Does source jitter matter with a Chord DAC, and would a reclocker, external clock or USB-to-SPDIF converter help?

Source jitter: what he says the DACs do with it

His position that his DACs remove source jitter has stayed the same since the original Hugo; what changed is whether he thought DAVE's USB clocking gave a sound benefit (see the section on where he changed his mind). In April 2014 he wrote that "the DPLL effectively eliminates source jitter anyway" Head-Fi, Apr 2014, and in June 2014 that "Jitter problem is solved within Hugo, so a separate USB unit will have no affect on jitter" Head-Fi, Jun 2014. In January 2016 he extended this to the whole range: "All the DAC's - Mojo, 2 Qute, Hugo, Hugo TT and Dave have identical source jitter rejection" Head-Fi, Jan 2016. In a recording published in August 2022 (recording date not stated) he said the same of "all of the DACs" when asked about jitter from the M Scaler AVstore 38:19. In February 2024, in the Mojo 2 thread, he wrote that "Clocking or jitter on the source does not matter at all with my DACs, but RF noise currents flowing through the DAC ground plane can have an influence on the sound quality" Head-Fi, Feb 2024, and in a podcast recorded in October 2025 (published March 2026) he said that with his DACs "it doesn't matter how much jitter I have on the input signal, it will have no measurable consequences or sound quality consequences" ecoustics 1:03:17.

He describes two mechanisms. On USB the timing comes from the DAC's own clock, so "the source clock is completely irrelevant" (DAVE, May 2018) Head-Fi, May 2018Head-Fi, Jun 2016. In March 2015, in a post naming no product, he called the USB mode "isochronous asynchronous", explaining that "within the FPGA it is synchronous - as the timing comes from the FPGA" Audiophile Style, Mar 2015. On optical and coax, his DPLL buffers the data and reads it out with a new word clock generated from the local 104.25 MHz oscillator and frequency locked to the source over seconds Head-Fi, Jun 2016Head-Fi, Dec 2017Head-Fi, Jun 2018. In 2020 and 2022 he said it should really be called a DFLL because phase is only used during initial lock, and that "the phase (and hence jitter) of the incoming word clock has zero influence on the generated word clock" Head-Fi, Aug 2020Head-Fi, Mar 2022. He has said several times that perfecting the DPLL took about six years, and that the goal was to make it sound the same as the large RAM buffer used in DAC64-era designs Head-Fi, Jun 2016Head-Fi, Mar 2022Soundnews 47:29.

His evidence is a measurement and a listening comparison. In May 2016, on DAVE: "When I add 2 uS (that's 2,000,000 pS of jitter) to the data input from the AP using optical or coax I measure absolutely no change whatsoever" Head-Fi, May 2016. Earlier, in July 2015, he reported J-test measurements on Hugo showing no source jitter artifacts on USB, optical or coaxial inputs down to a resolution he gives as 500 fS Head-Fi, Jul 2015. He repeated the 2 uS test in 2018 (Hugo 2, noise floor at -178 dB) and 2019 (FFT floor of -180 dB), adding that "2uS is a thousand times larger than jitter you would normally encounter on SPDIF" Head-Fi, Oct 2018Head-Fi, May 2019Head-Fi, Jul 2019. In the 2022 AVstore and 2023 Soundnews recordings he gives the visible floor as about -170 dB and -160 dB respectively AVstore 38:19Soundnews 47:29; these figures come and should be checked against the recordings. For listening, he says Hugo 2 was the first time he heard no change between USB and optical from his MSI laptop on headphones, and that later he heard the same result with DAVE Head-Fi, Jun 2017Head-Fi, Oct 2018Head-Fi, Mar 2022. He presents that result as proof that the DPLL is transparent Head-Fi, May 2018Head-Fi, Mar 2022. He qualified it in December 2017: with Hugo 2's analog outputs grounded "there is a small difference going from USB to optical", speculating that the result depends on how noisy the USB source is, and adding "your mileage may vary" Head-Fi, Dec 2017.

Jitter inside the DAC (master clock)

Separately from source jitter, he says the pulse array design makes master clock jitter produce only a fixed noise, not distortion or noise floor modulation Head-Fi, Oct 2015Head-Fi, May 2016Head-Fi, May 2017. His stated test is to stop all pulse array switching and re-measure: noise improves by only about 0.5 dB, which he attributes to master clock jitter plus element mismatch combined Head-Fi, Oct 2015Head-Fi, May 2017Head-Fi, Dec 2017Head-Fi, Jul 2019. In October 2015 he gave the figure as "127 dB to 127.5 dB" without naming a product Head-Fi, Oct 2015; in December 2017 he gave DAVE as "128 dB to 128.5 dB" on Head-Fi Head-Fi, Dec 2017, while his CanJam RMAF talk of October 2017 (video published December 2017) gives Hugo 2 as 126 to 126.5 dB and DAVE as 128.5 to 129 dB RMAF 43:11; the talk's figures come.

