Will a better supply than the 5V USB adapter shipped with Qutest improve it, and what voltage does it accept?
Short answer
Rob Watts says the supplied Qutest adapter should not need replacing: in 2018 he said Qutest was designed to be power supply immune Head-Fi, Jan 2018, and in a 2023 interview he said the supplied switch-mode supply sounded the same as a car battery Eric's Hi-Fi 19:18. Any USB supply must meet 5V +/-0.25V Head-Fi, Nov 2019Head-Fi, Dec 2023. If you want to test an alternative, he suggests a USB battery bank rather than a linear supply Head-Fi, May 2018.
Practical answer. Watts's position on Qutest is that the supplied adapter does not need upgrading. In 2018 he said it was "designed to be power supply immune" and that he did not expect improvements from a different one Head-Fi, Jan 2018. If you want to test that yourself, he recommended a USB battery bank as the comparison, and said that if you hear no change you should forget about upgrading Head-Fi, Mar 2018Head-Fi, Jan 2018.
What voltage it accepts.
- He gave the same figure in 2019, 2020 and 2023: USB spec, 5V +/-0.25V Head-Fi, Nov 2019Head-Fi, Dec 2020Head-Fi, Dec 2023. In 2019 he said 4.9V is fine, because all power rails are regulated internally and the absolute value is unimportant within the USB range Head-Fi, Nov 2019.
- In 2020 he said 6V would "send it to the great FPGA pile in the sky" Head-Fi, Dec 2020. In 2023 he said that more than 5V would blow the protection input diode, easy to replace, and that Chord had reported no such failures to him Head-Fi, Dec 2023.
- Current: in 2018 he said a 2A supply is shipped but a 1A 5V supply "will work fine" Head-Fi, Jan 2018. He also described a 5V/2.1A battery bank as better rated than Qutest needs Head-Fi, Apr 2018.
- USB power banks are fine in his 2023 answer: fast-charge voltages need a communication response from Qutest, which it will not give, so you would be safe Head-Fi, Dec 2023.
Will a better supply help?
- January 2018: he said he did not expect improvements, and that a battery-powered USB charger would be the ultimate PSU Head-Fi, Jan 2018. If you hear no change with a battery, he said, a better PSU than the shipped one is not possible Head-Fi, Jan 2018. He added that a USB battery pack will outperform a linear PSU because it eliminates RF noise from the mains Head-Fi, Jan 2018.
- March and May 2018: he said linear supplies are probably worse than a switcher because a switcher has RF filtering and a linear supply is open to RF from the mains Head-Fi, Mar 2018. In May he said the supplied PSU is as good as a battery in his listening, with the caveat YMMV, and that linear supplies are likely to sound worse Head-Fi, May 2018. In October 2018 he again said a battery bank sounds the same in his setup, YMMV Head-Fi, Oct 2018.
- He also said other amplifiers may be sensitive to the Qutest supply, which is why he suggests trying a USB battery yourself Head-Fi, Jan 2018. In 2019 he reported tiny differences in his own tests between the shipped supply and a battery, again saying it was his setup Head-Fi, Mar 2019.
- 2021: replying to a poster who preferred an Sbooster supply, he attributed the improvements described to more RF noise and noise floor modulation, and said reducing RF noise makes bass softer and treble warmer Head-Fi, Jan 2021.
- In a 2022 post and in 2023 and 2026 interviews he described redesigning Qutest's internal regulation and RF filtering until the supplied supply and a car battery sounded the same, and in 2023 said there is no point supplying a better one Head-Fi, Mar 2022Soundnews 39:49Soundnews 40:35Eric's Hi-Fi 19:18HiFi Buys 2:22:57.
Batteries, if you want to try one. He gave 2.5W as Qutest's consumption, so a 100Wh bank would last about 40 hours Head-Fi, Jan 2018. He said an 85Wh bank would give around 35 hours on paper Head-Fi, Oct 2018.
Hum or noise with a particular amp. In 2020 he told a poster that leakage current from the PSU was creating issues with the amp, and suggested earthing Qutest through the BNC inputs, RCA outputs, an earthed USB PSU or a chassis bolt, or earthing the amp Head-Fi, Aug 2020. In 2019 he said the supplied PSU has no ground on purpose, to eliminate the possibility of ground loops Head-Fi, Mar 2019.
