Help me understand the ESS SABRE DAC - Woo Audio

I have a Woo Audio WA7 Fireflies headphone dac/amp that I love with my Focal Clear headphones. I really like this setup. It plays everything in my collection, PCM and DSD. My player is foobar and the computer interface is USB.

So… How does this ESS SABRE ES9018K2M Reference DAC translate all these different rates and formats? What are the weaknesses of this DAC?

I like this setup, I want to upgrade it to their newer model that uses a newer ESS chip but I just can’t tear away from this unit… I know, schitzoid. The more I like something, the more I think their newer more expensive stuff would get me higher.

BTW, the unit can function as just a headphone amp with analog ins… I used my Direct Stream MkI as input and the sound was definitely improved… certainly should have, but honestly, the Woo sounds just great… and for only around $800 total, this Woo WA7 is just a fabulous deal IMO.

Bruce in Philly

Data Sheet on this DAC chip:

WA7 at Woo

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In extremely broad terms, it works in roughly the same way that the DS DAC does, just with different numbers of everything and a different approach to filtering incoming jitter. This is not ESS-specific: that comment is pretty much applicable to any DAC chip built around sigma-delta modulation for conversion.

The received data is run through a bunch of computation to produce a much higher sample rate with many fewer bits per sample, with quantisation noise shaped by the SDM process into ultrasonic ranges, then the D/A conversion takes place via a set of multiple parallel elements in order to average out the error of any individual one and increase the SNR. Finally an analog low-pass filter gets rid of most of the ultrasonic noise. Note that the ESS DACs do not go all the way to single-bit encoding (or technically single-trit in more recent FPGA versions!) the way the PS Audio DS DACs do. From memory it might have been 6-bit at one point but I’ll leave checking that as homework for somebody else.

The devils are in the details. These are tiny, cost-constrained integrated circuits. Compromises abound (alongside some brilliant innovations) in terms of computational resources, power and clock stability. For example, there’s a reason why the DS MK2 has adopted dual FPGAs with many multiples the capability of the unit in the MK1, and the relative lack of that capability in any fully integrated chip DAC limits its overall potential.


In addition to dvorak’s comments, ESS uses a MASH architecture for its sigma delta modulators. MASH has some nice properties, but it does require a multibit output as dvorak mentioned. Here’s a quote from Wikipedia:

Multi-stage noise shaping

[The] simple 1st-order modulation can be improved by cascading two or more overflowing accumulators, each of which is equivalent to a 1st-order delta-sigma modulator. The resulting multi-stage noise shaping (MASH) structure has a steeper noise shaping property, so is commonly used in digital audio. The carry outputs are combined through summations and delays to produce a binary output, the width of which depends on the number of stages (order) of the MASH. Besides its noise shaping function, it has two more attractive properties:

  • simple to implement in hardware; only common digital blocks such as accumulators, adders, and D flip-flops are required
  • unconditionally stable (there are no feedback loops outside the accumulators)

Back in the late 80’s, in one of my trips to Japan while working for Panasonic, I met the developer of the MASH circuit. His name escapes me but it’s nice to know his work lives on in digital to analog conversion.
Thanks for that reference.


Do you have the tube power supply? When I had the WA7 it made a surprisingly positive impact on the sound quality.

No, just the solid state one. The tube supply is about an additional $600. For that total, you can get their next gen amp/dac… kinda odd… the next gen does not use an optional tube supply.

Anywho, did you like your WA7? What did you think of it? What were its weaknesses?

Bruce in Philly

My second-ever CD player was a Panasonic portable in the early 90’s and it used MASH.


Their portables were fine indeed.

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I still have two of them in commission working under harsh conditions…rec room and woodshop.

I did like it. I only sold it because I got a deal on a WA33 (standard). To be honest it was a while ago so I don’t recall any weaknesses. It’s an amazing amp.

Mine was silver, which looked fantastic!