chris719
100+ Head-Fier
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WM8740 has internal op-amps already that are most likely worse than the very good op-amps you have available externally.
Originally Posted by cotdt as filters they seem to work just fine |
Originally Posted by cotdt try it without the low-pass filter first. it seems to sound fine without the low-pass filter straight out of the DAC chip, but I couldn't get much volume out of it so it's not a proper evaluation. |
Originally Posted by Cauhtemoc /img/forum/go_quote.gif If you are talking about the WM8740, I'm guessing this is because it already has an internal low-pass filter. Its cutoff frequency of 195 kHz is a bit on the high side however. I had planned to add an external low-pass filter with a cutoff of 40 kHz. You say you couldn't get much volume out of it, should I increase the gain of the beta22? I had planned to run with a gain of 2 (this is for balanced headphones), should I perhaps increase this to 5? About the coupling caps, these form a high pass filter together with the coupling resistors. I had planned to set this at around 5 Hz. Is there a minimum size I can use for the caps? Good film caps become rather expensive as the size go up. |
Originally Posted by Cauhtemoc /img/forum/go_quote.gif Looking at the schematic for the beta22, I'm having trouble deciding what 100 uF and 470 uF electrolytic capacitors to use. Any recommendations? What should I be looking for? Low impedance, high ripple current? |
Originally Posted by amb My advice is just to go with the recommendations at the β22 website parts list. There is no need to obsess about these caps as long as you don't use utter crap (and I wouldn't recommend those on the website). |