input and cannot change sound quality. Head-Fi, Sep 2018
• 2018-10-14Watts says Hugo 2 has USB RF filtering and measured no effect from 2uS input jitter, heard no USB vs optical difference, and advises avoiding source gadgets that add RF. Head-Fi, Oct 2018
• 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
• 2019-04-17Watts 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
• 2019-04-21Watts 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
• 2019-07-06Watts 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
• 2020-01-10Watts advises against adding a USB-to-optical stage, saying reported gains are RF brightness mistaken for transparency, and a Dell laptop worsened his APx555 THD and noise by about 2dB. Head-Fi, Jan 2020
• 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
• 2020-01-29Watts advises PCM unless an SACD's master was DSD, says he is making mains-powered USB match optical and battery, and warns modifying his optimized designs more likely harms than helps. Head-Fi, Jan 2020
• 2020-04-09Watts says mains conditioners neglect RF, a single-blind test tied a new HF filter's warmth to noise floor modulation, and DAVE is about 13-bit accurate, M scaler over 16. 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 USB matters through RF noise and signal-correlated ground currents, that his tests find noise floor modulation at -180 to -200 dB audible, and Chord USB filtering suffices. 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
• 2020-08-17Watts says Hugo 2 has no signal-path capacitors to upgrade thanks to the DC servo, and its noise shaper output and separate rails give 214 dB PSU rejection in SPICE. Head-Fi, Aug 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
• 2021-10-26Watts advises against the internal wiring modification: his single-piece sockets are soldered to the PCB, added wires add metal-to-metal interfaces, and it voids the warranty. Head-Fi, Oct 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
• 2022-10-04Watts 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
• 2022-12-13Watts says audiophile USB cables add RF or sound identical, optical (KableDirekt) is best, a phone or battery laptop is the reference source, and Wave Stream cables help. Head-Fi, Dec 2022
• 2023-06-18Watts says mains conditioners do little for RF, an external headphone amp only degrades transparency except perhaps with Susvara (92dB SPL max from Dave), and warns about 80dB. 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
• 2023-11-22Watts says RF via cables and mains matters more than screening, stays humble about unheard ground boxes, and repeats listening tests to guard against errors. Head-Fi, Nov 2023
• 2024-02-05Watts warns that replacing op-amps risks instability in the second-order analog noise shaper, which made two op-amps sound identical by raising gain-bandwidth from 40MHz to 80GHz. Head-Fi, Feb 2024
• 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