Which BNC cables, and what length, should I use between an M Scaler and my DAC?
Short answer
For the Hugo M Scaler, Watts said in 2018 to use genuine 75 ohm BNC cable, warning of a risk of worse sound otherwise Head-Fi, Aug 2018; by January 2023 he described impedance as a drop-out matter rather than a sound one, and said short 50 ohm cables work Head-Fi, Jan 2023. The supplied cables are to get you going, not for best performance Head-Fi, Oct 2021. With standard cables he said from November 2018 that longer sounds better, 2 m over 1 m, repeating it to 2023 Head-Fi, Nov 2018Head-Fi, Oct 2021Head-Fi, Jun 2023; in an August 2018 test he had heard no difference between 15 cm and 1.5 m once the headphone cable was kept clear, and wrote that length was not important Head-Fi, Aug 2018. With Wave cables length no longer matters, and an isolated power bank does the same job Head-Fi, Jun 2023. For the Quartet (2024) he says you need not worry about BNC cables the way you did with the Hugo M Scaler ConvinceMeAudio 10:47.
The practical answer
Hugo M Scaler: use genuine 75 ohm coaxial BNC. In August 2018 Watts wrote "make sure it is indeed 75 ohms, as this is the OP impedance of the M scaler", adding that it works without 75 ohms but "there is a risk it will sound worse" Head-Fi, Aug 2018. That month he said "audiophile BNC cables either sound the same as a quality 75 ohm RF cable or sound worse" Head-Fi, Aug 2018; in August 2020 he named Wave as the exception Head-Fi, Aug 2020.
The supplied cable is a starting point. In October 2021 he wrote that the supplied cables "are to get you going, and not intended for the best performance"; he insisted on them so drop-outs could be traced Head-Fi, Oct 2021. From 2020 to 2023 he said a mismatch at a connector or adaptor is not important, but the cable itself should be 75 ohm Head-Fi, Apr 2020Head-Fi, Jul 2022Head-Fi, Jan 2023. In January 2023 he said "it is important that long lengths of cable are 75 ohms", that he uses short lengths of 50 ohm cable with his M scaler and Hugo 2, and that it is "not a sound quality issue, but a drop-out issue" Head-Fi, Jan 2023. Against his August 2018 warning Head-Fi, Aug 2018, this treats impedance as a drop-out matter; both this post and an August 2018 one credit de-glitching circuitry for tolerating mismatch Head-Fi, Aug 2018Head-Fi, Jan 2023.
Length (Hugo M Scaler, standard 75 ohm cable)
In August 2018, testing 15 cm against 1.5 m into Hugo 2, he first heard a difference, but with the headphone cable kept clear he "could no longer hear a difference" and wrote that "length of the cable is not important" Head-Fi, Aug 2018. In November 2018 he wrote that, with standard 75 ohm cables, 2 m is "a bit better than 1m" Head-Fi, Nov 2018; in December 2018, that going longer than 2 m "does not give any significant benefit" and the cable should not be looped Head-Fi, Dec 2018. In October 2021 he called 2 m "quite a big upgrade" from 1 m and 5 m "not worth the hassle" Head-Fi, Oct 2021. In June 2022, in the DAVE thread, 5 m cables "perhaps sounded slightly better than 2m" and were "certainly no worse" Head-Fi, Jun 2022. His posts differ on going beyond 2 m. In June 2023 he repeated that longer standard cables sound better than short ones Head-Fi, Jun 2023.
In August 2020 he called the BNC effect "a significant difference on an AB test, but the scale of the change is forgotten about after a few days" Head-Fi, Aug 2020.
Wave cables, ferrites or a power bank
In August 2018, comparing the Hugo M Scaler with Blu 2, he wrote that its improved isolation meant "you don't need to worry about ferrites" Head-Fi, Aug 2018. In December 2018 and November 2019 he said solid core ferrites "do offer a small advantage", though not a huge one Head-Fi, Dec 2018Head-Fi, Nov 2019. With them, he wrote in 2020 and 2023, length no longer matters Head-Fi, Aug 2020Head-Fi, Jun 2023. He recommends Wave, but adds "I certainly do not say you have to use Wave cables or indeed have to use ferrites" Head-Fi, Aug 2020; in May 2022 he said he uses Wave Stream Head-Fi, May 2022.
In June 2023 he said an isolated power bank or Wave cables is enough, and you need only one Head-Fi, Jun 2023; in September 2023, that with a battery the stock BNC cables are fine Head-Fi, Sep 2023. Those battery tests used optical into the M Scaler Head-Fi, Dec 2022Head-Fi, Jan 2023Head-Fi, Sep 2023, and in April 2021 he said the outcome "depends upon your system, and how noisy the source is" Head-Fi, Apr 2021.
Avoid clip-on ferrites on the Hugo M Scaler: "you will actually degrade the SQ if you use clip on ferrites" (December 2018) Head-Fi, Dec 2018Head-Fi, Nov 2019.
By DAC
DAVE: use BNC 1 and 2 or 3 and 4 Head-Fi, Feb 2017. In February 2019 he said the left M scaler output goes to the bottom input (1 or 3) and the right to the top (2 or 4) Head-Fi, Feb 2019. In February 2020 he said DAVE requires sync, so length is important, while his other DACs do not need exact sync Head-Fi, Feb 2020; in August 2020, that differing lengths give different delays, which would show as drop-outs Head-Fi, Aug 2020.
Other Chord DACs: TT2 auto-switches left and right Head-Fi, Apr 2020; Qutest BNC inputs go into dual data mode automatically Head-Fi, Jan 2018.
