D-Noizator: a magic active noise canceller to retrofit & upgrade any 317-based V.Reg.

[woodturner-fran]

OK, so I've tried this, and I think all is well. The reduction in noise is (subjectively) bigger with the LM337 than LM317, but that is purely subjective, so treat that observation accordingly.

Again, thank you all for the help in understanding and getting these running properly.

 

[Mark Johnson]

Add a DPST relay to the PCB and drive its coil with a five second delay circuit. Voila, sharp and equal risetimes on Vreg_pos and Vreg_neg.

 

[maxpou]

View attachment 1097580

R12/R18 must be tweaked after you assembled everything, such that you have around 0.4V across C15/C20.

Hi Trileru,
I have 0.35V across C20, what flexibility can i have? Thank you! Maxpou

 

[carlmart]

Placing a provisional multiturn pot in R12/R18 it's more or less mandatory to find the right resistor.

 

[Trileru]

Hi Trileru,
I have 0.35V across C20, what flexibility can i have? Thank you! Maxpou

That should be good enough. How much does it overshoot at startup?

 

[maxpou]

Hi trileru,
i have approx 1 volt when i start and drop to 0.35V. Do you want I do another test? thank you! Maxpou

 

[Trileru]

I meant how much does the regulator output swing at startup?

 

[maxpou]

Placing a provisional multiturn pot in R12/R18 it's more or less mandatory to find the right resistor.

Yes i know that, but i dont have the good values here. Maxpou

 

[maxpou]

I meant how much does the regulator output swing at startup?

0.04V and the voltage up slowly and it stabilizes after 10 sec at 7.49V. The higher peak is 7.52V Maxpou

 

[Trileru]

That's nice and low.
I noticed on the NoNoiser that the base of the ADJ pin BJT is pretty sensitive. I had a hard time measuring with DMM across the coupling cap. Worked better to measure GND-base of ADJ pin BJT and GND-collector of denoiser BJT and subtract the values to get the voltage across the coupling cap. At least in my case.

 

[maxpou]

Ok, now i'm ready to install this circuit in my COD DAC for digital section or i haveto do another test? thank you! Maxpou

 

[Trileru]

What comp cap value did you use for denoiser BJT?

 

[maxpou]

C16: 4,7n

 

[Trileru]

Maybe up it to 10nF just to make sure. Apart from that it should be fine.

 

[carlmart]

C16: 4,7n

Sorry, which schematic?

 

[maxpou]

Post 2783, click on view attchment

 

[carlmart]

OK. That was with the 337?

 

[maxpou]

No 317

 

[carlmart]

Elvee,
Is it possible, or an absolute atrocity, to share one 3x7 with two denoisators? My feeling says it's not, but your expert opinion would better explain why.

 

[RickRay]

I will let Elvee answer, but I do not think that would be a good idea. The circuit is a feedback loop including the LN3*7. Attaching 2 feedback loops together through one part doesn't seem like a good idea.