Wednesday, February 25, 2009

It's getting better.........

I have finally added a discrete I/V board to the ESS Sabre DAC, bypassing the original I/V that used opamp. This discrete I/V is one of my previous design using all BJT that is in a single common base configuration.

The sound does open up a bit, the most noticeable improvement is the bass. With the opamp based I/V, bass is kinda artificial and colored a lot.
On the contrary, the discrete version gives an accurate presentation and somewhat more neutral.

The only draw back of this old design is that it's not direct coupled, I need an output cap to block the DC. I have an idea of improving the design by adding an "folded cascode" to the common base stage and an extra DC servo to monitor the output. A true balanced config is possible too.

Well, before I move on to a new I/V design. I have a good news that the newer ES9018 (Sabre32) chip has arrived and I'm ready to do a "transplant", replacing the ES9008 with the 9018.

The 9018 has a reconfigurable digital filter, ie. one can change the filter coefficients with an external processor. This allow a customizable filter that may (or may not) change the sound on the fly.

Let's wait and see if I like this new chip. :-)

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