Hi there,
In this post I would like to share some technical details about using the Vanity
203HD with DACs based on very popular ESS Sabre DAC chips (ES9018, ES9016, ES9038PRO, ES9028PRO and others, including the mobile versions). As you may know the ESS DACs implement a jitter reduction circuit that in principle works similarly to the Vanity's BLL (Buffer Locked Loop), but uses resampling to a fixed oscillator clock domain instead of synchronizing tunable oscillators. A part of this circuit called DPLL has several bandwidth settings which may affect the ability of the DAC to lock onto the incoming digital audio signal. These settings are usually hidden to the user and the DPLL bandwidth is fixed to one of the safe values. One can find a lot of details and experiments with optimal DPLL settings on the internet, let's use
this link as an example. If you google "ESS Sabre DPLL settings" or similar you can get a lot of relevant results.
On one or two occasions we had VanityHD board users reporting that so and so DAC doesn't work with the Vanity. The issue exhibited as irregular drops in the audio which were corresponding to the oscillators adjustments - MCU LEDs flashing - on the VanityHD. It turned out that those DACs used ESS Sabre chips, which in the instant of the oscillators adjustments were losing lock and causing dropouts.
Clock recovery and synchronization is a delicate task that can get influence by a lot of things. For this reason the ESS parts have configurable DPLL bandwidth and if a DAC manufacturer sets the bandwidth too narrow (i.e. not very tolerant) one can get synchronization problems - dropouts with virtually any digital audio input. Another reason might be various more or less successful modifications of the Sabre's clock circuitry, oscillator, regulators and other parts.
In the very unlikely situation when you experience dropouts with the VanityHD and an ESS Sabre based DAC the best way to fix that is to talk to the DAC's manufacturer and ask them what the DPLL bandwidth is and if they have a firmware with more tolerant DPLL setting for a particular input connected to the VanityHD board (SPDIF/I2S). A prime example
here.
Please feel free to share which DAC you use with the Vanity
203HD board, regardless of the DAC chip manufacturer.
Regards,
Pavel
Edited 4 time(s). Last edit at 11/14/2017 09:11AM by AP.