DacMagic vs Meridian Explorer 2 USB DAC’s & Audirvana 3 Plus

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DacMagic vs Meridian Explorer 2 USB DAC’s & Audirvana 3 Plus

Post by embleton » Wed Oct 18, 2017 9:27 pm

Even moderate specification audio equipment/software, as below, its frankly easy to hear the difference between three-music streaming service and equipment with the ear, those reviewers that don’t clearly need hearing aids. This is more a review of audiophile philosophy listening, than a portable general-purpose smartphone environment that all service support. But the latter will be explored with an iPhone 7 Plus using a pair of Bluetooth AirPods at a later stage.

Serious listening is with an outbound Digital to Analogue Converter (DAC) from Cambridge vs Meridian Audio via USB. But these are low-end DAC’s costing £350 and £129 respectively. And this article will go into detail about the philosophical aspects of DAC’s and computer logically calculations of Digital Signal Processing (DSP).

Apple and Tidal are through the Audirvana 3 Plus oversampling and an upsampler DSP software on a MacBook Air (late April 2015 model) with High Sierra OS. And Amazon using a browser that doesn’t employ Audirvana 3 Plus oversampling and upsampler with the same MacBook Air.

Audirvana 3 Plus iZotope DSP filter tuned for Meridian Explorer 2 USB DAC by ear:

Steepness: 128dB (7th-bit binary). Warmth, with higher values increasing warmth and decreasing resolution. Higher values increase artefacts. (default 160db).
Fix filter max length upsampler: 2 million samples/2Mbps. Higher the better, but higher figures more processing power and jitter. (default 0.5 million).
Cut off frequency: 1.2 * Nyquist (4Mhz), so 4.8Mhz. Higher values produce better and smoother harmonics but increase ringing. (default 1).
Anti-aliasing: 96 (5th/6th bit binary). Warmth with higher values reducing warmth but increasing resolution/detail. (default 200).
Pre-ringing: 0.8 (4th-bit binary). Higher values increase harmonic ringing, adjust with anti-aliasing; reduce anti-aliasing. (default 1).

Final upsampler is done by DAC. The iZotope parameters were based on the fact that the DSP digital filter works in integers on bits among other things, hence single bit boundary-less gate logic CPU processing power than otherwise through internal CPU circuitry. It’s my belief that this will reduce jitter, phase error correction and delay through the digital DSP filter across the spectrum for it necessitates fewer arithmetic calculations throughout.

Our Love is Easy by Melody Gardon; a symbol should be heard throughout after the beginning of the track clearly at 1 minute 14 seconds, twice in between close by and at 1 minute 58 seconds and later stages at intervals and at higher levels later in the song, which necessities high resolution resolving by the DSP & DAC and good hearing!

Musical clarity, detail, warmth and rhythm seem to correlate this with my engineer ears with the Meridian & DacMagic Plus DAC with the parameters chosen with 16-bit/44.1Khz soundtracks. The Meridian DAC was purer with its Texas instrument PCM5142 DAC chip than the DacMagic Plus with its Wolfson WMB8740 chips. Bass on the DacMagic Plus is lacking with its resolution and impact.

My assumption is that the oversampling to 384Khz from 44.1Khz is the culprit with the Wolfson DAC chips that gave me a slight headache with this arrangement. Oversampling at multiples when feed with the sampling frequency of 384Khz devisable by an integer generated fewer artefacts. I don’t agree with Cambridge’s method of oversampling to 384Khz with a music track sampled at a 44.1Khz rate.

The Texas instrument chip doesn’t do this but sample at multiples of the sample rate in all cases, something I agree with technically harmonically. This technique ensures that integers can be used whereas off frequency sampling needs floating point calculations that take longer to process with its unstable time domain through the floating-point logic of the DAC.

Most do not understand DSP oversampling and an upsampler and refer to the audio path as BitPerfect assuming the signal isn’t altered in any way with this terminology. This is not true; the resolution is improved, so taking a signal level of say x at a set point and at another point in time with DSP improvements.

The signal can be improved by complex mathematics and a signal calculated between many points in time. The signal lays between the points in both time & amplitude and doesn’t fall outside those parameters. This increases the resolution of the timeline, accordingly, along with harmonics.

Oversampling improves the amplitude resolution and an upsampler improves the harmonics inside and outside the waveform along the timeline. Final audio and subsonic upsampler are best done in the DAC, as it has better stable oscillating crystals than those in a computer when overclocking.

The front end, Apple MacBook Air with Audirvana 3 Plus DSP software oversampling bit depth 24-bit and upsampler frequency to 192Khz; for a DacMagic Plus DAC Linear Filter AFT2 to 384Khz upsampler via USB interface for Apple and Tidal Music. Also, a Meridian Explorer 2 USB DAC depth 24-bit & Master Quality Authenticated (MQA) sampling frequency at 176.4Khz/192Khz. The front end, Echo Dot for Amazon Music to Bluetooth Cambridge BT-100 plugged into a DacMagic Plus DAC upsampler and oversampling.

Amplifier, Onyko A-9010 into a pair of wall mounted, on metal stands, Tannoy DC6 SE speakers bi-wired to Amplifier.

Amazon Encoding, Variable Bit Rate (VBR) 256Kbps MP3 compressed audio. Apple Encoding, AAC 256Kbps fixed bit rate compressed audio. Tidal Encoding, Lossless 44.1Khz 16-bit depth/HD MQA 44.1Khz-192Khz 24-bit depth audio. Algorithmic upsampler iZotope 64bit SRC for Audirvana Plus 3.0, and AFT2 for Cambridge DacMagic Plus DAC upsampler and oversampling.

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