OPA based Ultra Low noise VREF for DAC

[babolcs]

Yeah I only have the PRO datasheet, forgot you were using K2M.

If I can buy later possibly I will try another OPA: LM7171 or something similar, which has 100mA output, just it is hard to buy in HU.

yes form me as having the k2M this current version is fine.

 

[babolcs]

If you are filtering the noise of the reference then it mostly doesn't matter what you are using as the reference, except at low frequencies where your filter may not be effective.

the increase of the CAP was dramatical for BASS. As I have written earlier it completely cleaned up.

at the beginning we had an argument with Mark, I didn't want to decrease the output R to 0, since instability, filtering, max current consideration. and it was not possible with NE5532.
But with the LME49720 I could and had the same effect as the CAP increase.
(basically both together helped to have a really nice bass structure)

 

[eziitis]

dramatic differences in the sound when changing an op-amp in the regulator usually indicate that the circuit is oscillating. perhaps keeping out of regulator load currents >1kHz may help?

 

[babolcs]

dramatic differences in the sound when changing an op-amp in the regulator usually indicate that the circuit is oscillating. perhaps keeping out of regulator load currents >1kHz may help?

Yes you are surely right. The 5532 was not stable.

 

[babolcs]

for those who just read the last posts, the finalized circuit was in the post 70.
Some oscilloscope based tests are still in front of me, according the listening it sounds nice.

 

[Sergelisses]

for those who just read the last posts, the finalized circuit was in the post 70.
Some oscilloscope based tests are still in front of me, according the listening it sounds nice.

Hello

Do you plan to make a pcb ?

Thanks
Serge

 

[babolcs]

Hello

Do you plan to make a pcb ?

Thanks
Serge

Later yes, now I'm trying to buy an acceptable scope solution and check if oscillation do not occure.
(Currently as you might have seen built on a trial panel)

 

[babolcs]

The lm7171 arrived but the circuit fruit did didn’t started with it. I had no time to check in details. Later I will give further details.

 

[kimschips]

Hi babolcs

How is it going with you 3.3 power supply?

Have you tried opa1 with lme49710/720 instead of opa134?
If so also with other power supply than salas shunt?
Thinking that a lme49710 opa1 feeding a lme49720 opa2 as power supply the lme49710 high PSSR will then do hard work so the whole circuit could be supplied with a lm7815 maybe?