Driving headphones and IEMs

Analog stage, outputs and amplification

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Everything he said on this topic (116)

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2014-04-15Watts rejects calling Hugo a DAC with a good headphone amp, defines transparency against live music, recounts Hugo's development, and explains its single-stage output, 0.075 ohm impedance and tap length. Head-Fi, Apr 2014
2014-04-15Watts says Hugo's output is limited to 5V RMS: 22 ohm or higher loads are fine until white volume, 8 ohms distorts at ultraviolet; HD800 at white was deafening. Head-Fi, Apr 2014
2014-04-26Watts says the headphone noise seems tied to low-impedance headphones and the USB source, notes 33 ohm tested fine, and proposes comparing via the RCA output. needs context Head-Fi, Apr 2014
2014-07-07Watts says the Shure SE846's very high sensitivity (114dB 1mW 9 ohms) means some hiss from Hugo, and suggests trying its in-line attenuator. Head-Fi, Jul 2014
2014-08-21Watts says Hugo needs no external amp (HD800 reaches 115dB SPL before clipping), and cites an HMX demo showing added harmonic distortion softens sound but flattens staging. Head-Fi, Aug 2014
2014-08-24Watts says some audible distortions are unmeasurable yet measurements matter, extra amps degrade transparency, and transparency aids musicality through variation and reduced brain strain. Head-Fi, Aug 2014
2014-08-31Watts says with his Noble K10s Hugo's noise is just audible when muted, below background noise, while master tape hiss becomes audible on CDs. Head-Fi, Aug 2014
2014-08-31Watts says Hugo's noise is 5uV A-weighted on every unit, with 120.0 dB +/- 0.1dB dynamic range, and a unit with much more should be checked. Head-Fi, Aug 2014
2014-09-02Watts says Hugo's 5uV residual noise would be just audible on the very sensitive Shure SE846, noting Hugo supplies 5V RMS and 0.5A RMS. Head-Fi, Sep 2014
2015-03-13Watts says Project xxxx's headphone drive has slightly more voltage and the same current as Hugo, and it cannot be battery powered since its FPGA dissipates 5W. Head-Fi, Mar 2015
2015-04-21Watts says every Hugo he measured shows 120 dB dynamic range within 0.1 dB, but sensitive SE846 earphones will hiss, so use their attenuator. Head-Fi, Apr 2015
2015-07-31Watts gives crosstalk of 120dB, distortion below -150dB and 21-bit noise, says such numbers do not show sound quality, and compares headphone drive with TT. Head-Fi, Jul 2015
2015-09-02Watts recommends the Nighthawks for a warm, smooth yet transparent sound and says adding external amps to Hugo will always degrade transparency. Head-Fi, Sep 2015
2015-11-23Watts says USB is Dave's best input by a tiny margin, then optical, and gives measurements: 6.8v RMS at 1% THD into 300 and 33 ohms, 55 milliohm output impedance. Head-Fi, Nov 2015
2015-11-23Watts says it reaches 121dB SPL with 6.8v driving it. needs context Head-Fi, Nov 2015
2015-11-23Watts says that would be 1W RMS, working out at 115 dB SPL. needs context Head-Fi, Nov 2015
2015-12-01Watts says do not drive headphones from Dave's balanced outputs; Dave drives the HE1000 easily at 1.4W into 33 ohms, and an external amp would add distortion. Head-Fi, Dec 2015
2015-12-30Watts says Dave's output stage is a second-order analog noise shaper, so distortion barely changes with current; he suspects it helped HF linearity; output is 6.8 V into 33 and 300 ohms. Head-Fi, Dec 2015
2016-01-29Watts explains that Hugo's sound hardened into low-impedance headphones, and that treating the output stage as a second-order analog noise shaper with nested feedback removed the distortion change at 32 ohms. article, Jan 2016
2016-02-19Watts says production Dave has short-circuit protection resistors on the balanced XLR, so it will not drive headphones, and he prefers crossfeed setting 3 as closer to loudspeakers. Head-Fi, Feb 2016
2016-03-01Watts says Dave was tested with HE1000 and all popular headphones and only one needed more power, no design suits every headphone, and he will stop answering a hostile poster. Head-Fi, Mar 2016
2016-03-02Watts says the Abyss is 46 ohms, so Dave clips only past +5 dB, about 150 mA at 6.8 V, far below its 0.5 A current limit. Head-Fi, Mar 2016
