Dual BNC, dual data and DX links

Inputs, sources, cables and clocking

Answers on this topic

• How do I connect the M Scaler to DAVE, and why does dual BNC only work with the output set to white?
• What are the DX outputs for, and what happened to the pulse array power amplifiers?
• Which BNC cables, and what length, should I use between an M Scaler and my DAC?
• 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?

Everything he said on this topic (86)

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

• 2015-10-29Watts says it supports dual data mode, output impedance is the PCB tracking, and the phono and XLR outputs can be used together with fixed gain. needs context Head-Fi, Oct 2015
• 2015-11-01Watts says Dave's 705/768 kHz DX outputs feed his non-switching digital power amps; the first, due next year, is 20W RMS with a 70W mono-block option. Head-Fi, Nov 2015
• 2015-11-21Watts says software updates may come for worthwhile gains via Chord or distributor visits, and AES is not dual data because it is poor; dual BNC reaches 768 kHz. Head-Fi, Nov 2015
• 2015-12-02Watts says Dave runs warm with large thermal margins, XLR headphone drive would distort, AES is poor for high rates, and Blu dual BNC works with proper RF cables. Head-Fi, Dec 2015
• 2016-05-21Watts says DAVE's DX output sends 705/768 kHz 24-bit at full level, carrying the volume setting and a DX identifier in user data for the DX power amp. Head-Fi, May 2016
• 2016-05-31Watts confirms a DX output works into a dual BNC input, since two DAVEs can be cascaded that way. Head-Fi, May 2016
• 2016-10-27Watts says two power amps can be used, hence four DX outputs, and plans a volume trim on the amps in DX mode since master volume is sent digitally. 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
• 2017-01-08Watts says Davina's bi-directional USB can send 768 kHz M scaler output to a PC, but Dave is meant to receive 768 kHz via isolated BNC, as with Blu Mk2. Head-Fi, Jan 2017
• 2017-01-29Watts says Dave's DX outputs will feed his digital-input power amps, with one global feedback loop, 4 passive parts, a third-order noise-shaper structure and non-switching output; first model 20W. Head-Fi, Jan 2017
• 2017-02-01Watts says the M scaler connects to Dave's dual BNC inputs (1 and 2 or 3 and 4); DX outputs are dual BNC 705/768 kHz SPDIF carrying volume data. Head-Fi, Feb 2017
• 2017-02-01Watts says DX uses one cable per channel, two identical outputs allow bi-amping, and the first amp is stereo but can run as a mono-bloc. Head-Fi, Feb 2017
• 2017-02-19Watts says Hugo 2 has dual coax inputs for desktop-mode convenience and dual data mode with M scalers at 768 kHz, using small jacks because two BNCs would not fit. Head-Fi, Feb 2017
• 2017-02-20Watts says DX is AES dual-data SPDIF with volume in user data; Mojo takes 768 only via USB, coax tops at 384 kHz, and Hugo 2 now accepts dual-data coax. Head-Fi, Feb 2017
• 2017-02-20Watts confirms dual data mode works and says he is adding a cyan source-switch color to indicate it. Head-Fi, Feb 2017
• 2017-03-19Watts says starter BNC cables will be supplied because 768 kHz SPDIF is new and cables must be true 75 ohm, though expensive BNC cables he tested all worked. Head-Fi, Mar 2017
• 2017-05-02Watts says the amp is mostly for driving speakers from Dave's DX outputs, though a few headphones would appreciate the power. Head-Fi, May 2017
• 2017-07-03Watts says more data could technically be added to the DX protocol in future to suit different products, as there are plenty of spare bits. Head-Fi, Jul 2017
• 2017-08-11Watts says the million-tap M scaler exceeds 16-bit accuracy, Hugo 2 takes 768 kHz dual BNC, better analog parts put DAVE ahead, and he flies with DAVE and Blu 2. Head-Fi, Aug 2017
