Dac WM8740 replacement AD797 with Opa1611

[uchu007]

Hello,
I am building the evaluation DAC WM8740 and I want to know if I can replace the AD797 output aop with the opa1611 without worry and without modification?

 

[uchu007]

No one to answer me?

 

[Extreme_Boky]

Yes.
You may like the 5534...
Or OPA627
Or, if you lower the Vcc/Vee voltage to + and - 10V, try the AD8065 on the adaptor board
My personal all-time favourite (doing the tasks similar to what your needs are), is AD8065 (single) and AD8066 (dual), but they do not like rails supply voltages above + and - 10V.
Try replacing the MC33078 with LM6172 and see what happens...

 

[JensH]

You probably can. The distortion and noise will most likely be dominated by the MC33078 anyway. If you use OPA1611 you don't need C21.

 

[Mark Tillotson]

Until you change the MC33078 for something with lower distortion and noise it won't make much difference what the differential amp is (AD797 and OPA1611 are pretty similar performers BTW). I'd suggest using NE5532 or OPA1612 for U4 in the first instance and see if that's making a difference. Check there is HF decoupling on that chip first though.


Note the decompensation capacitor arrangement on the AD797 is not compatible with the NE5534A, but you can switch directly to an OPA1611 there because pin 8 on the OPA1611 is not connected. Single-opamps have a variety of uses for the extra pins that are not always compatible.


Put another way C21 is not needed or useful for the OPA1611, and completely wrong for the NE5534A which requires compensation according to its own scheme.