Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › pupDAC Step-by-Step Build Thread
New Posts  All Forums:Forum Nav:

pupDAC Step-by-Step Build Thread - Page 19

post #271 of 272

Your lowest voltage is 127.5mV.

You want to adjust the value of the others to match this value.

The easiest way to figure out what value you need is to get

a 200k 20k trim pot and install it across the Riv resistors one at

a time. Adjust the trim pot until the voltage reads 127.5mV.

Unsolder the trim pot and measure the resistance. Find the

closest standard value and solder this on top of the Riv you

just measured. Repeat until all the Riv read 127.5mV.


 

This process will account for tolerance in the Riv resistors

and the tolerance of the PCM1794a.

 

Edit: changed trim pot value.

The expected values of the parallel trim resistor

will be in the 1k to 10k range.


Edited by Avro_Arrow - 5/11/14 at 4:26pm
post #272 of 272

As a test, I placed a 10K resistor (in parallel) on R14 and brought down the DC offset to around 3 mV. The noise was still there, and when I ran RMAA it reported way lower specs that what I'd originally measured. The dynamic range was around 70, noise around 70, crosstalk in the 60s, etc. Am I doing something wrong?

New Posts  All Forums:Forum Nav:
  Return Home
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › pupDAC Step-by-Step Build Thread