• 2017-10-28Watts says with a single DX input the amplifier turns its unused channel into an inverted channel, allowing bridging or bi-amping. Head-Fi, Oct 2017
• 2017-12-31Watts says rates up to 768 kHz run in dual data mode, detected either by the AES3 standard or by two exactly synchronized data streams on both coax inputs. Head-Fi, Dec 2017
• 2018-01-10Watts says Qutest remembers all configuration settings, and its BNC inputs are individually selected and switch automatically into dual data mode. Head-Fi, Jan 2018
• 2018-01-11Watts says Dave's DX output is a 705/768 kHz signal with volume data embedded, making Dave a DX pre-amp; Qutest accepts DX data but ignores the volume. Head-Fi, Jan 2018
• 2018-01-11Watts says Qutest is a fixed-level DAC, not a DX pre-amp: it has no DX outputs and will not decode volume on a DX input. Head-Fi, Jan 2018
• 2018-01-11Watts says only Dave has DX outputs. Head-Fi, Jan 2018
• 2018-01-25Watts explains AES dual data mode, says Hugo 2 and Qutest auto-assign channels while DAVE needs manual connection, and says a Mojo with Nighthawks or Aeons beats far costlier systems. Head-Fi, Jan 2018
• 2018-02-11Watts says a standard stereo 3.5mm cable connects Hugo 2 to an M scaler; cheap non-75-ohm cables worked at 705/768 kHz because of de-glitching and rise/fall adjustment. Head-Fi, Feb 2018
• 2018-03-17Watts says never upsample at the source into his DACs; cascading two DAVEs via DX helps slightly versus an M scaler's huge change; isolating FPGA noise was essential for DAVE. Head-Fi, Mar 2018
• 2018-03-17Watts says Davina will use Choral metalwork and all new DACs will accept M scaler dual data, which is why Qutest and Hugo 2 have that input. Head-Fi, Mar 2018
• 2018-07-21Watts describes auto video mode on 48 kHz input, automatic source switching when USB is silent, remote control, and a DX mode for DX power amplifiers still under development. c w 24:49
• 2018-07-22Watts says Hugo 2 accepts the M Scaler's full 768kHz dual data via 3.5mm to RCA cables and BNC adaptors, and mentions 50 flight hours with the pair. Head-Fi, Jul 2018
• 2018-07-23Watts explains Hugo 2's dual data link (two 384k cables), says FPGA RF noise keeps the scaler separate, shows his homemade flight cable, and rates USB and optical equal. Head-Fi, Jul 2018
• 2018-07-26Watts says Mojo can take the M Scaler's 384 kHz output but lacks dual coaxial inputs for the full 768 kHz. Head-Fi, Jul 2018
• 2018-07-27Watts explains dual-data and DX modes, M scaler DSD-to-PCM conversion with Hugo 2's 220 dB filter, says algorithm beats tap length, and compares R2R and delta-sigma timing errors. Head-Fi, Jul 2018
• 2018-08-04Watts says the issue is non-linear transient timing, the master clock and source jitter are unimportant thanks to the DPLL, and Hugo 2 gets full 1M taps via 3.5mm-to-BNC adaptors. Head-Fi, Aug 2018
• 2018-08-08Watts says Qutest has no DX input but accepts dual-data 768 kHz, ignoring the volume information in the user data. Head-Fi, Aug 2018
• 2018-09-05Watts explains the Hugo M scaler OP SR colors (red pass through, green 176.4/192, blue 352.8/384, white 705.6/768 1M taps); only white enables dual data mode. Head-Fi, Sep 2018
• 2018-09-22Watts says dual BNC operation applies only at full 1M taps at 705/768 kHz; otherwise it runs single-data mode at up to 352/384 kHz. Head-Fi, Sep 2018
• 2018-09-23Watts says the behavior is correct, dual BNC operation works only on white, and he will get the manual corrected. Head-Fi, Sep 2018
• 2018-10-18Watts has had no issues with cheap 1.5m or bodged screened cables on Hugo 2, suggests adaptors with supplied BNC cables, and says the M scaler auto enters low-power mode. Head-Fi, Oct 2018