2016-03-13Watts explains AES17 dynamic range, gives Dave's 2.6 uV residual (-128.4 dB re 6.8 V, -117.7 dB re 2 V), and says its unchanging noise shows no noise floor modulation. Head-Fi, Mar 2016
2016-03-17Watts says the balanced output is not for driving headphones because its current is too low and impedance too high. Head-Fi, Mar 2016
2016-10-21Watts says DAVE risks headphone clipping only at +5 dB volume, and a 33-ohm load does not harden its sound, owing to the second-order noise shaper and discrete output stage. Head-Fi, Oct 2016
2016-12-09Watts says HD800S gives 90dB SPL at 0.22v RMS, so 116 dB SPL from Hugo; much of external amps' supposed benefit is added distortion; he suggests EQ or Nighthawks. Head-Fi, Dec 2016
2016-12-12Watts says DAVE drives the 46-ohm Abyss linearly up to +4 dB, explains how its 0.055-ohm output impedance tightens bass and cuts load distortion, and suggests EQ rather than distortion. Head-Fi, Dec 2016
2017-02-15Watts says few headphones need more power than Hugo gives, he added Hugo 2 filters for a softer option, and doubts digital EQ reaches the 350 dB needed for depth. Head-Fi, Feb 2017
2017-02-19Watts says Hugo TT beats Hugo mainly through better references, USB isolation and more Class A bias, the PSU being about 20%, and Hugo drives all headphones below white. Head-Fi, Feb 2017
2017-04-15Watts says Hugo 2's residual noise is 2.6 uV, half of Hugo 1's, making hiss 6 dB quieter; whether it is silent depends on the IEM and listener. Head-Fi, Apr 2017
2017-11-15Watts says it will be voltage limited at 80 ohms, giving 350 mW. needs context Head-Fi, Nov 2017
2017-11-22Watts gives output figures of 5V RMS into 36 ohms and about 5.3V RMS into 80 ohms. needs context Head-Fi, Nov 2017
2017-12-09Watts says he tests from no load to 8 ohms for a headphone DAC and from no load to 1 ohm for loudspeaker amps. article, Dec 2017
2018-01-10Watts says get Hugo 2 for headphones as any external amp degrades transparency; with headphones USB sounded like optical, so isolation matters only with mains-powered amps. Head-Fi, Jan 2018
2018-01-10Watts says 2Qute's discrete stage was never meant for low impedances; Qutest uses the Mojo output stage with more drive but is a DAC only, its impedance unmeasured. Head-Fi, Jan 2018
2018-01-10Watts says Qutest was designed mainly for speaker systems; it suits those who like an external headphone amp's coloration, but for transparency with headphones he recommends Hugo 2 or Dave. Head-Fi, Jan 2018
2018-01-11Watts says supercaps' power delivery is needed for current-hungry headphones. needs context Head-Fi, Jan 2018
2018-01-13Watts says super caps would not help Dave, defends Hugo 2's output stage, and says Dave below +4 and Hugo 2 below white never clip with headphones. Head-Fi, Jan 2018
2018-01-30Watts lists ways amps add bass bloom (2nd harmonic, low damping, coupling-cap dielectric absorption), says Hugo 2 avoids all three, and advises EQ or better headphones instead. Head-Fi, Jan 2018
2018-01-31Watts says Hugo 2 is limited by its 8.2V battery voltage while DAVE is not, and that external amps are mostly not used for lack of power. Head-Fi, Jan 2018
2018-02-28Watts says Hugo 2 and Qutest share circuitry and FPGA code but Hugo 2's output stage is more advanced; for headphones it outperforms Qutest with a separate amp. Head-Fi, Feb 2018
2018-04-02Watts says the T5P is easy to drive: 90dB SPL needs only 0.045V RMS while Hugo 2 delivers 5.3V RMS, so external amps degrade transparency with no benefit. Head-Fi, Apr 2018
2018-04-04Watts says there are no plans for balanced designs: doubling signal-path parts degrades depth and detail, single-ended drives power-hungry headphones, and balanced is needed only for some loudspeakers. article, Apr 2018
2018-05-11Watts says TT2 is not wasted on easy-to-drive headphones, since it also brings improved noise shapers for better depth and 98k WTA taps. needs context Head-Fi, May 2018
2018-05-19Watts says balanced drive gives headphones no benefit, so use TT2's XLR only for voltage or power needs, balanced power amps or loudspeakers; HD800S are easy to drive. Head-Fi, May 2018
