Chord Hugo 2 Review – New dimensions for portable audio, Simply sublime

Rob Watts’ Technical Summary Presentation

Rather than me try to take snippets about the technical specifications/metrics of the Hugo 2, I thought it much better to share the detailed presentation that Rob Watts has kindly provided to earphonia.com

Thanks Rob for taking the time to put together this detailed information.

Timing – WTA filter -(Watts Transient Aligned)

• Hugo 2 has 49,152 tap 16FS WTA filter.
• It uses 45 208MHz DSP cores in parallel to create the WTA filters
• Following the first WTA filter is a second WTA filter going from 16FS to 256 FS
• This further improves timing reconstruction accuracy as the WTA filter recovers timing to 81 nS resolution
• Filter options – HF filter, 16FS WTA only or 16FS and 256FS filter to adjust the sound for taste – warm and soft or transparent and incisive
• HF filter is separate option set to 40 kHz -3dB

Noise floor modulation

• Noise floor modulation occurs when noise increases/decreases depending upon the music signal.
• The ear/brain is extremely sensitive to this problem as it interferes with the brain’s ability to separate sounds into individual entities
• Listening tests have shown sensitivity to noise floor modulation well below levels that are measureable
• Noise floor modulation makes the sound hard, bright and aggressive; it degrades instrument separation and focus; reducing noise floor modulation improves sense of focus, smoothness and refinement – it sounds much more natural

Hugo 2 and noise floor modulation

• The DAC architecture has a large influence on noise floor modulation – pulse array DAC’s have innately very low levels of modulation
• The reference power supply to the DAC is crucial, this is very low noise and low impedance, with individual references per channel
• RF noise is a major problem as it inter-modulates with the analogue electronics causing noise floor modulation – extensive RF filtering is employed, together with steps to reduce the analogue sensitivity
• Quad layer ground planes are used, so that ground induced noise and distortion is eliminated
• Jitter is a big source of noise floor modulation – incoming jitter is eliminated by a digital phase lock loop (DPLL).
• Hugo 2 has extremely low noise floor of -177 dB with no measurable noise floor modulation

Hugo 2 and DSD noise floor modulation

• DSD represents a severe challenge for noise floor modulation
• For example, DSD 64 has noise that is -20 dB down at 100kHz – this creates distortion and noise floor modulation and must be filtered for best sound quality
• DSD sources have large HF noise – this is digitally filtered by over 200dB at 100kHz giving much more natural sound quality for DSD
• Hugo 2 has a much improved DSD filter – it will also accommodate DSD64 to DSD512 in native and DoP modes (DoP to DSD 256). This filter has extraordinary performance with over 200 dB filtering eliminating the sound quality problems coming from DSD due to out of band distortion and noise

Hugo 2 noise shapers

• The noise shaper is crucial for performance, particularly for accurate depth perception
• Hugo 2 has 10 Pulse Array elements
• The noise shaper is much improved; its now 11th order, running at 104 MHz, with better than 260 dB performance – well over 1,000 times more resolution than before
• This ensures much better detail resolution and perception of sound-stage depth

Headphone drive

• Hugo 2 has a discrete OP stage integrated into the DAC output amplifier and filter
• It features second order noise shaping analogue section; this reduces distortion with load
• Hugo 2 has a boost PSU voltage to enable greater power output into low impedance loads
• The OP stage is full Class A (with 300 ohm loads)
• It is capable of 5.3 V RMS and peak output currents of 0.5A RMS
• The OP stage has an extremely low output impedance
• Digital cross-feed, with 3 settings, is implemented digitally at 16FS with two 48 bit DSP cores. The cross-feed uses an analogue type IIR filtering

Measurements Hugo 2

• Dynamic range 126 dB A wt.
• Noise 2.6 uV A wt., no measurable noise floor modulation
• Distortion 0.00007% at 2.65 V 300 ohms
• More power output – 1050 mW into 8 ohms, 740mW 33 ohms, 94mW 300 ohms
• 0.025 ohms output impedance

Measurements of Noise Floor Modulation

• Blue trace is 2.65 V 1kHz 300 ohms
• Red trace is zero signal
• No measurable noise floor modulation – noise floor is static at -177dB
• Distortion is only 0.00007%
• High order harmonics are all below -150 dB

Measurements of Distortion into 33 ohms

• Blue trace is 2.65 V 1kHz 33 ohms 213 mW output
• No measurable noise floor modulation – noise floor is still unvarying at -177dB
• Distortion barely increases to 0.00015%
• High order harmonics are all below -144 dB
• No sign of crossover distortion at all – due to the 2nd order analogue noise shaper amplifier

Measurements of Separation 33 ohms

• Left is 2.65v 1kHz 33 ohms 213 mW output – blue trace shows zero right channel
• Separation is better than 144dB with no noise floor modulation or other errors
• Separation is not important but distortion and noise from the other channel is vitally important
• This has separation distortion at -170 dB – extraordinarily low
• These state of the art measurements show how well Hugo 2 is isolated from its battery and the other channel

Measurements of Jitter

• No measurable jitter at all – a remarkable result
• USB input has improved RF isolation, RF filtering and PSU efficiency
• Because of the USB improvements, when using headphones and modern lap-tops the optical input sounds identical to the USB input

As you can tell there are a lot of impressive technical details about the Hugo 2 but more importantly how does this translate to performance and sound signature, read on to find out …