He says femto clocks with PLLs give low cycle-to-cycle jitter but more low frequency jitter, which creates audible skirts and a brighter sound, and that "This is why I do not use fempto S clocks or atomic clocks" (DAVE, September 2016) Head-Fi, Sep 2016Head-Fi, May 2017. In the RMAF talk, however, the transcript has him saying "we do use femto clocks, but we don't make a fuss about it" RMAF 43:11. This archive does not reconcile the two, and readers should check the recording. In June 2024 he added that low frequency master clock jitter cannot be fixed by DAC architecture, and that the DPLL "permanently fixed the low frequency jitter problem", leaving cycle-to-cycle jitter, which pulse array can make unmeasurable Head-Fi, Jun 2024.

Reclockers and other re-timing boxes

He has advised against them throughout; the reasons he gives are RF noise and, for the Remedy, sample rate conversion, not jitter Head-Fi, Oct 2015Head-Fi, Jan 2016. In October 2015, on USB purifiers: "for Dave, Hugo TT, 2 Qute don't bother as they are galvanically isolated" Head-Fi, Oct 2015. On the Remedy reclocker in 2016 he said it is a sample rate converter and "Not a good idea at all with my DAC's" (DAVE), and later called it "Possibly the fastest way to destroy the sound of Mojo or Dave IMHO" Head-Fi, Jan 2016Head-Fi, Dec 2016.

His most hedged statement is from May 2017 (Hugo 2 thread): "Re-timing for sure will have no benefit - period for all sources", although RF noise levels can make a difference. In his own system the Remedy would either sound worse or make no difference, "But with other sources then it may be beneficial". He added that he would not bother: "better spending the cash on music" Head-Fi, May 2017. A month later: "So do not bother with re-clockers as source jitter is completely eliminated" Head-Fi, Jun 2017.

In September 2018 he said that the servers and reclockers he had heard "all sounded brighter with poorer depth", and that "my DACs certainly do not need any form of jitter treatment" Head-Fi, Sep 2018. In March 2019, on Qutest, he described how a mains-powered USB reclocker can create a ground or mains loop that defeats the DAC's galvanic isolation even with an optical link, calling it "an example of a reclocker actually raising system noise" Head-Fi, Mar 2019. In October 2020 (TT2): "I don't see the point in USB clocks" Head-Fi, Oct 2020. His December 2022 summary: "Don't be tempted with USB re-clockers etc, as they again increase RF noise" Head-Fi, Dec 2022.

He applies the same reasoning to jitter on the M Scaler's output: "the extra amount of jitter that is being generated by the scaler is not a problem at all for Chord DACs" (2022), and the M Scaler was never designed for a low jitter output because the DAC removes it (2023) AVstore 39:08Eric's Hi-Fi 24:19Head-Fi, Aug 2020.

External master clocks, word clocks and I2S

From 2015 to 2023 he has rejected external clocks in strong terms. In October 2015: "Running the clock externally is a crazy thing to do" Head-Fi, Oct 2015. In January 2018: "External clocks are a disaster" Head-Fi, Jan 2018. In August 2022 he wrote that "they only increase jitter at the point where it matters", and at CanJam NYC 2023 (video published March 2023) "External clocks are a crazy idea" Head-Fi, Aug 2022The Headphone Show 5:29. His stated reasoning is that the clock must be transmitted and then rebuilt by a local analog PLL, which adds low frequency jitter, skirts and brightness that people mistake for transparency Head-Fi, Sep 2016Head-Fi, Jan 2018The Headphone Show 6:12. For DAVE in April 2018 he wrote that external clocks will either make it sound worse or have no effect, and that "the crucial clock is the one located within Dave a few mm away from the pulse array flip-flops" Head-Fi, Apr 2018; he repeated his objection to external clocks in the DAVE thread in 2020 and 2021 Head-Fi, Jun 2020Head-Fi, Mar 2021. He treats studio ADC clock sync as a case where an external clock is unavoidable, still calling it "a crazy idea" (2021) Head-Fi, Jan 2021. In September 2023 he said a future pro ADC would sync to external word clocks through sample rate conversion, "with (hopefully) no loss in sound quality", while repeating that "external clocks will always create issues" Head-Fi, Sep 2023. These are ADC statements, not advice for his DACs.

On word clock feedback to the source, he says he used it in earlier products but in 2016 called going back to word clocks "a big backward step", and in 2021 said it is not needed now that he has the DPLL Head-Fi, Jun 2016Head-Fi, Sep 2016Head-Fi, Mar 2021. On I2S (Qutest, January 2018): "So there is absolutely no benefit in using I2S" Head-Fi, Jan 2018Head-Fi, Aug 2018. In April 2024 he said a dedicated bit clock "will just increase the possibility of more RF noise" Head-Fi, Apr 2024.

