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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 KHz

The dam1021-12 rev7 is now in stock and ready for shipment. It will come with firmware with the updated PLL software. I will soon backport that PLL software to also support pre rev7 dam1021.

Sounds really nice! What was the update of the PLL now again and how has it affected the performance sound and measuring-wise?

Are you planning to also move the new PLL logic to the other products?

//
 
Sounds really nice! What was the update of the PLL now again and how has it affected the performance sound and measuring-wise?

Are you planning to also move the new PLL logic to the other products?

//

The PLL have been refined a little, the oscillator is now controlled in steps of 1/16 hz, and updated only when needed. That matter mostly when multiple dams have to track each other. As I have said before, not something you can hear or measure audio wise.

It will be ported to other products as firmware get updated anyway.
 
DC samples issue

Hi Soeren,

I'm trying to play some DC wave samples at different amplitude with my DAM1021 but I didn't succed.
The attached picture shows a DC wave sample 192kHz/24 bit where the MSB only is on (Big-endian 24 bit signed 4194304, hex 400000, binary 010000000000000000000000), please see the scope screenshot.

I expected to measure around 1 Vdc peak at the raw output of the DAC but I get noise only.

Is it due to the filter?
Is there a workaround to play the sample bit perfect?

Thank you
Andrea
 

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it's part of low-pass RC filter on ladder output.

as stated by Soren
C135 and C142 are 1500 pf NP0 ceramics, together with the 640 ohms impedance from the R-2R network they set the -3 dB 165 Khz point of the RC filter.
 

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Thanks, that's what I thought. I had also seen some mention/complaints of output coupling caps, but couldn't actually work out where they might be in the circuit. So confirming these are just filters, and have seemingly very little influence, is reassuring.

(Also worth noting that on rev7 boards, the equivalent caps aren't labelled. But it seems obvious which caps they are, right between the two polymer caps on each channel.)
 
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