2018-05-24Watts says TT2 would reach 103 dB on a 91 dB speaker, the balanced output has double the impedance, and SE would give 114 dB with an LCD-4. Head-Fi, May 2018
2018-05-25Watts says TT2 addresses headphone power (external amps mostly add coloration) and DAVE driving efficient speakers directly; its 18 watts drives any headphones, and he drives speakers from headphone sockets. Darko Audio 50
2018-06-17Watts says TT2's gain control applies to all outputs with separate remembered settings, and low gain limits output to 2.5V RMS and lowers residual noise for IEMs and power amps. Head-Fi, Jun 2018
2018-08-05Watts says TT2's SE output gives the Abyss 2W or 121 dB SPL, the balanced 8W or 127 dB, and the balanced path's extra parts slightly reduce transparency. Head-Fi, Aug 2018
2018-08-05Watts says TT2 gives an HD800 270 mW or 121 dB SPL from SE, warns that 100 dB damages hearing after 15 minutes, and advises no more than 85 dB beyond 8 hours. Head-Fi, Aug 2018
2018-08-14Watts says the first DX amp will have headphone outputs, Dave easily drives LCD-4 to 120 dB SPL with the best transparency, and suggests a TT2/Dave dealer demo. Head-Fi, Aug 2018
2018-09-16Watts says TT2 has a gain switch because its high power would leave too much noise for sensitive IEMs; low gain cuts residual noise to 1.7 uV. Head-Fi, Sep 2018
2018-10-30Watts says a black M scaler light means the source sends digital silence, calls a headphone amp after TT2 insane, and says the new DSD filter has aliasing below -250 dB. Head-Fi, Oct 2018
2018-11-05Watts says Hugo 2 drives the Aeon Closed easily. Head-Fi, Nov 2018
2018-11-17Watts says he always uses high gain, and low gain is for when lower noise is needed. Head-Fi, Nov 2018
2018-12-12Watts says Hugo One users claimed it could not drive some headphones, but usually they disliked a hard-sounding headphone and used a warm amplifier; he wanted to remove that issue. Pursuit Perfect System 36:40
2018-12-12Watts says a high output voltage lets it drive any headphone; supercaps, as in the original Hugo TT, on both rails with an inductor mean the supply draws only DC. Pursuit Perfect System 37:27
2018-12-12Watts says TT2's linear output current suits efficient speakers; it gives 7 W, or 18 W into 8 ohms balanced, and has a low-noise low gain mode for IEMs. Pursuit Perfect System 39:38
2018-12-16Watts explains output impedance matters for frequency response and back-EMF damping, recounts damping experiments from 35 years ago, and says damping still matters with planar headphones. Head-Fi, Dec 2018
2019-03-06Watts says low gain was intended for efficient IEMs, he runs normal headphones in high gain, and DAC mode is set to low gain, which he guesses is most appropriate for driving power amps directly. Head-Fi, Mar 2019
2019-03-13Watts lists TT2's advantages over Qutest: better noise shapers, DAVE reference circuitry, a second-order analog noise shaper, and a far simpler path than Qutest plus headphone amp. Head-Fi, Mar 2019
2019-06-01Watts finds the reported problem odd, perhaps an EMC issue with the Fostex, and suggests low gain mode, where -3L cannot clip, since the poster runs at -20H. needs context Head-Fi, Jun 2019
2019-06-10Watts says TT2 supplies the same current in both gain modes for the same voltage and load, but low gain is limited to about 3 V RMS, 1.5 A into 2 ohms. Head-Fi, Jun 2019
2019-06-14Watts says TT2 can output 10 A in SPICE modeling for short bursts, but peak current is meaningless; current linearity, with distortion stable into low loads, matters. Head-Fi, Jun 2019
2019-07-21Watts quotes dCS headphone specs (1.4W into 33Ω, 33Ω minimum) as identical power to Dave, presumably balanced, and notes Dave's 8Ω minimum suggests more current. Head-Fi, Jul 2019
2019-07-21Watts says the available voltage drive is identical, just over 6v RMS, and the lower minimum impedance indicates Dave can deliver higher currents. needs context Head-Fi, Jul 2019
2019-09-20Watts says Qutest uses Mojo's Class A stage for easy loads, while Hugo 2's noise shaper output is crossover-distortion free into 33 ohms, with 120 dB feedback at 20 kHz. Head-Fi, Sep 2019
2019-10-21Watts says the HE6 has low sensitivity, but Hugo 2 would drive it to 110dB SPL, way above safe limits. Head-Fi, Oct 2019
