CS8416 CS4398 kit issue.

[F1 FAN]

I have two of these kits CS8416 CS4398 192Khz/24Bit DAC USB Coaxial,Assembled | eBay .While they both work fine fed from a single transformer a problem occurs when using separate supplies for the digital and analog sections.(When using a single supply a jumper is added so the digital section recieves DC from the analogs positive supply). However when powering the analog section from + and - 12volt Salas shunt regulators with it's own transformer and the digital section it's own +13 volt DC supply a problem occurs.Regardless of input(USB or coax) it will not lock on to the signal.Anyone have any thoughts as what might be causing this weird issue when using dual supplies?

[Greg Erskine]

Originally Posted by F1 FAN

I have two of these kits CS8416 CS4398 192Khz/24Bit DAC USB Coaxial,Assembled | eBay .While they both work fine fed from a single transformer a problem occurs when using separate supplies for the digital and analog sections.(When using a single supply a jumper is added so the digital section recieves DC from the analogs positive supply). However when powering the analog section from + and - 12volt Salas shunt regulators with it's own transformer and the digital section it's own +13 volt DC supply a problem occurs.Regardless of input(USB or coax) it will not lock on to the signal.Anyone have any thoughts as what might be causing this weird issue when using dual supplies?

Hi Fi FAN,

How are you connecting DC to these boards? What components have you removed?

regards

[F1 FAN]

Hi Greg,On the digital side the bridge rectifier has been removed and jumpered appropriately then fed from an off board transformer ,bridge rec. filter capacitor assembly. On the analog side the bridge rectifier, main filter capacitors,voltage regulators and caps at the output of regulators have been removed.The off board Salas regulators are fed into the positions previously occupied by the caps following the regulators.

I should add that all the on board regulators are working it just won't lock on to signal unless I remove the voltage to digital section (fed from the off board digital supply) and take the feed from the positive Salas reg. Then it works fine.

[rss388]

I assembled one of these powered by offboard supplies but I retained the onboard cap positions to bypass with MUSE caps and that works fine. The supplies are galvanically separated and tied on board per the pcb.

Also, I looked up the CS4398 data sheet. The LPF filter design onboard is not the recommended one and I elected to modifiy to reflect the one in the datasheet. However, the analog output carries a 2.5V offset. I am curious how you handle that.

[F1 FAN]

I retained the 2200uf on the digital supply but removed the 2200uf from the analog supply as the Salas regs. work better without large values of capacitance at their outputs.

As for LPF I used somthing different as well but no offset issues.Might your offset be the result of using unequal components on each half of the filter as indicated in the 4398 datasheet?