Quartet M Scaler
What it is
Quartet M Scaler is the upsampler he designed to match DAVE HIFICLUBE.NET JVH 8Audiophile Junkie 16:33. He dates the work to 2018, when the Hugo M Scaler was finished article, Oct 2026The Source AV 7:30. He put the effort at six years in 2024 and eight in a talk published May 2026 (recording date not stated) ConvinceMeAudio 42Audio Force 1:05.
On the name: in August 2021 he promised "another xM scaler intended to match Dave" Head-Fi, Aug 2021. In 2022 and 2023 he described a Choral (DAVE chassis) M scaler on multiple 200T FPGAs, priced at DAVE level and not replacing the Hugo M Scaler, and in July 2023 said a new name was agreed Head-Fi, Feb 2022Head-Fi, Feb 2022Head-Fi, Jul 2023Head-Fi, Jul 2023. His posts first use "Quartet" in March 2024 Head-Fi, Mar 2024. In September 2024 he called Quartet a Choral range product The Source AV 17:15. He said the name comes from its 4 million taps, in 2024 and in 2026, adding "We could have called it Quintet, but Quartet rings better" AVstore 4:34The Speaker Shack 18article, Oct 2026.
Design
It holds five Xilinx 200T FPGAs, five times the Hugo M Scaler's count of the same chip Head-Fi, Apr 2024Audiophile Junkie 16:33ConvinceMeAudio 42Audio Force 24:08. He gave two million lines of code and about 2,500 discrete components in 2024 and 2,500 components in a podcast recorded in October 2025 (published March 2026), and in 2026 said "there are over 2,000 components within the Quartet board itself" after, he thought, nine prototypes ConvinceMeAudio 42HIFICLUBE.NET JVH 8ecoustics 1:24:36article, Oct 2026.
He gave 4 million taps in 2024 and 2026 Head-Fi, Jun 2024AVstore 4:31article, Oct 2026. He says the algorithm matters more than the count AVstore 4:40article, Oct 2026. In 2026 he said "So the 4 million taps isn’t the story. The story is the new algorithm, the new filter structure" article, Oct 2026. That structure, the Blackbird WTA, separates two effects a single-stage filter trades against each other; he said it is only for Quartet article, Oct 2026Audio Force 14:13Audio Force 14:59. He still wants more taps, in a future Ultima scaler article, Oct 2026. In 2024 corrected coefficients from a new unlimited-precision FFT kept his preferred settings but delayed everything by 3 months Head-Fi, Oct 2024.
In 2024 he said it has lossless EQ built in, with five settings, off and four user-set Head-Fi, Mar 2024Head-Fi, May 2024. He described testing it with bands alternating plus and minus half a dB, with no loss of transparency or depth (a Munich interview, likely May 2024, published February 2025; and 2026), and called it ten-band in 2026 audio-2G 18:39article, Oct 2026. It also has an analog input feeding a pulse array ADC, which he said Chord asked for article, Oct 2026article, Oct 2026Distorsiuni Interioare 15:29. An 18 kHz filter is part of the ADC decimation article, Oct 2026Distorsiuni Interioare 1:14:52.
Inputs, outputs and power
In May 2024 he gave the digital inputs as USB, optical and BNC ConvinceMeAudio 11:31. Outputs are dual BNC at 705.6/768 kHz plus optical and coax at 176.4/192 kHz; the single BNC and optical outputs are fixed at 176.4/192 kHz, decimated from 705.6/768 kHz Head-Fi, Mar 2024Head-Fi, Mar 2024. He said its two BNC output sets are not fully isolated from each other, sharing supply and ground, while the DACs are isolated from the scaler ConvinceMeAudio 14:16ConvinceMeAudio 14:42. It supports the dual AES format like the Hugo M Scaler Head-Fi, Jun 2024. He described three galvanic isolation stages in the BNC drivers against the Hugo M Scaler's one ConvinceMeAudio 11:00.
It is sold with a separate power supply of his own design, and "only the supplied unit will give the required performance" Head-Fi, Jan 2025ConvinceMeAudio 1:31. He gave the FPGA current as 75 amps in 2024 and as peak currents of 75 amps in a talk published March 2026 (recording date not stated) ConvinceMeAudio 1:31Hifi Pig TV 1:28Audio Force 24:08. His RF filters, which he calls pinch-off filters, have some 200 components each, one stopping noise escaping and one stopping it coming in ConvinceMeAudio 2:12article, Oct 2026. He gave HF rejection up to 10 GHz, with the mains-side supply switching at 70 kHz followed by a regulator above 500 kHz Head-Fi, Nov 2024. He said it matched his target, the sound of a very large lithium-ion battery article, Oct 2026Audio Force 26:36. He gave its delay as three seconds, against 0.7 for the Hugo M Scaler Audiophile Junkie 17:12.