2019-11-18Watts says Hugo 2 gives 1050 mW into 8 ohms against about 750mW for the original, and stays more linear into 33 ohms, sounding smoother and warmer. Head-Fi, Nov 2019
2020-01-06Watts says TT2 got huge headphone power after complaints about Hugo 2, helping drive speakers, that DAVE and Hugo 2 drive almost any headphone, and no DSP is fully transparent. Head-Fi, Jan 2020
2020-01-24Watts says M scaler/Dave can run at +9dB without clipping into loads above 16 ohms, and there is no news on the amps as he has been busy. Head-Fi, Jan 2020
2020-02-22Watts finds TT2 slightly warmer in high gain, says not to exceed -3L in low gain, to match volume numbers when comparing, and low gain is for IEMs. Head-Fi, Feb 2020
2020-02-22Watts says TT2's low gain only lowers residual noise, audible only with sensitive IEMs, and both modes measure nearly identically at -3 or lower. Head-Fi, Feb 2020
2020-04-06Watts says TT2 hum with sensitive IEMs comes from 100uA PSU leakage and is fixed by grounding via XLR pin 1, phono, BNC or DX grounds, not isolated USB. Head-Fi, Apr 2020
2020-07-29Watts advises staying single-ended for the Abyss TC on TT2; -20H is low, up to +6H is possible, but that would reach a hearing-damaging 121dB SPL. Head-Fi, Jul 2020
2020-08-08Asked the output into 42 ohms, Watts says just over two Watts from the headphone sockets. needs context Head-Fi, Aug 2020
2020-08-16Watts says analog cables matter so he makes his own, and active balanced headphone outputs degrade transparency with no benefit given TT2's 9.3 V RMS and 5 A single-ended drive. Head-Fi, Aug 2020
2020-11-27Watts suggests trying Hugo 2 driving the Abyss 1266 directly, saying it should give 115dB SPL on paper, an ear-damaging level. Head-Fi, Nov 2020
2021-01-09Watts confirms the XLR wiring and says TT2 XLR gives the Abyss 7W per channel (126 dB SPL) and single-ended 1.8W (120 dB), so stay single-ended. Head-Fi, Jan 2021
2021-01-20Watts says balanced adds amplifiers that cost transparency, so his DACs are single-ended; halving gain halves noise for IEMs; linear PSUs add RF and noise floor modulation. Head-Fi, Jan 2021
2021-01-20Watts says XLR pin 2 equals the RCA signal, the outputs handle over 5A RMS, single-ended drives the Abyss 1266 to 120dB, and balanced comparisons must be volume matched. Head-Fi, Jan 2021
2021-01-31Watts says an extra stage degrades transparency, so he won't design a headphone amp; for more power choose TT2, as more Hugo 2 power needs batteries or a charge pump. Head-Fi, Jan 2021
2021-03-26Watts says TT2's XLR outputs connect directly to high-current output stages, while Dave's go through 33 ohm resistors with a low-current negative leg, meant for amplifiers, not headphones. Head-Fi, Mar 2021
2021-03-29Watts compares dCS Bartok's quoted noise and headphone output (1.4W into 33 ohms) with TT2's 10W, and says fixed noise at -127dB is inaudible while signal-dependent noise matters. Head-Fi, Mar 2021
2021-04-01Watts says his Dave output figures from 300 to 33 ohms are accurate, 16 ohms should be OK, and the 8 ohm figure comes from measurements. needs context Head-Fi, Apr 2021
2021-04-20Watts says TT2 easily drives two headphones at once, and that two units share the same algorithm and crossfeed code, so a sound difference has another cause. needs context Head-Fi, Apr 2021
2021-04-26Watts says 2 ohms at 20k is fine but 0.5 ohms needs care; his travel headphones, closed Aeon 2, suit Dave, Hugo 2 or TT2 and beat Utopia. Head-Fi, Apr 2021
2021-08-11Watts says the LCD-4z is an easy load for Hugo 2, calculating 130dB SPL at clipping, so it needs no more power. Head-Fi, Aug 2021
2021-08-26Watts says Dave drives the Stealth with ease, reaching an ear damaging 125dB SPL at maximum volume. Head-Fi, Aug 2021
2021-09-28Watts says loads below 300 ohms give Qutest some small measurable crossover distortion; Qutest was designed to drive amplifiers, so use Hugo 2 for headphones. Head-Fi, Sep 2021
2021-11-28Watts says DAVE gives 111dB SPL without clipping into this easy headphone, so an extra amplifier would only add coloration and reduce transparency. Head-Fi, Nov 2021
2021-12-01Watts says DAVE gives 98dB SPL maximum with the 1266 and 102dB with the Diana Phi, both easy to drive for current. Head-Fi, Dec 2021