• 2018-10-24Watts says many audiophile cables are not true 75 ohm RF cables, so Chord supplies RF cables used in testing, and 768 kHz over SPDIF is technically very challenging. Head-Fi, Oct 2018
• 2018-10-25Watts says native DSD works on the M scaler (Roon, JRiver) using Dave code if SR OP is white, else it is silent; dual data needs 50 Mbit/s per cable. Head-Fi, Oct 2018
• 2018-11-18Watts lists three causes of DAVE dropouts with the M scaler: the source, DAVE's dual-data detector, and SPDIF losing lock; try BNC 3 and 4, else service. Head-Fi, Nov 2018
• 2018-12-28Watts says white is dual data mode, two mono signals at 352/384; Hugo 1 cannot accept it and treats one mono signal as stereo, so use single BNC instead. Head-Fi, Dec 2018
• 2019-01-09Watts confirms 768 kHz is reaching Hugo 2, since dual data is lit, the M scaler shows 48k, and Hugo 2 shows the right color. Head-Fi, Jan 2019
• 2019-01-22Watts explains dual data: each cable carries mono samples, two per 384 kHz period, giving 768 kHz per ear, so left and right need separate cables. Head-Fi, Jan 2019
• 2019-02-02Watts says the mute is for DX mode only. needs context Head-Fi, Feb 2019
• 2019-02-09Watts says a cyan input light shows M Scaler dual data and 1M taps; optical matching USB proves his DPLL removes source jitter, and simpler, lower-power sources sound better. Head-Fi, Feb 2019
• 2019-02-26Watts gives DAVE's BNC channel mapping for the M scaler, says the DX output is for future products, and warns 705 to 768 kHz conversion adds distortion and noise. Head-Fi, Feb 2019
• 2019-02-26Watts says the BNC cables are plugged into the wrong sockets and should be swapped. Head-Fi, Feb 2019
• 2019-02-26Watts says swapped cables only stop single-data rates working and reverse channels, levels are the same, and the unit enters low-power standby on digital silence. needs context Head-Fi, Feb 2019
• 2019-03-08Watts says the M scaler converts DSD to 705 kHz PCM, output only via dual BNC; in hindsight he could have passed DoP through, and TT2 solves this. Head-Fi, Mar 2019
• 2019-03-20Watts clarifies that Hugo 2 accepts 768 kHz via USB and via the dual SPDIF coax inputs. Head-Fi, Mar 2019
• 2019-04-12Watts says using both coax inputs at once can confuse auto DDATA mode if their sample rates are close; if so, turn off the inactive channel. Head-Fi, Apr 2019
• 2019-07-17Watts says a DX output is dual AES plus volume data, then argues listening judgements and measurements both need great care, saying only the APx555 measures noise floor modulation accurately. Head-Fi, Jul 2019
• 2019-08-10Watts says that in pass-through only one BNC cable is active, so the owner must connect the right cable or select the appropriate coax input. Head-Fi, Aug 2019
• 2019-11-05Watts says Dave's design has not changed, Chord tests Daves in dual BNC mode for drop-outs, a right-channel-only issue is strange, and he will raise it with Chord's production director. Head-Fi, Nov 2019
• 2020-01-27Watts says dual-BNC 768k on Mojo was dropped in 2015 to save power and the manual corrected; Mojo takes 768k on USB, and the algorithm matters more than tap length. Head-Fi, Jan 2020
• 2020-02-25Watts says cable length matters with DAVE because it requires sync, while his other DACs use the AES3 dual data flag and need no exact sync. Head-Fi, Feb 2020
• 2020-04-15Watts has not heard the M Scaler with the original Hugo TT, which would need one BNC as it is 384k max, and suggests trying TT2 with the M Scaler. Head-Fi, Apr 2020
• 2020-04-26Watts says TT2 and other DACs auto-switch dual BNC channels by data flag, but with DAVE the M scaler's left BNC must go to the bottom BNC pair. Head-Fi, Apr 2020
• 2020-07-17Watts says the analog and DX outputs run simultaneously on all DACs equipped with DX outputs. Head-Fi, Jul 2020
