Resistors for I/V conversion (R4 & R5)After deciding on all the capacitor options I focused on the I/V resistors. I always used Beyschlag metal film resistors. I've read somewhere they would sound o.k. Anyway, I never really bothered about resistors. After reading that Fedde Bouwman uses carbon resistors in his Nonoz DAC III, I wanted to find out if I can hear any difference between these. I ordered some carbon resistors(1/4W) from Reichelt and compared them to the Beyschlag. There is a difference. While the Beyschlags sound very clear and open, the carbon resistors more pronounce the midtones. It's probaply a question of personal taste. In my setup I prefer the warmer and more involving tonal balance of the carbon resistors. Especially voices have more colors.
R6 & R7I've read several recommandations on the www about these resistors. Fedde recomends carbon resistors not larger than 50kOhm, Doede uses 1MOhm and some people use no resistor at all. Comparisons between carbon and metal film resistors of the same value are easy to do. Test were done with carbon resitors as I/V. In that case I opt for Beyschlag metal film bacause the carbon resistors seem to hide information and slow down the performance a pit. When comparing different resistor values we have to keep in mind that the output level rises as we increase the resistance. That's maybe just the reason why I've chosen to use no resistor at all. Percussion and piano appeared to be more real.
P1 (Vref)I am still using a poti. I will repalce it by a fixed resitor soon. |