Yes, come'on indeed. Would you like to know the technical details?
Keep in mind, what follows below is not everybody's cup-of-tea and that is the reason that it is not stated explicitly on my website. There is no intention of sleight of hand or to be deceptive. So here goes.
The Sabre DAC family is a little different from what others offer. The output has a DC offset 1/2 of Vcc, which means half of 3.3V and hence 1.65V. So far so good, if we were to put a scope there, we would see that it is acting as a 'voltage' DAC capable of swing 6V peak-to-peak (the half voltage is a D-S DAC is 50% of the pulses are 'on' and the other 505 'off' - at least that is the easiest explanation.
If this was a normal voltage DAC, we should be sure that it looks into something that matches that 1.65V or else we might damage it. So then, even if we should use ESS recommendation, and we connect it to an I/V converter that will
not shorten it with respect to DC (that could damage the DAC), but it will see a short with regard to AC, which is our music signal.
This is known as a virtual earth as opposed to a physical earth.
In a similar way to conventional voltage DACs, they too usually have around half of 5V, hence the offset tends to be around 2.4V to 2.5V. This has to be matched to a similar DC or potential damage (been there).
Hopefully not boring too many, but at least here things does get a bit more interesting: The Sabre DAC is different.
Take the ES9018 DAC, it has four phases, that is 8 pins, and each pin has an output impedance of just under 800 Ohm. This impedance is permanent (very stable indeed). Because of this higher stable impedance, it means that we can shorten the phase to ground. No we shall have zero voltage DC offset,
but what we have done is created a current offset.
This is the mode I was alluding to. You have turned what looks like a voltage DAC into a current DAC with an offset current. The offset current is 1.65V/795R = 2.1mA and as I do in the Oppo 105, I parallel two pairs of phases up and create an offset current near
4.2mA per side.
So I am now using a physical earth rather than a virtual earth.
So I made a comment on my website that I am indeed using a different mode and I wonder if ESS the manufacturer knew that this could be done this way?
What did I do wrong?
But seriously, to most people this is boring stuff. I have a website that tries to be as informative as possible, so I have to draw a fine line, how technical do I get? I want it to be readable as I can make it.
At the top of every page on my website is my phone number, I get phone calls from many parts of the world. When I hear and understand their level of understanding, I will indeed get into far more technical details - indeed I am more open about what I do than just about anybody else out there.
Give me a call!
Let us now resume normality.
Cheers, Joe