• 2020-08-15Watts says differing BNC lengths affect delay, not sound quality, and since Dave uses sync detection mismatches could cause drop-outs or failure of 705/768 kHz dual data operation. Head-Fi, Aug 2020
• 2022-01-28Watts confirms 44.1 kHz goes to 705.6 kHz on dual BNC, and says the chart in question was not his since manuals come from Chord. Head-Fi, Jan 2022
• 2022-02-01Watts answers Mojo 2 questions: 2G buzz mitigation, dual-data ring contact, 0.35S latency, DSP cores, 9 hours 11 minutes battery on USB, and 99.5dB SPL into HD800. Head-Fi, Feb 2022
• 2022-04-26Watts says Mojo 2's dual port is only for use with an M Scaler, that a portable M Scaler needs 3 nm FPGAs probably 10 years away, and that he tested Mojo with one. Audio Force 16:02
• 2022-04-26Watts says he does not expect people to pair Mojo with an M Scaler, though they might; cheaper or simpler scalers will come, in 2 years or 10, and the input cost little power. Audio Force 16:50
• 2022-05-03Watts says something gives a small improvement, judged with two DAVEs via the DX output, far less than an M scaler; he notes his independence and refers pricing to Chord. needs context Head-Fi, May 2022
• 2022-05-23Watts says DAVE's DX outputs carry 705/768 kHz from its 164,000-tap WTA1 filter and should sound better than Qutest's 48k taps; Qutest ignores the embedded volume data. Head-Fi, May 2022
• 2022-05-23Watts says the DX protocol's volume data is for future DAC power amps without volume controls, and DAVE between an M scaler and TT2 would just pass data through. Head-Fi, May 2022
• 2022-08-19Watts says the M Scaler's big benefits need 768 kHz, he can't think of any DAC running 384 kHz over BNC, and some 192 kHz buyers later switched to Chord DACs. AVstore 26:46
• 2023-02-04Watts says TT2 gives 7 watts into 8 ohms; DX outputs are for future 100 to 400 watt DACs driving speakers directly, a program that has stalled. Dusty Audio 1:01:31
• 2023-02-04Watts says another Dave can connect to the DX outputs; testing two Daves, it sounded better as the second did no WTA processing, but he avoided promoting buying two. Dusty Audio 1:02:44
• 2023-07-15Watts says all M scalers will work with all current DACs, including Mojo 2 and Hugo 2 via dual data, that scaler benefits need long-term listening, and urges forum civility. Head-Fi, Jul 2023
• 2024-05-10Watts says dual BNC outputs are happening as well. Reactcore 0
• 2024-05-16Watts confirms it still uses dual BNC, saying he had to decide between an optical connection and keeping dual BNC. ConvinceMeAudio 10:10
• 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 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 it can be used with Mojo 2 or any Chord DAC, because they all accept dual BNC. ConvinceMeAudio 11:42
• 2024-05-16Watts says it depends on the splitter, which should have 75 ohm resistors; a splitter he bought 10 days ago lacked them and did not work. ConvinceMeAudio 13:15
• 2024-05-16Watts says a splitter with the resistors works, since the 4 volt output drops to 2 volts and 1 volt is needed, but he has not found one to recommend. ConvinceMeAudio 13:53
• 2024-05-16Watts says Quartet has two sets of BNC outputs, so it can feed two different products anyway. ConvinceMeAudio 14:16
• 2024-05-16Watts says Quartet has that built in, with separate drivers and separate outputs for each. ConvinceMeAudio 14:33
• 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
• 2024-06-18Watts 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
• 2024-06-28Watts says Quartet supports the dual AES format like the Hugo M Scaler, so a third party could build a dual BNC to USB converter, though not trivially. Head-Fi, Jun 2024