How he says to use it
He said it works with any Chord DAC, Mojo 2 included, because all accept dual BNC (see Which Chord DACs accept 705.6/768 kHz from an M Scaler, and how do…) ConvinceMeAudio 11:42Head-Fi, Apr 2024, though "You’d never buy a Quartet and use it with a Mojo 2" article, Oct 2026. He designed it so BNC cables matter less (see Which BNC cables, and what length, should I use between an M…) ConvinceMeAudio 10:47article, Oct 2026. He said owners will not be able to upgrade the supply, as it is already the best possible (see Should I replace the supplied power supply with a linear or…, Is battery power better than mains, and can I power the M Scaler…) Audio Force 26:36. Asked in writing for setup advice, he answered "Make sure the HF filter is set to 18K!" article, Oct 2026. On stacking he wrote "I have only ever stacked the units", expected no difference, and still had to prove it in supply listening tests (see Can I stack TT2 and an M Scaler, and how hot is too hot?) Head-Fi, Jul 2024.
Compared with other Chord models
Against the Hugo M Scaler he said it would not replace it and costs a lot more The Source AV 5:05, calling it "a major advance on Hugo M scaler" that "does everything that HMS does but more so" Head-Fi, Jun 2024. It has 4 times the taps and five times the FPGAs Hifi Pig TV 1:28Audio Force 24:08. In mid-2024 the Hugo M Scaler was still his choice on flights, though he also took the prototype Quartet when traveling; by October 2024 he traveled with Quartet and used it with Hugo 2 in hotels, and in 2025 said flying with only an M Scaler had become disappointing Head-Fi, Jun 2024Hifi Pig TV 3:43Hifi Pig TV 4:39Head-Fi, Oct 2024The Source AV 15:46. Of DAVE he wrote "In my humble opinion, Quartet lifts Dave into a whole new realm", and in 2025 said Quartet is not a DAVE replacement but an advanced Hugo M Scaler Head-Fi, May 2024The Source AV 8:42.
What he has not said
On price, in 2022 and 2023 he expected DAVE-level pricing, and from 2024 said it will cost more than DAVE Head-Fi, Feb 2022Eric's Hi-Fi 7:47ConvinceMeAudio 12:03The Source AV 18:58. In August 2026 he said he believed the UK price was £25,000 The Source AV 4:25. In a talk published March 2026 (recording date not stated) he spoke of finally launching it, and in an August 2026 livestream said the batch was pretty much sold out before units reached dealers Audio Force 4:40The Source AV 4:57.
Release and official documents
- In a talk published March 2026 he spoke of finally launching it; in August 2026 he said the first batch was almost sold out before reaching dealers.Audio Force 4:40The Source AV 4:57
From Chord Electronics. Links open Chord's own copies; reviews hosted on Chord's site are left out. Chord's Quartet M Scaler page.
Manuals and guides
Drivers (Windows)
Key figures
His own figures, dated. Where he gave different figures at different times, each appears.