Hugo 2: in July 2018 he wrote "you just need to use 3.5mm to RCA cable, plus RCA to BNC adaptors" Head-Fi, Jul 2018; a cheap non-75-ohm 1.5 m cable "worked perfectly at 705 and 768 kHz" in February 2018 Head-Fi, Feb 2018. In the August 2018 length test, keeping the headphone cable off the digital cable mattered most Head-Fi, Aug 2018.
Quartet
In May 2024 he said the link is still dual BNC ConvinceMeAudio 10:10 and you "don't have to worry about your BNC cables in the way that you used to have to worry with the Hugo M Scaler" ConvinceMeAudio 10:47. In July 2024 he said Quartet is "less sensitive to your BNC cables" HIFICLUB 46:35. A SoundNews conversation published in October 2026 has him describing the aim that "whatever BNC cable you use, it sounds the same" article, Oct 2026.
What he has not said
This archive gives no cable length for Quartet, Qutest or TT2. Apart from Wave, the only brand he mentions is a Belden another poster had named, in a 2023 suggestion to an owner with a noise problem Head-Fi, Jun 2023.
Quotes
“If you are going to buy a RF cable, make sure it is indeed 75 ohms, as this is the OP impedance of the M scaler.”2018-08-13 Head-Fi, Aug 2018
“For the connection from M scaler to the DAC, the longer the BNC the better the sound, as inductance increases with length”2021-10-21 Head-Fi, Oct 2021
“On the Hugo M scaler you have two choices - use an isolated power-bank, or use the Wave cables”2023-06-18 Head-Fi, Jun 2023
“you don't have to worry about your BNC cables in the way that you used to have to worry with the Hugo M Scaler.”2024-05-16 ConvinceMeAudio 10:47
Dated positions
| When | Products | Position |
|---|---|---|
| 2017-03 to 2018-10 | DAVE, Hugo M Scaler | Chord supplies 75 ohm RF cables so a technically correct connection is made and cable faults can be ruled out; in 2017 he found a range of expensive BNC cables also worked on the 768 kHz link to DAVE. Head-Fi, Mar 2017Head-Fi, Oct 2018 |
| 2018-02 to 2020-04 | Hugo 2 | A 3.5mm to BNC connection works for M scaler dual data, even with cheap non-75-ohm cable, thanks to de-glitch circuitry. Head-Fi, Feb 2018Head-Fi, Jul 2018Head-Fi, Apr 2020 |
| 2018-08 | Hugo M Scaler | Compared with Blu 2, the Hugo M Scaler's improved BNC isolation means you don't need to worry about ferrites. Head-Fi, Aug 2018 |
| 2018-08 to 2018-12 | Hugo M Scaler | Use genuine 75 ohm cable; in August 2018 heard no length difference once the headphone cable was kept clear, but said 2 m is a bit better than 1 m from November 2018; beyond 2 m no significant benefit; solid core ferrites offer a small advantage, clip-on ferrites degrade the sound. Head-Fi, Aug 2018Head-Fi, Nov 2018Head-Fi, Dec 2018Head-Fi, Aug 2018 |
| 2019-11 to 2021-10 | Hugo M Scaler | Clip-on ferrites make the sound worse; longer cables and solid core ferrite (Wave) cables help. Head-Fi, Nov 2019Head-Fi, Aug 2020Head-Fi, Oct 2021 |
| 2020-02 to 2020-08 | DAVE | DAVE needs sync on its dual data lines, so cable length and delay matter more than on his other DACs. Head-Fi, Feb 2020Head-Fi, Aug 2020 |
| 2022-06 | Hugo M Scaler, DAVE | 5 m regular 75 ohm BNC cables worked fine and perhaps sounded slightly better than 2 m. Head-Fi, Jun 2022 |
| 2022-07 to 2023-01 | Hugo M Scaler, Hugo 2 | Connector and adaptor mismatches are not important and short 50 ohm cables work; long lengths of cable should be 75 ohm, and this is a drop-out issue rather than sound quality. Head-Fi, Jul 2022Head-Fi, Jan 2023 |
| 2023-06 to 2023-09 | Hugo M Scaler | Either an isolated power bank or Wave cables is enough; with a battery (and optical input), stock BNC cables are fine; longer standard cables sound better than short ones. Head-Fi, Jun 2023Head-Fi, Sep 2023 |
| 2024-05 to 2026-10 | Quartet | Quartet is less sensitive to BNC cables, so cable choice matters less than with the Hugo M Scaler; the design aim was that any BNC cable sounds the same. ConvinceMeAudio 10:47The Speaker Shack 5:00HIFICLUB 46:35article, Oct 2026 |
Caveats and open points
- Most length and cable advice applies to the Hugo M Scaler; for the Quartet this archive only says cable choice matters less, with no length given.
- No length advice found for Qutest or TT2; the DAVE sync point is the only DAC-specific length statement.
- His statements on length differ: no difference between 15 cm and 1.5 m in August 2018, then 2 m better than 1 m from November 2018, and differing statements on going beyond 2 m in 2018, 2021 and 2022 posts.
- His battery observations were made with optical feeding the M Scaler, and in 2021 he said results depend on system and source.
- On impedance, his August 2018 advice linked non-75 ohm cable to a risk of worse sound; by January 2023 he called it a drop-out issue, not a sound quality one. He does not say he changed his view on sound; both the 2018 and 2023 posts credit de-glitching circuitry for tolerance of impedance mismatch.
Topics: Cables, adaptors and ferrites, Dual BNC, dual data and DX links