Thanks seems like you have a lot of experience with Dac building and modificatins?
Yes i have es9018 Dac with ad797 power supply and oscon capacitors. I have checked dacs on eBay but it seems they don't use so fine power supply today?
Please check my attached schematic hope it is okay for "audiodesine"
From a brief look at the schematic, there are a few thoughts that come to mind. (1) Better to use a low noise voltage reference for the AD797 AVCC buffers rather than DVCC, which is pretty noisy. LT3042 can make a good reference, so can LTC6655. Up to you though. (2) ES9018 is an older chip and not the best sounding one ESS ever made. I would go for ES9028PRO if possible. (3) ESS dacs have some low level RF coming out of the dac chip analog outputs. Very slight filtering before the I/V opamp can help some and then much more passive filtering before the differential summing stage can help remove audible distortion from RF that does not show up so well on typical distortion FFTs. Any filter before the I/V has to be very mild since any series resistance will increase distortion, and any capacitance to ground will cause gain peaking in the I/V opamp. I have use twisted pair wire wrap wire running along the dac board ground plane between the dac outputs and the I/V inputs with some success. Other people have found their own solutions such as Allo recently talking about with respect to their new 'revolution' ES9038Q2M-based dac. Passive filtering after the I/V is less tricky, but it helps to attenuate any RF as much as possible before the differential summing stage since that particular opamp topology seems a bit more sensitive the RF than the inverting topology of the I/V opamps. EDIT: ESS is now using OPA1612 opamps for the output stage in their latest evaluation boards, rather than AD797. Don't know if cost is the only issue or not. EDIT: (4) Sabre dacs sound best with ASRC disabled and in 128_fs mode, which is to say they sound best in fully synchronous operation rather than async. That means the end up looking a lot like an AKM based dac in that there are separate master clocks for 44khz family and 48kHz family sample rates. (5) Schematics don't show layout information nor other external connected circuitry. There are some considerations there to think about too, such as number of PCB layers, layout of voltage regulators, output stage etc. The document at ESS downloads page is a good start but probably not completely up to date: http://www.esstech.com/files/4514/4095/4306/Application_Note_Component_Selection_and_PCB_Layout.pdf
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I am not using the IV stage I have connected zapfilter 2 instead it sounds great but with reduced volume in the dac arduino firmware about -15dB.
Because zapfilter is not made for ess Dac with high output current, so that could also be a compromise.
Yes thinking upgrading/replacing iv stage to get right output level and maybe get higher sound quality than zapfilter 2.
Because zapfilter is not made for ess Dac with high output current, so that could also be a compromise.
Yes thinking upgrading/replacing iv stage to get right output level and maybe get higher sound quality than zapfilter 2.
Likely so IMHO. I/V, filtering, and some kind of differential summing are needed in order to minimize distortion.
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