2022-01-04Watts says Dave drives the Susvara to 92 dB SPL, voltage limited, and gives volume limits (+4 solo, +7 with M scaler); preferring an amp means preferring distortion. Head-Fi, Jan 2022
2022-01-04Watts says Dave drives the Stealth to an ear damaging 100dB SPL, some 8dB more than the Susvara. Head-Fi, Jan 2022
2022-01-13Watts explains tempo perception depends on note starts and stops; timing modulation harms separation so the loudest instrument dominates; headphone sensitivity is rated at 1mW while volume is voltage. 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
2022-02-02Watts explains Mojo 2's FPGA charger, 0.5A to 2A charging, 99.3dB SPL with the HEKV2, why coupling caps soften bass, why Mojo lacked a DC servo, and USB-C for Poly. Head-Fi, Feb 2022
2022-03-19Watts says the test used +9 dB at 20 Hz, -9 dB at 20 kHz and a 6 kHz sine; volume now spans -108 to +18 dB for sensitive IEMs. MFG Audio Reviews 39:06
2022-03-27Watts says he would run Susvara from TT2 single-ended (95dB SPL; XLR gives 101 dB), warns over 80dB long-term damages hearing, and would never add a headphone amp. Head-Fi, Mar 2022
2022-03-31Watts says 32-bit integer reaches TT2's FPGA but 32-bit float is unsupported; he runs TT2 at +7 via M scaler, and Utopia needs high gain, low gain suiting IEMs. Head-Fi, Mar 2022
2022-04-04Watts says high current and low output impedance let two headphones share the output, Mojo 2 uses 98% of the FPGA versus 33%, and he avoids trivial updates. Head-Fi, Apr 2022
2022-04-09Watts advises low gain for sensitive IEMs, explains how power splits between two headphones by impedance, says unplug only when silent, and has asked Chord about the handbooks. Head-Fi, Apr 2022
2022-04-25Watts says TT2 and M Scaler can be stacked, but are better apart with Wave or solid-ferrite BNC cables; use high gain unless IEMs hiss; avoid wireless subwoofer links. Head-Fi, Apr 2022
2022-04-27Watts says he designed his own for the ADCs, video leaves headroom to go above white without clipping, and Hugo 2 and Mojo 2 give the Stealth ample volume. Head-Fi, Apr 2022
2022-08-27Watts says external headphone amps, with their connectors, cables and parts, always degrade transparency, so DACs should be simple yet drive all headphones; he also clarifies pulse array remarks. Head-Fi, Aug 2022
2022-11-09Watts says Qutest uses the same output stage as Mojo and will safely drive 25 ohm loads, so a TH-600 is no concern. Head-Fi, Nov 2022
2023-02-05Watts says the downside of a separate headphone amplifier is the extra set of interconnect cables. Soundnews 12:25
2023-02-05Watts says another signal path and electronics always degrade transparency, so he makes the DAC powerful enough for any headphone; DAVE handles 99% of headphones. Soundnews 12:37
2023-02-05Watts says TT2 was made more powerful so no separate headphone amp is needed; in analog simpler is better, as each solder joint, contact and amplifier audibly degrades sound. Soundnews 13:10
2023-02-26Watts says more voltage comes from amp gain, more elements raise I/V current if the PSU and output stage allow, and Stealth gets ample volume from DAVE or Hugo 2. Head-Fi, Feb 2023
2023-03-30Watts gives Stealth SPL at 0dBFS (98.3 dB Hugo/Mojo, 100.0 Dave, 103.4 TT2 headphone, 109.1 balanced), warns against long listening above 80dB, and suggests volume settings. Head-Fi, Mar 2023
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
2023-06-21Watts breaks down background noise sources and Mojo 2's trade-offs (2.2 nV/rtHz, 5.2 V RMS), warns attenuators harm sound, and cites 4.4 mm connector cost. Head-Fi, Jun 2023
2024-01-08Watts says some headphones are said to sound better with external amps although Mojo 2 and Hugo 2 drive them easily to ear-splitting levels. Head-Fi, Jan 2024
2024-11-11Watts advises sending bit-perfect data in its mastered format, calls DSD technically flawed, and says he uses Hugo 2 with Stealth, so Mojo 2 will drive Stealth fine. Head-Fi, Nov 2024
2025-01-09Watts describes a transient reconstruction test giving the M Scaler 22-bit accuracy but says raw numbers miss perception, and rejects an extra amp since DAVE drives Stealth to ear-damaging levels. Head-Fi, Jan 2025