best resistor value for I/V for AD1865?

[MaciekP]

Hello,
Can you give me good arguments for using a specific value for such a resistor? The most common in between 270 and 380 ohm, but you can also find values like 25ohm and 900ohm. I.like to use it with 1:2 or 2:1 transformer (digital-analog board).
Currentaly I'm using 2:1 trnasformer with 550 or 380ohm resistor. I prefer the sound of 550ohm, but I faced the very strong pressure for advocates of using very small resistor with a huge step-up transformer (like 1:18). The chip linearity is the most common argument here. At the same time I here about the problems with chip heat dissiparion of such a configuration and a problem with chip current source efficiency. For me lowering the resistor value gives the hard sound. Any comments will be appraciated.
Regards
Maciek

[vernon.taylor]

Salut

I've built a DAC (differential in my case) using this chip. It differs from the more usual current o/p DACs in that the o/p impedence is given at 1k7 - so up to 1k should be OK and my first proto had just that - a 1k I/V resistor. You'll find that you can easily hear the difference between a good and bad resistor here - I didn't really believe that one could hear the difference between resistors before.

BTW with the +/-1mA current output you'll theoretically get a +/-1V peak to peak o/p.

@+

Vernon

[MaciekP]

Hi!
I was onced in Lyon going to Le Trois Vallees:-) Nice place!

Do you think, that using I/V resistor as a shunt to primary windings of transformer changing the thinking of a proper value of I/V resistors? For sure, the primary inductance should be adjusted to this value, but in general which approach looks better? Small resistor-step-up transformer or big resistor and 1:1 ratio?