Show all 25 figures
| Figure | Value | When | Source |
|---|---|---|---|
| Interpolation filter taps | 4 million taps, which he called 4 times the tap length of the Hugo M Scaler | 2024-05 | AVstore 4:31The Speaker Shack 18Head-Fi, Jun 2024Hifi Pig TV 1:28 |
| Interpolation filter taps | 4 million taps ("Quartet. Four million taps.") | 2026-10 | article, Oct 2026 |
| FPGAs | five Xilinx 200T (five times the Hugo M Scaler's chip count) | 2024-04 | Head-Fi, Apr 2024ConvinceMeAudio 42Audiophile Junkie 16:33Audio Force 24:08 |
| Lines of code | two million | 2024-05 | ConvinceMeAudio 42HIFICLUBE.NET JVH 8The Speaker Shack 4:00 |
| Discrete components | two and a half thousand | 2024-05 | ConvinceMeAudio 42HIFICLUBE.NET JVH 8The Speaker Shack 4:00 |
| Components on the boards | two and a half thousand | 2025-10 (recorded; published 2026-03) | ecoustics 1:24:36 |
| Components on the Quartet board | over 2,000; he thought nine prototypes | 2026-10 | article, Oct 2026 |
| DSP cores | two and a half thousand, from five 200T FPGAs of 720 cores each | 2025-05 | Audiophile Junkie 16:33 |
| FPGA supply current | 75 amps | 2024-05 | ConvinceMeAudio 1:31Hifi Pig TV 1:28 |
| FPGA peak current | 75 amps | 2025-10 (recorded) and 2026-03 (published) | Audio Force 24:08ecoustics 1:10:13 |
| RF filter size | over 200 components per filter, one at Quartet's input and one at the supply output | 2024-05 | ConvinceMeAudio 2:12 |
| RF filter size | two pinch-off filters, one against noise escaping and one against noise coming in, each some 200 components | 2026-10 | article, Oct 2026 |
| RF rejection | up to 10 GHz | 2024-11 | Head-Fi, Nov 2024ConvinceMeAudio 1:31 |
| Mains-side switching frequencies | 70 kHz SMPS, output regulator above 500 kHz | 2024-11 | Head-Fi, Nov 2024 |
| Galvanic isolation stages in the BNC drivers | three (Hugo M Scaler: one) | 2024-05 | ConvinceMeAudio 11:00 |
| Dual BNC output rate | 705.6/768 kHz | 2024-03 | Head-Fi, Mar 2024 |
| Single BNC, optical and coax output rate | 176.4/192 kHz | 2024-03 | Head-Fi, Mar 2024Head-Fi, Mar 2024 |
| Delay | three seconds (Hugo M Scaler: 0.7 of a second) | 2025-05 | Audiophile Junkie 17:12 |
| Video delay mode | 1 s, for the Nvidia Shield's video delay (stated for the Choral M scaler prototype in 2022, and in an interview published October 2026 (recording date not stated; its transcript places it before May 2026) in the sentence after he says he watches movies with Quartet) | 2022-10 and 2026 (interview published 2026-10) | Head-Fi, Oct 2022Head-Fi, Jul 2022HiFi Buys 2:14:45 |
| EQ settings | 5 settings: off plus 4 user-set | 2024-05 | Head-Fi, May 2024 |
| EQ bands | ten-band equalizer | 2026-10 | article, Oct 2026 |
| HF filter | 18 kHz | 2026-10 | article, Oct 2026article, Oct 2026Distorsiuni Interioare 1:14:52 |
| ADC test recordings | one at 768 kHz 24-bit, one at 192 kHz 24-bit (the 192 kHz one from an analog tape) | 2026-10 | article, Oct 2026 |
| Development time | 6 years | 2024-05 | ConvinceMeAudio 42 |
| Development time | 8 years, from 2018 | 2026-03 (published; recording date not stated) | Audio Force 4:40Audio Force 9:36 |
Quotes
“So the 4 million taps isn’t the story. The story is the new algorithm, the new filter structure.”2026-10-17 article, Oct 2026
“In my humble opinion, Quartet lifts Dave into a whole new realm.”2024-05-28 Head-Fi, May 2024
“Quartet has unique demands on the PSU, and only the supplied unit will give the required performance.”2025-01-13 Head-Fi, Jan 2025
“Quartet M scaler is a major advance on Hugo M scaler - and it does everything that HMS does but more so.”2024-06-24 Head-Fi, Jun 2024
Caveats and open points
- He never equates the Choral M scaler and Quartet in a post. The link rests on his September 2024 remark that Quartet is a Choral range product, his "Exactly" when a Munich interviewer placed it in the Choral line, and matching features (DAVE pairing, multiple 200T FPGAs) The Source AV 17:15ConvinceMeAudio 11:53ConvinceMeAudio 12:03Head-Fi, Jul 2023. In February 2022 he wrote of the high-end M scaler then in progress "I don't know where this idea of 4M taps came from, as it's not that"; the 4 million figure dates from 2024, and he did not address the difference Head-Fi, Feb 2022Head-Fi, Jun 2024.
- Most 2024 figures describe a prototype. In May 2024 he said the production version would differ slightly from the unit shown, and in September 2024 he said the design was not finished and the coefficient work was redone Head-Fi, May 2024The Source AV 5:24Head-Fi, Oct 2024. He did not list which figures changed.