USB-to-SPDIF and USB-to-optical converters

Here he frames the question as RF noise and ground loops, not jitter, and his advice has varied. In October 2014 (Hugo): "Some people have reported that USB to optical works well with Hugo, and they should work OK" Head-Fi, Oct 2014. In January 2020 he advised against adding one: "My advice is to keep the source as simple as possible, so stick with what you have" Head-Fi, Jan 2020. The same month he said a mains-powered converter can create an RF loop, but "if you have such a device, then give it a try" and keep whichever sounds warmer with better depth Head-Fi, Jan 2020. In May 2021 (Hugo 2): "As a general advice I would avoid using digital to digital converters (DDC)" Head-Fi, May 2021. In May 2022 he said he was surprised that Qutest would show a major difference with a USB to optical converter, since Qutest is galvanically isolated Head-Fi, May 2022.

From late 2022 he has been more positive about bus-powered converters. In October 2022 (TT2 thread) he said to "only use one that does not require an external PSU", adding "I haven't tried it, but Douk Audio U2 USB Converter looks like a good bet to try" Head-Fi, Oct 2022. At CanJam NYC in March 2024 he said converters powered from the computer "work perfectly fine", while those with separate supplies risk mains loops MFG Audio Reviews 59:13.

Where he changed his mind

On USB versus optical, his account changed in steps. In June 2016 he spoke of "the benefit of clocks being sourced from the DAC" with DAVE's USB Head-Fi, Jun 2016, and in July 2016 said optical was not as good as USB because USB "has zero jitter/timing issues as the clock comes from Dave" Head-Fi, Jul 2016. In October 2017 he said he was surprised to hear no difference between optical and USB on Hugo 2 because optical "is not locked to Hugo 2's master clock (bad) unlike USB" Head-Fi, Oct 2017. In January 2018 he wrote "I have changed my mind on this now" and then "I was wrong about that, the brightness is not better timing as the clock comes from Dave, but worse RF noise pick-up" Head-Fi, Jan 2018Head-Fi, Jan 2018. In February 2019, in the Qutest thread, he still wrote "Technically USB is better from the clock POV; but in practice I have had optical sound identical to USB" Head-Fi, Feb 2019. In March 2022 he said of his 2016 preference for USB on DAVE, "You have discovered a post where I made a mistake", and that "Optical should always be considered the reference (best) input" Head-Fi, Mar 2022. In October 2022 he wrote that "there is no technical benefit to using USB over optical when using my DACs" Head-Fi, Oct 2022. That differs from his February 2019 wording, and this page does not choose between them.

What he has not said: this archive has no test or comment from him on named reclockers or DDCs other than the Remedy and the untried Douk U2, and no measurements of any reclocker, external clock or converter with his DACs Head-Fi, Jan 2016Head-Fi, Oct 2022. His converter advice is general, not product specific, and he ties it to the source and set-up Head-Fi, Jan 2020Head-Fi, May 2022, with an explicit "YMMV" in 2018 Head-Fi, Oct 2018.

Quotes

“All the DAC's - Mojo, 2 Qute, Hugo, Hugo TT and Dave have identical source jitter rejection, that is the DAC eliminates it.”2016-01-21 Head-Fi, Jan 2016

“So do not bother with re-clockers as source jitter is completely eliminated.”2017-06-13 Head-Fi, Jun 2017

“Don't be tempted with USB re-clockers etc, as they again increase RF noise and then give the false impression of better transparency.”2022-12-13 Head-Fi, Dec 2022

“Clocking or jitter on the source does not matter at all with my DACs, but RF noise currents flowing through the DAC ground plane can have an influence on the sound quality”2024-02-06 Head-Fi, Feb 2024

Dated positions

Caveats and open points

• The RMAF 2017 transcript ('we do use femto clocks') conflicts with his Head-Fi statements that he does not use femto clocks; this archive does not resolve this.
• His DAVE noise figures differ between the December 2017 Head-Fi post (128 to 128.5 dB) and the October 2017 RMAF talk, published December 2017 (128.5 to 129 dB).
• Head-Fi, Oct 2020 carries a date estimated from its post ID.
• His converter and reclocker advice depends on source and system (mains loops, battery power, headphones versus grounded amps), and he qualifies it with YMMV.
• The 0.5 dB switching-off figures vary by post: 127 to 127.5 dB (2015, no product named), 128 to 128.5 dB for DAVE (2017 Head-Fi).
• The 2020 and 2021 converter advice (Head-Fi, Jan 2020, Head-Fi, Jan 2020) was posted in Watts Up...?, not tied to a product; the products listed for that position reflect the 2021 Hugo 2 thread post.

Topics: Jitter, clocks and the DPLL, Add-on tweaks and modifications