Headphones

Dethonray has not skimped on its choice of DACs for the M1, specifying AKM’s top flight AK4191EQ upsampling/noise-shaper with no fewer than two partnering AK4499EXEQ converters. However, its final performance, in respect of distortion, jitter, etc, is markedly below what we know to be possible. That said, Dethonray’s own <0.02% specification for distortion suggests it is not aiming for the 0.00005% achieved elsewhere, and this is reflected in the 0.0076-0.034% measured at the M1’s maximum 2.87V line/RCA output. Distortion does fall to a min. of 0.0016% over the top 20dB of its dynamic range through the midrange but there remains a marked increase (typ. x20) at HF, these figures not significantly influenced by either ‘Reference’ or ‘Direct’ Timbre Mode settings. Neither is the response affected by these settings. The AK4191EQ is a 1536kHz/DSD1024-compatible modulator that includes six filter coefficients, of which one – the ‘Sharp’ linear phase type – has been chosen as the default by Dethonray. This filter offers an excellent 94dB stopband rejection and while capable of ruler-flat responses, these are rolled off to –1.3dB/20kHz, –4.4dB/45kHz and –10.5dB/90kHz with 48kHz, 96kHz and 192kHz media, respectively.

The A-wtd S/N is a respectable 109.6dB, while resolution is good to ±0.5dB over a full 110dB dynamic range, but jitter is a high ~1000psec with 96kHz data. All sample rates show low-rate ±4Hz, ±8Hz and ±16Hz sidebands while the main spectrum exposes a low-level interference that persists across the M1’s ‘analogue’ noise floor. Changing the AC wall-wart for a Ferrum Hypsos PSU does not improve things, suggesting this is cross-processor noise.

Dist. vs. 48kHz/24-bit digital signal level over a 120dB dynamic range (1kHz, black; 20kHz, blue)

High-res 48kHz/24-bit jitter spectrum showing spuriae and low-rate sidebands [inset x100; ±35Hz]

Maximum output level / Impedance	2.87Vrms / 307-345ohm (RCA)
A-wtd S/N ratio (line / USB)	100.6dB / 109.6dB
Distortion (1kHz, 0dBFs/–30dBFs)	0.0076% / 0.001%
Distortion & Noise (20kHz, 0dBFs/–30dBFs)	0.034% / 0.011%
Freq. resp. (20Hz-20kHz/40kHz/90kHz)	+0.0 to –1.3dB/–4.4dB/–11dB
Digital jitter (48kHz / 96kHz / 192kHz)	155psec / 1150psec / 971psec
Resolution (re. –100dBFs / –110dBFs)	±0.1dB / ±0.5dB
Power consumption	8W
Dimensions (WHD) / Weight	270x33x170mm / 600g
Price	£2599