- His development-time figures rise with the date he gave them, as a 2018 start would predict: six years (May 2024, and a Munich-show interview likely from May 2024 and published February 2025), six or seven (September 2025 and the October 2025 podcast), eight (items published March, May, August and October 2026) ConvinceMeAudio 42audio-2G 4:00The Source AV 8:42ecoustics 21:04Audio Force 4:40Audio Force 1:05The Source AV 2:17Part-Time Audiophile 52:36. In a launch-event podcast published October 2026 (recording date not stated) he said newly found issues took an extra 2 years Distorsiuni Interioare 9:38. Components: about 2,500 (2024, October 2025) and over 2,000 on the board (2026) ConvinceMeAudio 42ecoustics 1:24:36article, Oct 2026. The Soundnews introduction gives 3,700 DSP cores, the author's figure, against his 2,500 article, Oct 2026Audiophile Junkie 16:33.
- Three seconds is his only stated standard delay for Quartet (2025); the 1 s figure is a video mode. The 2026 figures of 900 trillion years and tens of seconds describe the filter his research called for and a future Ultima scaler, not Quartet's own delay Audiophile Junkie 17:12article, Oct 2026article, Oct 2026article, Oct 2026. In the HiFi Buys interview (published October 2026; recording date not stated, and its transcript places it before May 2026) the remark 'it's got one second delay mode' says 'it'; the preceding sentence names Quartet, and in 2022 he said the Choral M scaler would have a video mode for the Nvidia Shield's 1 s delay HiFi Buys 2:14:01HiFi Buys 2:14:45Head-Fi, Jul 2022Head-Fi, Oct 2022.
- Soundnews dating: the conversation dates from autumn 2026, not April. The introduction describes April as a listening visit to the Chord factory (no year given) and thanks AVstore for hosting the Romanian launch and making the conversation possible. Watts speaks in the past tense of his CanJam LA studio session (a livestream of 30 August 2026 puts it on the Friday of that CanJam) and puts the Munich 2024 showing 'just over two years ago'. The written answers came later. The introduction's launch month and figures are the author's article, Oct 2026article, Oct 2026article, Oct 2026article, Oct 2026article, Oct 2026The Source AV 3:00The Source AV 18:09. The ecoustics podcast was recorded 2025-10-28 (publisher's page) and published 2026-03-17, so his 'launching next year' means 2026 ecoustics 21:04.
- Head-Fi, May 2024 (EQ settings) answers a question the archive does not hold, so which feature request it answers is not shown beyond his words Head-Fi, May 2024.
- The German Hifistatement interview (June 2024) is the publisher's translation of his English answers, and its English is a machine back-translation, so nothing here quotes or cites it.
Questions about this product
Owning and setting up
- How does the Quartet M Scaler differ from the Hugo M Scaler?
- Does an M Scaler help Mojo, Mojo 2 or a non-Chord DAC?
- What does the M Scaler actually do, and is it worth adding to my DAC?
- Can I stack TT2 and an M Scaler, and how hot is too hot?
- Has Rob published his own recordings, and how were they made?
- How many taps and pulse array elements does each Chord DAC have?
- Should I put ferrites on my BNC or USB cables, and which kind?
- Which Chord DACs accept 705.6/768 kHz from an M Scaler, and how do I connect Hugo 2 or Qutest to get the full 1M taps?
- Which headphones, speakers and sources does Rob use himself, and which pair well with Chord DACs?
In depth
- Is the filter algorithm more important than the tap count, and would more than a million taps keep improving the sound?
- How can upscaling to 705.6/768 kHz improve sound if the recording has nothing above 22 kHz?
- What does Rob mean by depth, and what in a DAC improves or collapses it?
- Why are half-band decimation filters and studio sample-rate conversion a problem, and how much aliasing rejection is enough?
- How do Chord DACs handle DSD, and does Rob consider DSD better or worse than PCM?
- How do microphones, studio conversion and mastering limit what a DAC can reproduce?
- How were Chord's current DACs and the M Scaler developed, and how long did each take?
- Should I upsample in software (HQPlayer, PGGB or my player) before a Chord DAC, and can it match an M Scaler?
- What does Rob mean by 'starting and stopping of notes', timbre variation and 'sense of flow', and what causes them?
- What does Rob think of Class D amplifiers, and how do his pulse array power amps differ from them?
- What is Davina, and what happened to the pulse array ADC?
- Why does Rob design to -301 dB, how can that be verified, and how does small-signal accuracy relate to depth?
- Why does Rob distinguish perception from hearing, and why does he distrust psychoacoustic thresholds?