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

[grunf]

I have one constructive question, will the regulator work (not oscillate) if its load has low esr capacitors in it, eg sanyo os-con 560uF 6.3V which has 7 mOhms

[tombo56]

Well, this low ESR capacitor load will be connected with some length of wire and there will be some pcb traces as well, meaning some inductance in between. That could provide stable conditions, …. or not. Hard to say without real conditions test. I don’t have such low ESR capacitor at hand to make test but will order one.

[iamwhoiam]

Thanks to all for the recent updates. The impedance for the final output electrolytic has been very useful. Seems like Nichicon PW or Panasonic FC in 63V 100uF guise would work. The series resistor is a smart move which I've put into the next revision.

My board arrived, going to populate it for 24V over the new few weeks. Not in a hurry! Have a BOM ready to fire away.

I've sent one to Nisbeth, and have two spare if anyone is interested to test them out (non-profit fabcrication cost only). They are 120x100mm on board transformer, single rail, 230v. More info a few posts back

[iamwhoiam]

Originally Posted by iamwhoiam

Thanks to all for the recent updates. The impedance for the final output electrolytic has been very useful. Seems like Nichicon PW or Panasonic FC in 63V 100uF guise would work. The series resistor is a smart move which I've put into the next revision.

My board arrived, going to populate it for 24V over the new few weeks. Not in a hurry! Have a BOM ready to fire away.

I've sent one to Nisbeth, and have two spare if anyone is interested to test them out (non-profit production-only cost). They are 120x100mm on board single rail, more info a few posts back

Here is the BOM

[Khadgar2007]

@Grunf
I guess you are thinking to use denoiser for some DAC supply. We're you thinking about using just denoiser or add some regulator near DAC? If you think adding local regulator then i think denoiser is not needed cause modern regulators like LT3045(or similar) don't need really noiseless input cause they are good as they are.
I'm not sure if i said that to you on local forum but i consider denoiser cheap,easy build PSU with really good specs but for some specific use where you need regulator near circuit then i would go like you and put some modern LDO so PCB tracks are really short and it takes less space then denoiser.

And if you wanna see how this tests with os-con build one yourself, it's cheap and easy to make.
I can send you PCB if you wanna.

[tombo56]

There was question whether regulator will be stable with attached load containing a capacitor with very low esr (organic polymer for instance). Short answer is: yes, it is rock stable.
After receiving today 1000 uF/8 mΩ organic polymer capacitor, I prepared test contraption worthy of best Grunf’s achievements. BTW, Grunf is comic book character famous for his inventions made of junk that spectacularly fail during secret agent’s missions.

Output load was 250 mA constant load + 2 kHz 50 mA square wave dynamic load. Even with 6 cm long supply leads to the load with 1000 uF/8mΩ capacitor, it was impossible to spot any oscillation using oscilloscope and small AM radio as sniffer. There was some small AM noise, as square waves are involved, but noise was originating from the proto board with load and not from the regulator.

Organic polymer capacitor was then moved directly to the regulator’s output connector and after that directly in parallel with 100 uF output capacitor. Again, no oscillations at all.

Output voltage is stable and visible noise is in fact environment noise picked up by crappy oscilloscope probe that came along with the device. I will order decent one.

All measurements were done with 1 MHz low pass filtering.
With 50 mA change, output voltage was varying around 1 mV.

As we were discussing instability/oscillation problems recently, those findings paint another picture.

[Khadgar2007]

Do you have some LNA connected to denoiser output or did you connected it directly into scope? That is question just for ripple measurement, for oscillations you can spot them from miles distance as i did when i placed untested value of bias resistors for BC337. Oscillations we're few Vpp and you couldn't miss them.

[tombo56]

No LNA involved, direct scope connection.
I was looking for the smallest hint of the oscillation, but not even a mV over picked environment noise level. That’s why AM radio in the MW range was used as a bloodhound.

[grunf]

Originally Posted by Khadgar2007

@Grunf
I guess you are thinking to use denoiser for some DAC supply. We're you thinking about using just denoiser or add some regulator near DAC? If you think adding local regulator then i think denoiser is not needed cause modern regulators like LT3045(or similar) don't need really noiseless input cause they are good as they are.
I'm not sure if i said that to you on local forum but i consider denoiser cheap,easy build PSU with really good specs but for some specific use where you need regulator near circuit then i would go like you and put some modern LDO so PCB tracks are really short and it takes less space then denoiser.

And if you wanna see how this tests with os-con build one yourself, it's cheap and easy to make.
I can send you PCB if you wanna.

i have no intention of using this regulator in my DAC, i am just asking for others as there is a discussion going on about the characteristics of the output capacitor and the oscillation problem so i wanted to point out a possible problem.

[Elvee]

Originally Posted by tombo56

There was question whether regulator will be stable with attached load containing a capacitor with very low esr (organic polymer for instance). Short answer is: yes, it is rock stable.

That confirms my own experience (only for the 317): a good layout combined with a single, good cap does not seem to be problematic.
In fact, with its compensation, the denoiser might act as an active compensation, and contribute to the stability.
There might however be a penalty: a noise peak could appear in the tens of kHz range.
I didn't check it, because it would be complicated with my current instruments configuration, but if someone has the means to do it simply and easily, it might be worth checking

All measurements were done with 1 MHz low pass filtering.
With 50 mA change, output voltage was varying around 1 mV.

That's not really bad, but it leaves to be desired: it represents ~0.02ohm, which must be about the same as the naked 317.
The denoiser should push that below 1milliohm.
There might be some wiring/connection issue degrading the output impedance