Warranty. His statements differ. In 2018 he said that if the attached PSU "meets USB specifications then you will not void the warranty", after checking with Chord Head-Fi, Jan 2018. In 2020, about PSUs with slow ramp-up and ramp-down, he said that not using the stock PSU "invalidates the Chord warranty" and is at your own risk Head-Fi, Jun 2020. Chord's current terms are on its warranty policy page.
Other products. This answer covers Qutest only. In 2023 he said the same situation applies to TT2, with M Scaler a separate case Eric's Hi-Fi 19:18.
What he has not said. This archive has no measurement showing an audible gain from any third-party supply on Qutest. His 2022 post and two 2023 interview passages refer to a 12V supply or input for Qutest Head-Fi, Mar 2022Eric's Hi-Fi 18:34Soundnews 39:13, and in 2018 he told the car-battery story about the earlier Qute and 2Qute rather than Qutest Head-Fi, Feb 2018. These items do not reconcile that with his USB posts; for the USB socket, follow the 5V +/-0.25V figure he repeated in 2023 Head-Fi, Dec 2023.
Quotes
“A 2A supply is shipped with qutest, but it will work fine with a 1A 5V supply.”2018-01-09 Head-Fi, Jan 2018
“My view is for one to try a USB battery bank - and if you can hear no change (in my system I can't) then forget about upgrading the PSU”2018-03-11 Head-Fi, Mar 2018
“All power rails are regulated internally, so the absolute value of the PSU voltage is unimportant - as long as it meets USB specs of 5v +/- 0.25v.”2019-11-22 Head-Fi, Nov 2019
“It must be USB voltage compliant, that is 5v +/- 0.25v.”2020-12-14 Head-Fi, Dec 2020
Dated positions
| When | Products | Position |
|---|---|---|
| 2018-01 to 2018-10 | Qutest | Qutest was designed to be power supply immune, so he did not expect a better supply to help; a battery bank sounded the same as the supplied PSU in his system (YMMV), and he recommended a USB battery bank, not a linear supply, as the comparison. Head-Fi, Jan 2018Head-Fi, Jan 2018Head-Fi, Jan 2018Head-Fi, Mar 2018Head-Fi, May 2018Head-Fi, Oct 2018 |
| 2019-03 | Qutest | The shipped supply has no ground on purpose to avoid ground loops, and he argued that its RF filtering beats audiophile linear supplies, while reporting tiny differences with a battery in his own setup. Head-Fi, Mar 2019 |
| 2019-11 to 2023-12 | Qutest | The USB input must meet 5V +/-0.25V; 4.9V is fine, 6V would destroy the FPGA (2020), more than 5V would blow the protection diode (2023), and power banks are fine. Head-Fi, Nov 2019Head-Fi, Dec 2020Head-Fi, Dec 2023 |
| 2018-01 to 2020-06 | Qutest | He said in 2018 that a USB-compliant PSU would not void the warranty, but in 2020, on slow-ramp PSUs, that not using the stock PSU invalidates it and is at the user's risk. Head-Fi, Jan 2018Head-Fi, Jun 2020 |
| 2021-01 | Qutest | Replying to a listener who preferred an Sbooster supply, he attributed the described improvements to more RF noise and noise floor modulation. Head-Fi, Jan 2021 |
| 2022-03 to 2026-10 | Qutest | He said he improved Qutest's regulation and RF filtering until the supplied switch-mode supply and a car battery sounded the same, so a better supply is unnecessary. Head-Fi, Mar 2022Soundnews 39:49Soundnews 40:35Eric's Hi-Fi 19:18HiFi Buys 2:22:57 |
Caveats and open points
- A 2022 post and 2023 interview passages mention a 12V supply or input for Qutest, while his USB posts give 5V +/-0.25V; in 2018 he told the car-battery redesign story about Qute and 2Qute instead. The items do not reconcile this.
- His warranty statements differ between 2018 and 2020; Chord's current terms are on its warranty policy page.
- Several statements are described by him as listening results in his own system (YMMV); no measurements of third-party supplies on Qutest appear in these items.
- A 2018-10 post about a 15V rated input and a 12V battery setting does not name the product and was not applied to Qutest; a 2021 warranty remark about changing the PSU was about DAVE and was not applied.
Topics: Power supplies and battery packs